Network Working Group P. Saint-Andre Internet-Draft XMPP Standards Foundation Intended status: Informational October 4, 2007 Expires: April 6, 2008 Interdomain Presence Scaling Analysis for the Extensible Messaging and Presence Protocol (XMPP) draft-saintandre-xmpp-presence-analysis-02 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 April 6, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document analyzes the scalability of presence sharing between domains that federate using the Extensible Messaging and Presence Protocol (XMPP). This analysis is provided as a source of comparison with a similar analysis being performed regarding the presence extensions to the Session Initiation Protocol (SIP). Saint-Andre Expires April 6, 2008 [Page 1]
Internet-Draft XMPP Presence Analysis October 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Protocol Flows . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Constants . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Initial Messages . . . . . . . . . . . . . . . . . . . . . 7 4.3. Steady State Messages . . . . . . . . . . . . . . . . . . 8 4.4. Termination Messages . . . . . . . . . . . . . . . . . . . 8 4.5. Bottom Line . . . . . . . . . . . . . . . . . . . . . . . 9 5. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.1. Basic . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5.2. Widely Distributed Inter-Domain Presence . . . . . . . . . 11 5.3. Very Large Network Peering . . . . . . . . . . . . . . . . 13 5.4. Intra-Domain Peering . . . . . . . . . . . . . . . . . . . 15 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 8. Informative References . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Saint-Andre Expires April 6, 2008 [Page 2]
Internet-Draft XMPP Presence Analysis October 2007 1. Introduction Presence is information about the network availability of an individual (or, more precisely, of a presence address of the kind that is often but not necessarily associated with an individual). As typically designed and deployed, presence is shared only with authorized entities, where the authorization takes the form of a subscription. (In this document, we employ the term "user" to signify an account that generates presence information and the term "contact" to signify an annount that is subscribed to the user's presence.) The sharing of presence information can result in a large volume of traffic as users log on or off throughout the life of a presence session, especially for users with large numbers of contacts (e.g., the author of this document has over 1,500 contacts in his list of presence subscribers). The volume is increased by communication of information beyond basic on-off network availability, such as availability substates (e.g., "away" and "do not disturb"). The volume is further increased if the presence "transport" is used to communicate information such as geolocation, mood, activity, even the music to which an individual is listening. Such traffic may be a concern even in a standalone presence domain. However, when presence is shared across domain boundaries then such traffic may introduce a more significant impact on the functioning of the Internet as a whole. Therefore it is important to analyze the traffic generated during interdomain communication of presence information. There are several standardized technologies for sharing presence information. One is a set of extensions (commonly called "SIMPLE") to the Session Initiation Protocol (SIP), where the base protocol is defined in [SIP] and the extensions are defined in [SIP-EVENT] and [SIP-PRES]. Another is the Extensible Messaging and Presence Protocol (XMPP) as defined in [XMPP-CORE] and [XMPP-IM]. [PROBLEM] analyzes several factors regarding the scalability of interdomain communication of presence information using SIP/SIMPLE technologies. For the sake of comparison, this document aims to provide a similar analysis regarding XMPP technologies. In particular, this document focuses on traffic load exclusively since bandwidth usage has the greatest potential impact on the Internet. By contrast, issues such as state management and server processing of presence information are implementation-specific. This document also briefly mentions existing methods for improving the scalability of XMPP presence (and presence-like) communications. Saint-Andre Expires April 6, 2008 [Page 3]
