Annotated Example SDP for WebRTC

A typical web based real-time multimedia communication session can be characterized as below: It has zero or more Audio only, Video only or Audio/Video RTP Sessions, may contain zero or more non-media data sessions, All the sessions are secured with DTLS-SRTP, Supports NAT traversal using ICE mechanism, Provides RTCP based feedback mechanisms, Sessions can be over IPv4-only or IPv6-only or dual-stack based clients, Supports BUNDLE based grouping of media streams over a single 5-tuple transport.

The examples given in this document follow the conventions listed below: In all the examples, Alice and Bob are assumed to be the WebRTC peers. It is assumed that for most of the examples, the support for is established a priori either out-of-band or as a consequence of successful Offer/Answer negotiation between Alice and Bob, unless explicitly stated otherwise. Call-flow diagrams that accompany the use-cases capture only the prominent aspects of the system behavior and intentionally are not detailed to improve readability. Even though the call-flow diagrams show SDP being exchanged between the parties, it doesn't represent the only way an WebRTC setup is expected to work. Other approaches may involve WebRTC applications to exchange the media setup information via non-SDP mechanisms as long as they conform to the API specification. The SDP examples deviate from actual on-the-wire SDP notation in several ways. This is done to facilitate readability and to conform to the restrictions imposed by the RFC formatting rules. Visual markers/Empty lines in any SDP example are inserted to make functional divisions in the SDP clearer, and are not actually part of the SDP syntax. Excepting the above two conventions, line endings are to be interpreted as <CR><LF> pairs (that is, an ASCII 13 followed by an ASCII 10). Against each SDP line, pointers to the appropriate RFCs are provided for further informational reference. Also an attempt has been made to provide explanatory notes to enable better understanding of the SDP usage, wherever appropriate. The following SDP details are common across all the use-cases defined in this document unless mentioned otherwise. DTLS fingerprint for SRTP (a=fingerprint) RTP/RTCP Multiplexing (a=rtcp-mux) RTCP Feedback support (a=rtcp-fb) Host and server-reflexive candidate lines (a=candidate) DTLS-SRTP Setup framework parameters (a=setup) RTCP attribute (a=rtcp) RTP header extension indicating audio-levels from client to the mixer For specific details, readers must refer to specification. The term "Session" is used rather loosely in this document to refer to either a "Communication Session" or a "RTP Session" or a "RTP Stream" depending on the context. Payload type 109 is usually used for OPUS, 0 for PCMU, 8 for PCMA, 99 for H.264 and 120 for VP8 in most of the examples to maintain uniformity. The IP Address:Port combinations '192.0.2.4:61665' (host) and '203.0.113.141:54609' (Server Reflexive) is typically used for Alice. The IP Address:Port combinations '198.51.100.7:51556' (host) and '203.0.113.77:49203' (Server Reflexive) is typically used for Bob. The IPv6 addresses 2001:db8:8101:3a55:4858:a2a9:22ff:99b9 and 2001:db8:30c:1266:5916:3779:22f6:77f7 are used to represent Alice and Bob host addresses respectively. In actual use the values that represent SSRCs, ICE candidate foundations, WebRTC Mediastream, MediaStreamTrack Ids values shall be much larger and/or random than the ones shown in the examples. tls-id attribute values 89J2LRATQ3ULA24G9AHWVR31VJWSLB68 and UKA29UQLTF69OJW4WNPNUO2Y0GF1FJOZ are used for Alice. The values CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 and 9AIFS8AQ009IXF5D6QQUJ7P8BXPEZJ8G are used for Bob. identity attribute values are split across multiple lines to enhance readability, thus any line breaks and indentations in the value must be ignored. SDP attributes in the examples closely follow the checklist defined in section .

This common scenario shows SDP for secure two-way audio session with Alice offering Opus, PCMU, PCMA and Bob accepting all the offered audio codecs. This example also shows the endpoints being compliant by including "ice2" ice-options attribute.

