SIMPLE WG A. Houri Internet-Draft IBM Intended status: Informational E. Aoki Expires: February 28, 2010 AOL LLC S. Parameswar T. Rang Microsoft Corporation V. Singh H. Schulzrinne Columbia U. August 27, 2009 Presence Interdomain Scaling Analysis for SIP/SIMPLE draft-ietf-simple-interdomain-scaling-analysis-08.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 28, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights Houri, et al. Expires February 28, 2010 [Page 1] Internet-Draft Presence Scaling Analysis August 2009 and restrictions with respect to this document. Abstract This document analyzes the traffic that is generated by presence subscriptions between domains and shows that the amount of traffic can be extremely large. This document also analyzes the effects of a large presence system on the memory footprint and the CPU load. Approved and in-work optimizations to the Session Initiation Protocol are analyzed, considering the possible impact on the load. Separate documents contain the requirements for optimizations and suggestions for new optimizations. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Message Load . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Message Load Optimizations Considered . . . . . . . . . . 5 2.2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3.1. Constants . . . . . . . . . . . . . . . . . . . . . . 8 2.3.2. Initial Messages . . . . . . . . . . . . . . . . . . . 10 2.3.3. Steady State Messages . . . . . . . . . . . . . . . . 10 2.3.4. Termination Messages . . . . . . . . . . . . . . . . . 11 2.3.5. Bottom Line . . . . . . . . . . . . . . . . . . . . . 12 2.3.6. Rush Hour Calculations . . . . . . . . . . . . . . . . 12 2.4. No optimizations used . . . . . . . . . . . . . . . . . . 13 2.5. Dialog optimization used . . . . . . . . . . . . . . . . . 15 2.6. NOTIFY optimization used . . . . . . . . . . . . . . . . . 17 2.7. Dialog and NOTIFY optimizations used . . . . . . . . . . . 19 2.8. Presence Federation Scenarios . . . . . . . . . . . . . . 21 2.8.1. Widely distributed inter-domain presence . . . . . . . 22 2.8.2. Associated inter-domain presence . . . . . . . . . . . 26 2.8.3. Large network peering . . . . . . . . . . . . . . . . 27 2.8.4. Intra-domain peering . . . . . . . . . . . . . . . . . 31 2.9. Partial Notifications Optimization . . . . . . . . . . . . 36 2.10. Extremely Optimized SIP . . . . . . . . . . . . . . . . . 38 3. State Management . . . . . . . . . . . . . . . . . . . . . . . 42 3.1. State Size Calculations . . . . . . . . . . . . . . . . . 43 3.1.1. Tiny System . . . . . . . . . . . . . . . . . . . . . 44 3.1.2. Medium System . . . . . . . . . . . . . . . . . . . . 44 3.1.3. Large System . . . . . . . . . . . . . . . . . . . . . 44 3.1.4. Larger System . . . . . . . . . . . . . . . . . . . . 44 3.1.5. Notes on the calculations . . . . . . . . . . . . . . 44 4. Processing complexities . . . . . . . . . . . . . . . . . . . 45 4.1. Aggregation . . . . . . . . . . . . . . . . . . . . . . . 45 4.2. Partial Publish and Notify . . . . . . . . . . . . . . . . 46 Houri, et al. Expires February 28, 2010 [Page 2] Internet-Draft Presence Scaling Analysis August 2009 4.3. Filtering . . . . . . . . . . . . . . . . . . . . . . . . 46 4.4. Authorization . . . . . . . . . . . . . . . . . . . . . . 46 4.5. Resource List Service . . . . . . . . . . . . . . . . . . 47 5. Current Optimizations . . . . . . . . . . . . . . . . . . . . 48 6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 55 8. Security Considerations . . . . . . . . . . . . . . . . . . . 56 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 57 10. Changes from Previous Versions . . . . . . . . . . . . . . . . 57 10.1. Changes in version 07 . . . . . . . . . . . . . . . . . . 57 10.2. Changes in version 06 . . . . . . . . . . . . . . . . . . 57 10.3. Changes in version 05 . . . . . . . . . . . . . . . . . . 57 10.4. Changes in version 04 . . . . . . . . . . . . . . . . . . 57 10.5. Changes in version 03 . . . . . . . . . . . . . . . . . . 58 10.6. Changes in version 02 . . . . . . . . . . . . . . . . . . 58 10.7. Changes in version 01 . . . . . . . . . . . . . . . . . . 58 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 58 12. Informational References . . . . . . . . . . . . . . . . . . . 59 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 60 Houri, et al. Expires February 28, 2010 [Page 3] Internet-Draft Presence Scaling Analysis August 2009 1. Introduction The document analyzes the traffic that is generated by Session Initiation Protocol (SIP) for presence (as defined by the SIMPLE working group) due to presence subscriptions between domains. It shows that the number of messages and the amount of data generated can be extremely large. This document also analyzes the effects of a large presence system on the memory footprint and the CPU load. Approved and in-work optimizations to SIP are analyzed, considering the possible impact on the load. Another document provides requirements for optimizations [1] while other documents contain suggestions for new optimizations: [2] and [3] This document is intended to drive work on possible solutions that will make the deployment of a SIP-based presence server a less challenging task. Deployment of highly scalable presence systems is challenging by its nature, and protocol developers design their own techniques for optimizing their protocols. Comparing protocols is beyond the scope of this document. This document discusses the following areas, showing the complexity and load that the presence server handles in order to provide its service: o Message load - By computing the number of messages that are required for connecting presence systems, the document shows that the number of messages and the required bandwidth are large, and that it is quite obvious that optimizations are needed. o State management - Due to the nature of the service that the presence server provides, the presence server has to manage a relatively large and complex state. Some computations are provided in the document. o Processing complexities - The presence server maintains many small objects and performs frequent operations on these objects. We show that these operations, as well as the optimizations that are intended to reduce the amount of data sent between watchers and presence servers, are not so simple and may create a heavy processing load on the presence server. o Groups - Resource List Servers [4] optimize the number of sessions that are created between the watchers and the presence server. However, this optimization may create an exponential increase in the size of subscriptions as a result of the minimal effort of subscribing to large groups. The terms "presence domain" or "presence system" appear in this document frequently. These terms refer to SIP-based presence servers that provide presence subscription and notification services to their users. A presence system can be deployed in a small enterprise or in Houri, et al. Expires February 28, 2010 [Page 4] Internet-Draft Presence Scaling Analysis August 2009 a large consumer network. 2. Message Load Some optimizations are approved or are being defined for the SIP presence protocol, but even with these optimizations, a large number of messages and wide bandwidth are needed in order to establish federation between presence systems of large communities. Further thinking is needed in order to make large deployment of presence systems less resource demanding. Note that even though this document talks about inter-domain traffic, the introduction of resource list servers (RLSs) [4] introduces similar traffic patterns intra-domain and inter-domain. See the detailed discussion on resource lists in Section 4.5. 2.1. Message Load Optimizations Considered The current optimizations that were approved as RFCs or are approved as working group items in the SIMPLE working group can be divided into two categories: o Dialog-saving optimizations - Here we refer to optimizations such as the resource list RFC [4] or to the URI list subscriptions RFC [5]. These documents define ways to reduce the number of dialogs that are required between the subscriber and the presence system. Note that the terms "dialog optimization" or "RLS usage", as used in this document, refer to the usage of a URI that represents a list of URI lists between domains and not within the same domain. An example is a user Alice in domain example.org who subscribes to the URI external-reps-list at example.com or uses a URI list to subscribe to her watch list in example.com. Note also that, when calculating the traffic due to the RLS within a domain, the traffic between the RLS and the presence agents should also be considered. However, because we are mostly concerned with inter- domain traffic, we are not taking into account the traffic between the RLS and the presence agents. o Notification optimizations - Here we refer to the optimizations covered in the subnot-etags draft [6], which describes the suppression of unnecessary NOTIFYs when subscriptions are refreshed. There are other drafts that reduce the size of messages by using partial notifications or filtering. This document shows that partial optimizations can reduce the bandwidth but do not reduce the number of messages. Houri, et al. Expires February 28, 2010 [Page 5] Internet-Draft Presence Scaling Analysis August 2009 One optimization that was not considered is the reception of presence information outside of SIP. An example of this is the ability to download persistent presence information directly from a web site. The calculations assume that all presence data is carried within SIP and not by other means. These out-of-band optimizations may improve the number of messages and number of bytes significantly, but they are out of scope for this document. 2.2. Assumptions In this document, several assumptions are used regarding size of messages, rate of presence change and more. It should be noted that these assumptions are not directly based on rigorous statistics from actual SIP-based deployments of presence systems but more on some experience with other types of presence-based systems. The following numbers are given more as examples from real deployments and they are not intended to be complete. In a large consumer network, we have seen the following patterns: o There are approximately 110 users on a watch list on average. o There are approximately 12 billion status changes a day (139k/ second) across the network. When a proprietary binary protocol conveys the status changes, the average message size is about 188 bytes. When a SIP NOTIFY is used, the average is about 1228 bytes. o The average number of logins/logouts in the system is about 2000 logins per second and about 4000 logouts per second. When a promotion, contest, or network hiccup causes many users to login and logout simultaneously, there are about 20,000 logins per second. o The peak number of instant messages sent is about 50,000 messages per second. In an enterprise deployment, we have seen the following patterns: o Average watch list size was 200 users. o About half of the registered users were online at peak time. o Status change rate was 2 changes per hour. o The average logins/logouts in the system was about 5 logins per second with additional 15 logins/logouts during start/end of day rush hours. Even though the assumptions in this document are not based on rigorous statistical data, the target here is not to analyze a specific system but to show that even with VERY moderate assumptions (which are even less than the observations mentioned above), the Houri, et al. Expires February 28, 2010 [Page 6] Internet-Draft Presence Scaling Analysis August 2009 number of messages, the network bandwidth, the required state management, and the CPU load are high. Real-life systems could have much larger scalability challenges. For example, the presence state change that we assumed (one presence state change per hour) is maybe one of the most moderate assumptions that we have taken. Experience from consumer networks shows that the frequency can be much higher, especially with the younger generation using more presence attributes like mood, etc. In an environment where a user may have several devices and other resources for presence information such as geographical location and calendar, the frequency of presence state changes will be much higher. It is hard to measure presence load because it depends heavily on the behavior of users, and the behavior of users differs widely. Some users will have a small number of presentities in their watch list, while others may have hundreds, or even thousands. Some users will change their state frequently and have many sources of presence information, while others may have small number of changes during the day. In addition, the "rush hour" calculations of when the day starts and ends were not included in this document. Rush hour differs between different enterprises and is different still in the consumer presence systems. It is hard, if not impossible, to include in a static document all the possible combinations. Throughout the calculations, a certain number of users are assumed for the different models. That does not mean that in actual deployments all the users of the domain are actually subscribed to presence documents and/or have published their presence documents. Observing actual deployments shows that, in the consumer market, the number of users that use presence services may be 10 percent or less of the registered users. In the enterprise market, the numbers tend to be around 50 percent of the actual enterprise registered users. The same is true for the number of watched presentities per watcher. If only some percentage of the domain users are online at a given time, then this number should match that percentage. However, adding this assumption to the calculations will make the calculations more complex because the effect of the watched offline presentities would need to be considered. This means that empty NOTIFYs would be sent for offline presentities when the subscription is created and there are no updates on them. In order to make the computations less complex (they are complex enough as they are), the number of the watched presentities used in the calculations is the number of the federated presentities from the watcher list that are online. Houri, et al. Expires February 28, 2010 [Page 7] Internet-Draft Presence Scaling Analysis August 2009 2.3. Analysis The basic SIP subscription dialog involves the following message- transfer: o SUBSCRIBE/200 o Initial NOTIFY/200 o (j) NOTIFY/200 where "j" is the number of presence changes seen by the watcher o (k) SUBSCRIBE/200 where "k" is the number of subscription dialog refresh periods o SUBSCRIBE/200 with Expires = 0 to terminate the dialog o NOTIFY/200 ending the dialog An individual watcher will generate X number of SIP subscription dialogs corresponding to the number of presentities it chooses to watch. The amount of traffic generated is significantly affected by several factors: o Number of watchers connected to the system. o Number of presentities connected to the system. o Frequency of changes to presence information. This document contains several calculations that show the expected message rate and bandwidth between presence domains. The following sections explain the assumptions and methods behind the calculations. 