Internet-Draft XMPP Presence Analysis October 2007 2. Assumptions The model for XMPP presence subscriptions is different from that of SIP. In particular, XMPP presence subscriptions are long-lived, and once established last until cancelled. Thus XMPP does not have subscription timeouts and refresh periods as SIP presence does. In addition, this document does not include presence subscriptions in its protocol flows since in XMPP they are preconditions for the exchange of presence notifications (in any case, the number of XML stanzas exchanged in the process of establishing a presence subscription is negligible compared to the volume of presence notifications). XMPP presence subscriptions are typically bidirectional (i.e., the contact has a subscription to the user's presence and the user has a subscription to the contact's presence). However, because [PROBLEM] assumes that subscriptions are uni-directional (i.e., the contact has a subscription to the user's presence but not vice-versa), the same assumption is made herein. Although an XMPP user or contact may have multiple connected "resources" (e.g., client or device) at any one time, for the sake of simplification this document assumes that each entity has only one simultaneous resource. Note that, unlike in SIP, XMPP packets are not typically acknowledged with the equivalent of a 200/OK message. [PROBLEM] assumes that presence notification packets will typically be on the order of 3.5 kilobytes in size (not including TCP or UDP overhead). XMPP presence notification packets tend to be much smaller than SIP presence notification packets; in this document we assume (based on deployment experience) that they are typically 200 bytes in size for basic on-off presence. However, some XMPP applications may include additional information in a presence notification packet, such as entity capabilities as described in [XEP-0115]. Both [XMPP-CORE] and [XMPP-IM] strongly recommend that XMPP presence notifications should include only information that is relevant to a user's willingness or ability to communicate using real-time methods such as instant messaging. However, some XMPP applications include information that is not communications-relevant, such as the hash of a user's avatar icon (see [XEP-0153] and even metadata about the music to which a user is listening (see [XEP-0118]). Although it is recommended to communicate such information using the XMPP publish- subscribe extension (see [XEP-0060]) and appropriate profiles thereof (e.g., [XEP-0163]), some existing XMPP clients send non- Saint-Andre Expires April 6, 2008 [Page 4]
Internet-Draft XMPP Presence Analysis October 2007 communications-relevant information using presence notifications instead of dedicated publish-subscribe nodes. Such behavior marginally increases notification size but can drastically increase the number of notifications sent (e.g., one notification every 3 or 4 minutes when the user begins listening to a new music track). This document does not discuss such usage, since it is actively discouraged and borders on abusive. This document does not discuss various optimizations for SIMPLE (for which see [PROBLEM]) or XMPP. The primary deployed optimization for XMPP is stream compression, implemented either at the TLS level via native TLS compression or at the XMPP level where TLS compression is not available (see [XEP-0138]). Because XMPP communications occur over long-lived TCP connections and associated long-lived XML streams, such compression has been found to yield significant bandwidth savings, up to 90% or even 95%. Stream compression is therefore the recommended method for reducing bandwidth consumption in XMPP systems. 3. Protocol Flows When a contact (in these examples romeo@example.net) becomes available, the contact's server sends an XMPP presence stanza of type "probe" to the user (in these examples juliet@example.com) on behalf of the contact, as shown in the following example (this can be seen as similar to the initial SUBSCRIBE in SIP presence): Contact's server sends presence probe to user (82 bytes): <presence from='romeo@example.net/orchard' to='juliet@example.com' type='probe'/> If the user's server determines that the contact is authorized to see the user's presence, the user's server return's the user's current presence state to the contact (this is equivalent to the "Initial NOTIFY" in SIP presence). Saint-Andre Expires April 6, 2008 [Page 5]
