--- 1/draft-ietf-mmusic-media-loopback-00.txt 2006-02-05 00:26:44.000000000 +0100 +++ 2/draft-ietf-mmusic-media-loopback-01.txt 2006-02-05 00:26:44.000000000 +0100 @@ -1,54 +1,56 @@ K. Hedayat Internet Draft Brix Networks - Expires: June 30, 2005 P. Jones + Expires: December 27,2005 P. Jones Cisco Systems, Inc. A. Roychowdhury - Hughes Software Systems + Flextronics Software Systems C. SivaChelvan Cisco Systems, Inc. N. Stratton BroadVoice - December 2, 2004 + June 27, 2005 An Extension to the Session Description Protocol (SDP) for Media Loopback - draft-ietf-mmusic-media-loopback-00.txt + draft-ietf-mmusic-media-loopback-01.txt Status of this Memo - By submitting this Internet-Draft, we certify that any applicable - patent or other IPR claims of which we are aware have been - disclosed and any of which we become aware will be disclosed, in - accordance with RFC 3668 (BCP 79). - - By submitting this Internet-Draft, we accept the provisions of - Section 3 of RFC 3667 (BCP 78). + 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. + Copyright Notice + + Copyright (C) The Internet Society (2005). + Abstract + The wide deployment of VoIP and Video over IP services has introduced new challenges in managing and maintaining voice/video quality, reliability, and overall performance. In particular, media delivery is an area that needs attention. One method of meeting these challenges is monitoring the media delivery performance by looping media back to the transmitter. This is typically referred to as "active monitoring" of services. Media loopback is especially popular in ensuring the quality of transport to the edge of a given VoIP or Video over IP service. Today in networks that deliver real-time media, short of running ' ping' and @@ -58,41 +60,45 @@ SDP media attributes which enables establishment of media sessions where the media is looped back to the transmitter. Such media sessions will serve as monitoring and troubleshooting tools by providing the means for measurement of more advanced VoIP and Video Over IP performance metrics. Table of Contents 1. Introduction..................................................3 2. Terminology...................................................3 - 3. Offering Entity Behavior......................................3 + 3. Offering Entity Behavior......................................4 4. Answering Entity Behavior.....................................4 5. SDP Constructs Syntax.........................................4 5.1 Loopback Type Attribute...................................4 - 5.2 Loopback Mode Attribute...................................5 - 5.3 Generating the Offer for Loopback Session.................5 - 5.4 Generating the Answer for Loopback Session................6 - 5.5 Offerer Processing of the Answer..........................7 - 5.6 Modifying the Session.....................................7 - 6. RTP Requirements..............................................7 - 7. RTCP Requirements.............................................8 - 8. Examples......................................................8 - 8.1 Offer for specific media loopback type....................8 - 8.2 Offer for choice of media loopback type...................9 - 8.3 Response to INVITE request rejecting loopback media......10 - 9. Implementer Guidelines.......................................11 - 10. Security Considerations.....................................11 - 11. IANA Considerations.........................................11 - 12. Acknowledgements............................................11 - 13. References..................................................11 - 13.1 Normative References....................................11 + 5.2 Loopback Mode Attribute...................................6 + 5.3 Generating the Offer for Loopback Session.................6 + 5.4 Generating the Answer for Loopback Session................7 + 5.5 Offerer Processing of the Answer..........................8 + 5.6 Modifying the Session.....................................8 + 6. RTP Requirements..............................................8 + 7. RTCP Requirements.............................................9 + 8. Examples......................................................9 + 8.1 Offer for specific media loopback type....................9 + 8.2 Offer for choice of media loopback type..................10 + 8.3 Offer for choice of media loopback type with + rtp-start-loopback...........................................11 + 8.4 Response to INVITE request rejecting