| | | | | | Answer(Audio:Opus,PCMU,PCMA) | |<------------------------------------| | | | | |Two-way Opus Audio (preferred-codec) | |.....................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 a=identity:eyJpZHAiOnsiZG9tYWluIjoibmlpZi5odSIsInByb3RvY29sIjoiaWRwLmh0bWwifSwiYXNzZXJ0a W9uIjoiZXlKaGJHY2lPaUpTVXpJMU5pSXNJblI1Y0NJNklrcFhVeUo5LmV5SmpiMjUwWlc1MGN5STZleUptYVc1b lpYSndjbWx1ZENJNlczc2lZV3huYjNKcGRHaHRJam9pYzJoaExUSTFOaUlzSW1ScFoyVnpkQ0k2SWprek9rTXdPa kl6T2pKR09rRXlPakF3T2pBd09qQkVPalV4T2tGRE9rUXlPalUwT2pZMU9rWTBPak5DT2pkRU9qa3lPa1JET2pnN E9qTXpPalV4T2pJek9qUXdPamN5T2preE9qZ3pPalZDT2pBeE9qSkdPalV3T2pjNE9qTkdJbjFkZlN3aWFXUmxib lJwZEhraU9pSnRhWE5wUUc1cGFXWXVhSFVpZlEuSTVQdGhKNFFDT05TOFVXd25OOUh3MEdaTDl3d0RBVGRrTWtFW llmdlNVTTJ6Umd5R09WSGgzRmpnc2FPZklkRnFsNUx6azBFbndVOTNQOUlCQ0xZOWtia3V1c0V1S25YRGVNLTNIN WFmdTJvZl9CTlZjUnB3MmdBdlNBbVR6SlltcEpqMFEtdmV0TmtVT1huZE9HLUIzT3ZGb3QwZVNENlZSNUdhb2wyc GduS3FSTktOd3dacEZ1eUZZbFRodHJIdGNiT19WV3o4QnZpTThKS25OdExWd1JxNUhMX2ZLTlRCNzFDYkoyWmh5W XU1UEdwWDhXcXJMWC1ybm5YSFY3RnhoTTh5OHdrLWd5cnRZazVnbFlZeUFrcTVqZklSXzRzWER5d19Qc1BWTW1aZ XltenVGV3BQTzVFWlJYR0ZpRjFET0o4Q0Q3Z3Zta2dUdlBXSWpkemtBIn0= Section 7.4 of ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 - Opus Codec 48khz, 2 channels a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:074c6550 - ICE user fragment a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - ICE password a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - DTLS Fingerprint for SRTP a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux - Alice can perform RTP/RTCP Muxing a=rtcp:60065 IN IP4 203.0.113.141 a=rtcp-rsize - Alice intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level Alice supports RTP header extension to indicate audio levels a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host - RTP Host Candidate a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 - RTP Server Reflexive ICE Candidate a=candidate:0 2 UDP 2122194687 192.0.2.4 61667 typ host - RTCP Host Candidate a=candidate:1 2 UDP 1685987071 203.0.113.141 60065 typ srflx raddr 192.0.2.4 rport 61667 - RTCP Server Reflexive ICE Candidate a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 a=identity:ew0KICAiaWRwIjp7DQogICAgImRvbWFpbiI6ICJjaXNjb3NwYXJrLmNvbSIsDQogICAg InByb3RvY29sIjogImRlZmF1bHQiDQogIH0sDQogICJhc3NlcnRpb24iOiAibEp3WkVocmFVOXBTblJo V0U1d1VVYzFjR0ZYV1hWaFNGVnBabEV1U1RWUWRHaEtORkZEVDA1VE9GVlhkMjVPT1VoM01FZGFURGwz ZDBSQlZHUnJUV3RGVw0KICAgICAgICAgICAgICBsbG1kbE5WVFRKNlVtZDVSMDlXU0dnelJtcG5jMkZQ Wmtsa1JuRnNOVXg2YXpCRmJuZFZPVE5RT1VsQ1EweFpPV3RpYTNWMWMwVjFTMjVZUkdWTkxUTklODQog ICAgICAgICAgICAgIFdGbWRUSnZabDlDVGxaalVuQjNNbWRCZGxOQmJWUjZTbGx0Y0VwcU1GRXRkbVYw VG10VlQxaHVaRTlITFVJelQzWkdiM1F3WlZORU5sWlNOVWRoYjJ3eWMNCiAgICAgICAgICAgICAgR2R1 UzNGU1RrdE9kM2RhY0VaMWVVWlpiRlJvZEhKSWRHTmlUMTlXVjNvNFFuWnBUVGhLUzI1T2RFeFdkMUp4 TlVoTVgyWkxUbFJDTnpGRFlrb3lXbWg1VyINCn0= Section 7.4 of ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Bob can send and recv audio a=rtpmap:109 opus/48000/2 Opus Codec a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:05067423 - ICE user fragment a=ice-pwd:1747d1ee3474a28a397a4c3f3af08a068 - ICE password parameter a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - DTLS Fingerprint for SRTP a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing on port 49203 a=rtcp-rsize - Bob intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level Bob supports audio level RTP header extension as well a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 198.51.100.7 51556 typ host - RTP/RTCP Host ICE Candidate a=candidate:1 1 UDP 1685987071 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 - RTP/RTCP Server Reflexive ICE Candidate a=end-of-candidates

Alice and Bob establish a two-way audio and video session with Opus as the audio codec and H.264 as the video codec.

| | | | | | Answer(Audio:Opus,Video:H.264) | |<-------------------------------------------| | | | | | Two-way Opus Audio, H.264 Video | |............................................| | | ]]>

This section shows the IPv4 only Offer/Answer exchange. Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video - Alice wants to lip sync her audio and video sreams a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 - Opus Codec 48khz, 2 channels a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:074c6550 - ICE user fragment a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - ICE password parameter a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - DTLS Fingerprint for SRTP a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux - Alice can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize - Alice intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host - RTP/RTCP Host Candidate a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 - RTP/RTCP Server Reflexive ICE Candidate a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 99 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv - Alice can send and recv video a=rtpmap:99 H264/90000 - H.264 Video Codec a=fmtp:99 profile-level-id=4d0028;packetization-mode=1 a=rtpmap:120 VP8/90000 - VP8 video codec a=rtcp-fb:99 nack - Indicates NACK RTCP feedback support a=rtcp-fb:99 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:99 ccm fir - Full Intra Frame Request-Codec Control Message support a=rtcp-fb:120 nack - Indicates NACK RTCP feedback support a=rtcp-fb:120 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:120 ccm fir - Full Intra Frame Request-Codec Control Message support a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video - Bob agrees to do the same a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Bob can send and recv audio a=rtpmap:109 opus/48000/2 - Bob accepts only Opus Codec a=maxptime:120 a=ice-ufrag:c300d85b - ICE username frag a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 - ICE password a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - DTLS Fingerprint for SRTP a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize - Bob intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 3618095783 198.51.100.7 49203 typ host - RTP/RTCP Host ICE Candidate a=candidate:1 1 UDP 565689203 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 - RTP/RTCP Server Reflexive ICE Candidate a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 99 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv - Bob can send and recv video a=rtpmap:99 H264/90000 - Bob accepts H.264 Video Codec. a=fmtp:99 profile-level-id=4d0028;packetization-mode=1 a=rtcp-fb:99 nack - Indicates support for NACK based RTCP feedback a=rtcp-fb:99 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:99 ccm fir - Full Intra Frame Request- Codec Control Message support a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