Internet-Draft XMPP Presence Analysis October 2007 User's server sends presence to contact (170 bytes): <presence from='juliet@example.com/balcony' to='romeo@example.net/orchard' xml:lang='en'> <show>away</show> <status>be right back</status> <priority>0</priority> </presence> If the user subsequently changes her presence, the user's server sends an updated presence notification to the contact. User's server sends updated presence to contact (160 bytes): <presence from='juliet@example.com/balcony' to='romeo@example.net/orchard' xml:lang='en'> <show>xa</show> <status>bbiab</status> <priority>0</priority> </presence> A presence session can include any number of presence changes. When the user goes offline, the user's server sends a presence stanza of type "unavailable" to the contact. User's server sends unavailable presence to contact (96 bytes): <presence from='juliet@example.com/balcony' to='romeo@example.net/orchard' type='unavailable'/> Naturally, similar protocol flows are generated by the contact during the life of his presence session. 4. Analysis To enable valid comparison between SIMPLE and XMPP with regard to interdomain presence scaling, this document adheres as closely as possible to the analysis presented in [PROBLEM], with appropriate modifications given differences between the two technologies. In particular, traffic calculations are based on the following inputs Saint-Andre Expires April 6, 2008 [Page 6]
Internet-Draft XMPP Presence Analysis October 2007 and formulae, where the numbering follows that in [PROBLEM] and the terminology is adjusted to conform to XMPP. 4.1. Constants o (C01) Presence session lifetime in hours -- assumed to be 8 hours. o (C02) Presence state changes per hour -- assumed to be 3 times per hour. o (C03) Subscription refresh interval per hour -- does not apply since XMPP presence subscriptions are long-lived. o (C04) Total federated contacts per user -- varies based on the scenario under discussion. o (C05) Number of dialogs to maintain per watcher -- does not apply to XMPP since XMPP presence subscriptions are long-lived, for purposes of calculation treated as equal to C04. o (C06) Number of federated users -- varies based on the scenario under discussion. o (C07) Subscription request size in bytes -- 100 bytes. o (C08) Subscription approval size in bytes -- 100 bytes. o (C09) Presence notification size in bytes -- 200 bytes. o (C10) Presence notification ack size in bytes -- does not apply since XMPP presence notifications are not acked. o (C11) Presence document size in bytes -- does not apply since XMPP presence notifications do not include presence documents. 4.2. Initial Messages o (I01) Number of initial subscribe requests per presence session -- the XMPP equivalent is a presence probe, of which there is 1 per contact ( = C04 ), equal in size to a presence subscription request or approval (100 bytes). o (I02) Number of initial subscription approvals per presence session -- does not apply since XMPP presence probes are not acked. o (I03) Number of initial presence notifications -- 1 per contact ( = C04 ). o (I04) Number of initial presence acks -- does not apply since XMPP presence notifications are not acked. o (I05) Total number and bytes of initial subscribe messages -- Number = (I01*C06) and Bytes = (I01*C06*C07). o (I06) Total number and bytes of initial subscribe acks -- Number = (I02*C06) and Bytes = (I02*C06*C07), both equal to zero since I02 equals zero for XMPP. o (I07) Total number and bytes of initial notifications -- Number = (I03*C06) and Bytes = (I03*C06*C09), note that this formula does not take into account optimizations of the kind discussed in [PROBLEM]. Saint-Andre Expires April 6, 2008 [Page 7]
Internet-Draft XMPP Presence Analysis October 2007 o (I08) Total number and bytes of initial notification acks -- Number = (I04*C10) and Bytes = (I04*C06*C10), both equal to zero since I02 equals zero for XMPP. o (I09) Total number and bytes of initial messages per presence session -- Number = (numbers in I05+I06+I07+I08) and Bytes = (bytes in I05+I06+I07+I08). 4.3. Steady State Messages o (S01) Presence notifications caused by state changes -- (C02*C01) - 2). o (S02) Notification acks for state change notifications -- zero since XMPP presence notifications are not acked. o (S03) Number and size of presence notifications caused by state changes -- Number = (S01*C06*C04), Bytes = (S01*C06*C04)*(C09+C10+ C11). o (S04) Subscription refreshes -- zero since XMPP presence subscriptions are long-lived. o (S05) Acks for subscription refreshes -- zero since there are no subscription refreshes in XMPP. o (S06) Notify messages caused by subscription refreshes -- zero since there are no subscription refreshes in XMPP. o (S07) Acks for notify messages caused by subscription refreshes -- zero since there are no subscription refreshes in XMPP. o (S08) Number and size of messages caused by subscription refreshes -- zero since there are no subscription refreshes in XMPP. o (S09) Total number and bytes of steady-state messages per session -- Number = (numbers in S03+S08), Bytes = (bytes in S03+S08). 