2.3.1. Constants The following are the "constants" that we use in the calculations. Some of the constants are used throughout the calculations while others change between use cases. o (C01) Subscription lifetime (hours) - The assumed lifetime of a subscription, in hours. We assume 8 hours for all calculations. Note that the term "day" that is used in the document and C01 are synonymous. o (C02) Presence state changes / hour - The average time that a presentity changes his/her status in one hour. We assumed 3 times per hour for most calculations. Note that for some users in consumer messaging systems, the actual number of changes is likely to be much higher. o (C03) Subscription refresh interval / hour - The duration of the SUBSCRIBE session, after which it needs to be refreshed. We assumed that the duration is one hour. o (C04) Total federated presentities per watcher - The number of presentities that the watcher is watching. The number here changes in this document according to the type of the specific Houri, et al. Expires February 28, 2010 [Page 8] Internet-Draft Presence Scaling Analysis August 2009 deployment. o (C05) Number of dialogs to maintain per watcher - The number of the SUBSCRIBE dialogs that are maintained per watcher. If a dialog optimization is not assumed, this number is equal to C04, otherwise it is 1. o (C06) Total number of watchers in the federated presence domains. The number here is the number of all watchers in all the federated domains. o (C07) SUBSCRIBE message size, in bytes. We assume 450 bytes in all calculations. The size is based on a typical SUBSCRIBE taken from RFCs. o (C08) 200 OK for SUBSCRIBE message size, in bytes. We assume 370 bytes in all calculations. The size is based on a typical 200 OK taken from RFCs. o (C09) NOTIFY message size, not including the presence document. The size of this message for a single presentity is assumed to be 500 bytes for the NOTIFY message itself (based on sizes from examples in RFCs). o (C10) 200 OK for NOTIFY message size, in bytes. We assume 370 bytes in all calculations. The size is based on a typical 200 OK taken from RFCs. o (C11) Size of an average presence document, in bytes. Two sizes of average presence doucment are used. One is the minimal size of the PIDF [7] document, assumed to be 350 bytes based on examples from RFCs, and the other is 3000 bytes for a rich presence document [8]. It should be noted that 3000 bytes for a presence document is relatively modest if we take into account multiple devices and location information. o (C12) The size of a NOTIFY, in bytes, when partial notification [9] is used. We have taken this size to be 200 bytes, much smaller than the example given in [9], which assumes multiple changes in the presence document. Here we assume a single change. When dialog optimization [4] is used, an RLMI document, which contains the presence documents for the users on the watch list, is sent. In a previous version of this document, we had omitted the overhead of the RLMI document. This "bug" was found by Victoria Beltran-Martinez and is fixed in this version by adding the following constants C13, C14 and C15 to the calculations. o (C13) Item size per each contact in RLMI document, 160 bytes. o (C14) The size of the multipart boundary in RLMI notifications, 144 bytes. o (C15) The size of the XML root node in RLMI document (once per notification), 144 bytes. Houri, et al. Expires February 28, 2010 [Page 9] Internet-Draft Presence Scaling Analysis August 2009 2.3.2. Initial Messages The following are the calculations for the messages in the initial phase of the establishment of the subscriptions. The calculations contain both the number of messages and the number of bytes. o (I01) Number of initial SUBSCRIBE messages per watcher = C05. o (I02) Number of initial 200 OK messages for SUBSCRIBE messages per watcher = C05. o (I03) Number of initial NOTIFY messages per watcher = C05. o (I04) Number of initial 200 OK messages for NOTIFY messages per watcher = C05. o (I05) Total number and bytes of initial SUBSCRIBE messages for all watchers = Number: I01*C06, Bytes: I01*C06*C07. o (I06) Total number and bytes of initial 200 OK for SUBSCRIBE messages for all watchers = Number: I01*C06, Bytes: I01*C06*C08. o (I07) Total number and bytes of initial NOTIFY messages for all watchers = Number: I01*C06. The calculation for the size in bytes is different depending on the use of dialog optimization: * When dialog optimization is not applied, the number of bytes is calculated by (I01*C06*C09)+(I01*C06*C11). * When dialog optimization is applied, the number of bytes is calculated by (I01*C06*(C09+C14+C15))+(I01*C06*C04*(C11+C13+ C14)). o (I08) Total number and bytes of initial 200 OK for NOTIFY messages for all watchers = Number: I04*C06, Bytes: I04*C06*C10. o (I09) Total number and bytes of initial messages per day = Number: numbers in I05+I06+I07+I08, Size: sizes in I05+I06+I07+I08. 2.3.3. Steady State Messages Here we describe the calculations for steady state messages. Steady state is the time between the initial subscription and the teardown of the subscription. It contains the NOTIFYs due to state change and the subscription refreshes. o (S01) NOTIFY messages due to state change per watched presentity per day (less 2, because the NOTIFYs for initial and terminating states are included in the initial and terminating calculations) = (C02*C01-2). o (S02) 200 messages (for NOTIFYs due to state change) per watched presentity per day (less 2, because the NOTIFYs for initial and terminating states are included in the initial and terminating calculations) = (C02*C01-2). o (S03) Total number and size of messages due to state change per day = Number: (S01+S02)*C06*C04. The calculation for the size in bytes depends on the use of dialog Houri, et al. Expires February 28, 2010 [Page 10] Internet-Draft Presence Scaling Analysis August 2009 optimization: * When dialog optimization is not applied, the number of bytes is calculated by (C06*C04)*((S01*(C09+C11))+(S02*C10)). * When dialog optimization is applied, the number of bytes is calculated by (C06*C04)*((S01*(C09+C11+C13+C14+C15+C14))+ (S02*C10)). This includes the multipart boundary of the resource list. Note that for dialog optimization it is assumed that only a single presentity is changed and partial state notification is used. o (S04) Number of SUBSCRIBE messages for refreshes per watcher per day = ((C01/C03)-1)*C05. One is subtracted because the termination is calculated separately. For example, if there are 8 hours in the day and a refresh should occur every hour, there are 7 refreshes during the day and not 8. o (S05) Number of 200 OK messages for SUBSCRIBE messages for refreshes per watcher per day = ((C01/C03)-1)*C05. o (S06) Number of NOTIFY messages for refreshes per watcher per day = ((C01/C03)-1)*C05. If NOTIFY optimization is used [6], there is no need to send NOTIFYs for refreshes, and S06 will be zero. o (S07) Number of 200 OK messages for NOTIFY messages for refreshes per watcher per day = ((C01/C03)-1)*C05. If NOTIFY optimization is used [6], there is no need to send NOTIFYs for refreshes, and S07 will be zero. o (S08) Total number and size of messages due to SUBSCRIBE refreshes per day = Number: (S04+S05+S06+S07)*C06. The size in bytes is calculated by adding the SUBSCRIBE bytes (S04*C06*C07), the OK bytes for the SUBSCRIBE (S05*C06*C08), the NOTIFY bytes C06*(S06*(C09+C11)) and the OK bytes for the NOTIFY (S07*C06*C10). * Note that the formula for the NOTIFY bytes assumes that dialog optimization is not used. When dialog optimization is used, the formula is: C06*(S06*((C09+C14+C15)+(C04*(C11+C13+C14)))). * Note that a full state should be given in SUBSCRIBE refreshes in resource lists. See section 5.2 in [4]. The fact that the full state needs to be returned in a NOTIFY response to refresh makes the NOTIFY optimization more efficient in conjunction with the dialog optimization. o (S09) Total number and bytes of steady messages per day = Number: numbers in S03+S08, Bytes: sizes in S03+S08. 2.3.4. Termination Messages The following are the calculations for the messages in the termination phase of the subscriptions. The calculations contain both the number of messages and the number of bytes. Houri, et al. Expires February 28, 2010 [Page 11] Internet-Draft Presence Scaling Analysis August 2009 o (T01) Number of terminating SUBSCRIBE messages per watcher = C05. o (T02) Number of terminating 200 OK messages for SUBSCRIBE messages per watcher = C05. o (T03) Number of terminating NOTIFY messages per watcher = C05. If NOTIFY optimization is used [6], there is no need to send a NOTIFY for terminations, and T03 will be zero. o (T04) Number of terminating 200 OK messages for NOTIFY messages per watcher = C05. If NOTIFY optimization is used [6], there is no need to send a NOTIFY for terminations, and T04 will be zero. o (T05) Total number and bytes of terminating SUBSCRIBE messages for all watchers = Number: T01*C06, Bytes: T01*C06*C07. o (T06) Total number and bytes of terminating 200 OK for SUBSCRIBE messages for all watchers = Number: T01*C06, Bytes: T01*C06*C08. o (T07) Total number and bytes of terminating NOTIFY messages for all watchers = Number: T01*C06. The number of bytes is calculated to be: * (T03*C06*(C09+C11) when dialog optimization is not used, and * (T03*C06*(C09+C14+C15))+(T03*C06*C04*(C11+C13+C14)) when dialog optimization is used. Note that a full state should be given in SUBSCRIBE refreshes in resource lists. See section 5.2 in [4]. o (T08) Total number and bytes of terminating 200 OK for NOTIFY messages for all watchers = Number: T04*C06, Bytes: T04*C06*C10. o (T09) Total number and bytes of terminating messages per day = Number: numbers in T05+T06+T07+T08, Size: sizes in T05+T06+T07+ T08. 2.3.5. Bottom Line The following are the calculations of several totals that are based on the above calculations. o (B01) Total number of messages and bytes during the day = Messages: number of messages in I09+S09+T09, Bytes: number of bytes in I09+S09+T09. o (B02) Total number of messages and bytes per second = Messages: number of messages in B01/(C01*3600), Bytes: number of bytes in B01/(C01*3600). o (B03) Total number of message and bytes per user per day = Messages: number of messages in B01/C06, Bytes: number of bytes in B01/C06. 2.3.6. Rush Hour Calculations With the way that the calculations are built, it is relatively easy to see the effect of rush hours at the beginning and the end of the day. For the beginning of the day, we should look at the numbers of "(I09) Total number and bytes of initial messages per day" and for Houri, et al. Expires February 28, 2010 [Page 12] Internet-Draft Presence Scaling Analysis August 2009 the end of the day we should look at the number of "(T09) Total number and bytes of terminating messages per day". Taking these numbers with some assumed percentage of the number of users logging in at the same hour should give good indication for the rush hour load. 2.4. No optimizations used The following table uses some common presence characteristics to demonstrate the effect these factors have on state and message rate within a presence domain using base SIP without any proposed optimizations. In this example, there are two presence domains with a total of 40,000 federating users with an average of 4 contacts per user in the peer domain. Note that the main calculation is done for a presence document size of 350 bytes, which is the base PIDF [7] document size, but the bottom-line calculation is also given for a presence document size for rich presence [8], which is assumed to be 3000 bytes, based on the examples given in the RFCs. This two-fold calculation is done for every use case in this document. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher................4 (C05) Number of dialogs to maintain per watcher...............4 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................4 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............4 (I03) Initial NOTIFY msgs per watcher.........................4 (I04) Initial 200 OK msgs (NOTIFY) per watcher................4 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................72,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...............160,000 Bytes for all watchers....................136,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Houri, et al. Expires February 28, 2010 [Page 13] Internet-Draft Presence Scaling Analysis August 2009 Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............640,000 Bytes for all watchers....................326,400,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.............7,040,000 Bytes for all watchers..................4,294,400,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day................................28 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day................................28 (S06) Number of NOTIFY msgs for refreshes per watcher per day................................28 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day................................28 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.....4,480,000 Bytes for all watchers per day..........2,284,800,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers............11,520,000 Bytes for all watchers..................6,579,200,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................4 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........4 (T03) Terminating NOTIFY msgs per watcher.....................4 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............4 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers.............. 160,000 Bytes for all watchers.....................72,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers...............160,000 Bytes for all watchers....................136,000,000 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...............640,000 Houri, et al. Expires February 28, 2010 [Page 14] Internet-Draft Presence Scaling Analysis August 2009 Bytes for all watchers....................326,400,000 ** Bottom Line (B01) Total of messages between domains..............12,800,000 Total of bytes between domains (PD=350).....7,232,000,000 Total of bytes between domains (PD=3000)...20,376,000,000 (B02) Total number of messages / second.. ..................444 Total of bytes per second (PD=350)................251,111 Total of bytes per second (PD=3000)...............707,500 (B03) Total number of by msgs per user/day......... ........320 Total number of bytes per user/day (PD=350).......180,800 Total number of bytes per user/day (PD=3000)......509,400 Figure 1: No optimizations used 2.5. Dialog optimization used The same analysis provided above is repeated here with the assumption that the dialog optimization is applied. Note that while the sign-in (ramp up) and sign-out message flows are positively affected, the steady state rates are not. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher................4 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................1 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Houri, et al. Expires February 28, 2010 [Page 15] Internet-Draft Presence Scaling Analysis August 2009 Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers................40,000 Bytes for all watchers....................136,160,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............160,000 Bytes for all watchers....................183,760,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.............7,040,000 Bytes for all watchers..................6,378,240,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................7 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................7 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.....1,120,000 Bytes for all watchers per day..........1,286,320,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers.............8,160,000 Bytes for all watchers..................7,664,560,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1 (T03) Terminating NOTIFY msgs per watcher.....................1 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............1 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers................40,000 Houri, et al. Expires February 28, 2010 [Page 16] Internet-Draft Presence Scaling Analysis August 2009 Bytes for all watchers....................136,160,000 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...............160,000 Bytes for all watchers....................183,760,000 ** Bottom Line (B01) Total of messages between domains...............8,480,000 Total of bytes between domains (PD=350).....8,032,080,000 Total of bytes between domains (PD=3000)...21,176,080,000 (B02) Total number of messages / second.....................294 Total of bytes per second (PD=350)................278,892 Total of bytes per second (PD=3000)...............735,281 (B03) Total number of by msgs per user/day..................212 Total number of bytes per user/day (PD=350).......200,802 Total number of bytes per user/day (PD=3000)......529,042 Figure 2: Dialog optimization used 2.6. NOTIFY optimization used The analysis provided in Figure 1 is repeated here with the assumption that the notification optimization is applied. The optimization saves the need for NOTIFY upon refreshing a SUBSCRIBE if there was no change since the last NOTIFY. It is assumed here that there are no NOTIFY messages for SUBSCRIBE refreshes and terminations. As expected, this optimization affects the steady and termination states and does not affect the initial state. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher................4 (C05) Number of dialogs to maintain per watcher...............4 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................4 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............4 (I03) Initial NOTIFY msgs per watcher.........................4 Houri, et al. Expires February 28, 2010 [Page 17] Internet-Draft Presence Scaling Analysis August 2009 (I04) Initial 200 OK msgs (NOTIFY) per watcher................4 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................72,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...............160,000 Bytes for all watchers....................136,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............640,000 Bytes for all watchers....................326,400,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.............7,040,000 Bytes for all watchers..................4,294,400,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day................................28 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day................................28 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.....2,240,000 Bytes for all watchers per day............918,400,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers.............9,280,000 Bytes for all watchers..................5,212,800,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................4 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........4 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers.............. 160,000 Bytes for all watchers.....................72,000,000 Houri, et al. Expires February 28, 2010 [Page 18] Internet-Draft Presence Scaling Analysis August 2009 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............160,000 Bytes for all watchers.....................59,200,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...............320,000 Bytes for all watchers....................131,200,000 ** Bottom Line (B01) Total of messages between domains..............10,240,000 Total of bytes between domains (PD=350).....5,670,400,000 Total of bytes between domains (PD=3000)...15,422,400,000 (B02) Total number of messages / second.....................356 Total of bytes per second (PD=350)................196,889 Total of bytes per second (PD=3000)...............535,500 (B03) Total number of by msgs per user/day..................256 Total number of bytes per user/day (PD=350).......141,760 Total number of bytes per user/day (PD=3000)......385,560 Figure 3: NOTIFY optimization used 2.7. Dialog and NOTIFY optimizations used Here, both optimizations are combined. In all the subsequent use cases, we will show only the analysis with no optimizations and with both optimizations combined. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher................4 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 Houri, et al. Expires February 28, 2010 [Page 19] Internet-Draft Presence Scaling Analysis August 2009 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................1 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers................40,000 Bytes for all watchers....................136,160,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............160,000 Bytes for all watchers....................183,760,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.............7,040,000 Bytes for all watchers..................6,378,240,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.......560,000 Bytes for all watchers per day............229,600,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers.............7,600,000 Bytes for all watchers..................6,607,840,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1 (T03) Terminating NOTIFY msgs per watcher.....................0 Houri, et al. Expires February 28, 2010 [Page 20] Internet-Draft Presence Scaling Analysis August 2009 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers................80,000 Bytes for all watchers.....................32,800,000 ** Bottom Line (B01) Total of messages between domains...............7,840,000 Total of bytes between domains (PD=350).....6,824,400,000 Total of bytes between domains (PD=3000)...16,576,400,000 (B02) Total number of messages / second.....................272 Total of bytes per second (PD=350)................236,958 Total of bytes per second (PD=3000)...............575,569 (B03) Total number of by msgs per user/day..................196 Total number of bytes per user/day (PD=350).......170,610 Total number of bytes per user/day (PD=3000)......414,410 Figure 4: Dialog and NOTIFY optimizations used 2.8. Presence Federation Scenarios While scalability issues exist in any large deployment, certain deployments have characteristics that are conducive to the existing optimizations, and others have characteristics that are not. What follows is a list of federation scenarios that have varying usage characteristics. For each, a message rate and bandwidth table is provided reflecting typical changes message rates. Those characteristics can alter the overall effectiveness of existing optimizations. Note that the number of users considered is not the total number of users in the domains but the number of actual logged-in users. As was mentioned before, not all the domain users will use the presence service at the same time. The numbers used for watchers and watched presentities are for online users. Houri, et al. Expires February 28, 2010 [Page 21] Internet-Draft Presence Scaling Analysis August 2009 2.8.1. Widely distributed inter-domain presence In some environments, presence federation may be common, perhaps even more common than intra-domain presence. An example of this type of environment is a small ISV or public server. Users in that small ISV are not likely to subscribe to the presence of other users in the their server because they do not necessarily have any relationship with each other aside from receiving service from the same provider. They are much more likely to be subscribed to the presence of users in one of the federated domains (whether in consumer domains, academic domains, other ISVs, etc). Common characteristics of this deployment are these: o Federated subscriptions are the majority of subscription traffic. o Individual users are likely to subscribe to multiple users in any one domain. o The intersection of users in the deployment watching the same presentities is quite small (that is, the probability that multiple watchers in the domain are subscribed to the same presentity is low). To account for the extraordinarily high percentage of federation traffic, the number of federated presentities is increased to 20. Although the number of watchers in the domain could also be adjusted to allow for an expected larger community of users being peered with, it is omitted here for simplification. The first table below provides the calculations without optimizations. The second table provides the calculations with optimizations. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............20 (C05) Number of dialogs to maintain per watcher..............20 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher.....................20 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............20 (I03) Initial NOTIFY msgs per watcher........................20 Houri, et al. Expires February 28, 2010 [Page 22] Internet-Draft Presence Scaling Analysis August 2009 (I04) Initial 200 OK msgs (NOTIFY) per watcher...............20 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................360,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................296,000,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................680,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................296,000,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers.............3,200,000 Bytes for all watchers..................1,632,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers............35,200,000 Bytes for all watchers.................21,472,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day...............................140 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day...............................140 (S06) Number of NOTIFY msgs for refreshes per watcher per day...............................140 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day...............................140 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day....22,400,000 Bytes for all watchers per day.........11,424,000,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers............57,600,000 Bytes for all watchers.................32,896,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher.................20 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........20 (T03) Terminating NOTIFY msgs per watcher....................20 (T04) Terminating 200 OK msgs (NOTIFY) per watcher...........20 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................360,000,000 Houri, et al. Expires February 28, 2010 [Page 23] Internet-Draft Presence Scaling Analysis August 2009 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................296,000,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................680,000,000 