This section captures offer/answer exchange when Alice and Bob support both IPv4 and IPv6 host addresses. Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video - Alice wants to lip sync her audio and video sreams a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 - Opus Codec 48khz, 2 channels a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:074c6550 - ICE user fragment a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - ICE password parameter a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - DTLS Fingerprint for SRTP a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux - Alice can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize - Alice intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host - RTP/RTCP Host Candidate a=candidate:0 1 UDP 2122194687 2001:db8:8101:3a55:4858:a2a9:22ff:99b9 61665 typ host - RTP/RTCP IPv6 Host Candidate a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 99 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv - Alice can send and recv video a=rtpmap:99 H264/90000 - H.264 Video Codec a=fmtp:99 profile-level-id=4d0028;packetization-mode=1 a=rtpmap:120 VP8/90000 - VP8 video codec a=rtcp-fb:99 nack - Indicates NACK RTCP feedback support a=rtcp-fb:99 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:99 ccm fir - Full Intra Frame Request-Codec Control Message support a=rtcp-fb:120 nack - Indicates NACK RTCP feedback support a=rtcp-fb:120 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:120 ccm fir - Full Intra Frame Request-Codec Control Message support a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video - Bob agrees to do the same a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Bob can send and recv audio a=rtpmap:109 opus/48000/2 - Bob accepts only Opus Codec a=maxptime:120 a=ice-ufrag:c300d85b - ICE username frag a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 - ICE password a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - DTLS Fingerprint for SRTP a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize - Bob intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 3618095783 198.51.100.7 49203 typ host - RTP/RTCP Host ICE Candidate a=candidate:0 1 UDP 3618095783 2001:db8:30c:1266:5916:3779:22f6:77f7 49203 typ host - RTP/RTCP IPv6 Host ICE Candidate a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 99 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv - Bob can send and recv video a=rtpmap:99 H264/90000 - Bob accepts H.264 Video Codec. a=fmtp:99 profile-level-id=4d0028;packetization-mode=1 a=rtcp-fb:99 nack - Indicates support for NACK based RTCP feedback a=rtcp-fb:99 nack pli - Indicates support for Picture loss Indication and NACK a=rtcp-fb:99 ccm fir - Full Intra Frame Request- Codec Control Message support a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

This scenario illustrates the SDP negotiated to setup a data-only session based on the SCTP Data Channel, thus enabling use-cases such as file-transfer, real-time game control for example.

| | | | | | Answer(DataChannel) | |<--------------------------------| | | | | | Two-way SCTP based DataChannel | |.................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE data a=ice-options:trickle a=ice-options:ice2 ****** Application m=line ********* ***************************** m=application 54609 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.141 a=mid:data a=sendrecv - Alice can send and recv non-media data a=sctp-port:5000 a=max-message-size:100000 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=ice-ufrag:074c6550 - Session Level ICE parameter a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - Session Level ICE parameter a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - Session DTLS Fingerprint for SRTP a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 1694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE data ****** Application m=line ********* ***************************** m=application 49203 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.77 a=mid:data a=sendrecv - Bob can send and recv non-media data a=sctp-port:5000 a=max-message-size:100000 a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=ice-ufrag:c300d85b - Session Level ICE username frag a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 - Session Level ICE password a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - Session DTLS Fingerprint for SRTP a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates

Alice calls Bob, but when Bob answers he places Alice on hold by setting the SDP direction attribute to a=inactive in the Answer.

| | | | | | Answer(Audio:Opus,a=inactive) | |<--------------------------------| | | | | | One-way Opus Audio | |.................................| | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 - Opus Codec 48khz, 2 channels a=maxptime:120 a=ice-ufrag:074c6550 - ICE user fragment a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - ICE password a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - DTLS Fingerprint for SRTP a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux - Alice can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=inactive - Bob puts call On Hold a=rtpmap:109 opus/48000/2 - Bob accepts Opus Codec a=maxptime:120 a=ice-ufrag:c300d85b - ICE username frag a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 - ICE password a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - DTLS Fingerprint for SRTP a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host - Host candidate a=candidate:1 1 UDP 1685987071 203.0.113.141 49203 typ srflx raddr 198.51.100.7 rport 51556 - Server Reflexive candidate a=end-of-candidates

In this example, Alice wishes to establish two separate audio streams, one for normal audio and the other for telephone-events. Alice offers first audio stream with three codecs and the other with tones (for DTMF). Bob accepts both the audio streams by choosing Opus as the audio codec and telephone-event for the other stream.

| | | | | | Answer(Audio:Opus, Audio:telephone-event) | |<--------------------------------------------------| | | | | | Opus audio stream and telephone-event stream | |...................................................| | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio dtmf a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 - Opus Codec 48khz, 2 channels a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:074c6550 - ICE user fragment a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 - ICE password parameter a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 - DTLS Fingerprint for SRTP a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux - Alice can perform RTP/RTCP Muxing a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** DTMF m=line ********* ***************************** m=audio 0 UDP/TLS/RTP/SAVPF 126 c=IN IP4 203.0.113.141 a=bundle-only a=mid:dtmf a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly - Alice can send DTMF Events a=rtpmap:126 telephone-event/8000 a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio dtmf ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Bob can send and receive Opus audio a=rtpmap:109 opus/48000/2 - Bob accepts Opus Codec a=maxptime:120 a=ice-ufrag:c300d85b - ICE username frag a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 - ICE password a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 - Fingerprint for SRTP a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing on port 49203 a=rtcp-mux-only a=rtcp-rsize - Alice intends to use reduced size RTCP for this session a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1685987071 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** DTMF m=line ********* ***************************** m=audio 0 UDP/TLS/RTP/SAVPF 126 c=IN IP4 203.0.113.77 a=bundle-only a=mid:dtmf a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly - Alice can receive DTMF events a=rtpmap:126 telephone-event/8000 a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

In this scenario Alice and Bob engage in a 1 way audio and video session with Bob receiving Alice's audio and her presentation slides as video stream.

| | | | | | (Audio:Opus, Video: VP8) | |<-----------------------------------------------------| | | | | | One-way Opus Audio, VP8 Video | |......................................................| | Bob can hear Alice and see her presentation slides.| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly - Send only audio stream a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 203.0.113.141 54609 typ host a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly - Send only video stream a=rtpmap:120 VP8/90000 a=content:slides - Alice's presentation video stream a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly - Receive only audio stream a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-mux-only a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 203.0.113.77 49203 typ host a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly a=rtpmap:120 VP8/90000 a=content:slides - presentation stream a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