4.4. Termination Messages o (T01) Number of terminating subscribe messages -- zero since XMPP presence subscriptions are long-lived. o (T02) Number of acks for terminating subscribe messages -- zero since there are no terminating subscribe messages in XMPP. o (T03) Number of terminating notifications -- in XMPP this is unavailable presence sent when user goes offline = C05. o (T04) Number of acks for terminating notifications -- zero since XMPP presence notifications are not acked. o (T05) Total number and size of terminating subscribe messages -- zero since there are no terminating subscribe messages in XMPP. o (T06) Total number and size of acks for terminating subscribe messages -- zero since there are no terminating subscribe messages in XMPP. o (T07) Total number and size of terminating notifications -- Number = (numbers in T03*C06), Bytes = (T03*C06*(C09+C11)). Saint-Andre Expires April 6, 2008 [Page 8]
Internet-Draft XMPP Presence Analysis October 2007 o (T08) Total number and size of acks for terminating notifications -- zero since XMPP presence notifications are not acked. o (T09) Total number and size of terminating messages per session -- Number = (numbers in T05+T06+T07+T08), Bytes = (bytes in T05+T06+ T07+T08). 4.5. Bottom Line o (B01) Total number and bytes per presence session = (I09+S09+T09). o (B02) Total number and bytes per second = (B01/(C01*3600)). 5. Scenarios 5.1. Basic This scenario assumes two domains, each with 20,000 users, where each user has 4 contacts in the other domain and changes presence 3 times per hour during an 8-hour presence session. The calculations are as follows. CONSTANTS (C01) Presence session lifetime (hours) ....................... 8 (C02) Presence state changes per hour ......................... 3 (C03) Subscription refresh interval per hour ................ N/A (C04) Total federated contacts per user ....................... 4 (C05) Number of dialogs to maintain per watcher ............... 4 (C06) Number of federated users .......................... 40,000 (C07) Subscription request size in bytes .................... 100 (C08) Subscription approval size in bytes ................... 100 (C09) Presence notification size in bytes ................... 200 (C10) Presence notification ack size in bytes ............... N/A (C11) Presence document size in bytes ....................... N/A INITIAL MESSAGES (I01) Initial subscribe requests per presence session ......... 4 (I02) Initial subscription approvals per presence session ..... 0 (I03) Number of initial presence notifications ................ 4 (I04) Number of initial presence acks ......................... 0 (I05) Total number and bytes of initial subscribe messages Number ...................................... 160,000 Bytes ................................... 16,000,000 (I06) Total number and bytes of initial subscribe acks Number ............................................ 0 Bytes ............................................. 0 (I07) Total number and bytes of initial notifications Number ...................................... 160,000 Bytes ................................... 32,000,000 Saint-Andre Expires April 6, 2008 [Page 9]
Internet-Draft XMPP Presence Analysis October 2007 (I08) Total number and bytes of initial notification acks Number ............................................ 0 Bytes ............................................. 0 (I09) Total number and bytes of initial messages Number ...................................... 320,000 Bytes ................................... 48,000,000 STEADY STATE MESSAGES (S01) Presence notifications caused by state changes ......... 22 (S02) Notification acks for state change notifications ........ 0 (S03) Number and size of steady-state presence notifications Number .................................... 3,520,000 Bytes ................................... 704,000,000 (S04) Subscription refreshes .................................. 0 (S05) Acks for subscription refreshes ......................... 0 (S06) Notify messages caused by refreshes ..................... 0 (S07) Acks for notify messages caused by refreshes ............ 0 (S08) Number and size of messages caused by refreshes ......... 0 (S09) Total number and bytes of steady-state messages Number .................................... 3,520,000 Bytes ................................... 704,000,000 TERMINATION MESSAGES (T01) Number of terminating subscribe messages ................ 0 (T02) Number of acks for terminating subscribe messages ....... 