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers...............800,000 Bytes for all watchers....................296,000,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers.............3,200,000 Bytes for all watchers..................1,632,000,000 ** Bottom Line (B01) Total of messages between domains..............64,000,000 Total of bytes between domains (PD=350)....36,160,000,000 Total of bytes between domains (PD=3000)..101,880,000,000 (B02) Total number of messages / second...................2,222 Total of bytes per second (PD=350)..............1,255,556 Total of bytes per second (PD=3000).............3,537,500 (B03) Total number of by msgs per user/day................1,600 Total number of bytes per user/day (PD=350).......904,000 Total number of bytes per user/day (PD=3000)....2,547,000 Figure 5: Widely distributed inter-domain with no optimizations ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............20 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains................40,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................1 Houri, et al. Expires February 28, 2010 [Page 24] Internet-Draft Presence Scaling Analysis August 2009 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers................40,000 Bytes for all watchers....................554,720,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............160,000 Bytes for all watchers....................602,320,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers............35,200,000 Bytes for all watchers.................31,891,200,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.......560,000 Bytes for all watchers per day............229,600,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers............35,760,000 Bytes for all watchers.................32,120,800,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers................40,000 Bytes for all watchers.....................18,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Houri, et al. Expires February 28, 2010 [Page 25] Internet-Draft Presence Scaling Analysis August 2009 Number of msgs for all watchers................40,000 Bytes for all watchers.....................14,800,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers................80,000 Bytes for all watchers.....................32,800,000 ** Bottom Line (B01) Total of messages between domains..............36,000,000 Total of bytes between domains (PD=350)....32,755,920,000 Total of bytes between domains (PD=3000)...81,515,920,000 (B02) Total number of messages / second...................1,250 Total of bytes per second (PD=350)..............1,137,358 Total of bytes per second (PD=3000).............2,830,414 (B03) Total number of by msgs per user/day..................900 Total number of bytes per user/day (PD=350).......818,898 Total number of bytes per user/day (PD=3000)....2,037,898 Figure 6: Widely distributed inter-domain with optimizations 2.8.2. Associated inter-domain presence In this type of environment, the domain is a collection of associated users, such as an enterprise. Here, federation is once again common. However, there is also a strong association between some users in the deployment. These associations make it somewhat more likely that users in that domain are watchers of the same presentity. This can occur because of business relationships (for example, two co-workers on a project federating with a partner company). Common characteristics of this deployment are these: o Federated subscriptions are large minority or small majority of subscription traffic. o Individual users are likely to subscribe to multiple users in any one domain, especially their own. o The intersection of users in the deployment watching the same presentities increases. This federation type has traffic rates similar to the previous examples but with different levels of association of the users. Houri, et al. Expires February 28, 2010 [Page 26] Internet-Draft Presence Scaling Analysis August 2009 2.8.3. Large network peering In this environment, two or more Large networks create a peering relationship, allowing their users to subscribe to presence in the other domains. Whereas the number of users in other deployment types ranges from hundreds to several hundred thousand, these large networks host up to hundreds of millions of users. Examples of these networks are large wireless carriers and consumer instant messaging networks. Common characteristics of this deployment are these: o As users become accustomed to network boundaries disappearing, federated subscriptions become as common as subscriptions within the same domain. o Individual users are highly likely to want to see presence of multiple presentities in the peer network. o The intersection of users in the deployment watching the same presentities is high (that is, two or more users in network A are extremely likely to be watching a same user in network B). o Status changes increase greatly due to typical observed consumer behavior. The first table below provides the calculations without optimizations; the second table provides the calculations with optimizations. Even though the optimizations help a lot (cut the number of messages almost in half), the numbers are still high. Note also that the bandwidth required is high. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................6 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher..............10 (C06) Total number of watchers in domains............20,000,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher.....................10 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10 (I03) Initial NOTIFY msgs per watcher........................10 (I04) Initial 200 OK msgs (NOTIFY) per watcher...............10 (I05) Total number & bytes of initial SUBSCRIBE msgs Houri, et al. Expires February 28, 2010 [Page 27] Internet-Draft Presence Scaling Analysis August 2009 Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................90,000,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................74,000,000,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers................170,000,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................74,000,000,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...........800,000,000 Bytes for all watchers................408,000,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................46 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................46 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers........18,400,000,000 Bytes for all watchers.............11,224,000,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day................................70 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day................................70 (S06) Number of NOTIFY msgs for refreshes per watcher per day................................70 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day................................70 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.5,600,000,000 Bytes for all watchers per day......2,856,000,000,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers........24,000,000,000 Bytes for all watchers.............14,080,000,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher.................10 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10 (T03) Terminating NOTIFY msgs per watcher....................10 (T04) Terminating 200 OK msgs (NOTIFY) per watcher...........10 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................90,000,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...........200,000,000 Houri, et al. Expires February 28, 2010 [Page 28] Internet-Draft Presence Scaling Analysis August 2009 Bytes for all watchers.................74,000,000,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers................170,000,000,000 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................74,000,000,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...........800,000,000 Bytes for all watchers................408,000,000,000 ** Bottom Line (B01) Total of messages between domains..........25,600,000,000 Total of bytes bet. domains (PD=350)...14,896,000,000,000 Total of bytes bet. domains (PD=3000)..44,046,000,000,000 (B02) Total number of messages / second.................888,889 Total of bytes per second (PD=350)............517,222,222 Total of bytes per second (PD=3000).........1,529,375,000 (B03) Total number of by msgs per user/day................1,280 Total number of bytes per user/day (PD=350).......744,800 Total number of bytes per user/day (PD=3000)....2,202,300 Figure 7: Large network peering with no optimizations ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................6 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains............20,000,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................1 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers............20,000,000 Houri, et al. Expires February 28, 2010 [Page 29] Internet-Draft Presence Scaling Analysis August 2009 Bytes for all watchers..................9,000,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................7,400,000,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers................146,560,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................7,400,000,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers............80,000,000 Bytes for all watchers................170,360,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................46 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................46 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers........18,400,000,000 Bytes for all watchers.............16,670,400,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day...280,000,000 Bytes for all watchers per day........114,800,000,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers........18,680,000,000 Bytes for all watchers.............16,785,200,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................9,000,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................7,400,000,000 Houri, et al. Expires February 28, 2010 [Page 30] Internet-Draft Presence Scaling Analysis August 2009 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers............40,000,000 Bytes for all watchers.................16,400,000,000 ** Bottom Line (B01) Total of messages between domains..........18,800,000,000 Total of bytes bet. domains (PD=350)...16,971,960,000,000 Total of bytes bet. domains (PD=3000)..41,881,960,000,000 (B02) Total number of messages / second.................652,778 Total of bytes per second (PD=350)............589,304,167 Total of bytes per second (PD=3000).........1,454,234,722 (B03) Total number of by msgs per user/day..................940 Total number of bytes per user/day (PD=350).......848,598 Total number of bytes per user/day (PD=3000)....2,094,098 Figure 8: Large network peering with optimizations 2.8.4. Intra-domain peering Within a particular domain, multiple presence infrastructures are deployed, with users split between them. This scenario is unique, in that federated messages do not pass outside the administrative domain's network. The two infrastructures peer directly inside the domain. A common example of this is an enterprise IT system that has deployed multiple, independent-vendor presence solutions (for example, a presence solution for desktop messaging deployed alongside a presence solution for IP telephony). Common characteristics of this deployment are these: o The differences between subscriptions to presentities in one system versus the other are completely arbitrary. Any one presentity is as likely to be homed on one infrastructure as on the other. o Active users are almost guaranteed to subscribe to many users in the peer infrastructure. o The level of intersection of presentities is extremely high. The first table below provides the calculations without optimizations. The second table provides the calculations with optimization. Although relatively conservative numbers are used, the Houri, et al. Expires February 28, 2010 [Page 31] Internet-Draft Presence Scaling Analysis August 2009 number of messages is still high even though optimization may cut the traffic by more than half. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher..............10 (C06) Total number of watchers in domains...............120,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher.....................10 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10 (I03) Initial NOTIFY msgs per watcher........................10 (I04) Initial 200 OK msgs (NOTIFY) per watcher...............10 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................540,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................444,000,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers..................1,020,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................444,000,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers.............4,800,000 Bytes for all watchers..................2,448,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers............52,800,000 Bytes for all watchers.................32,208,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day................................70 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes Houri, et al. Expires February 28, 2010 [Page 32] Internet-Draft Presence Scaling Analysis August 2009 per watcher per day................................70 (S06) Number of NOTIFY msgs for refreshes per watcher per day................................70 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day................................70 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day....33,600,000 Bytes for all watchers per day.........17,136,000,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers............86,400,000 Bytes for all watchers.................49,344,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher.................10 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10 (T03) Terminating NOTIFY msgs per watcher....................10 (T04) Terminating 200 OK msgs (NOTIFY) per watcher...........10 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................540,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................444,000,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers..................1,020,000,000 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.............1,200,000 Bytes for all watchers....................444,000,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers.............4,800,000 Bytes for all watchers..................2,448,000,000 ** Bottom Line (B01) Total of messages between domains..............96,000,000 Total of bytes between domains (PD=350)....54,240,000,000 Total of bytes between domains (PD=3000)..152,820,000,000 (B02) Total number of messages / second...................3,333 Total of bytes per second (PD=350)..............1,883,333 Total of bytes per second (PD=3000).............5,306,250 B(03 )Total number of by msgs per user/day..................800 Total number of bytes per user/day (PD=350).......452,000 Total number of bytes per user/day (PD=3000)....1,273,500 Figure 9: Intra-domain peering with no optimizations ** Constants Houri, et al. Expires February 28, 2010 [Page 33] Internet-Draft Presence Scaling Analysis August 2009 (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................3 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains...............120,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............1 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................1 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................54,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................44,400,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...............120,000 Bytes for all watchers....................879,360,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................44,400,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...............480,000 Bytes for all watchers..................1,022,160,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................22 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................22 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers............52,800,000 Bytes for all watchers.................47,836,800,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................7 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................7 Houri, et al. Expires February 28, 2010 [Page 34] Internet-Draft Presence Scaling Analysis August 2009 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.....1,680,000 Bytes for all watchers per day............688,800,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers............54,480,000 Bytes for all watchers.................48,525,600,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........1 (T03) Terminating NOTIFY msgs per watcher.....................1 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............1 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................54,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................44,400,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers...............120,000 Bytes for all watchers.....................44,400,000 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...............240,000 Bytes for all watchers.....................98.400,000 ** Bottom Line (B01) Total of messages between domains..............55,200,000 Total of bytes between domains (PD=350)....49,646,160,000 Total of bytes between domains (PD=3000)..122,796,160,000 (B02) Total number of messages / second...................1,917 Total of bytes per second (PD=350)..............1,723,825 Total of bytes per second (PD=3000).............4,263,408 (B03) Total number of by msgs per user/day..................460 Total number of bytes per user/day (PD=350).......413,718 Total number of bytes per user/day (PD=3000)....1,023,218 Figure 10: Intra-domain peering with optimizations Houri, et al. Expires February 28, 2010 [Page 35] Internet-Draft Presence Scaling Analysis August 2009 2.9. Partial Notifications Optimization RFC 5263 [9] defines a way for the watcher to request getting only what was changed in the presence document. The following calculation shows the bandwidth saved in the large peering network case when we add partial notification to the dialog and NOTIFY optimizations. It is assumed that, except for the initial NOTIFY, all other NOTIFY messages will be partial. It is also assumed that only a single attribute in the presence document will be changed each time, thus the size of the partial presence document is assumed to be 200 bytes. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................6 (C03) Subscription refresh interval / hour....................1 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher..............10 (C06) Total number of watchers in domains............20,000,000 (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..................350 (C12) Size of an average partial presence document..........200 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher.....................10 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher............10 (I03) Initial NOTIFY msgs per watcher........................10 (I04) Initial 200 OK msgs (NOTIFY) per watcher...............10 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................90,000,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers..................74,00,000,000 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers................170,000,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers..................74,000,000,000 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...........800,000,000 Bytes for all watchers................408,000,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change Houri, et al. Expires February 28, 2010 [Page 36] Internet-Draft Presence Scaling Analysis August 2009 per watched presentity per day.....................46 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day.....................46 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers........18,400,000,000 Bytes for all watchers..............9,844,000,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day................................70 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day................................70 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.2,800,000,000 Bytes for all watchers per day......1,148,000,000,000 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers........21,200,000,000 Bytes for all watchers.............10,992,000,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher.................10 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher........10 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................90,000,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................74,000,000,000 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...........400,000,000 Bytes for all watchers................164.000,000,000 ** Bottom Line (B01) Total of messages between domains..........22,400,000,000 Total of bytes bet. domains (PD=350)...11,564,000,000,000 Total of bytes bet. domains (PD=3000)..12,094,000,000,000 (B02) Total number of messages / second.................777,778 Total of bytes per second (PD=350)............401,527,778 Houri, et al. Expires February 28, 2010 [Page 37] Internet-Draft Presence Scaling Analysis August 2009 Total of bytes per second (PD=3000)...........419,930,556 (B03) Total number of by msgs per user/day................1,120 Total number of bytes per user/day (PD=350).......578,200 Total number of bytes per user/day (PD=3000)......604,700 Figure 11: Large networks peering with NOTIFY and partial optimizations 2.10. Extremely Optimized SIP SIP is a network-agnostic protocol, therefore, the protocol carries additional messages like "200 OK" that would be redundant in a protocol that is TCP-based only. The following calculation assumes an imaginary TCP-only version of SIP that optimizes the following: o There is no "200 OK" for each message. because only TCP would be supported, there is no need to compensate for issues arising with other transport protocols. o There is no refresh for subscriptions. o There is no NOTIFY upon termination of the subscription. o The size of each message is smaller, because there is no need for the various header fields that SIP uses for routing, etc. So we need to assume smaller message sizes, while keeping the size of the presence document the same. As noted above, the calculations in this document do not assume offline means of receiving presence information. Therefore, in addition to the above optimizations, the other optimizations that were assumed in the document are assumed here also. These includes partial notifications and dialog optimizations. The NOTIFY optimization is not relevant here, because there are no refreshes of subscriptions. The following is a calculation for the large network peering scenario assuming an imaginary TCP-only SIP. It is interesting to note that the dialog optimization does not reduce the number of bytes when partial notification optimization is applied (on the contrary), due to the RLMI overhead. ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................6 (C03) Subscription refresh interval / hour....................0 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher...............1 (C06) Total number of watchers in domains............20,000,000 Houri, et al. Expires February 28, 2010 [Page 38] Internet-Draft Presence Scaling Analysis August 2009 (C07) SUBSCRIBE message size in bytes.......................150 (C08) 200 OK for SUBSCRIBE message size in bytes..............0 (C09) NOTIFY message size not including presence doc........150 (C10) 200 OK for NOTIFY message size in bytes.................0 (C11) Size of an average presence document..................350 (C12) Size of an average partial presence document..........200 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher......................1 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............0 (I03) Initial NOTIFY msgs per watcher.........................1 (I04) Initial 200 OK msgs (NOTIFY) per watcher................0 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................3,000,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers................136,680,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers............40,000,000 Bytes for all watchers................139,680,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................46 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day......................0 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.........9,200,000,000 Bytes for all watchers..............8,666,400,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................0 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................0 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.............0 Bytes for all watchers per day......................0 (S09) Total number & bytes of steady messages per day Houri, et al. Expires February 28, 2010 [Page 39] Internet-Draft Presence Scaling Analysis August 2009 Number of msgs for all watchers.........9,200,000,000 Bytes for all watchers..............8,666,400,000,000 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher..................1 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........0 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers............20,000,000 Bytes for all watchers..................3,000,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers............20,000,000 Bytes for all watchers..................3,000,000,000 ** Bottom Line (B01) Total of messages between domains...........9,260,000,000 Total of bytes between domains (PD=350).8,809,080,000,000 Total of bytes bet. domains (PD=3000)...9,339,080,000,000 (B02) Total number of messages / second.................321,528 Total of bytes per second (PD=350)............305,870,833 Total of bytes per second (PD=3000)...........324,273,611 (B03) Total number of by msgs per user/day..................463 Total number of bytes per user/day (PD=350).......440,454 Total number of bytes per user/day (PD=3000)......466,954 Figure 12: Large networks peering, TCP only SIP+Partial+Dialog optimizations ** Constants (C01) Subscription lifetime (hours)...........................8 (C02) Presence state changes / hour...........................6 (C03) Subscription refresh interval / hour....................0 (C04) Total federated presentities per watcher...............10 (C05) Number of dialogs to maintain per watcher..............10 (C06) Total number of watchers in domains............20,000,000 (C07) SUBSCRIBE message size in bytes.......................150 (C08) 200 OK for SUBSCRIBE message size in bytes..............0 Houri, et al. Expires February 28, 2010 [Page 40] Internet-Draft Presence Scaling Analysis August 2009 (C09) NOTIFY message size not including presence doc........150 (C10) 200 OK for NOTIFY message size in bytes.................0 (C11) Size of an average presence document..................350 (C12) Size of an average partial presence document..........200 ** Initial Messages (I01) Initial SUBSCRIBE msgs per watcher.....................10 (I02) Initial 200 OK msgs (SUBSCRIBE) per watcher.............0 (I03) Initial NOTIFY msgs per watcher........................10 (I04) Initial 200 OK msgs (NOTIFY) per watcher................0 (I05) Total number & bytes of initial SUBSCRIBE msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................30,000,000,000 (I06) Total number & bytes of initial 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (I07) Total number & bytes of initial NOTIFY msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers................100,000,000,000 (I08) Total number & bytes of initial 