In this example, since Alice is unsure of the Bob's support of the BUNDLE framework, following steps are performed in order to negotiate and setup a BUNDLE Address for the session An SDP Offer, in which the Alice assigns unique addresses to each "m=" line in the BUNDLE group, and requests the Answerer to select the Offerer's BUNDLE address. An SDP Answer, in which Bob indicates support for BUNDLE, selects the offerer's BUNDLE address, selects its own BUNDLE address and associates it with each BUNDLED m=line within the BUNDLE group. Once the Offer/Answer exchange completes, both Alice and Bob each end up using single RTP Session for both the Media Streams.

| | |Bob | |supports | |BUNDLE, | |Uses | |identical | |address | Answer(Audio:Opus Video:VP8) | |<-----------------------------------------------------| | | | 2 Way Call with Audio and Video Multiplexed | |......................................................| | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video Alice supports grouping of m=lines under BUNDLE semantics a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp:54610 IN IP4 203.0.113.141 - RTCP port different from RTP Port a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host - RTP host candidate a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 - RTP Server Reflexive candidate a=candidate:0 2 UDP 2122194687 192.0.2.4 61666 typ host - RTCP host candidate a=candidate:1 2 UDP 1685987071 203.0.113.141 54610 typ srflx raddr 192.0.2.4 rport 61666 - RTCP Server Reflexive candidate ****** Video m=line ********* ***************************** m=video 62537 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=mid:video Video m=line part of the Bundle group with a unique port number a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=ice-ufrag:6550074c a=ice-pwd:74af08a068a28a397a4c3f31747d1ee34 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:UKA29UQLTF69OJW4WNPNUO2Y0GF1FJOZ a=rtcp-mux a=rtcp:62538 IN IP4 203.0.113.141 a=rtcp-rsize a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61886 typ host - RTP Host candidate a=candidate:1 1 UDP 1685987071 203.0.113.141 62537 typ srflx raddr 192.0.2.4 rport 61886 - RTP Server Reflexive candidate a=candidate:0 2 UDP 2122194687 192.0.2.4 61888 typ host - RTCP host candidate a=candidate:1 2 UDP 1685987071 203.0.113.141 62538 typ srflx raddr 192.0.2.4 rport 61888 - RTCP Server Reflexive candidate Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video Bob supports BUNDLE semantics. a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio Audio m=line part of the BUNDLE group a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 198.51.100.7 49203 typ host a=candidate:1 1 UDP 1685987071 203.0.113.77 51556 typ srflx raddr 198.51.100.7 rport 49203 ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video Video m=line part of the BUNDLE group with the port from audio line repeated a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

This example shows SDP for negotiating a session with Audio, Video and data streams between Alice and Bob with BUNDLE support known.

| | |Bob does | |the same | Answer(Audio:Opus,Video:VP8 Data) | |<-------------------------------------------| | | | | | | | Two-way Audio,Video, Data multiplexed | |............................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video data a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=mid:audio a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid ****** Application m=line ********* ***************************** m=application 0 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.141 a=bundle-only a=mid:data a=sctp-port:5000 a=max-message-size:100000 a=sendrecv Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video data a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=mid:audio a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1685987071 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid ****** Application m=line ********* ***************************** m=application 0 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.77 a=bundle-only a=mid:data a=sctp-port:5000 a=max-message-size:100000 a=sendrecv

This use-case illustrates SDP Offer/Answer exchange where the far-end (Bob) either doesn't support media bundling or doesn't want to group m=lines over a single 5-tuple. This is indicated by dropping the "a=group:BUNDLE" line and BUNDLE RTP header extension in the Answer SDP. On successful Offer/Answer exchange, Alice and Bob each end up using unique 5-tuple for audio and video media streams respectively.

| | |Bob | |doesn't | |support | |BUNDLE | Answer(Audio:Opus Video:VP8) | |<-----------------------------------------------------| | |Bob uses | |unique | |addresses | |across the | |m=lines | | |2Way Call with Audio and Video on different 5-tuples | |......................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video Alice supports grouping of m=lines under BUNDLE semantics a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp:55232 IN IP4 203.0.113.141 - RTCP port different from RTP port a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 61665 typ host a=candidate:1 1 UDP 1685987071 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=candidate:0 2 UDP 2122194687 192.0.2.4 61666 typ host a=candidate:1 2 UDP 1685987071 203.0.113.141 55232 typ srflx raddr 192.0.2.4 rport 61666 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 54332 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=mid:video Video m=line part of the BUNDLE group with a unique port number a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=ice-ufrag:7872093 a=ice-pwd:ee3474af08a068a28a397a4c3f31747d1 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass - Alice can act as DTLS client or server a=tls-id:UKA29UQLTF69OJW4WNPNUO2Y0GF1FJOZ a=rtcp-mux a=rtcp:60052 IN IP4 203.0.113.141 a=rtcp-rsize a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2122194687 192.0.2.4 71775 typ host a=candidate:1 1 UDP 1685987071 203.0.113.141 54332 typ srflx raddr 192.0.2.4 rport 71775 a=candidate:0 2 UDP 2122194687 192.0.2.4 71776 typ host a=candidate:1 2 UDP 1685987071 203.0.113.141 60052 typ srflx raddr 192.0.2.4 rport 71776 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 53214 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active - Bob is the DTLS client a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=candidate:0 1 UDP 2122194687 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1685987071 203.0.113.77 53214 typ srflx raddr 198.51.100.7 rport 51556 a=candidate:0 2 UDP 2122194687 198.51.100.7 51558 typ host a=candidate:1 2 UDP 1685987071 203.0.113.77 60065 typ srflx raddr 198.51.100.7 rport 51558 ****** Video m=line ********* ***************************** m=video 58679 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=ice-ufrag:85bC300 a=ice-pwd:325921d5d47efbabd9a2de4e99bd291c a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35 :DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active - Bob is the DTLS client a=tls-id:9AIFS8AQ009IXF5D6QQUJ7P8BXPEZJ8G a=rtcp-mux a=rtcp-rsize a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=candidate:0 1 UDP 2122194687 198.51.100.7 61556 typ host a=candidate:1 1 UDP 1685987071 203.0.113.77 58679 typ srflx raddr 198.51.100.7 rport 61556 a=end-of-candidates