0 (T03) Number of terminating notifications ..................... 4 (T04) Number of acks for terminating notifications ............ 0 (T05) Total number and size of terminates Number ............................................ 0 Bytes ............................................. 0 (T06) Total number and size of acks for terminates Number ............................................ 0 Bytes ............................................. 0 (T07) Total number and size of terminating notifications Number ...................................... 160,000 Bytes ................................... 16,000,000 (T08) Total number and size of acks for terminating notifications Number ............................................ 0 Bytes ............................................. 0 (T09) Total number and size of terminating messages per session Number ...................................... 160,000 Bytes ................................... 16,000,000 BOTTOM LINE (B01) Total number and bytes per presence session Number .................................... 4,000,000 Bytes .................................. 768,000,000 (B02) Total number and bytes per second Saint-Andre Expires April 6, 2008 [Page 10]
Internet-Draft XMPP Presence Analysis October 2007 Number .......................................... 139 Bytes ....................................... 26,667 For the bottom-line figures, the comparable numbers for SIMPLE in a non-optimized state (see [PROBLEM]) are 12,800,000 total messages, 20,376,000,000 bytes, 444 messages per second, and 707,500 bytes per second; thus for this scenario XMPP uses 31% of the messages and 3.8% of the bytes used by SIMPLE. 5.2. Widely Distributed Inter-Domain Presence This scenario assumes two domains, each with 20,000 users, where each user has 20 contacts in the other domain and changes presence 3 times per hour during an 8-hour presence session. The calculations are as follows. CONSTANTS (C01) Presence session lifetime (hours) ....................... 8 (C02) Presence state changes per hour ......................... 3 (C03) Subscription refresh interval per hour ................ N/A (C04) Total federated contacts per user ...................... 20 (C05) Number of dialogs to maintain per watcher .............. 20 (C06) Number of federated users .......................... 40,000 (C07) Subscription request size in bytes .................... 100 (C08) Subscription approval size in bytes ................... 100 (C09) Presence notification size in bytes ................... 200 (C09) Presence notification ack size in bytes ............... N/A (C11) Presence document size in bytes ....................... N/A INITIAL MESSAGES (I01) Initial subscribe requests per presence session ........ 20 (I02) Initial subscription approvals per presence session ..... 0 (I03) Number of initial presence notifications ............... 20 (I04) Number of initial presence acks ......................... 0 (I05) Total number and bytes of initial subscribe messages Number ...................................... 800,000 Bytes ................................... 80,000,000 (I06) Total number and bytes of initial subscribe acks Number ............................................ 0 Bytes ............................................. 0 (I07) Total number and bytes of initial notifications Number ...................................... 800,000 Bytes .................................. 160,000,000 (I08) Total number and bytes of initial notification acks Number ............................................ 0 Bytes ............................................. 0 (I09) Total number and bytes of initial messages Number .................................... 1,600,000 Saint-Andre Expires April 6, 2008 [Page 11]
Internet-Draft XMPP Presence Analysis October 2007 Bytes .................................. 240,000,000 STEADY STATE MESSAGES (S01) Presence notifications caused by state changes ......... 22 (S02) Notification acks for state change notifications ........ 0 (S03) Number and size of steady-state presence notifications Number ................................... 17,600,000 Bytes ................................. 3,520,000,000 (S04) Subscription refreshes .................................. 0 (S05) Acks for subscription refreshes ......................... 0 (S06) Notify messages caused by refreshes ..................... 0 (S07) Acks for notify messages caused by refreshes ............ 0 (S08) Number and size of messages caused by refreshes ......... 0 (S09) Total number and bytes of steady-state messages Number ................................... 17,600,000 Bytes ................................. 