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (I09) Total number & bytes of initial messages per day Number of msgs for all watchers...........400,000,000 Bytes for all watchers................130,000,000,000 ** Steady State Messages (S01) NOTIFY msgs due to state change per watched presentity per day.....................46 (S02) 200 (for NOTIFY due to state change) msgs per watched presentity per day......................0 (S03) Total number and size of msgs due to state change per day Number of msgs for all watchers.........9,200,000,000 Bytes for all watchers..............3,220,000,000,000 (S04) Number of SUBSCRIBE msgs for refreshes per watcher per day.................................0 (S05) Number of 200 OK msgs for SUBSCRIBE msgs for refreshes per watcher per day.................................0 (S06) Number of NOTIFY msgs for refreshes per watcher per day.................................0 (S07) Number of 200 OK msgs for NOTIFY msgs for refreshes per watcher per day.................................0 (S08) Total number and size of msgs due to SUBSCRIBE refreshes Number of msgs for all watchers per day.............0 Bytes for all watchers per day......................0 (S09) Total number & bytes of steady messages per day Number of msgs for all watchers.........9,200,000,000 Bytes for all watchers..............3,220,000,000,000 Houri, et al. Expires February 28, 2010 [Page 41] Internet-Draft Presence Scaling Analysis August 2009 ** Termination Messages (T01) Terminating SUBSCRIBE msgs per watcher.................10 (T02) Terminating 200 OK msgs (SUBSCRIBE) per watcher.........0 (T03) Terminating NOTIFY msgs per watcher.....................0 (T04) Terminating 200 OK msgs (NOTIFY) per watcher............0 (T05) Total number & bytes of Terminating SUBSCRIBE msgs Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................30,000,000,000 (T06) Total number & bytes of terminating 200 OK (SUBSCRIBE) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T07) Total number & bytes of terminating NOTIFY msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T08) Total number & bytes of terminating 200 OK (NOTIFY) msgs Number of msgs for all watchers.....................0 Bytes for all watchers..............................0 (T09) Total number & bytes of terminating messages per day Number of msgs for all watchers...........200,000,000 Bytes for all watchers.................30,000,000,000 ** Bottom Line (B01) Total of messages between domains...........9,800,000,000 Total of bytes between domains (PD=350).3,380,000,000,000 Total of bytes bet. domains (PD=3000)...3,910,280,000,000 (B02) Total number of messages / second.................340,278 Total of bytes per second (PD=350)............117,361,111 Total of bytes per second (PD=3000)...........135,763,889 (B03) Total number of by msgs per user/day..................490 Total number of bytes per user/day (PD=350).......169,000 Total number of bytes per user/day (PD=3000)......195,500 Figure 13: Large networks peering, TCP only SIP+Partial optimizations 3. State Management In previous sections, we discussed the large number of messages that need to be sent to/from a presence server. In this section, we will analyze the state that needs to be maintained by a presence server and will show it to be far from trivial. The presence server has two parallel tasks: 1. Maintain the state of the presentities to which watchers subscribe. Houri, et al. Expires February 28, 2010 [Page 42] Internet-Draft Presence Scaling Analysis August 2009 2. Maintain the state of the subscriptions of watchers and provide timely updates to the watchers. For a single subscription from a single watcher on a presentity, the presence server has to maintain the following state: o Subscription state, including all the parameters that are needed to maintain the subscription as timers. o Optional filtering information that was requested by the watcher, which includes information needed for filtering. If partial notification is supported for the subscription, additional information has to be maintained. o Optional rate management information as throttling. o Watcher information ([10], [11]) that is the result of the subscription, in order to allow watched presentities to know who is watching them. For each presentity with subscriptions in the presence server, the presence server has to maintain the following state: o A list of the subscriptions for the presentity. Note that the size calculation is already handled by the subscription state above. o Authorization information for the presentity. For each presentity that has published a state other than a default value, the presence server has to maintain the current value of the presentity's state. 3.1. State Size Calculations Let's assume the following sizes: o Subscription size - 2K bytes. This includes watcher information that the presence server creates for each subscription. This is for every subscription created by a watcher to each presentity that the watcher is watching. So, if we have 10K watchers, we should have 10K of these. o Subscribed-to resource - 1K bytes for privacy information and other management information. This is for each watched presentity, regardless of the number of its watchers. The subscriptions themselves are already calculated in the previous bullet. o Resource with a state - 6K bytes. This is a moderate assumption if we consider the amount of data, including calendar and geographical information, placed in a presence document by multiple devices. This is for each presentity, watched or not, that has state other than the default empty state. Houri, et al. Expires February 28, 2010 [Page 43] Internet-Draft Presence Scaling Analysis August 2009 3.1.1. Tiny System o 10K subscriptions = 19M bytes. o 5K subscribed-to presentities = 5M bytes. o 10K presentities with state = 58M bytes. Total is 82M bytes. 3.1.2. Medium System o 100K subscriptions = 195M bytes. o 50K subscribed-to presentities = 49M bytes. o 100K presentities with state = 586M bytes. Total is 830M bytes. 3.1.3. Large System o 6M subscriptions = 11,718M bytes. o 3M subscribed-to presentities = 2,929M bytes. o 4M presentities with state = 23,437M bytes. Total is 38G bytes. 3.1.4. Larger System o 150M subscriptions = 292,969M bytes. o 75M subscribed-to presentities = 73,242M bytes. o 100M presentities with state = 585,937M bytes. Total is 952G bytes, which is a large number for dynamic storage as needed by the presence server. 3.1.5. Notes on the calculations Although the numbers above may seem moderate enough for the sizes that the presence server is handling, we should consider the following: o Dynamic state - Although the state may not seem so large for databases, even for the larger system, we need to remember that this state is dynamic. Subscriptions come and go all the time, the statuses of presentities are being updated, and so forth. This means that the presence server has to manage its state in a dynamic medium, and for such large sizes, this task is not trivial. Houri, et al. Expires February 28, 2010 [Page 44] Internet-Draft Presence Scaling Analysis August 2009 o Interlinked state - The subscriptions and the subscribed-to presentities are dependent on each other. There needs to be a link from the presentity to the subscriptions and vice versa. See Section 4.5 about the interlinkage that is created due to resource lists. o Moderate assumptions - The size assumptions that were made above are quite moderate. Presence is becoming more a core middleware functionality that holds much of the user's data. In real life, the numbers above may be even higher, and the presence server can have additional overhead such as managing the SIP sessions, networking, and more. Although the above calculations do not show that there is a real issue with state management of presence in medium systems or even in large systems, because state could be divided among different machines, the state size is still large. A bigger issue with the state involves resource lists, which create an interlinked state between many servers. In that case, the division of large state to multiple servers becomes less trivial. 4. Processing complexities The basic presence paradigm comprises a watcher and a presentity that the watcher watches. It sounds simple enough, but the presence server has to manage many additions and extensions, which makes processing complex. In this section, we show that in addition to the large number of messages and the large state that the presence server has to handle, it also has to handle quite intensive processing for aggregation, partial notification and publish, filtering, and privacy. This adds complexity to the presence server on the CPU front in addition to the network and memory fronts that were described before. 4.1. Aggregation A presence document may contain multiple resources. These resources can be devices of the presentity, information from external providers of presence information such as geographical location, calendars, and more. The presence server needs to receive the updates from all the resources and to aggregate them correctly into a single presence document. Although this is just an "XML processing" task, the number of updates that the presence server may receive, the need to keep the presence document aligned with its schema, and the need to notify the users as soon as possible create a significant processing burden on Houri, et al. Expires February 28, 2010 [Page 45] Internet-Draft Presence Scaling Analysis August 2009 the presence server. 4.2. Partial Publish and Notify Partial notification [9] and partial publish [12] define a way for the watcher to request notification only on what was changed in the presence document, and for the publisher of presence information to publish only what was changed in the presence document since the last publish. Although these optimizations help reduce the amount of the data that is sent from/to the presence server, these optimizations create additional processing burden on the presence server. When a partial publish arrives at the presence server, the presence server has to be able to process the partial publish and change only what is indicated in the partial publish, while keeping the presence document well-formed according to the schema. In partial notification the processing is even more complex, because each watcher needs to get the partial update based on the last update that was received by that watcher. Therefore, [9] specifies a versioning mechanism that enables the watcher to get the updates based on the previous state that it has seen. This versioning mechanism has to be maintained by the presence server for each watcher that is subscribed to a presentity and requires partial notification. 4.3. Filtering Filtering, as defined in RFCs [13] and [14], enables a watcher to request to be notified only when the presence document fulfills certain conditions. Although this is a convenient feature for watchers, the burden put on the presence server is quite large. For each change in the presence document, the presence server needs to compute the filtering expressions, which can be complex, and to decide whether and what to send to the watcher that has requested filtering. 4.4. Authorization RFC [15] defines presence authorization rules that allow presentities to specify what each watcher can see in their presence documents. The processing that the presence server performs here is similar to filtering. When a presence document with defined authorization rules changes, the presence server creates different notifications for different watchers according to those rules. Houri, et al. Expires February 28, 2010 [Page 46] Internet-Draft Presence Scaling Analysis August 2009 4.5. Resource List Service RFC [4] defines a way to subscribe to a single URI that represents a list of resources that are subscribed to by a single subscription. Although this quite useful mechanism significantly reduces the number of sessions between the watcher and the presence server (as we show in the calculations of messages), this feature has the potential to complicate the scaling of presence systems. The reasons that resource lists may make the scaling of the presence server even more complex are these: o Subscriptions and state - The resource list may contain references to many other presence servers in many other domains. This requires the RLS to create subscriptions to other presence servers and buffer the state of all presentities so that it can provide the full state of the presentities in the list when needed. So in the overall system, the number of subscriptions reduced between the watcher and the presence server is moved to the backend system, while state is duplicated among the various presence servers that serve the various presentities and the RLSs. This issue could have been mitigated if there were a way for the RLS to retrieve the presence information for many watchers, while adhering to privacy when sending the actual notifications to the watchers. o Interlinkage - The resource list subscription will reach one RLS that will open it and send it to many presence servers and to other RLSs (if there is a subgroup inside the list). This creates a complex linkage among the states of many components. This linkage makes state management and other maintenance of presence systems quite complex. o Big lists are easy - There are two types of groups that may be used with this feature: private groups that are defined by/for each watcher, and public groups that are defined in the system and can be used by any watcher. Although we should expect IT administrators to be cautious when creating public groups, this may not be the case in real life. The connection between the size of the public group and the load on the presence system may not be apparent to everyone. Furthermore, many public groups may have been created for other purposes, such as email systems (where the size of the lists is not as important), and are now used in the presence systems. For example, a public group including all the users in the enterprise is used by many users in the enterprise, thus overwhelming the presence server. Note that this is not a protocol or design issue, but more a usage issue that may have a real impact on the presence system. Houri, et al. Expires February 28, 2010 [Page 47] Internet-Draft Presence Scaling Analysis August 2009 o Stopping notifications - A watcher may accidentally subscribe to an extensive list and be overwhelmed by the number of NOTIFYs that it receives from the presence server. There is no current way to stop this stream of NOTIFYs, and even canceling the subscription may take time before being effective. These issues show how an optimization can help in one part of the system, but create even bigger problems in the overall system. There is a need to think about the problems listed above, but, more than that, there is a need to make sure that introducing an optimization does not create issues in other places. 