--- 1/draft-ietf-mmusic-media-loopback-11.txt 2010-02-16 19:10:57.000000000 +0100 +++ 2/draft-ietf-mmusic-media-loopback-12.txt 2010-02-16 19:10:58.000000000 +0100 @@ -1,28 +1,28 @@ Internet Draft K. Hedayat - Expires: March 7, 2010 EXFO + Expires: June 30, 2010 EXFO N. Venna EXFO P. Jones Cisco Systems, Inc. A. Roychowdhury Hughes Systique Corp. C. SivaChelvan Cisco Systems, Inc. N. Stratton BlinkMind, Inc. - October 7, 2009 + January 30, 2010 An Extension to the Session Description Protocol (SDP) for Media Loopback - draft-ietf-mmusic-media-loopback-11 + draft-ietf-mmusic-media-loopback-12 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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. @@ -32,21 +32,21 @@ 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 August 18, 2009. + This Internet-Draft will expire on June 30, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -80,51 +80,55 @@ Table of Contents 1. Introduction .................................................. 3 2. Terminology ................................................... 4 3. Offering Entity Behavior ...................................... 4 4. Answering Entity Behavior ..................................... 4 5. SDP Constructs Syntax ......................................... 5 5.1 Loopback Type Attribute ................................... 5 5.2 Loopback Mode Attribute ................................... 6 - 5.3 Generating the Offer for Loopback Session ................. 7 - 5.4 Generating the Answer for Loopback Session ................ 8 - 5.5 Offerer Processing of the Answer ......................... 10 - 5.6 Modifying the Session .................................... 10 + 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 .......................... 9 + 5.6 Modifying the Session ..................................... 9 + 5.7 Priming the loopback pump ................................. 9 6. RTP Requirements ............................................. 10 7. Payload formats for Packet loopback .......................... 11 7.1 Encapsulated Payload format .............................. 11 7.2 Direct loopback RTP payload format ....................... 13 - 8. RTCP Requirements ............................................ 15 - 9. Congestion Control ........................................... 15 - 10. Examples .................................................... 15 - 10.1 Offer for specific media loopback type .................. 15 - 10.2 Offer for choice of media loopback type ................. 16 - 10.3 Offer for choice of media loopback type with - rtp-start-loopback ........................................... 17 - 10.4 Response to INVITE request rejecting loopback media ..... 18 - 10.5 Response to INVITE request rejecting loopback media with - rtp-start-loopback ........................................... 19 - 11. Security Considerations ..................................... 20 - 12. Implementation Considerations ............................... 20 - 13. IANA Considerations ......................................... 20 - 13.1 SDP Attributes .......................................... 20 - 13.2 MIME Types .............................................. 21 - 14. Acknowledgements ............................................ 30 - 15. Normative References ........................................ 30 + 8. Payload formats for Priming the Loopback Pump ................ 15 + 8.1 Usage of RTP Header fields ............................... 15 + 8.2 Usage of SDP ............................................. 15 + 9. RTCP Requirements ............................................ 15 + 10. Congestion Control .......................................... 16 + 11. Examples .................................................... 16 + 11.1 Offer for specific media loopback type .................. 16 + 11.2 Offer for choice of media loopback type ................. 17 + 11.3 Offer for choice of media loopback type with loopback + primer ....................................................... 18 + 11.4 Response to INVITE request rejecting loopback media ..... 19 + 11.5 Response to INVITE request rejecting loopback media with + loopback primer payload type ................................. 20 + 12. Security Considerations ..................................... 20 + 13. Implementation Considerations ............................... 21 + 14. IANA Considerations ......................................... 21 + 14.1 SDP Attributes .......................................... 21 + 14.2 MIME Types .............................................. 22 + 15. Acknowledgements ............................................ 