Network Working Group P. Saint-Andre Internet-Draft XSF Expires: October 13, 2007 April 11, 2007 Interdomain Presence Scaling Analysis for the Extensible Messaging and Presence Protocol (XMPP) draft-saintandre-xmpp-presence-analysis-00 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 October 13, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document analyzes the traffic that is generated as a result of presence subscriptions between users of federated domains that support the Extensible Messaging and Presence Protocol (XMPP). This analysis is provided as a source of comparison with a similar analysis being performed regarding domains that support federated presence using Session Initiation Protocol (SIP) for Instant Messaging and Presence Leveraging Extensions (SIMPLE). Saint-Andre Expires October 13, 2007 [Page 1]
Internet-Draft XMPP Presence Analysis April 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Traffic Load . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Protocol Flows . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4.1. Basic . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4.2. Widely Distributed Inter-Domain Presence . . . . . . . 7 2.4.3. Very Large Network Peering . . . . . . . . . . . . . . 8 2.4.4. Intra-Domain Peering . . . . . . . . . . . . . . . . . 8 3. Security Considerations . . . . . . . . . . . . . . . . . . . 9 4. Informative References . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . . . 11 Saint-Andre Expires October 13, 2007 [Page 2]
Internet-Draft XMPP Presence Analysis April 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 approximately 1,500 contacts in his list of presence subscribers). The volume is increased by communication of information beyond boolean 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. While such traffic may not be a concern in a standalone presence domain, interdomain communications may introduce a more significant impact on the functioning of the Internet as a whole. There are several standardized technologies for sharing presence information. One is a set of extensions 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 its first iteration, it discusses traffic load exclusively since bandwidth usage has the greatest potential impact on the Internet (whereas issues such as state management and server processing of presence information are implementation-specific). 2. Traffic Load Saint-Andre Expires October 13, 2007 [Page 3]
Internet-Draft XMPP Presence Analysis April 2007 2.1. 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 4 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. 2.2. 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): Saint-Andre Expires October 13, 2007 [Page 4]
Internet-Draft XMPP Presence Analysis April 2007 Contact's server sends presence probe to user: <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). User's server sends presence to contact: <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: <presence from='juliet@example.com/balcony' to='romeo@example.net/orchard' xml:lang='en'> <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: <presence from='juliet@example.com/balcony' to='romeo@example.net/orchard' type='unavailable' xml:lang='en'/> Saint-Andre Expires October 13, 2007 [Page 5]
Internet-Draft XMPP Presence Analysis April 2007 Naturally, similar protocol flows are generated by the contact during the life of his presence session. 2.3. 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], witih appropriate modifications given differences between the two technologies. In particular, traffic calculations are based on the following inputs and formulae, where the numbering follows that in [PROBLEM] and the terminology is adjusted to conform to XMPP: o (A01) Presence session lifetime in hours -- assumed to be 8 hours. o (A02) Presence state changes per hour -- assumed to be 3 times per hour. o (A03) Subscription refresh interval per hour -- does not apply to XMPP. o (A04) Total federated contacts per user -- varies based on the scenario under discussion. o (A05) Number of dialogs to maintain per watcher -- does not apply to XMPP. o (A06) Number of contacts in a federated presence domain -- varies based on the scenario under discussion. o (A07) Initial presence subscription exchange -- deemed out of scope here since XMPP presence subscriptions are long-lived. o (A08) Initial presence notification -- on the model of SIP NOTIFY plus 200, this is XMPP presence probe plus initial notification, thus 2 per contact. o (A09) Total initial messages -- (A08*A06). o (A10) Presence notifications per user = (A02*A01*A04). o (A11) Subscription refreshes -- does not apply to XMPP. o (A12) NOTIFY/200 due to subscribe refresh -- does not apply to XMPP. o (A13) Number of steady state messages = (A10*A06). o (A14) SUBSCRIBE termination -- does not apply to XMPP. o (A15) Unavailable presence -- sent when user goes offline (equivalent to NOTIFY terminated), 1 per contact. o (A16) Number of sign-out messages = (A15*A06). o (A17) Total number of messages between domains = ((A09+A13+ A16)*2). o (A18) Total number of messages per second = (A17/A01/3600). o (A19) Total number of kilobytes per second = (A18*.2). 