5. Current Optimizations This section highlights several optimizations that either are already part of SIP or have been suggested in various drafts. Several other optimizations that have been suggested but have not been discussed in any working group yet are summarized in [2] and in [3]. Note that trials with batched NOTIFYs optimization, described in [2], showed an improvement of 117% in the whole throughput of presence traffic. o Subnot-etags - [6]. This draft suggests ways to suppress the sending of unnecessary NOTIFYs when, for example, a subscription is refreshed. This suggestion seems to be an efficient optimization, because it reduces both the number of messages sent and the processing time of the presence server. o Resource List Service - [4] enables creating a single subscription session between the watcher and the presence server for subscribing to a list of users. This reduces the number of sessions that are created between watchers and presence servers. However, this mechanism enables creating large numbers of subscriptions in the presence server/RLS system, thus enabling the creation of a large number of subscriptions between presence servers and RLSs with relatively few clients, especially if large public groups are used. It seems that, in order to really optimize in this area, the usage of large public groups should not be considered as BCP, and there should be a way for an RLS to create a single subscription for multiple occurrences of the same resource in resource lists. See consolidated subscriptions below. o Partial notify/publish - [9] and [12] define a way for the subscriber to request getting only what was changed in the presence document, and for the publisher of presence information to publish only what was changed in the presence document since the last publish. Although these optimizations reduce the amount of actual data sent from/to the presence server, these optimizations create additional processing burden on the presence server, as was discussed above. Houri, et al. Expires February 28, 2010 [Page 48] Internet-Draft Presence Scaling Analysis August 2009 o Filtering, as defined in [13] and [14], enables a watcher to request to be notified only when the presence document fulfills certain conditions. Although this optimization reduces the number of messages that are sent from the presence server to the watcher, this optimization burdens the processing time of the presence server, as was discussed above. o Throttling - [16] defines a mechanism by which a watcher requests updates only at certain intervals. Although this mechanism may add some extra load on the presence server, that load is negligible and the reduction of the number of messages sent from the presence server to the watchers is significant. This optimization is even more important with resource lists, which can contain many resources, because the watcher may receive a large number of notifications if the traffic caused by updates on resource list is not regulated. o Presence-specific SigComp dictionary - [17] defines a SigComp [18] dictionary for presence. This optimization reduces the number of bytes that are transferred in presence systems by compressing the textual SIP messages. By using the specialized presence dictionary, the compression may be more significant than just using SigComp as-is. Note that number of actual messages will remain the same, and a calculation of the number of bytes that will be saved may be useful here. o Content Indirection - [19] enables the sending of only the URI of the presence document to the watcher, thus relieving the presence server from sending the entire presence document to the watcher. This optimization may be useful in some cases, especially when a large number of users receive the same presence document. 6. Summary The following summary of the various calculations is provided here to help support the conclusions listed below. The following table summarizes the constants that are used in ALL calculations: Houri, et al. Expires February 28, 2010 [Page 49] Internet-Draft Presence Scaling Analysis August 2009 (C01) Subscription lifetime (hours)...........................8 (C03) Subscription refresh interval / hour....................1 (C05) Number of dialogs to maintain per watcher = Number of federated presentities when dialog optimization is not used and to 1 when dialog optimization is used. (C07) SUBSCRIBE message size in bytes.......................450 (C08) 200 OK for SUBSCRIBE message size in bytes............370 (C09) NOTIFY message size not including presence doc........500 (C10) 200 OK for NOTIFY message size in bytes...............370 (C11) Size of an average presence document..........350 or 3000 Calculations are done for both sizes (C12) Size of an average partial presence document..........200 (C13) Additional data per document in RLMI..................160 (C14) Multiparty boundary in RLMI document..................144 (C15) XML root node in RLMI document........................144 Figure 14: Constants in ALL calculations The following table summarizes the results of various optimization factors for the basic use case. C02 Presence state changes / hour.............................3 C04 Total federated presentities per watcher..................4 C06 Total # of watchers in the federated domains.........40,000 No optimizations are applied (B01) Total of messages between domains..............12,800,000 Total of bytes between domains (PD=350).....7,232,000,000 Total of bytes between domains (PD=3000)...20,376,000,000 (B02) Total number of messages / second.. ..................444 Total of bytes per second (PD=350)................251,111 Total of bytes per second (PD=3000)...............707,500 (B03) Total number of by msgs per user/day......... ........320 Total number of bytes per user/day (PD=350).......180,800 Total number of bytes per user/day (PD=3000)......509,400 Dialog optimization is applied (B01) Total of messages between domains...............8,480,000 Total of bytes between domains (PD=350).....8,032,080,000 Total of bytes between domains (PD=3000)...21,176,080,000 (B02) Total number of messages / second.....................294 Total of bytes per second (PD=350)................278,892 Total of bytes per second (PD=3000)...............735,281 (B03) Total number of by msgs per user/day..................212 Total number of bytes per user/day (PD=350).......200,802 Total number of bytes per user/day (PD=3000)......529,042 Houri, et al. Expires February 28, 2010 [Page 50] Internet-Draft Presence Scaling Analysis August 2009 Notify optimization is applied (B01) Total of messages between domains..............10,240,000 Total of bytes between domains (PD=350).....5,670,400,000 Total of bytes between domains (PD=3000)...15,422,400,000 (B02) Total number of messages / second.....................356 Total of bytes per second (PD=350)................196,889 Total of bytes per second (PD=3000)...............535,500 (B03) Total number of by msgs per user/day..................256 Total number of bytes per user/day (PD=350).......141,760 Total number of bytes per user/day (PD=3000)......385,560 Dialog and notify optimizations are applied (B01) Total of messages between domains...............7,840,000 Total of bytes between domains (PD=350).....6,824,400,000 Total of bytes between domains (PD=3000)...16,576,400,000 (B02) Total number of messages / second.....................272 Total of bytes per second (PD=350)................236,958 Total of bytes per second (PD=3000)...............575,569 (B03) Total number of by msgs per user/day..................196 Total number of bytes per user/day (PD=350).......170,610 Total number of bytes per user/day (PD=3000)......414,410 Figure 15: Basic use case The following table summarizes the results of various optimization factors for the widely distributed inter-domain use case. Houri, et al. Expires February 28, 2010 [Page 51] Internet-Draft Presence Scaling Analysis August 2009 C02 Presence state changes / hour.............................3 C04 Total federated presentities per watcher.................20 C06 Total # of watchers in the federated domains.........40,000 No optimizations are applied (B01) Total of messages between domains..............64,000,000 Total of bytes between domains (PD=350)....36,160,000,000 Total of bytes between domains (PD=3000)..101,880,000,000 (B02) Total number of messages / second...................2,222 Total of bytes per second (PD=350)..............1,255,556 Total of bytes per second (PD=3000).............3,537,500 (B03) Total number of by msgs per user/day................1,600 Total number of bytes per user/day (PD=350).......904,000 Total number of bytes per user/day (PD=3000).....,547,000 Dialog and notify optimizations are applied (B01) Total of messages between domains..............36,000,000 Total of bytes between domains (PD=350)....32,755,920,000 Total of bytes between domains (PD=3000)...81,515,920,000 (B02) Total number of messages / second...................1,250 Total of bytes per second (PD=350)..............1,137,358 Total of bytes per second (PD=3000).............2,830,414 (B03) Total number of by msgs per user/day..................900 Total number of bytes per user/day (PD=350).......818,898 Total number of bytes per user/day (PD=3000)....2,037,898 Figure 16: Widely distributed inter-domain The following table summarizes the results of various optimization factors for the intra-domain peering use case. Houri, et al. Expires February 28, 2010 [Page 52] Internet-Draft Presence Scaling Analysis August 2009 C02 Presence state changes / hour.............................3 C04 Total federated presentities per watcher.................10 C06 Total # of watchers in the federated domains........120,000 No optimizations are applied B01 Total of messages between domains................96,000,000 Total of bytes between domains (PD=350)........54,240,000,000 Total of bytes between domains (PD=3000)......152,820,000,000 B02 Total number of messages / second.....................3,333 Total of bytes per second (PD=350)..................1,883,333 Total of bytes per second (PD=3000).................5,306,250 B03 Total number of by msgs per user/day....................800 Total number of bytes per user/day (PD=350)...........452,000 Total number of bytes per user/day (PD=3000)........1,273,500 Dialog and notify optimizations are applied (B01) Total of messages between domains..............55,200,000 Total of bytes between domains (PD=350)....49,646,160,000 Total of bytes between domains (PD=3000)..122,796,160,000 (B02) Total number of messages / second...................1,917 Total of bytes per second (PD=350)..............1,723,825 Total of bytes per second (PD=3000).............4,263,408 (B03) Total number of by msgs per user/day..................460 Total number of bytes per user/day (PD=350).......413,718 Total number of bytes per user/day (PD=3000)....1,023,218 Figure 17: Inter-domain peering The following table summarizes the results of various optimization factors for the large-scale peering networks use case. C02 Presence state changes / hour.............................6 C04 Total federated presentities per watcher.................10 C06 Total # of watchers in the federated domains.....20,000,000 No optimizations are applied (B01) Total of messages between domains..........25,600,000,000 Total of bytes bet. domains (PD=350)...14,896,000,000,000 Total of bytes bet. domains (PD=3000)..44,046,000,000,000 (B02) Total number of messages / second.................888,889 Total of bytes per second (PD=350)............517,222,222 Total of bytes per second (PD=3000).........1,529,375,000 (B03) Total number of by msgs per user/day................1,280 Total number of bytes per user/day (PD=350).......744,800 Total number of bytes per user/day (PD=3000)....2,202,300 Houri, et al. Expires February 28, 2010 [Page 53] Internet-Draft Presence Scaling Analysis August 2009 Dialog and notify optimizations are applied (B01) Total of messages between domains..........18,800,000,000 Total of bytes bet. domains (PD=350)...16,971,960,000,000 Total of bytes bet. domains (PD=3000)..41,881,960,000,000 (B02) Total number of messages / second.................652,778 Total of bytes per second (PD=350)............589,304,167 Total of bytes per second (PD=3000).........1,454,234,722 (B03) Total number of by msgs per user/day..................940 Total number of bytes per user/day (PD=350).......848,598 Total number of bytes per user/day (PD=3000)....2,094,098 Partial and notify optimizations are applied (B01) Total of messages between domains..........22,400,000,000 Total of bytes bet. domains (PD=350)...11,564,000,000,000 Total of bytes bet. domains (PD=3000)..12,094,000,000,000 (B02) Total number of messages / second.................777,778 Total of bytes per second (PD=350)............401,527,778 Total of bytes per second (PD=3000)...........419,930,556 (B03) Total number of by msgs per user/day................1,120 Total number of bytes per user/day (PD=350).......578,200 Total number of bytes per user/day (PD=3000)......604,700 TCP only SIP+Partial+Dialog optimizations (B01) Total of messages between