This example showcases SDP for negotiating a session with Audio, Video and data streams between Alice and Bob with data stream not being part of the BUNDLE group. This is shown by assigning unique port for data media section and not adding the "mid" identification tag to the BUNDLE group.

| | | | | | Answer(Audio:Opus Video:VP8, Data) | |<-----------------------------------------------------| | | | | |2 Way Call with Audio, Video Multiplexed except data | |......................................................| | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio video Alice wants to BUNDLE only audio and video media. a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 54609 typ host a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid ****** Application m=line ********* ***************************** m=application 10000 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.141 a=mid:data a=sctp-port:5000 a=max-message-size:100000 a=sendrecv a=setup:actpass a=tls-id:UKA29UQLTF69OJW4WNPNUO2Y0GF1FJOZ a=ice-ufrag:89819013 a=ice-pwd:1747d1ee3474af08a068a28a397a4c3f3 a=fingerprint:sha-256 29:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=candidate:0 1 UDP 2113667327 192.0.2.4 10000 typ host a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 49203 typ host a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid ****** Application m=line ********* ***************************** m=application 20000 UDP/DTLS/SCTP webrtc-datachannel c=IN IP4 203.0.113.77 a=mid:data a=sctp-port:5000 a=max-message-size:100000 a=setup:active a=tls-id:9AIFS8AQ009IXF5D6QQUJ7P8BXPEZJ8G a=sendrecv a=ice-ufrag:991Ca2a5e a=ice-pwd:921d5d47efbabd9a2de4e99bd291c325 a=fingerprint:sha-256 7B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=candidate:0 1 UDP 2113667327 198.51.100.7 20000 typ host a=end-of-candidates

This example involves 2 Offer/Answer exchanges. First one is used to negotiate and setup BUNDLE support for Audio-only session followed by an updated Offer/Answer exchange to add video stream to the ongoing session. Also the newly added video stream is BUNDLED with the audio stream.

| | |Bob | |supports | |BUNDLE | Answer(Audio:Opus) | |<-----------------------------------------------------| | |Alice adds | |video stream | Updated Offer(Audio:Opus, Video:VP8) |to BUNDLE |----------------------------------------------------->| | | | |Bob accepts | Updated Answer(Audio:Opus, Video:VP8) | |<-----------------------------------------------------| | | | 2Way Call with Audio and Video Multiplexed | |......................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio Alice adds audio m=line to the BUNDLE group a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates Updated Offer SDP Contents RFC#/Notes v=0 o=- 20518 1 IN IP4 0.0.0.0 Version number incremented s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 Alice wants to use the same DTLS association a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.141 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Updated Answer SDP Contents RFC#/Notes v=0 Version number incremented o=- 16833 1 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio video a=group:LS audio video a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 - Bob agrees to use the same DTLS association a=rtcp-mux a=rtcp-mux-only a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 120 c=IN IP4 203.0.113.77 a=bundle-only a=mid:video a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:120 VP8/90000 a=rtcp-fb:120 nack a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

This section provides examples related to multi-source, multi-stream negotiation such as layered coding, simulcast. Further included are few examples that cover techniques to deal with providing robustness against transmission errors such as FEC and RTX. Also to note, mechanisms such as FEC and RTX could be envisioned in the above basic scenarios as well.

The SDP below shows Offer/Answer exchange with one audio and two video sources (say 2 video cameras). Each of the video source can be sent at two different resolutions. One video source corresponds to VP8 encoding, while the other corresponds to H.264 encoding. framework is used to further constrain the media format encodings and map the payload types (PT) to the 'rid' identifiers. framework identifies the simulcast streams via their 'rid' identifiers. bundle-only attribute is used for the video sources in the Offer to ensure enabling video sources in the context of BUNDLE alone. BUNDLE grouping framework enables multiplexing of all the 5 Source RTP Streams (1 audio stream + 4 video streams) over a single RTP Session. Also, the audio and one video source RTP stream form a lip sync group while the other video source RTP stream represents a non-interactive media data.

| | | | | | Answer(Audio:Opus Video1:VP8,Video2:H.264) | |<------------------------------------------------| | | |One-Way 1 Opus, 2 H.264 and 2 VP8 video streams, | | all multiplexed | |.................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 m2 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video-1 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 100 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly - Send only video stream a=rtpmap:98 VP8/90000 a=fmtp:98 max-fr=30 a=rtpmap:100 VP8/90000 a=fmtp:100 max-fr=15 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=rid:1 send pt=98;max-width=1280;max-height=720 1:1 rid mapping to payload type and specify resolution constraints a=rid:2 send pt=100;max-width=640;max-height=480 1:1 rid mapping to payload type and specify resolution constraints a=simulcast:send 1;~2 Alice can send 2 resolutions identified by the 'rid' identifiers Also, the second stream is initially paused. ****** Video-2 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 101 102 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m2 Video m=line part of BUNDLE group a=msid:ma tc Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tc) a=sendonly - Send only video stream a=rtpmap:101 H264/90000 a=rtpmap:102 H264/90000 a=fmtp:101 profile-level-id=42401f;packetization-mode=0 Camera-2,Encoding-1 a=fmtp:102 profile-level-id=42401f;packetization-mode=1 Camera-2,Encoding-2 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=rid:3 send pt=101;max-width=1280;max-height=720;max-fr=30 1:1 rid mapping to payload type and specify resolution constraints a=rid:4 send pt=102;max-width=640;max-height=360;max-fr=15 1:1 rid mapping to payload type and specify resolution constraints a=simulcast:send 3;4 Alice can send 2 resolutions identified by the 'rid' identifiers Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 m2 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 61665 a=end-of-candidates ****** Video-1 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 100 BUNDLE accepted c=IN IP4 203.0.113.77 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly - receive only video stream a=rtpmap:98 VP8/90000 a=rtpmap:100 VP8/90000 a=fmtp:98 max-fr=30 a=fmtp:100 max-fr=15 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=rid:1 recv pt=98;max-width=1280;max-height=720 Bob accepts the offered payload format constraints a=rid:2 recv pt=100;max-width=640;max-height=480 Bob accepts the offered payload format constraints a=simulcast:recv 1;2 Bob accepts the offered simulcast streams and removes the paused state of stream with 'rid' value 2. ****** Video-2 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 101 102 BUNDLE accepted c=IN IP4 203.0.113.77 a=bundle-only a=mid:m2 Video m=line part of BUNDLE group a=msid:ma tc Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tc) a=recvonly a=rtpmap:101 H264/90000 a=rtpmap:102 H264/90000 a=fmtp:101 profile-level-id=42401f;packetization-mode=1 a=fmtp:102 profile-level-id=42401f;packetization-mode=1 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=rid:3 recv pt=101;max-width=1280;max-height=720;max-fr=30 Bob accepts the offered payload format constraints a=rid:4 recv pt=102;max-width=640;max-height=360;max-fr=15 Bob accepts the offered payload format constraints a=simulcast:recv 3;4 Bob accepts the offered simulcast streams.