35 + 16. Normative References ........................................ 36 1. Introduction 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, Real-time Text or Video over IP session. A way to achieve @@ -183,132 +187,89 @@ 5.1 Loopback Type Attribute The loopback type is a property media attribute with the following syntax: a=loopback: Following is the Augmented BNF [RFC5234] for loopback-type: - loopback-type = loopback-type-choices | loopback-type-choice-3 - loopback-choices = loopback-type-choice-1 | loopback-type-choice-2 - | loopback-type-choice-1 1*space loopback-type-choice-2 | - loopback-type-choice-2 1*space loopback-type-choice-1 - loopback-type-choice-1 = "rtp-pkt-loopback" - loopback-type-choice-2 = "rtp-media-loopback" - loopback-type-choice-3 = "rtp-start-loopback" + loopback-type = loopback-choice [1*SP loopback-choice] + loopback-choice = loopback-type-pkt / loopback-type-media + loopback-type-pkt = "rtp-pkt-loopback" + loopback-type-media = "rtp-media-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. + loopback-type values are rtp-pkt-loopback, and rtp-media-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. In this mode the RTP packets are looped back with a new payload type and format. Section 7 describes the payload formats that MUST be used for this type of loopback. 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 loopback-source is blocked by a network - element until the loopback-mirror starts transmitting packets. - - Loopback-source and loopback-mirror are loopback modes defined in - section 5.2. 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 loopback-source's packets are dropped by the - RTP relay until the loopback-mirror 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 loopback-mirror prior to the - loopback process for the purpose of setting media state within the - network. In the presence of this loopback attribute the - loopback-mirror will transmit media, according to the description - that contains this attribute, until it receives media from the - loopback-source. The loopback-mirror MAY include this attribute in - the answer if it is not present in the offer. This may be - necessary if the loopback-mirror is aware of NAT's, firewalls, or - RTP relays on the path of the call. In this case the loopback- - source MUST accept media according to rtp-start-loopback attribute. - After the first media packet is received from the loopback-source, - the loopback-mirror 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 loopback-source 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 are additional mode attributes like sendonly, recvonly, etc. The syntax of the loopback mode media attribute is: 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 receiver for - transmission in the mirrored stream unless rtp-start-loopback is - requested by the loopback-source or included in the response by + transmission in the mirrored stream unless the loopback primer + payload type (described in Section 8 of this document) is requested + by the loopback-source or included in the response by loopback-mirror. - is a media format description. The format descrption has the + is a media format description. The format description has the semantics as defined in section 5.14 of RFC 4566[RFC4566]. When loopback-mode is specified as loopback-source, the media format corresponds to the RTP payload types the source is willing to send. When loopback-mode is specified as loopback-mirror, the media format corresponds to the RTP payload types the mirror is willing to receive. The payload types specified in m= line for a loopback-source specify the payloads the source is willing to receive. Similarly, for the loopback-mirror these payload types specify the payloads it is willing to send. - The loopback mode attribute does not apply to rtp-start-loopback - 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: m=audio 41352 RTP/AVP 0 8 + Example: m=audio 41352 RTP/AVP 0 8 100 a=loopback:rtp-media-loopback - a=loopback-source:0 8 + a=loopback-source:0 8 100 + a=rtpmap:0 pcmu/8000 + a=rtpmap:8 pcma/8000 + a=rtpmap:100 G7221/16000/1 Note: A loopback offer in a given media description MUST NOT contain the standard mode attributes sendonly, recvonly, sendrecv or inactive. The loopback-mode attributes (loopback-source and loopback-mirror) replace the standard attributes. 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 are accepted by the answerer. The answerer SHOULD give preference to the first loopback-type in the SDP offer. @@ -426,20 +387,48 @@ target UA. 