loopback media......12 + 8.5 Response to INVITE request rejecting loopback media with + rtp-start-loopback...........................................13 + 9. Security Considerations......................................13 + 10. IANA Considerations.........................................14 + 11. Acknowledgements............................................14 + 12. References..................................................14 + 12.1 Normative References....................................14 + 1. Introduction The overall quality, reliability, and performance of VoIP and Video over IP services relies on the performance and quality of the media path. In order to assure the quality of the delivered media there is a need to monitor the performance of the media transport. One method of monitoring and managing the overall quality of VoIP and Video over IP Services is through monitoring the quality of the media in an active session. This type of "active monitoring" of services is a method of pro-actively managing the performance and @@ -155,70 +162,111 @@ Two new media attributes are defined: one indicates the type of loopback and one indicates the mode of the loopback. 5.1 Loopback Type Attribute The loopback type is a property media attribute with the following syntax: a=loopback: - Following is the Augmented BNF (RFC 2234) [RFC2234] for loopback- - type: + Following is the Augmented BNF (RFC 2234) [RFC2234] for + loopback-type: loopback-type = loopback-type-choice [ space loopback-type-choice ] - loopback-type-choice = "rtp-pkt-loopback" | "rtp-media-loopback" + loopback-type-choice = "rtp-pkt-loopback" | "rtp-media-loopback | + rtp-start-loopback" The loopback type is used to indicate the type of loopback. The - loopback-type values are rtp-pkt-loopback and rtp-media-loopback. + loopback-type values are rtp-pkt-loopback, rtp-media-loopback, and + rtp-start-loopback. rtp-pkt-loopback: In this mode, the RTP packets are looped back to the sender at a point before the encoder/decoder function in the receive direction to a point after the encoder/decoder function in the send direction. This effectively re-encapsulates the RTP payload with the RTP/UDP/IP overheads appropriate for sending it in the reverse direction. Any type of encoding related functions, such as packet loss concealment, MUST NOT be part of this type of loopback path. rtp-media-loopback: This loopback is activated as close as possible to the analog interface and after the decoder so that the RTP packets are subsequently re-encoded prior to transmission back to the sender. + rtp-start-loopback: In certain scenarios it is possible that the + media transmitted by the offering entity is blocked by a network + element until the answering entity starts transmitting packets. + One example of this scenario is the presence of an RTP relay in the + path of the media. RTP relays exist in VoIP networks for purpose + of NAT and Firewall traversal. If an RTP relay is present the + offering entityÆs packets are dropped by the RTP relay until the + answering entity has started transmitting media and the media state + within the RTP relay is established. This loopback attribute is + used to specify the media type for transmitting media packets by + the answering entity prior to the loopback process for the purpose + of setting media state within the network. In the presence of this + loopback attribute the answering entity will transmit media, + according to the description that contains this attribute, until it + receives media from the offering entity. After the first media + packet is received from the offering entity, the answering entity + MUST terminate the transmission of rtp-start-loopback media and + MUST start looping back media as defined by the other loopback + attributes present in the offer. If an offer includes the + rtp-start-loopback attribute it MUST also include at least one + other attribute as defined in this section. The offering entity is + able to filter rtp-start-loopback packets from other types of + loopback with the payload type of the packet. The media port number + for rtp-start-loopback MUST be the same as the corresponding + loopback attribute that will take over after the reception of first + media packet from the offering entity. + + It is recommended that an offering entity specifying media with + either rtp-pkt-loopback or rtp-media-loopback attribute also + specify the rtp-start-loopback attribute unless the offering entity + is certain that its media will not be