This section shows an SDP Offer/Answer for a session with an audio and a single video source. The video source being encoded both as non-scalable and scalable H.264-SVC RTP stream (in the SST mode). The Answerer picks the payload type corresponding to scalable encoding.

| | | | |Bob accepts Alice's | |offered Codec | |operation points | |for scalable encoding | | | Answer(Video:H.264-SVC) | |<------------------------------------------------| | | |One-Way H.264-SVC video streams | |.................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 96 100 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly - Send only video stream a=rtpmap:96 H264/90000 a=fmtp:96 profile-level-id=4d0028; packetization-mode=1;max-fs=8040 H.264 Non Scalable a=rtpmap:100 H264-SVC/90000 a=fmtp:100 profile-level-id=53001f;packetization-mode=0 H.264 Scalable Encoding a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667326 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302206 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 100 BUNDLE accepted. c=IN IP4 203.0.113.77 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly - Receive only video stream a=rtpmap:100 H264-SVC/90000 a=fmtp:100 profile-level-id=53001f;packetization-mode=0 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid

This section shows an SDP Offer/Answer exchange for a simulcast scenario with 3 resolutions and has style re-transmission flows. framework is used to specify all the (3) resolution constraints mapped to a single Payload Type (98). framework identifies the simulcast streams via their 'rid' identifiers.

| | | | | | Answer (Bob accepts Alice's offer) | |<--------------------------------------------------------| | | | | |One-Way 1 Opus, 3 VP8 and RTX video streams,all muxed | |.........................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 103 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly a=rtpmap:98 VP8/90000 a=fmtp:98 max-fr=30 a=rtpmap:103 rtx/90000 a=fmtp:103 apt=98;rtx-time=200 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 send pt=98;max-fs=921600;max-fr=30 a=rid:2 send pt=98;max-fs=614400;max-fr=15 a=rid:3 send pt=98;max-fs=230400;max-fr=30 a=simulcast:send 1;2;3 Alice can send all the simulcast streams Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Bob supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667326 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302206 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 103 BUNDLE accepted c=IN IP4 203.0.113.77 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly a=rtpmap:98 VP8/90000 a=fmtp:98 max-fr=30 a=rtpmap:103 rtx/90000 a=fmtp:103 apt=98;rtx-time=200 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 recv pt=98;max-fs=921600;max-fr=30 a=rid:2 recv pt=98;max-fs=614400;max-fr=15 a=rid:3 recv pt=98;max-fs=230400;max-fr=30 a=simulcast:recv 1;2;3 Bob accepts the offered simulcast streams

This section shows an SDP Offer/Answer exchange for a simulcast scenario with two resolutions. It also showcases where Bob rejects one of the Simulcast Video Stream which results in the rejection of the associated repair stream implicitly.

| | | | |Bob accepts 1 | |simulcast,rtx | |rejects the | |other | Answer(Audio:Opus Video:VP8 with 1 res & RTX Stream) | |<--------------------------------------------------------| | | | | |1-way audio,video session and its associated RTX stream, | | all multiplexed | |.........................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 100 101 103 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb a=sendonly a=rtpmap:98 VP8/90000 a=rtpmap:100 VP8/90000 a=rtpmap:101 rtx/90000 a=rtpmap:103 rtx/90000 a=fmtp:98 max-fr=30;max-fs=8040 a=fmtp:100 max-fr=15;max-fs=1200 a=fmtp:101 apt=98;rtx-time=200 a=fmtp:103 apt=100;rtx-time=200 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 send pt=98 1:1 mapping between the PT and the 'rid' identifier a=rid:2 send pt=100 1:1 mapping between the PT and the 'rid' identifier a=simulcast:send 1;2 Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Bob supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667326 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302206 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 101 BUNDLE accepted c=IN IP4 203.0.113.77 a=bundle-only a=mid:m1 a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly a=rtpmap:98 VP8/90000 a=rtpmap:101 rtx/90000 a=fmtp:101 apt=98;rtx-time=200 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 recv pt=98 a=simulcast:recv 1 Bob rejects the second simulcast stream and the associated rtx stream.