2.4. Scenarios Saint-Andre Expires October 13, 2007 [Page 6]
Internet-Draft XMPP Presence Analysis April 2007 2.4.1. 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. The calculations are as follows: o (A01) = 8. o (A02) = 3. o (A03) N/A. o (A04) = 4. o (A05) N/A. o (A06) = 20,000. o (A07) N/A. o (A08) = 8. o (A09) = (A08*A06) = 160,000. o (A10) = (A02*A01*A04) = 96. o (A11) N/A. o (A12) N/A. o (A13) = (A10*A06) = 1,920,000. o (A14) N/A. o (A15) = 4. o (A16) = (A15*A06) = 80,000. o (A17) = ((A09+A13+A16)*2) = 4,320,000 total messages. o (A18) = (A17/A01/3600) = 150 messages per second. o (A19) = (A18*.2) = 30 kilobtyes per second. For the last three factors, the comparable numbers for SIMPLE (from [PROBLEM]) are 14,080,000 total messages, 489 messages per second, and 830 kilobytes per second. 2.4.2. 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. The calculations are as follows: o (A01) = 8. o (A02) = 3. o (A03) N/A. o (A04) = 20. o (A05) N/A. o (A06) = 20,000. o (A07) N/A. o (A08) = 40. o (A09) = (A08*A06) = 800,000. o (A10) = (A02*A01*A04) = 480. Saint-Andre Expires October 13, 2007 [Page 7]
Internet-Draft XMPP Presence Analysis April 2007 o (A11) N/A. o (A12) N/A. o (A13) = (A10*A06) = 9,600,000. o (A14) N/A. o (A15) = 20. o (A16) = (A15*A06) = 400,000. o (A17) = ((A09+A13+A16)*2) = 21,600,000 total messages. o (A18) = (A17/A01/3600) = 750 messages per second. o (A19) = (A18*.2) = 150 kilobtyes per second. For the last three factors, the comparable numbers for SIMPLE (from [PROBLEM]) are 70,400,000 total messages, 2,444 messages per second, and 1,968 kilobytes per second. 2.4.3. 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. The calculations are as follows: o (A01) = 8. o (A02) = 6. o (A03) N/A. o (A04) = 10. o (A05) N/A. o (A06) = 10,000,000. o (A07) N/A. o (A08) = 20. o (A09) = (A08*A06) = 200,000,000. o (A10) = (A02*A01*A04) = 480. o (A11) N/A. o (A12) N/A. o (A13) = (A10*A06) = 4,800,000,000. o (A14) N/A. o (A15) = 10. o (A16) = (A15*A06) = 100,000,000. o (A17) = ((A09+A13+A16)*2) = 10,200,000,000 total messages. o (A18) = (A17/A01/3600) = 354,166 messages per second. o (A19) = (A18*.2) = 70,833 kilobtyes per second. For the last three factors, the comparable numbers for SIMPLE (from [PROBLEM]) are 27,200,000,000 total messages, 944,444 messages per second, and 880,555 kilobytes per second. 2.4.4. 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 Saint-Andre Expires October 13, 2007 [Page 8]
Internet-Draft XMPP Presence Analysis April 2007 per hour. The calculations are as follows: o (A01) = 8. o (A02) = 3. o (A03) N/A. o (A04) = 10. o (A05) N/A. o (A06) = 60,000. o (A07) N/A. o (A08) = 20. o (A09) = (A08*A06) = 1,200,000. o (A10) = (A02*A01*A04) = 240. o (A11) N/A. o (A12) N/A. o (A13) = (A10*A06) = 14,400,000. o (A14) N/A. o (A15) = 10. o (A16) = (A15*A06) = 600,000. o (A17) = ((A09+A13+A16)*2) = 32,400,000 total messages. o (A18) = (A17/A01/3600) = 1125 messages per second. o (A19) = (A18*.2) = 225 kilobtyes per second. For the last three factors, the comparable numbers for SIMPLE (from [PROBLEM]) are 105,600,000 total messages, 3,667 messages per second, and 3,683 kilobytes per second. 3. Security Considerations This document introduces and addresses no security concerns above and beyond those already defined in [XMPP-CORE] and [XMPP-IM]. 4. Informative References [PROBLEM] Houri, A., "Problem Statement for SIP/SIMPLE", draft-ietf-simple-interdomain-scaling-analysis-00 (work in progress), February 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. Saint-Andre Expires October 13, 2007 [Page 9]
Internet-Draft XMPP Presence Analysis April 2007 [SIP-PRES] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. [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: xmpp:stpeter@jabber.org Saint-Andre Expires October 13, 2007 [Page 10]
Internet-Draft XMPP Presence Analysis April 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 October 13, 2007 [Page 11]