3,520,000,000 TERMINATION MESSAGES (T01) Number of terminating subscribe messages ................ 0 (T02) Number of acks for terminating subscribe messages ....... 0 (T03) Number of terminating notifications .................... 20 (T04) Number of acks for terminating notifications ............ 0 (T05) Total number and size of terminates Number ............................................ 0 Bytes ............................................. 0 (T06) Total number and size of acks for terminates Number ............................................ 0 Bytes ............................................. 0 (T07) Total number and size of terminating notifications Number ...................................... 800,000 Bytes .................................. 160,000,000 (T08) Total number and size of acks for terminating notifications Number ............................................ 0 Bytes ............................................. 0 (T09) Total number and size of terminating messages per session Number ...................................... 800,000 Bytes .................................. 160,000,000 BOTTOM LINE (B01) Total number and bytes per presence session Number ................................... 20,000,000 Bytes ................................ 3,920,000,000 (B02) Total number and bytes per second Number .......................................... 694 Bytes ...................................... 136,111 For the bottom-line figures, the comparable numbers for SIMPLE in a non-optimized state (see [PROBLEM]) are 65,000,000 total messages, Saint-Andre Expires April 6, 2008 [Page 12]
Internet-Draft XMPP Presence Analysis October 2007 101,880,000,000 bytes, 2,222 messages per second, and 3,537,500 bytes per second; thus for this scenario XMPP uses 31% of the messages and 3.8% of the bytes used by SIMPLE. 5.3. Very Large Network Peering This scenario assumes two domains, each with 10,000,000 users, where each user has 10 contacts in the other domain and changes presence 6 times per hour during an 8-hour presence session. The calculations are as follows. CONSTANTS (C01) Presence session lifetime (hours) ....................... 8 (C02) Presence state changes per hour ......................... 6 (C03) Subscription refresh interval per hour ................ N/A (C04) Total federated contacts per user ...................... 10 (C05) Number of dialogs to maintain per watcher .............. 10 (C06) Number of federated users ...................... 20,000,000 (C07) Subscription request size in bytes .................... 100 (C08) Subscription approval size in bytes ................... 100 (C09) Presence notification size in bytes ................... 200 (C09) Presence notification ack size in bytes ............... N/A (C11) Presence document size in bytes ....................... N/A INITIAL MESSAGES (I01) Initial subscribe requests per presence session ........ 10 (I02) Initial subscription approvals per presence session ..... 0 (I03) Number of initial presence notifications ............... 10 (I04) Number of initial presence acks ......................... 0 (I05) Total number and bytes of initial subscribe messages Number .................................. 200,000,000 Bytes ............................... 20,000,000,000 (I06) Total number and bytes of initial subscribe acks Number ............................................ 0 Bytes ............................................. 0 (I07) Total number and bytes of initial notifications Number .................................. 200,000,000 Bytes ............................... 40,000,000,000 (I08) Total number and bytes of initial notification acks Number ............................................ 0 Bytes ............................................. 0 (I09) Total number and bytes of initial messages Number .................................. 400,000,000 Bytes ............................... 60,000,000,000 STEADY STATE MESSAGES (S01) Presence notifications caused by state changes ......... 46 (S02) Notification acks for state change notifications ........ 0 Saint-Andre Expires April 6, 2008 [Page 13]