This section shows an SDP Offer/Answer exchange for Simulcast video stream at two resolutions with based forward error correction mechanisms. On completion of the Offer/Answer exchange mechanism, we end up with one audio stream, 2 simulcast video streams and associated FEC stream(s), all sent over a single 5-tuple.

| | | | |Bob | |accepts | |Alice's | |offer |Answer(Audio:Opus Video:VP8 with 2 resolutions w/FEC Streams) | |<--------------------------------------------------------------| | | |One-Way Audio,Video session with 4 video streams(Simulcast | | and FEC) all multiplexed | |...............................................................| | | | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=rtcp-mux a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 100 101 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendonly a=rtpmap:98 VP8/90000 a=rtpmap:100 VP8/90000 a=rtpmap:101 flexfec/90000 a=fmtp:98 max-fr=30;max-fs=8040 a=fmtp:100 max-fr=15;max-fs=1200 a=fmtp:101 repair-window=200000 a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 send pt=98 1:1 mapping between the PT and the 'rid' identifier a=rid:2 send pt=100 1:1 mapping between the PT and the 'rid' identifier a=simulcast:send 1;2 Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.77 a=mid:m0 Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=recvonly a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667326 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302206 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 100 101 BUNDLE accepted. c=IN IP4 203.0.113.77 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=recvonly a=rtpmap:98 VP8/90000 a=rtpmap:100 VP8/90000 a=rtpmap:101 flexfec/90000 a=fmtp:98 max-fr=30;max-fs=8040 a=fmtp:100 max-fr=15;max-fs=1200 a=fmtp:101 repair-window=200000 a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id a=rid:1 recv pt=98 a=rid:2 recv pt=100 a=simulcast:recv 1;2

The examples in the section provide SDP Offer/Answer exchange for a variety of scenarios related to RTP Header extension for conference usages, Legacy Interop scenarios and more.

This example shows Alice indicating the support of the RTP header extension to include the audio-level of the audio sample carried in the RTP packet.

| | | | | | Answer(Audio:Opus,PCMU,PCMA) | |<----------------------------------------| | | | |Bob accepts and | |indicates his | |support as well | | | Two way Opus Audio | |.........................................| | | |Per packet audio-level is included in the| |RTP header | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=rtcp-fb:* nack a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Bob can send and recv audio a=rtpmap:109 opus/48000/2 - Bob accepts only Opus Codec a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux - Bob can perform RTP/RTCP Muxing on port 49203 a=rtcp-rsize a=rtcp-fb:* nack a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates

This example shows SDP for RTP header extension that allows RTP-level mixers in audio conferences to deliver information about the audio level of individual participants.

| | | | | |Answer(Audio:Opus,PCMU,PCMA) | |<----------------------------------------| | | | |Mixer indicates | |it can provide | |audio-levels |Two way Opus Audio | |.........................................| | | |Audio-levels per CSRCS is included in the| |RTP header | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.141 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv - Alice can send and recv audio a=rtpmap:109 opus/48000/2 a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp-rsize a=rtcp-fb:* nack a=extmap:1/recvonly urn:ietf:params:rtp-hdrext:csrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:3 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=end-of-candidates Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 - Session Origin Information s=- t=0 0 a=group:BUNDLE audio a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 0 8 c=IN IP4 203.0.113.77 a=mid:audio a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=rtpmap:0 PCMU/8000 PCMU Audio Codec a=rtpmap:8 PCMA/8000 PCMA Audio Codec a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=tls-id:CJ6FF9ZZMJW7MDRJIR7XVIQM48GE1G31 a=rtcp-mux a=rtcp-rsize a=rtcp-fb:* nack a=extmap:1/sendonly urn:ietf:params:rtp-hdrext:csrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=end-of-candidates

In the scenario described below, Alice is a multi-stream capable WebRTC endpoint while Bob is a legacy VOIP end-point. The SDP Offer/Answer exchange demonstrates successful session setup with fallback to audio only stream negotiated via bundle-only framework between the end-points. Specifically, Offer from Alice describes 2 cameras via 2 video m=lines with both marked as bundle-only. Bob doesn't recognize BUNDLE mechanism and since Alice has marked both the video m=lines with port 0, Bob accepts just the audio stream from Alice. NOTE: Alice is unaware of whether Bob supports the BUNDLE framework. Alice includes separate RTP/RTCP ports and candidate information.

VOIP Interop Alice Bob | | | | | Alice is a multistream capable WebRTC end-point | | & Bob is behind a legacy VOIP system | | | |Offer(Audio:Opus Video:1 VP8,1 H.264 Stream) with | | bundle-only | |---------------------------------------------------------->| | Alice marks both the video streams as bundle-only | | | | | | Answer(Audio:Opus) | |<----------------------------------------------------------| | |Bob | |accepts | |audio | |stream, | |since he | |doesn't | |recognize | |bundle-only | | | Two way Opus Audio | |...........................................................| | | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 a=group:BUNDLE m0 m1 m2 Alice supports grouping of m=lines under BUNDLE semantics a=group:LS m0 m1 a=ice-options:trickle a=ice-options:ice2 ****** Audio m=line ********* ***************************** m=audio 54609 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=mid:m0 Audio m=line part of BUNDLE group with a unique port number a=msid:ma ta Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (ta) a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=setup:actpass a=tls-id:89J2LRATQ3ULA24G9AHWVR31VJWSLB68 a=rtcp-mux a=rtcp:64678 IN IP4 203.0.113.141 a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid a=candidate:0 1 UDP 2113667327 192.0.2.4 61665 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54609 typ srflx raddr 192.0.2.4 rport 61665 a=candidate:0 1 UDP 2113667326 192.0.2.4 61667 typ host a=candidate:1 1 UDP 1694302206 203.0.113.141 64678 typ srflx raddr 192.0.2.4 rport 61667 ****** Video-1 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m1 Video m=line part of BUNDLE group a=msid:ma tb Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tb) a=sendrecv a=rtpmap:98 VP8/90000 a=imageattr:98 [x=1280,y=720] a=fmtp:98 max-fr=30 a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid ****** Video-2 m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 101 bundle-only video line with port number set to zero c=IN IP4 203.0.113.141 a=bundle-only a=mid:m2 Video m=line part of BUNDLE group a=msid:ma tc Identifies RTCMediaStream ID (ma) and RTCMediaStreamTrack ID (tc) a=sendrecv a=rtpmap:101 H264/90000 a=fmtp:101 profile-level-id=4d0028;packetization-mode=1 Camera-2,Encoding-1 Resolution a=rtcp-fb:* nack a=rtcp-fb:* nack pli a=rtcp-fb:* ccm fir a=extmap:2 urn:ietf:params:rtp-hdrext:sdes:mid Answer SDP Contents RFC#/Notes v=0 o=- 20519 0 IN IP4 0.0.0.0 s=- t=0 0 ****** Audio m=line ********* ***************************** m=audio 49203 UDP/TLS/RTP/SAVPF 109 c=IN IP4 203.0.113.141 a=rtcp:60065 IN IP4 203.0.113.141 a=sendrecv a=rtpmap:109 opus/48000/2 a=maxptime:120 a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35:DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08 a=setup:active a=rtcp-rsize a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level a=candidate:0 1 UDP 2113667327 198.51.100.7 51556 typ host a=candidate:1 1 UDP 694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 51556 a=candidate:0 2 UDP 2113667326 198.51.100.7 51558 typ host a=candidate:1 2 UDP 1694302206 203.0.113.77 60065 typ srflx raddr 198.51.100.7 rport 51558 ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 98 Bob doesn't recognize bundle-only and hence the m=line is rejected implicitly due to port 0 ****** Video m=line ********* ***************************** m=video 0 UDP/TLS/RTP/SAVPF 101 Bob doesn't recognize bundle-only and hence the m=line is rejected implicitly due to port 0