blocked by a network entity + as explained above. + 5.2 Loopback Mode Attribute The loopback mode is a value media attribute that is used to indicate the mode of the loopback. These attributes can be viewed as additional mode attributes similar to sendonly, recvonly, etc. The syntax of the loopback mode media attribute is: a= - The loopback-mode values are loopback-source and loopback-mirror.. + The loopback-mode values are loopback-source and loopback-mirror. loopback-source: This attribute specifies that the sender is the media source and expects the receiver to act as a loopback-mirror. loopback-mirror: This attribute specifies that the receiver will mirror (echo) all received media back to the sender of the RTP stream. No media is generated locally by the reciver for transmission in the mirrored stream. + The loopback mode attribute does not apply to rtp-start-loopback + attribute and MAY be omitted. If the loopback mode attribute is + present with the rtp-start-loopback attribute it MUST be ignored by + the answering entity. + 5.3 Generating the Offer for Loopback Session If an offerer wishes to make a loopback request, it MUST include both the loopback-type and loopback-mode attribute in a valid SDP offer: - Example: a=loopback-type:rtp-media-loopback + Example: a=loopback:rtp-media-loopback a=loopback-source + Note: A loopback offer in a given media description MUST NOT contain the standard mode attributes sendonly, recvonly, sendrecv or inactive. The offerer may offer more than one loopback-type in the SDP offer. In this case the answer MUST include only one of the loopback types that is accepted by the answerer. The answerer SHOULD give preference to the first loopback-type in the SDP offer. For loopback-source media (e.g. audio) streams, the port number and @@ -233,42 +281,42 @@ If an answerer wishes to accept the loopback request it MUST include both the loopback mode and loopback type attribute in the answer. If a stream is offered with loopback-source or loopback-mirror attributes, the corresponding stream MUST be loopback-mirror or loopback-source respectively, provided that answerer is capable of supporting the requested loopback-type. For example, if the offer contains: - a=loopback-type:rtp-media-loopback + a=loopback:rtp-media-loopback a=loopback-source The answer that is capable of supporting the offer MUST contain: - a=loopback-type:rtp-media-loopback + a=loopback:rtp-media-loopback a=loopback-mirror As previously stated if a stream is offered with multiple loopback type attributes, the corresponding stream MUST contain only one loopback type attribute selected by the answerer. For example, if the offer contains: - a=loopback-type:rtp-media-loopback rtp-pkt-loopback + a=loopback:rtp-media-loopback rtp-pkt-loopback a=loopback-source + The answer that is capable of supporting the offer and chooses to loopback the media using the rtp-media-loopback type MUST contain: - a=loopback-type:rtp-media-loopback + a=loopback:rtp-media-loopback a=loopback-mirror - 5.4.1 Rejecting the Loopback Offer An offered stream with loopback-source MAY be rejected, if the loopback-type is not specified, the specified loopback-type is not supported, or the endpoint cannot honor the offer for any other reason. The Loopback request may be rejected by setting the media port number to zero, according to RFC 3264 [RFC3264], in the answer. 5.5 Offerer Processing of the Answer @@ -397,21 +447,64 @@ e=user@example.com c=IN IP4 224.2.17.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-pkt-loopback a=loopback-mirror The server is accepting to mirror the media from the client at the packet level. - 8.3 Response to INVITE request rejecting loopback media + 8.3 Offer for choice of media loopback type with rtp-start-loopback + + A client sends an INVITE request with SDP which looks like: + + v=0 + o=user1 2890844526 2890842807 IN IP4 126.16.64.4 + s=Example + i=An example session + e=user@example.com + c=IN IP4 224.2.17.12/127 + t=0 0 + m=audio 49170 RTP/AVP 0 + a=loopback:rtp-media-loopback rtp-pkt-loopback + a=loopback-source + m=audio 49170 RTP/AVP 100 + a=loopback:rtp-start-loopback + + The client is offering to source the media and expects the server + to mirror the RTP stream at either the media or rtp level. The + client also expects the server to source media until it receives + packets from the server per media described with the + rtp-start-loopback attribute. + + A server sends a response with SDP which looks like: + + v=0 + o=user1 2890844526 