--- 1/draft-ietf-mmusic-media-loopback-02.txt 2006-06-27 01:12:46.000000000 +0200 +++ 2/draft-ietf-mmusic-media-loopback-03.txt 2006-06-27 01:12:46.000000000 +0200 @@ -1,26 +1,23 @@ K. Hedayat Internet Draft Brix Networks - Expires: May 11, 2006 P. Jones + Expires: December 2006 P. Jones Cisco Systems, Inc. A. Roychowdhury - Flextronics Software Systems + Hughes C. SivaChelvan Cisco Systems, Inc. N. Stratton - BroadVoice - November 7, 2005 - An Extension to the Session Description Protocol (SDP) for Media Loopback - draft-ietf-mmusic-media-loopback-02 + draft-ietf-mmusic-media-loopback-03 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 @@ -33,42 +30,43 @@ 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). + Copyright (C) The Internet Society (2006). 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 - 'traceroute' to the edge, service providers are left without the - necessary tools to actively monitor, manage, and diagnose quality - issues with their service. The extension defined herein adds new - 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. + The wide deployment of Voice over IP (VoIP), Real-time Text and + Video over IP services has introduced new challenges in managing + and maintaining voice/real-time Text/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, + Real-time Text or Video over IP service. Today in networks that + deliver real-time media, short of running 'ping' and 'traceroute' + to the edge, service providers are left without the necessary tools + to actively monitor, manage, and diagnose quality issues with their + service. The extension defined herein adds new 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, Real-time Text and + Video Over IP performance metrics. Table of Contents 1. Introduction..................................................3 2. Terminology...................................................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...................................6 @@ -79,57 +77,56 @@ 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 + 9. Security Considerations......................................14 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 - quality of VoIP based services. + The overall quality, reliability, and performance of VoIP, + Real-time Text and Video over IP services rely 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, Real-time Text 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 quality of VoIP based + services. The goal of active monitoring is to measure the media quality of a - VoIP or Video over IP session. A way to achieve this goal is to - request an endpoint to loop media back to the other endpoint and to - provide media statistics (e.g., RTCP and RTCP XR information). - Another method involves deployment of special endpoints that always - loop incoming media back for sessions. Although the latter method - has been used and is functional, it does not scale to support large - networks and introduces new network management challenges. - Further, it does not offer the granularity of testing a specific - endpoint that may be exhibiting problems. + VoIP, Real-time Text or Video over IP session. A way to achieve + this goal is to request an endpoint to loop media back to the other + endpoint and to provide media statistics (e.g., RTCP and RTCP XR + information). Another method involves deployment of special + endpoints that always loop incoming media back for sessions. + Although the latter method has been used and is functional, it does + not scale to support large networks and introduces new network + management challenges. Further, it does not offer the granularity + of testing a specific endpoint that may be exhibiting problems. The extension defined in this memo introduces new SDP media attributes that enable establishment of media sessions where the media is looped back to the transmitter. The offer/answer model - per RFC 3264 [RFC3264] is used to establish a loopback connection. - Furthermore, this extension provides guidelines on handling RTP - (RFC 3550) [RFC3550], as well as usage of RTCP (RFC 3550) [RFC3550] - and RTCP XR (RFC 3611) [RFC3611] for reporting media related - measurements. + [RFC3264] is used to establish a loopback connection. Furthermore, + this extension provides guidelines on handling RTP [RFC3550], as + well as usage of RTCP [RFC3550] and RTCP XR [RFC3611] for reporting + media related measurements. 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [RFC3264] and indicate requirement levels for compliant implementations. 3. Offering Entity Behavior @@ -145,43 +142,43 @@ 4. Answering Entity Behavior An answering entity compliant to this specification and receiving an offer containing media descriptions with the "loopback" media attributes, MUST acknowledge the request by including the received "loopback" media attributes for each media description in its response. The server MAY reject the "loopback" request for specific media types as defined in section 5.4.1 of this specification. - An answering entity that is not compliant to this specification - and which receives an offer with the "loopback" media attributes - MAY safely ignore the attribute and treat the incoming offer as a - normal request. + An answering entity that is not compliant to this specification and + which receives an offer with the "loopback" media attributes MAY + ignore the attribute and treat the incoming offer as a normal + request. 5. SDP Constructs Syntax 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 [RFC2234] for loopback-type: - loopback-type = loopback-type-choice [ space loopback-type-choice ] - loopback-type-choice = "rtp-pkt-loopback" | "rtp-media-loopback | - rtp-start-loopback" + loopback-type = 1*2(loopback-type-choice) [ space "rtp-start- + 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, 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 @@ -201,24 +198,29 @@ 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 entity’s 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 + receives media from the offering entity. The answering entity MAY + include this attribute in the answer if it is not present in the + offer. This may be necessary if the answering entity is aware of + NAT’s, firewalls, or RTP relays on the path of the call. In this + case the offering entity MUST accept media according to + rtp-start-loopback attribute. 