Internet-Draft XMPP Presence Analysis October 2007 (S03) Number and size of steady-state presence notifications Number ............................... 9,200,000,000 Bytes ............................ 1,840,000,000,000 (S04) Subscription refreshes .................................. 0 (S05) Acks for subscription refreshes ......................... 0 (S06) Notify messages caused by refreshes ..................... 0 (S07) Acks for notify messages caused by refreshes ............ 0 (S08) Number and size of messages caused by refreshes ......... 0 (S09) Total number and bytes of steady-state messages Number ............................... 9,200,000,000 Bytes ............................ 1,840,000,000,000 TERMINATION MESSAGES (T01) Number of terminating subscribe messages ................ 0 (T02) Number of acks for terminating subscribe messages ....... 0 (T03) Number of terminating notifications .................... 10 (T04) Number of acks for terminating notifications ............ 0 (T05) Total number and size of terminates Number ............................................ 0 Bytes ............................................. 0 (T06) Total number and size of acks for terminates Number ............................................ 0 Bytes ............................................. 0 (T07) Total number and size of terminating notifications Number .................................. 200,000,000 Bytes ............................... 20,000,000,000 (T08) Total number and size of acks for terminating notifications Number ............................................ 0 Bytes ............................................. 0 (T09) Total number and size of terminating messages per session Number .................................. 200,000,000 Bytes ............................... 20,000,000,000 BOTTOM LINE (B01) Total number and bytes per presence session Number ................................ 9,800,000,000 Bytes ............................. 1,920,000,000,000 (B02) Total number and bytes per second Number ...................................... 340,278 Bytes ................................... 66,666,667 For the bottom-line figures, the comparable numbers for SIMPLE in a non-optimized state (see [PROBLEM]) are 25,600,000,000 total messages, 44,046,000,000,000 bytes, 888,889 messages per second, and 1,529,375,333 bytes per second; thus for this scenario XMPP uses 38% of the messages and 4.4% of the bytes used by SIMPLE. Saint-Andre Expires April 6, 2008 [Page 14]
Internet-Draft XMPP Presence Analysis October 2007 5.4. Intra-Domain Peering This scenario assumes two domains, each with 60,000 users, where each user has 10 contacts in the other domain and changes presence 3 times per hour during an 8-hour presence session. The calculations are as follows. CONSTANTS (C01) Presence session lifetime (hours) ....................... 8 (C02) Presence state changes per hour ......................... 3 (C03) Subscription refresh interval per hour ................ N/A (C04) Total federated contacts per user ...................... 10 (C05) Number of dialogs to maintain per watcher .............. 10 (C06) Number of federated users ......................... 120,000 (C07) Subscription request size in bytes .................... 100 (C08) Subscription approval size in bytes ................... 100 (C09) Presence notification size in bytes ................... 200 (C09) Presence notification ack size in bytes ............... N/A (C11) Presence document size in bytes ....................... N/A INITIAL MESSAGES (I01) Initial subscribe requests per presence session ........ 10 (I02) Initial subscription approvals per presence session ..... 0 (I03) Number of initial presence notifications ............... 10 (I04) Number of initial presence acks ......................... 0 (I05) Total number and bytes of initial subscribe messages Number .................................... 1,200,000 Bytes .................................. 120,000,000 (I06) Total number and bytes of initial subscribe acks Number ............................................ 0 Bytes ............................................. 0 (I07) Total number and bytes of initial notifications Number .................................... 1,200,000 Bytes .................................. 240,000,000 (I08) Total number and bytes of initial notification acks Number ............................................ 0 Bytes ............................................. 0 (I09) Total number and bytes of initial messages Number .................................... 2,400,000 Bytes .................................. 360,000,000 STEADY STATE MESSAGES (S01) Presence notifications caused by state changes ......... 22 (S02) Notification acks for state change notifications ........ 0 (S03) Number and size of steady-state presence notifications Number ................................... 26,400,000 Bytes ................................. 5,280,000,000 (S04) Subscription refreshes .................................. 0 Saint-Andre Expires April 6, 2008 [Page 15]