2890842807 IN IP4 126.16.64.4 + s=Example + i=An example session + e=user@example.com + c=IN IP4 224.2.17.12/127 + t=0 0 + m=audio 49170 RTP/AVP 0 + a=loopback:rtp-pkt-loopback + a=loopback-mirror + m=audio 49170 RTP/AVP 100 + a=rtpmap:100 pcmu/8000 + a=loopback:rtp-start-loopback + + The server is accepting to mirror the media from the client at the + packet level. The server is also accepting to source media until + it receives media packets from the client. + + 8.4 Response to INVITE request rejecting loopback media A client sends an INVITE request with SDP which looks like: v=0 o=user1 2890844526 2890842807 IN IP4 126.16.64.4 s=Example i=An example session e=user@example.com c=IN IP4 224.2.17.12/127 t=0 0 @@ -432,51 +525,87 @@ c=IN IP4 224.2.17.12/127 t=0 0 m=audio 0 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-mirror NOTE: Loopback request may be rejected by either not including the loopback mode attribute(for backward compatibility) or setting the media port number to zero, or both, in the response. - 9. Implementer Guidelines + 8.5 Response to INVITE request rejecting loopback media with + rtp-start-loopback - This section provides guidelines to the implementers of this - extension. + A client sends an INVITE request with SDP which looks like: - 10. Security Considerations + v=0 + o=user1 2890844526 2890842807 IN IP4 126.16.64.4 + s=Example + i=An example session + e=user@example.com + c=IN IP4 224.2.17.12/127 + t=0 0 + m=audio 49170 RTP/AVP 0 + a=loopback:rtp-media-loopback + a=loopback-source + m=audio 49170 RTP/AVP 100 + a=loopback:rtp-start-loopback + + The client is offering to source the media and expects the server + to mirror the RTP stream at the media level. The client also + expects the server to source media until it receives packets from + the server per media described with the rtp-start-loopback + attribute. + + A server sends a response with SDP which looks like: + + v=0 + o=user1 2890844526 2890842807 IN IP4 126.16.64.4 + s=Example + i=An example session + e=user@example.com + c=IN IP4 224.2.17.12/127 + t=0 0 + m=audio 0 RTP/AVP 0 + a=loopback:rtp-media-loopback + a=loopback-mirror + m=audio 0 RTP/AVP 0 + a=loopback:rtp-start-loopback + NOTE: Loopback request may be rejected by either not including the + loopback mode attribute(for backward compatibility) or setting the + media port number to zero, or both, in the response. + + 9. Security Considerations The security considerations of [RFC3261] apply. Furthermore, given - that media loopback may be automated without the end userÆs + that media loopback may be automated without the end user's knowledge, the server of the media loopback should be aware of denial of service attacks. It is recommended that sessions with media loopback are authenticated and the frequency of such sessions are limited by the server. - 11. IANA Considerations + 10. IANA Considerations There are no IANA considerations associated with this specification. - 12. Acknowledgements + 11. Acknowledgements The authors wish to thank Flemming Andreasen, Jeff Bernstein, Paul Kyzivat, and Dave Oran for their comments and suggestions. - 13. References + 12. References - 13.1 Normative References + 12.1 Normative References [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. - and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, STD 1, June 2002. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with the Session Description Protocol (SDP)", RFC 3264, STD 1, June 2002. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, STD 1, July 2003. @@ -503,29 +632,30 @@ Paul E. Jones Cisco Systems, Inc. 7025 Kit Creek Rd. Research Triangle Park, NC 27709 US Phone: +1 919 392 6948 EMail: paulej@packetizer.com URI: http://www.cisco.com/ + Arjun Roychowdhury - Hughes Software Systems + Flextronics Software Systems 11717 Exploration Lane Germantown, MD 20876 US Phone: +1 301 212 7860 - EMail: aroychow@hssworld.com - URI: http://www.hssworld.com/ + EMail: arjun.roy@flextronicssoftware.com + URI: http://www.flextronicssoftware.com/ Chelliah SivaChelvan Cisco Systems, Inc. 2200 East President George Bush Turnpike Richardson, TX 75082 US Phone: +1 972 813 5224 EMail: chelliah@cisco.com URI: http://www.cisco.com/ @@ -571,20 +701,20 @@ an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY 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. Copyright Notice - Copyright (C) The Internet Society (2004). + Copyright (C) The Internet Society (2005). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society.