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 @@ -236,52 +238,56 @@ a= 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. + stream. No media is generated locally by the receiver for + transmission in the mirrored stream unless rtp-start-loopback is + requested The loopback mode attribute does not apply to rtp-start-loopback - attribute and MUST be ignored if received by the answering entityt. + attribute and MUST be ignored if received 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: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 + that are 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 - the address in the offer indicates where the offerer would like to + the address in the offer indicate where the offerer would like to receive the media stream. The payload type numbers indicate the value of the payload the offerer expects to receive, and would prefer to send. However, the answer might indicate a different payload type number for the same codec. In that case, the offerer MUST send the payload type received in the answer. + Note: NAT devices may change the actual port number that is used + for transmission and the expected receive port. + 5.4 Generating the Answer for Loopback Session 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: @@ -331,32 +337,29 @@ 5.6 Modifying the Session At any point during the loopback session, either participant may issue a new offer to modify the characteristics of the previous session. In case of SIP this is defined in section 8 of RFC 3264 [RFC3264]. This also includes transitioning from a normal media processing mode to loopback mode, and vice a versa. 6. RTP Requirements - An answering entitity that is compliant to this specification and - accepting a media with rtp-pkt-loopback loopback-type MUST - re-generate all of the RTP header fields as it does when - transmitting other media. However, the answering entity MUST - maintain the timing information of the received RTP packets when - generating the RTP timestamp for the transmit packets. Maintaining - the timing information of the RTP packets enables the offerer to - re-construct the incoming media and take account for impairments - from gaps in the media due to packet loss. Note that RTP Sequence - numbers are re-generated by the answering entity and will not - provide packet loss information to the receiver of the loopback - media. + An answering entity that is compliant to this specification and + accepting a media with rtp-pkt-loopback loopback-type MUST loopback + the incoming RTP packets while re-generating only the SSRC field of + the RTP header. Note that during the rtp-pkt-loopback mode the + answering entity does not have control over the encoding of the + media and cannot perform certain functions including congestion + control on the looped back media. However, since the purpose of the + loopback is to characterize the round-trip path at the RTP level, + this limitation is acceptable. An answering entity that is compliant to this specification and accepting a media with rtp-media-loopback loopback-type MUST transmit all received media back to the sender . The incoming media MUST be treated as if it were to be played (e.g. the media stream MAY receive treatment from PLC algorithms). The answering entity MUST re-generate all the RTP header fields as it would when transmitting media. The answering entity MAY choose to encode the loopback media according to any of the media descriptions supported by the offering entity. Furthermore, in cases where the same media @@ -380,68 +383,66 @@ 3611 [RFC3611]. 8. Examples This section provides examples for media descriptions using SDP for different scenarios. The examples are given for SIP-based transactions and are abbreviated and do not show the complete signaling for convenience. 8.1 Offer for specific media loopback type - 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 + c=IN IP4 192.168.0.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-source The client is offering to source the media and expects the server to mirror the RTP stream per rtp-media-loopback loopback type. 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 + c=IN IP4 192.168.0.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-mirror The server is accepting to mirror the media from the client at the media level. 8.2 Offer for choice of media loopback type 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 + c=IN IP4 192.168.0.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback rtp-pkt-loopback a=loopback-source - The client is offering to source the media and expects the server to mirror the RTP stream at either the media or rtp level. 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 @@ -438,60 +439,60 @@ The client is offering to source the media and expects the server to mirror the RTP stream at either the media or rtp level. 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 + c=IN IP4 192.168.0.12/127 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 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 + c=IN IP4 192.168.0.12/127 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 + c=IN IP4 192.168.0.12/127 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 @@ -499,42 +500,41 @@ 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 + c=IN IP4 192.168.0.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-source The client is offering to source the media and expects the server to mirror the RTP stream at the media level. 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 + c=IN IP4 192.168.0.12/127 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. 8.5 Response to INVITE request rejecting loopback media with rtp-start-loopback A client sends an INVITE request with SDP which looks like: v=0 @@ -535,42 +535,42 @@ 8.5 Response to INVITE request rejecting loopback media 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 + c=IN IP4 192.168.0.12/127 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 + c=IN IP4 192.168.0.12/127 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. @@ -569,41 +569,41 @@ 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 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. + is limited by the server. 10. IANA Considerations There are no IANA considerations associated with this specification. 11. Acknowledgements - The authors wish to thank Flemming Andreasen, Jeff Bernstein, Paul - Kyzivat, and Dave Oran for their comments and suggestions. + The authors wish to thank Nagarjuna Venna, Flemming Andreasen, Jeff + Bernstein, Paul Kyzivat, and Dave Oran for their comments and + suggestions. 12. 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. @@ -634,49 +635,46 @@ 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 - Flextronics Software Systems - 11717 Exploration Lane - Germantown, MD 20876 + Hughes Systique Corp. + 15245 Shady Grove Rd, Ste 330 + Rockville MD 20850 US - Phone: +1 301 212 7860 - EMail: arjun.roy@flextronicssoftware.com - URI: http://www.flextronicssoftware.com/ + Phone: +1 301 527 1629 + EMail: arjun@hsc.com + URI: http://www. hsc.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/ Nathan Stratton - BroadVoice - 900 Chelmsford Street - Tower Three - Lowell, MA 01851 - US + + 663 Salem St. + Lynnfield, MA 01940 Phone: +1 410 908 7587 EMail: nathan@robotics.net - URI: http://www.broadvoice.com/ + URI: http://www.robotics.net/ IPR Disclosure Acknowledgement 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 @@ -701,20 +699,20 @@ 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 (2005). + Copyright (C) The Internet Society (2006). 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.