domains...........9,260,000,000 Total of bytes between domains (PD=350).8,809,080,000,000 Total of bytes bet. domains (PD=3000)...9,339,080,000,000 (B02) Total number of messages / second.................321,528 Total of bytes per second (PD=350)............305,870,833 Total of bytes per second (PD=3000)...........324,273,611 (B03) Total number of by msgs per user/day..................463 Total number of bytes per user/day (PD=350).......440,454 Total number of bytes per user/day (PD=3000)......466,954 TCP only SIP+Partial optimizations (B01) Total of messages between domains...........9,800,000,000 Total of bytes between domains (PD=350).3,380,000,000,000 Total of bytes bet. domains (PD=3000)...3,910,280,000,000 (B02) Total number of messages / second.................340,278 Total of bytes per second (PD=350)............117,361,111 Total of bytes per second (PD=3000)...........135,763,889 (B03) Total number of by msgs per user/day..................490 Total number of bytes per user/day (PD=350).......169,000 Total number of bytes per user/day (PD=3000)......195,500 Houri, et al. Expires February 28, 2010 [Page 54] Internet-Draft Presence Scaling Analysis August 2009 Figure 18: Large scale peering networks 7. Conclusions The following conclusions can be drawn from the above numbers: o Due to the overhead of RLMI, the dialog optimization does not help reduce the number of bytes nor the number of the messages. It seems to be more important from the point of view of the user, because it enables convenient management of his/her watch list on, for example, a web page. o The notify optimization significantly reduces both the number of messages and the number of bytes. o Partial notification saves a large number of bytes, especially when the presence document is a rich presence document, which is relatively large. o Extremely optimized SIP (imaginary TCP-only SIP) cuts the number of messages by about half. The number of bytes is also reduced by about half. o From the perspective of the number of bytes that a user "consumes" per day, the numbers may not look so large. Nevertheless, we should remember that the overall effect on the network may be quite large, because the network will have to convey dozens of gigabytes of presence traffic per day for the modest use cases that are described in this document. Recalling that presence is only an enabler for other media, these numbers are not so easy to handle. This document analyzes the scalability of presence systems in general and of SIP-based presence systems in particular. It is apparent that the scalability of these systems is far from being trivial from several perspectives: number of messages, network bandwidth, state management, and CPU load. As part of the analysis, we assessed several optimizations and showed the effect of these optimizations on the number of messages and the number of bytes that are sent between the federating domains. We have also computed the number of messages and bytes for a large- scale peering network while assuming a protocol that has much less overhead than SIP. Even with that protocol, we calculated relatively high numbers. It is possible that the issues described in this document are inherent to presence systems in general and not specific to the SIMPLE protocol. Organizations need to be prepared to invest a lot in network and hardware in order to create real large systems. Houri, et al. Expires February 28, 2010 [Page 55] Internet-Draft Presence Scaling Analysis August 2009 However, it is apparent that not all the possible optimizations have been done yet, and further work is needed in the IETF in order to provide better scalability. Nevertheless, we should remember that SIP was originally designed for end-to-end session creation, and that the number and size of messages are of secondary importance for end-to-end session negotiation. For large scale and especially for large scale presence, the number of messages that are needed and the size of each message are of extreme importance. It seems that we need to think about the problem in a different way. We need to think about scalability as part of the protocol design. The IETF tends not to think about actual deployments when designing a protocol, but in this case it seems that if we do not think about scalability with the protocol design, it will be hard to scale. We should also consider whether using the same protocol between clients and servers and between servers is a good choice with this problem. It may be that in interdomain or even between servers in the same domain (as between RLSs and presence servers) there is a need to have a different protocol that will be extremely optimized for the load and that can make some assumptions about the network (for example, use only TCP, and not an unreliable protocol such as UDP). When a server connects to another server using the current protocol, there will be an extreme number of redundant messages due to the overhead of supporting UDP and the need to send multiple presence documents for the same watched user due to privacy issues. A server- to-server protocol will have to address these issues. Some initial work to address these issues can be found in [2], [3] and [20] Another issue that concerns protocol design is whether NOTIFY messages should be considered as media, the way audio, video and even text messaging are considered. The SUBSCRIBE method can be extended to create a three-way handshake similar to INVITE, and negotiate where the NOTIFY messages should go, rate, and other parameters. This way, the load can be shifted to specialized NOTIFY "relays", and taken off the control path of SIP. One of the possible ideas (due to Marc Willekens) is to use the SIP stack for the client/server NOTIFY, but make use of a more optimized and controllable protocol for the server-to-server interface. Another possibility is to use the MSRP ([21], [22]) protocol for the NOTIFYs. 8. Security Considerations This document discusses scalability issues with the existing SIP/ Houri, et al. Expires February 28, 2010 [Page 56] Internet-Draft Presence Scaling Analysis August 2009 SIMPLE presence protocol and model. Therefore, there are no security considerations to be considered for this document. However, many of the possible optimizations that should emerge as a result of this document will have security implications that will need to be solved. 9. IANA Considerations This document has no actions for IANA. 10. Changes from Previous Versions 10.1. Changes in version 07 Added clarifications, fixed typos and language usage issues raised during the IETF last call. 10.2. Changes in version 06 Updated to conform with new IETF IPR boilerplate and updated references. 10.3. Changes in version 05 o Fixed mistakes in calculations that were found by Victoria Beltran-Martinez, both relate to dialog optimizations. One mistake was not including the multipart boundary of the resource list itself in S03 when dialog optimizations were used. The other one was assuming in T07 that only a single presentity is returned in termination in T07 calculation. o Fixed nits that were referred to me by Robert Sparks 10.4. Changes in version 04 o Fixed mistake in the formula of I07 and S08 (RLMI was not included). Effect on total number of bytes was infitesimile. o Fixed mistake in the text of the calculation of number of bytes for S08 for non dialog optimization. No actual change in number of bytes, because the excel file calculations were done correctly. o Removed general references throughout the text to "other protocols". This was done in order to avoid the impression that the document tries to compare SIP protocol with any other presence base protocol. o Several other editorial and clarification changes Houri, et al. Expires February 28, 2010 [Page 57] Internet-Draft Presence Scaling Analysis August 2009 10.5. Changes in version 03 o Added some input from real life deployments and input on a test with batched notifies. o Added Calculations of messages and bytes per user. o Calculations are now done both for minimal size of presence document and for an average size of rich presence document. o Comparison with other protocol is now done using small, tiny and rich presence document sizes. o Removed dialog optimization with partial notification, because it is not relevant o Fixed a few issues in calculations that were found by Victoria Beltran-Martinez: o * Added overhead for RLMI for dialog optimizations (list subscription). This calculation fix actually shows that dialog optimization is not a real optimization from the point of view of bytes and number of messages. * When NOTIFY optimizations are applied no need for final NOTIFY * The usage of RLS between domains was clarified. o Significantly enhanced the conclusions section o Several typo fixes 10.6. Changes in version 02 o Fixed a bug in the calculations. Thanks to Marc Willekens for finding the bug. 10.7. Changes in version 01 o Clarifications and corrections of the computation model and the computations. o Added several more computations to show the influence of different optimizations. o The requirements were moved to [1] o The new suggestions for optimizations were moved to [2] 11. Acknowledgments We would like to thank Jonathan Rosenberg, Ben Campbell, Robert Sparks, Markus Isomaki Piotr Boni, David Viamonte, Aki Niemi and Peter-Saint Andre for ideas and input. Special thanks to Marc Willekens and Victoria Beltran- Martinez for finding several issues in the calculations. Additional special thanks to A. Jean Mahoney, Joel M. Halpern and Barry Leiba, for their dedicated review as part of the IETF last call. Houri, et al. Expires February 28, 2010 [Page 58] Internet-Draft Presence Scaling Analysis August 2009 12. Informational References [1] Houri, A., Parameswar, S., Aoki, E., Singh, V., and H. Schulzrinne, "Scaling Requirements for Presence in SIP/SIMPLE", draft-ietf-sipcore-presence-scaling-requirements-01 (work in progress), July 2009. [2] Houri, A., "Scaling Optimizations for Presence in SIP/SIMPLE", draft-houri-simple-interdomain-scaling-optimizations-00 (work in progress), July 2007. [3] Rosenberg, J., Donovan, S., and K. McMurry, "Optimizing Federated Presence with View Sharing", draft-ietf-simple-view-sharing-02 (work in progress), November 2008. [4] Roach, A., Campbell, B., and J. Rosenberg, "A Session Initiation Protocol (SIP) Event Notification Extension for Resource Lists", RFC 4662, August 2006. [5] Camarillo, G., Roach, A., and O. Levin, "Subscriptions to Request-Contained Resource Lists in the Session Initiation Protocol (SIP)", RFC 5367, October 2008. [6] Niemi, A., "An Extension to Session Initiation Protocol (SIP) Events for Conditional Event Notification", draft-ietf-sipcore-subnot-etags-02 (work in progress), April 2009. [7] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and J. Peterson, "Presence Information Data Format (PIDF)", RFC 3863, August 2004. [8] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg, "RPID: Rich Presence Extensions to the Presence Information Data Format (PIDF)", RFC 4480, July 2006. [9] Lonnfors, M., Costa-Requena, J., Leppanen, E., and H. Khartabil, "Session Initiation Protocol (SIP) Extension for Partial Notification of Presence Information", RFC 5263, September 2008. [10] Rosenberg, J., "A Watcher Information Event Template-Package for the Session Initiation Protocol (SIP)", RFC 3857, August 2004. [11] Rosenberg, J., "An Extensible Markup Language (XML) Based Format for Watcher Information", RFC 3858, August 2004. Houri, et al. Expires February 28, 2010 [Page 59] Internet-Draft Presence Scaling Analysis August 2009 [12] Niemi, A., Lonnfors, M., and E. Leppanen, "Publication of Partial Presence Information", RFC 5264, September 2008. [13] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa- Requena, "Functional Description of Event Notification Filtering", RFC 4660, September 2006. [14] Khartabil, H., Leppanen, E., Lonnfors, M., and J. Costa- Requena, "An Extensible Markup Language (XML)-Based Format for Event Notification Filtering", RFC 4661, September 2006. [15] Rosenberg, J., "Presence Authorization Rules", RFC 5025, December 2007. [16] Niemi, A., Kiss, K., and S. Loreto, "Session Initiation Protocol (SIP) Event Notification Extension for Notification Rate Control", draft-ietf-sipcore-event-rate-control-00 (work in progress), May 2009. [17] Garcia-Martin, M., "The Presence-Specific Static Dictionary for Signaling Compression (Sigcomp)", RFC 5112, January 2008. [18] Price, R., Bormann, C., Christoffersson, J., Hannu, H., Liu, Z., and J. Rosenberg, "Signaling Compression (SigComp)", RFC 3320, January 2003. [19] Burger, E., "A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages", RFC 4483, May 2006. [20] Rosenberg, J., Houri, A., Smyth, C., and F. Audet, "Models for Intra-Domain Presence and Instant Messaging (IM) Bridging", draft-ietf-simple-intradomain-federation-04 (work in progress), July 2009. [21] Campbell, B., Mahy, R., and C. Jennings, "The Message Session Relay Protocol (MSRP)", RFC 4975, September 2007. [22] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions for the Message Sessions Relay Protocol (MSRP)", RFC 4976, September 2007. Houri, et al. Expires February 28, 2010 [Page 60] Internet-Draft Presence Scaling Analysis August 2009 Authors' Addresses Avshalom Houri IBM Science Park Rehovot, Israel Email: avshalom@il.ibm.com Edwin Aoki AOL LLC 401 Ellis St. Mountain View, CA 94043 USA Email: aoki@aol.net Sriram Parameswar Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA Email: Sriram.Parameswar@microsoft.com Tim Rang Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA Email: timrang@microsoft.com Vishal Singh Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 US Email: vs2140@cs.columbia.edu URI: http://www.cs.columbia.edu/~vs2140 Houri, et al. Expires February 28, 2010 [Page 61] Internet-Draft Presence Scaling Analysis August 2009 Henning Schulzrinne Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 US Phone: +1 212 939 7004 Email: hgs+ecrit@cs.columbia.edu URI: http://www.cs.columbia.edu/~hgs Houri, et al. Expires February 28, 2010 [Page 62]