Internet Engineering Task Force Internet Draft Suman Choudhary Document: draft-suman-sipping-stat-00.txt Huawei Technologies Expires: December 2004 June 2004 Statistics in SIP Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [i]. 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 document is an individual submission to the IETF. Comments should be directed to the authors. Abstract SIP has emerged as a popular protocol for session setup and management. But feedback is an important attribute of any session. The objective of this document is to provide a generic framework which could be used by user agents to provide feedback about the session when it terminates. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [ii]. Table of Contents Suman Choudhary Expires - December 2004 [Page 1] Statistics in SIP June 2004 1. Overview.......................................................2 2. Rationale......................................................2 3. Introduction...................................................2 4. IANA Considerations............................................4 5. Formal Syntax..................................................4 6. Illustrative Examples..........................................5 7. Security Considerations........................................5 References........................................................6 Acknowledgments...................................................6 Author's Addresses................................................6 1. Overview The document defines a extension mechanism to the existing SIP protocol to support session characteristics. Feedback is an important attribute of any session. The objective of this document is to provide a generic framework which could be used by user agents to provide feedback about the completed session. The framework is designed so as to accommodate sessions of various types. The motivation for writing this draft was to monitor the quality of service over Voice over IP networks. 2. Rationale A typical scenario where this idea would be useful is explained to highlight its importance. Diagnosing voice quality problems in a Voice over IP environment is a complex and tedious job. Several tools have been designed to analyze voice packets and generate cumulative statistical data which are then analyzed using computational methods to arrive at figures like Mean Opinion Score, which is the final rating providing a qualitative figure for user level satisfaction for voice quality. Since the user agents are directly involved in the session, and have gathered all useful information, it is always preferable to transfer this information to controlling entity. The controlling entity can use this information to arrive at a conclusion regarding the quality of the session. The document assumes that the information available from the user agent is reliable. It also helps the service providers to constantly evaluate the performance of the network real-time on a per session basis, apart from traffic measurement and modeling research. 3. Introduction Currently SIP protocol does not provide any mechanism for the session participants to provide feedback regarding the session. The objective of this document is to provide a generic framework for Suman Choudhary Expires - December 2004 [Page 2] Statistics in SIP June 2004 reporting statistics information which could be used by network entities to collect session related statistics. The framework is designed so as to accommodate sessions of various types. A typical session among participants would involve a voice dialog established between participants. In this case, the feedback is provided in the form of parameters like latency, jitter buffer, packets lost on the IP channel, those that have been received but then discarded by the receiving jitter buffer, out of sequence packets, duplicate packets, packets sent, packets received, etc. Although the previous paragraph emphasized the importance of the draft with respect to a session carrying voice packets, the concept holds good and has importance for any session. Any session is characterized by certain parameters which describe its attributes. For a video session, additional parameters can be provided in the form of feedback, they could include frames received, frames sent, frames lost, etc. For a data session which could possibly involve the transfer of fax information, they could include the number of fax pages sent, number of fax pages received, etc. Table 1 illustrates some of the parameters which have been considered in the basic framework. Additional parameters can be added based on the importance, its application and usage in a specific environment. Parameter-name Meaning ps Number of packets sent pr Number of packets received po Number of packets received out of sequence pl Number of packets lost dur Duration of the session del Average propagation delay expressed in ms la Average latency encountered vji Average Voice Jitter encountered mos Mean Opinion Score fpgs Number of fax pages sent fpgr Number of fax pages received vfr Video Frame Rate frms Number of frames sent frmr Number of frames received Table 1: List of Parameter Names Suman Choudhary Expires - December 2004 [Page 3] Statistics in SIP June 2004 User Agents which support this draft will send this information at the end of the session. If the controlling entity does not support this draft, it MUST ignore these parameters and continue normal processing. The parameters will be routed till the destination. Any intermediate proxies who need this information will parse the contents. If the user agent initiates the termination of the session, then the feedback information is sent in the BYE message. If the user agent receives BYE, then it sends the feedback information the response to BYE. 4. IANA Considerations This draft registers the "application/stat" MIME media type. The statistics information is text-based. It follows the recommendations of RFC 2045[10] for the usage of text-based data for MIME. This media type is defined by the following information: Media type name: application Media subtype name: stat Required Parameters: None Encoding scheme: ASCII Security considerations: See section 7. 5. Formal Syntax The grammar for this mime-type is mostly derived out of the SIP specification (RFC 3261[1]). The following definitions are derived from the SIP specification (RFC 3261[1]). token DIGIT HCOLON COMMA quoted-string Session-information = 1*( Session-Header CRLF) Session-Header = ( Session-type / Session-id / Session-Info / ExtensionParameter ) ExtensionParameter = token Session-type = ( "voice" | "data" | "video" | "application" | "control" | other-service-type) CRLF other-service-type = quoted-string Suman Choudhary Expires - December 2004 [Page 4] Statistics in SIP June 2004 ; it is suggested that the otehr-service-type ; should be in accordance with the new ; media-type token defined in sdp in "m=" ; parameter Session-id = 1*DIGIT CRLF ; ; this is obtained from the "o=" field of SDP ; Session-Info = SessionParameter 0*( COMMA 0*(WSP) SessionParamter ) CRLF SessionParamter = SessionParameterName HCOLON [ SessionParameterValue ] SessionParameterName = "ps" / "pr" / "po" / "pl" / "dur" / "del" "la" / "vji" / "mos" / "fpgs" /"fpgr" / "vfr" / "frms" / "frmr" SessionParameterValue = *( field-content | LWS ) ; refer RFC 2543 for field-content 6. Illustrative Examples A provision for Statistics information at the end of the session is taken as an example. BYE sip:callee@example.com SIP/2.0 From: "Caller" ;tag=12sdfa.234 To: "Callee" ;tag=exdsra.ert Call-ID: 12345@example.com CSeq: 2 BYE Via: SIP/2.0/UDP 169.100.1.1;branch=z9hG4bKnashds10 Content-Type: application/stat Content-Length: 251 Session_type: voice Session_id: 6722 Session_param: ps = 1723, pr = 1234, pl = 234, po = 234, ji = 4, la = 2, mos = 3.5 Session_type: data Session_id: 8890 Session_param: pgs = 234, pgr = 234, pgl = 0 7. Security Considerations The document does not define any new security mechanism for the transfer of statistics information. Suman Choudhary Expires - December 2004 [Page 5] Statistics in SIP June 2004 References 1 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. 2 Bradner, S., "The Internet Standards Process -- Revision 3", BCP9, RFC 2026, October 1996. 3 Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997 4 Freed, N., Klensin, J. and J. Postel, "Multipart Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996. 5 Freed, N. and N. Borenstein, "Multipart Internet Mail Extensions(MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. 6 Freed, N. and N. Borenstein, "Multipart Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, November 1996. 7 Troost, R., Dorner, S. and K. Moore, "Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field", RFC 2183, August 1997. 8 Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. Acknowledgments Thanks to Veer Kamesh, Kannan, Ranjit, Prasanna and Jaspreet, all belonging to Huawei India for helping me carry this work forward and providing the idea and comments. Author's Addresses Suman Choudhary Huawei Technologies 4th Floor, Leela Galleria, Leela Palace, Bangalore Email: sumanc@huawei.com Suman Choudhary Expires - December 2004 [Page 6] Statistics in SIP June 2004 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Suman Choudhary Expires - December 2004 [Page 7]