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. + 5.7 Priming the loopback pump + In certain scenarios it is possible that the media transmitted by + the loopback-source is blocked by a network element until the + loopback-mirror 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 loopback-source's + packets are dropped by the RTP relay until the loopback-mirror has + started transmitting media and the media state within the RTP relay + is established. This results in a chicken and egg scenario as the + looback-mirror cannot transmit any media until it receives the + media packets from the loopback-source but for the loopback-mirror + to receive any packets it needs to send one first. In order to + resolve this dilemma, Section 8 introduces a new payload type whose + sole purpose is to establish the media state in the intermediate + devices. In the presence of this payload type, the loopback-mirror + will transmit media according to the payload description until it + receives media from the loopback-source. The loopback-mirror MAY + include this payload type in the answer if it is not present in the + offer. This may be necessary if the loopback-mirror is aware of + NAT's, firewalls, or RTP relays on the path of the call. In this + case the loopback-source MUST accept media corresponding to this + payload type. After the first media packet is received from the + loopback-source, the loopback-mirror MUST terminate the + transmission of media for this payload type and MUST start looping + back media as defined by the other loopback attributes present in + the offer. + 6. RTP Requirements 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 using either the encapsulated RTP payload format or the direct loopback RTP payload format as defined in section 7 of this specification. An answering entity that is compliant to this specification and accepting a media with rtp-media-loopback loopback-type MUST @@ -485,26 +474,27 @@ used or more likely signaled dynamically out-of-band (e.g., using SDP; section 7.1.3 defines the name binding). Marker (M) bit: If the received RTP packet is looped back in multiple RTP packets, the M bit is set to 1 in the last packet, otherwise it is set to 0. Extension (X) bit: Defined by the RTP Profile used. Sequence Number: The RTP sequence number SHOULD be generated by the - loopback-mirror in the usual manner with a constant random offset. + loopback-mirror in the usual manner with a constant random offset + as described in RFC 3550 [RFC3550]. Timestamp: The RTP timestamp denotes the sampling instant for when the loopback-mirror is transmitting this packet to the loopback- - source. The RTP timestamp MUST be based on the same clock used by - the loopback-source. The initial value of the timestamp SHOULD be + source. The RTP timestamp MUST use the same clock rate used by the + loopback-source. The initial value of the timestamp SHOULD be random for security reasons (see Section 5.1 of RFC 3550 [RFC3550]). SSRC: set as described in RFC 3550 [RFC3550]. CC and CSRC fields are used as described in RFC 3550 [RFC3550]. 7.1.2 RTP Payload Structure The RTP header in the encapsulated packet MUST be followed by the @@ -529,26 +519,27 @@ | contributing source (CSRC) identifiers | | .... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 12 octets after the receive timestamp are identical to the RTP header in the received packet except for the first 4 bits of the first octet. Receive Timestamp: 32 bits - The Receieve timestamp denotes the sampling instant for when the - last octet of the media packet that is being encapsulated by the - loopback-mirror is received from the loopback-source. The Receive - timestamp MUST be based on the same clock used by the loopback- - source. The initial value of the timestamp SHOULD be random for - security reasons (see Section 5.1 of RFC 3550 [RFC3550]). + The Receive timestamp denotes the sampling instant for when the + last octet of the received media packet that is being encapsulated + by the loopback-mirror is received from the loopback-source. The + Receive timestamp MUST be based on the same clock used by the + loopback-source. The initial value of the timestamp SHOULD be + random for security reasons (see Section 5.1 of RFC 3550 + [RFC3550]). Fragmentation (F): 2 bits First Fragment (00) /Last Fragment (01) /No Fragmentation(10)/ Intermediate Fragment (11). This field identifies how much of the received packet is encapsulated in this packet by the loopback- mirror. If the received packet is not fragmented, this field is set to 10; otherwise the packet that contains the first fragments sets this field to 00, the packet that contains the last fragment sets this field to 01, all other packets set this field to 11. @@ -623,298 +614,331 @@ negotiated using a mechanism like SDP. There is no static payload type assignment for the stream, so dynamic payload type numbers MUST be used. The binding to the name is indicated by an rtpmap attribute. The name used in this binding is "rtploopback". The following is an example SDP fragment for encapsulated RTP. m=audio 41352 RTP/AVP 112 a=rtpmap:112 rtploopback/8000 - 8. RTCP Requirements + 8. Payload format for Priming the Loopback Pump + + The sole purpose of the payload format described in this section is + to prime the loopback pump in cases where the loopback process + cannot start because of intermediate devices in the network as + described in Section 5.7. + + 8.1 Usage of RTP Header fields + + Payload Type (PT): The assignment of an RTP payload type for this + packet format is outside the scope of this document; it is either + specified by the RTP profile under which this payload format is + used or more likely signaled dynamically out-of-band (e.g., using + SDP; section 8.2 defines the name binding). + + All other fields are set as described in RFC 3550 [RFC3550]. + + 8.2 Usage of SDP + + The payload type number for the loopback primer stream can be + negotiated using a mechanism like SDP. There is no static payload + type assignment for the loopback primer stream, so dynamic payload + type numbers MUST be used. The binding to the name is indicated by + an rtpmap attribute. The name used in this binding is + "loopbkprimer". + + The following is an example SDP fragment for loopback primer RTP + stream. + + m=audio 41352 RTP/AVP 112 + a=rtpmap:112 loopbkprimer/8000 + + 9. RTCP Requirements The use of the loopback attribute is intended for monitoring of media quality of the session. Consequently the media performance information should be exchanged between the offering and the answering entities. An offering or answering entity that is compliant to this specification SHOULD support RTCP per [RFC3550] and RTCP-XR per RFC 3611 [RFC3611]. Furthermore, if the client or the server choose to support RTCP-XR, they SHOULD support RTCP-XR Loss RLE report block, Duplicate RLE report block, Statistics Summary report block, and VoIP Metric Reports Block per sections 4.1, 4.2, 4.6, and 4.7 of RFC 3611 [RFC3611]. The client and the server MAY support other RTCP-XR reporting blocks as defined by RFC 3611 [RFC3611]. - 9. Congestion Control + 10. Congestion Control All the participants in a loopback session SHOULD implement congestion control mechanisms as defined by the RTP profile under which the loopback mechanism is implemented. For audio video profiles, implementations SHOULD conform to the mechanism defined in Section 2 of RFC 3551. - 10. Examples + 11. 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. - 10.1 Offer for specific media loopback type + 11.1 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-source:0 + a=rtpmap:0 pcmu/8000 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49270 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-mirror:0 + a=rtpmap:0 pcmu/8000 The server is accepting to mirror the media from the client at the media level. - 10.2 Offer for choice of media loopback type + 11.2 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49170 RTP/AVP 0 112 113 a=loopback:rtp-media-loopback rtp-pkt-loopback a=loopback-source:0 + a=rtpmap:0 pcum/8000 a=rtpmap:112 encaprtp/8000 a=rtpmap:113 rtploopback/8000 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49270 RTP/AVP 112 a=loopback:rtp-pkt-loopback a=loopback-mirror:0 + a=rtpmap:0 pcmu/8000 a=rtpmap:112 encaprtp/8000 The server is accepting to mirror the media from the client at the packet level using the encapsulated RTP payload format. - 10.3 Offer for choice of media loopback type with rtp-start-loopback + 11.3 Offer for choice of media loopback type with loopback primer A client sends an INVITE request with SDP which looks like: v=0 o=user1 2890844526 2890842807 IN IP4 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 - m=audio 49170 RTP/AVP 0 112 113 + m=audio 49170 RTP/AVP 0 112 113 114 a=loopback:rtp-media-loopback rtp-pkt-loopback a=loopback-source:0 + a=rtpmap:0 pcmu/8000 a=rtpmap:112 encaprtp/8000 a=rtpmap:113 rtploopback/8000 - m=audio 49170 RTP/AVP 100 - a=loopback:rtp-start-loopback + a=rtpmap:114 loopbkprimer/8000 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. + packets from the server per media described with the loopbkprimer + payload type. A server sends a response with SDP which looks like: v=0 o=user1 2890844526 2890842807 IN IP4 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49270 RTP/AVP 113 a=loopback:rtp-pkt-loopback - a=loopback-mirror:0 + a=loopback-mirror:0 114 + a=rtpmap:0 pcmu/8000 a=rtpmap:113 rtploopback/8000 - m=audio 49270 RTP/AVP 100 - a=rtpmap:100 pcmu/8000 - a=loopback:rtp-start-loopback + a=rtmpa:114 loopbkprimer/8000 The server is accepting to mirror the media from the client at the packet level using the direct loopback RTP payload format. The server is also accepting to source media until it receives media packets from the client. - 10.4 Response to INVITE request rejecting loopback media + 11.4 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 49170 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-source:0 + a=rtpmap:0 pcmu/8000 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 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 0 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-mirror:0 + a=rtpmap:0 pcmu/8000 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. - 10.5 Response to INVITE request rejecting loopback media with - rtp-start-loopback + 11.5 Response to INVITE request rejecting loopback media with loopback + primer payload type A client sends an INVITE request with SDP which looks like: v=0 o=user1 2890844526 2890842807 IN IP4 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 - m=audio 49170 RTP/AVP 0 + m=audio 49170 RTP/AVP 0 100 a=loopback:rtp-media-loopback a=loopback-source:0 - m=audio 49170 RTP/AVP 100 - a=loopback:rtp-start-loopback + a=rtpmap:0 pcum/8000 + a=rtpmap:100 loopbkprimer/8000 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. + the server using the loopbkprimer payload type. A server sends a response with SDP which looks like: v=0 o=user1 2890844526 2890842807 IN IP4 192.0.2.11 s=Example i=An example session e=user@example.com c=IN IP4 192.0.2.12/127 t=0 0 m=audio 0 RTP/AVP 0 a=loopback:rtp-media-loopback a=loopback-mirror:0 - 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. - 11. Security Considerations + 12. 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 is limited by the server. - 12. Implementation Considerations + 13. Implementation Considerations The media loopback approach described in this document is a complete solution that would work under all scenarios. However, it is believed that the solution may not be light-weight enough for the common case. In light of this concern, this section clarifies which features of the loopback proposal MUST be implemented for all implementations and which features MAY be deferred if the complete solution is not desired. All implementations MUST support the rtp-pkt-loopback option for loopback-type attribute. In addition, for the loopback-mode attribute, all implementations of an offerer MUST at a minimum be able to act as a loopback-source. All implementation MUST also at a - minimum support the direct media loopback payload type. Remaining - attribute values including rtp-media-loopback and - rtp-start-loopback MAY be implemented in complete implementations - of this draft. + minimum support the direct media loopback payload type. The rtp- + media-loopback attribute MAY be implemented in complete + implementations of this draft. - 13. IANA Considerations + 14. IANA Considerations - 13.1 SDP Attributes + 14.1 SDP Attributes This document defines three new media-level SDP attributes. IANA has registered the following attributes: Contact name: Kaynam Hedayat . Attribute name: "loopback". - Type of attribute: Media level. Subject to charset: No. Purpose of attribute: The 'loopback' attribute is used to indicate the type of media loopback. Allowed attribute values: The parameters to 'loopback' may be - one or more of "rtp-pkt-loopback," - "rtp-media-loopback," and - "rtp-start-loopback". See section 5 + one or more of "rtp-pkt-loopback" and + "rtp-media-loopback". See section 5 of this document for syntax. Contact name: Kaynam Hedayat . Attribute name: "loopback-source". Type of attribute: Media level. + Subject to charset: No. Purpose of attribute: The 'loopback-source' attribute specifies that the sender is the media source and expects the receiver to act as a loopback-mirror. Allowed attribute values: The parameter to 'loopback-source' is a media format ("") description as defined in RFC 4566 Section 5.14. Contact name: Kaynam Hedayat @@ -923,31 +947,32 @@ Type of attribute: Media level. Subject to charset: No. Purpose of attribute: The 'loopback-mirror' attribute specifies that the receiver will mirror (echo) all received media back to the sender of the RTP stream. Allowed attribute values: The parameter to 'loopback-mirror' is a media format ("") description as defined in RFC 4566 Section 5.14. - 13.2 MIME Types + 14.2 MIME Types The IANA has registered the following MIME types: - 13.2.1 audio/encaprtp + 14.2.1 audio/encaprtp To: ietf-types@iana.org Subject: Registration of media type audio/encaprtp Type name: audio + Subtype name: encaprtp Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none @@ -947,21 +972,21 @@ rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -979,42 +1004,42 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.2 video/encaprtp + 14.2.2 video/encaprtp To: ietf-types@iana.org Subject: Registration of media type video/encaprtp Type name: video Subtype name: encaprtp Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1032,30 +1057,29 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.3 text/encaprtp + 14.2.3 text/encaprtp To: ietf-types@iana.org Subject: Registration of media type text/encaprtp Type name: text Subtype name: encaprtp - Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. @@ -1053,21 +1077,21 @@ rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1085,24 +1109,23 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.4 application/encaprtp + 14.2.4 application/encaprtp To: ietf-types@iana.org - Subject: Registration of media type application/encaprtp Type name: application Subtype name: encaprtp Required parameters: rate:RTP timestamp clock rate, which is equal to the @@ -1107,21 +1130,21 @@ rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1139,42 +1162,42 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.5 audio/rtploopback + 14.2.5 audio/rtploopback To: ietf-types@iana.org Subject: Registration of media type audio/rtploopback Type name: audio Subtype name: rtploopback Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1186,47 +1210,48 @@ EMail: kaynam.hedayat@exfo.com Intended usage: COMMON Restrictions on usage: This media type depends on RTP framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: + Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.6 video/rtploopback + 14.2.6 video/rtploopback To: ietf-types@iana.org Subject: Registration of media type video/rtploopback Type name: video Subtype name: rtploopback Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1244,44 +1269,45 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.7 text/rtploopback + 14.2.7 text/rtploopback To: ietf-types@iana.org Subject: Registration of media type text/rtploopback Type name: text Subtype name: rtploopback Required parameters: rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none + Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. Additional information: none @@ -1296,21 +1322,21 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 13.2.8 application/rtploopback + 14.2.8 application/rtploopback To: ietf-types@iana.org Subject: Registration of media type application/rtploopback Type name: application Subtype name: rtploopback @@ -1318,21 +1344,21 @@ rate:RTP timestamp clock rate, which is equal to the sampling rate. The typical rate is 8000; other rates may be specified. Optional parameters: none Encoding considerations: This media type is framed binary data. - Security considerations: See Section 11 of this document. + Security considerations: See Section 12 of this document. Interoperability considerations: none Published specification: This MIME type is described fully within this document. Applications which use this media type: Applications wishing to monitor and ensure the quality of transport to the edge of a given VoIP, Real-Time Text or Video Over IP Service. @@ -1350,31 +1376,242 @@ framing, and hence is only defined for transfer via RTP. Transfer within other framing protocols is not defined at this time. Author: Kaynam Hedayat. Change controller: IETF Audio/Video Transport working group delegated from the IESG. - 14. Acknowledgements + 14.2.9 audio/loopbkprimer + + To: ietf-types@iana.org + + Subject: Registration of media type audio/loopbkprimer + + Type name: audio + + Subtype name: loopbkprimer + + Required parameters: + + rate:RTP timestamp clock rate, which is equal to the + sampling rate. The typical rate is 8000; other rates + may be specified. + + Optional parameters: none + + Encoding considerations: This media type is framed + binary data. + + Security considerations: See Section 12 of this document. + + Interoperability considerations: none + + Published specification: This MIME type is described fully + within this document. + + Applications which use this media type: Applications wishing + to monitor and ensure the quality of transport to the + edge of a given VoIP, Real-Time Text or Video Over IP + Service. + + Additional information: none + + Person & email address to contact for further information: + + Kaynam Hedayat + EMail: kaynam.hedayat@exfo.com + + Intended usage: COMMON + + Restrictions on usage: This media type depends on RTP + framing, and hence is only defined for transfer via + RTP. Transfer within other framing protocols is not + defined at this time. + + Author: + Kaynam Hedayat. + + Change controller: IETF Audio/Video Transport working + group delegated from the IESG. + + 14.2.10 video/loopbkprimer + + To: ietf-types@iana.org + + Subject: Registration of media type video/loopbkprimer + + Type name: video + + Subtype name: loopbkprimer + + Required parameters: + + rate:RTP timestamp clock rate, which is equal to the + sampling rate. The typical rate is 8000; other rates + may be specified. + + Optional parameters: none + + Encoding considerations: This media type is framed + binary data. + + Security considerations: See Section 12 of this document. + + Interoperability considerations: none + + Published specification: This MIME type is described fully + within this document. + + Applications which use this media type: Applications wishing + to monitor and ensure the quality of transport to the + edge of a given VoIP, Real-Time Text or Video Over IP + Service. + + Additional information: none + + Person & email address to contact for further information: + + Kaynam Hedayat + EMail: kaynam.hedayat@exfo.com + + Intended usage: COMMON + + Restrictions on usage: This media type depends on RTP + framing, and hence is only defined for transfer via + RTP. Transfer within other framing protocols is not + defined at this time. + + Author: + Kaynam Hedayat. + + Change controller: IETF Audio/Video Transport working + group delegated from the IESG. + + 14.2.11 text/loopbkprimer + + To: ietf-types@iana.org + + Subject: Registration of media type text/loopbkprimer + + Type name: text + + Subtype name: encaprtp + + Required parameters: + + rate:RTP timestamp clock rate, which is equal to the + sampling rate. The typical rate is 8000; other rates + may be specified. + + Optional parameters: none + Encoding considerations: This media type is framed + binary data. + + Security considerations: See Section 12 of this document. + + Interoperability considerations: none + + Published specification: This MIME type is described fully + within this document. + + Applications which use this media type: Applications wishing + to monitor and ensure the quality of transport to the + edge of a given VoIP, Real-Time Text or Video Over IP + Service. + + Additional information: none + + Person & email address to contact for further information: + + Kaynam Hedayat + EMail: kaynam.hedayat@exfo.com + + Intended usage: COMMON + + Restrictions on usage: This media type depends on RTP + framing, and hence is only defined for transfer via + RTP. Transfer within other framing protocols is not + defined at this time. + + Author: + Kaynam Hedayat. + + Change controller: IETF Audio/Video Transport working + group delegated from the IESG. + + 14.2.12 application/loopbkprimer + + To: ietf-types@iana.org + + Subject: Registration of media type + application/loopbkprimer + + Type name: application + + Subtype name: loopbkprimer + + Required parameters: + + rate:RTP timestamp clock rate, which is equal to the + sampling rate. The typical rate is 8000; other rates + may be specified. + + Optional parameters: none + + Encoding considerations: This media type is framed + binary data. + + Security considerations: See Section 12 of this document. + + Interoperability considerations: none + + Published specification: This MIME type is described fully + within this document. + + Applications which use this media type: Applications wishing + to monitor and ensure the quality of transport to the + edge of a given VoIP, Real-Time Text or Video Over IP + Service. + + Additional information: none + + Person & email address to contact for further information: + + Kaynam Hedayat + EMail: kaynam.hedayat@exfo.com + + Intended usage: COMMON + + Restrictions on usage: This media type depends on RTP + framing, and hence is only defined for transfer via + RTP. Transfer within other framing protocols is not + defined at this time. + + Author: + Kaynam Hedayat. + + Change controller: IETF Audio/Video Transport working + group delegated from the IESG. + + 15. Acknowledgements The authors wish to thank Nagarjuna Venna, Flemming Andreasen, Jeff Bernstein, Paul Kyzivat, and Dave Oran for their comments and suggestions. - 15. Normative References + 16. 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, June 2002. [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with the Session Description Protocol (SDP)", RFC 3264, June 2002. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.