Internet-Draft XMPP Presence Analysis October 2007 (S05) Acks for subscription refreshes ......................... 0 (S06) Notify messages caused by refreshes ..................... 0 (S07) Acks for notify messages caused by refreshes ............ 0 (S08) Number and size of messages caused by refreshes ......... 0 (S09) Total number and bytes of steady-state messages Number ................................... 26,400,000 Bytes ................................. 5,280,000,000 TERMINATION MESSAGES (T01) Number of terminating subscribe messages ................ 0 (T02) Number of acks for terminating subscribe messages ....... 0 (T03) Number of terminating notifications .................... 10 (T04) Number of acks for terminating notifications ............ 0 (T05) Total number and size of terminates Number ............................................ 0 Bytes ............................................. 0 (T06) Total number and size of acks for terminates Number ............................................ 0 Bytes ............................................. 0 (T07) Total number and size of terminating notifications Number .................................... 1,200,000 Bytes .................................. 240,000,000 (T08) Total number and size of acks for terminating notifications Number ............................................ 0 Bytes ............................................. 0 (T09) Total number and size of terminating messages per session Number .................................... 1,200,000 Bytes .................................. 240,000,000 BOTTOM LINE (B01) Total number and bytes per presence session Number ................................... 30,000,000 Bytes ................................. 5,880,000,000 (B02) Total number and bytes per second Number ......................................... 1042 Bytes ...................................... 204,167 For the bottom-line figures, the comparable numbers for SIMPLE in a non-optimized state (see [PROBLEM]) are 96,000,000 total messages, 152,820,000,000 bytes, 3,333 messages per second, and 5,306,250 bytes per second; thus for this scenario XMPP uses 31% of the messages and 3.8% of the bytes used by SIMPLE. 6. Conclusion With respect to presence scaling, the differences between XMPP systems and SIP-based systems are startling. In particular, this Saint-Andre Expires April 6, 2008 [Page 16]
Internet-Draft XMPP Presence Analysis October 2007 analysis indicates that XMPP requires only about 1.5% of the bandwidth required by SIMPLE. There are two primary causes for this disparity: (1) XMPP requires only about 25% of the packets required by SIMPLE and (2) XMPP packets are about 5% of the size of SIMPLE packets for presence notifications and 20% of the size for subscribe packets. Together, these two factors appear to result in a significant disparity with respect to the scalability of presence technologies. Naturally, real-world studies of deployed systems will be necessary to determine if these theorized differences occur in reality. 7. Security Considerations This document introduces and addresses no security concerns above and beyond those already defined in [XMPP-CORE] and [XMPP-IM]. 8. Informative References [PROBLEM] Houri, A., "Presence Interdomain Scaling Analysis for SIP/ SIMPLE", draft-ietf-simple-interdomain-scaling-analysis-01 (work in progress), July 2007. [SIP] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [SIP-EVENT] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [SIP-PRES] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. [XEP-0060] Millard, P., Saint-Andre, P., and R. Meijer, "Publish- Subscribe", XSF XEP 0060, September 2007. [XEP-0115] Hildebrand, J., Saint-Andre, P., and R. Troncon, "Entity Capabilities", XSF XEP 0115, August 2007. [XEP-0118] Saint-Andre, P., "User Tune", XSF XEP 0118, June 2007. Saint-Andre Expires April 6, 2008 [Page 17]
Internet-Draft XMPP Presence Analysis October 2007 [XEP-0138] Hildebrand, J. and P. Saint-Andre, "Stream Compression", XSF XEP 0138, September 2007. [XEP-0153] Saint-Andre, P., "vCard-Based Avatars", XSF XEP 0153, August 2006. [XEP-0163] Saint-Andre, P. and K. Smith, "Personal Eventing via Pubsub", XSF XEP 0163, September 2007. [XMPP-CORE] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 3920, October 2004. [XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence", RFC 3921, October 2004. Author's Address Peter Saint-Andre XMPP Standards Foundation P.O. Box 1641 Denver, CO 80201 USA Email: stpeter@jabber.org URI: https://stpeter.im/ Saint-Andre Expires April 6, 2008 [Page 18]
Internet-Draft XMPP Presence Analysis October 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Saint-Andre Expires April 6, 2008 [Page 19]