In the scenario described below, Alice is a legacy end-point which sends Offer with RTP/AVP based audio and video descriptions along with DTLS fingerprint and RTCP feedback information. On the other hand, Bob, being a WebRTC end-point, follows procedures in section 5.1.2 of and accepts the Alice's offer for DTLS-SRTP based session with RTCP feedback.

VOIP Interop Alice Bob | | | | |Alice is a legacy VOIP End-point & Bob is a WebRTC End-Point| | | | | | | | Offer(Audio:Opus Video:H.264) | |----------------------------------------------------------->| | | | | |Alice includes : | |Legacy compliant media description (RTP/AVP) with dtls | |fingerprint and rtcp feedback support | | | | Answer(Audio:Opus, Video:H.264) | |<-----------------------------------------------------------| | |Bob | |accepts | |"legacy | |compliant" | |m=line | | | | | Two way Opus Audio, H.264 Video | |............................................................| | Session also supports RTP/RTCP Mux, RTCP Feedback | | | ]]> Offer SDP Contents RFC#/Notes v=0 o=- 20518 0 IN IP4 0.0.0.0 s=- t=0 0 a=ice-ufrag:074c6550 a=ice-pwd:a28a397a4c3f31747d1ee3474af08a068 a=rtcp-rsize ****** Audio m=line ********* ***************************** m=audio 54732 RTP/AVP 109 Alice includes RTP/AVP audio stream description c=IN IP4 203.0.113.141 a=fingerprint:sha-256 19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04:BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2 a=rtpmap:109 opus/48000 a=ptime:20 a=sendrecv a=rtcp-mux Alice still includes RTP/RTCP Mux support a=rtcp:64678 IN IP4 203.0.113.141 a=candidate:0 1 UDP 2113667327 192.0.2.4 54732 typ host a=candidate:1 1 UDP 694302207 203.0.113.141 54732 typ srflx raddr 192.0.2.4 rport 54732 a=candidate:0 2 UDP 2113667326 192.0.2.4 64678 typ host a=candidate:1 2 UDP 1694302206 203.0.113.141 64678 typ srflx raddr 192.0.2.4 rport 64678 ****** Video m=line ********* ***************************** m=video 62445 RTP/AVP 120 Alice includes RTP/AVP video stream description c=IN IP4 203.0.113.141 a=fingerprint:sha-256 DC:B8:5F:64:1A:24:C2:43:F0:A1:58:D0:A1:2C:19:08:6B:8B:F0:65:5F:78:E2:51:3B:AC:6F:F3:3F:46:1B:35 a=rtpmap:120 VP8/90000 a=sendrecv a=rtcp-mux Alice intends to perform RTP/RTCP Mux a=rtcp:54721 IN IP4 203.0.113.141 a=candidate:0 1 UDP 2113667327 192.0.2.4 62445 typ host a=candidate:1 1 UDP 1694302207 203.0.113.141 62537 typ srflx raddr 192.0.2.4 rport 62445 a=candidate:0 2 UDP 2113667326 192.0.2.4 54721 typ host a=candidate:1 2 UDP 1694302206 203.0.113.141 54721 typ srflx raddr 192.0.2.4 rport 54721 a=rtcp-fb:120 nack pli Alice indicates support for Picture loss Indication and NACK RTCP feedback a=rtcp-fb:120 ccm fir Answer SDP Contents RFC#/Notes v=0 o=- 16833 0 IN IP4 0.0.0.0 s=- t=0 0 ****** Audio m=line ********* ***************************** m=audio 49203 RTP/AVP 109 Bob accepts RTP/AVP based audio stream c=IN IP4 203.0.113.77 a=rtpmap:109 opus/48000 a=ptime:20 a=sendrecv a=ice-ufrag:c300d85b a=ice-pwd:de4e99bd291c325921d5d47efbabd9a2 a=fingerprint:sha-256 BB:05:2F:70:9F:04:A9:0E:05:E9:26:33:E8:70:88:A2:19:E2:1C:3B:4B:9F:81:E6:B8:5C:F4:A5:A8:D8:73:04 a=rtcp-mux a=candidate:0 1 UDP 2113667327 198.51.100.7 49203 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 49203 typ srflx raddr 198.51.100.7 rport 49203 ****** Video m=line ********* ***************************** m=video 63130 RTP/AVP 120 Bob accepts RTP/AVP based video stram c=IN IP4 203.0.113.77 a=rtpmap:120 VP8/90000 a=sendrecv a=ice-ufrag:e39091na a=ice-pwd:dbc325921d5dd29e4e99147efbabd9a2 a=fingerprint:sha-256 BB:0A:0E:05:E9:26:33:E8:70:88:A2:2F:70:9F:04:19:E2:1C:3B:4B:9F:81:56:2F:70:9F:04:F4:A5:A8:D8 a=rtcp-mux a=candidate:0 1 UDP 2113667327 198.51.100.7 63130 typ host a=candidate:1 1 UDP 1694302207 203.0.113.77 63130 typ srflx raddr 198.51.100.7 rport 63130 a=rtcp-fb:120 nack pli a=rtcp-fb:120 ccm fir