Session Description Protocol (SDP) Parameters 2001-06-15 2026-03-05 Standards Action media audio media video media text media application media message media image media haptics RFC Required Standards Track RFC preferred. proto RTP/AVP proto udp proto vat proto rtp proto udptl ITU-T Recommendation T.38, 'Procedures for real-time Group 3 facsimile communication over IP networks', June 1998. (Section 9) proto TCP proto RTP/AVPF proto TCP/RTP/AVP proto RTP/SAVP proto TCP/BFCP proto TCP/TLS/BFCP proto TCP/TLS proto FLUTE/UDP proto TCP/MSRP proto TCP/TLS/MSRP proto DCCP proto DCCP/RTP/AVP proto DCCP/RTP/SAVP proto DCCP/RTP/AVPF proto DCCP/RTP/SAVPF proto RTP/SAVPF proto UDP/TLS/RTP/SAVP proto DCCP/TLS/RTP/SAVP proto UDP/TLS/RTP/SAVPF proto DCCP/TLS/RTP/SAVPF proto UDP/MBMS-FEC/RTP/AVP proto UDP/MBMS-FEC/RTP/SAVP proto UDP/MBMS-REPAIR proto FEC/UDP proto UDP/FEC proto TCP/MRCPv2 proto TCP/TLS/MRCPv2 proto PSTN proto UDP/TLS/UDPTL proto voice proto fax proto pager proto TCP/RTP/AVPF proto TCP/RTP/SAVP proto TCP/RTP/SAVPF proto TCP/DTLS/RTP/SAVP proto TCP/DTLS/RTP/SAVPF proto TCP/TLS/RTP/AVP proto TCP/TLS/RTP/AVPF proto TCP/WS/BFCP proto TCP/WSS/BFCP proto UDP/DTLS/SCTP proto TCP/DTLS/SCTP proto TCP/DTLS/BFCP proto UDP/BFCP proto UDP/TLS/BFCP historic Standards Action bwtype CT NORMAL bwtype AS SUM bwtype RS SUM bwtype RR SUM bwtype TIAS SPECIAL RFC Required nettype IN IP4, IP6 nettype TN RFC2543 nettype ATM NSAP, GWID, E164 nettype PSTN E164 RFC Required addrtype IP4 addrtype IP6 addrtype NSAP addrtype GWID addrtype E164 REGISTRY OBSOLETED - No further registrations accepted enckey clear enckey base64 enckey uri enckey prompt Specification Required Flemming Andreasen attribute 3ge2ae media IDENTICAL 3GPP TS 24.229 12.14.0 attribute 3gpp_MaxRecvSDUSize session, media NORMAL 3GPP TS 26.114 v16.3.0 attribute 3gpp_mtsi_app_adapt media IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 attribute 3gpp_sync_info session, media NORMAL 3GPP TS 26.114 v16.3.0 attribute 3GPP-Adaptation-Support media CAUTION attribute 3GPP-Asset-Information session, media CAUTION attribute 3GPP-Integrity-Key session CAUTION attribute 3GPP-QoE-Metrics session, media CAUTION attribute 3GPP-SDP-Auth session CAUTION attribute 3GPP-SRTP-Config media CAUTION attribute 3gpp-videopostdecbufsize media CAUTION attribute 3gpp.iut.replication session, media TBD 3GPP TS 24.337 10.7.0 attribute aal2CPS media CAUTION attribute aal2CPSSDUrate media CAUTION attribute aal2sscs3661assured media CAUTION attribute aal2sscs3661unassured media CAUTION attribute aal2sscs3662 media CAUTION attribute aal5sscop media CAUTION attribute aalApp media CAUTION attribute aalType media CAUTION attribute abrParms media CAUTION attribute abrSetup media CAUTION attribute acap session, media INHERIT attribute accept-types media, dcsa (msrp) TBD attribute accept-wrapped-types media, dcsa (msrp) TBD attribute acfg media SPECIAL attribute alt media CAUTION attribute alt-default-id media CAUTION attribute alt-group session CAUTION attribute altc media TRANSPORT attribute anbr media IDENTICAL 3GPP TS 26.114 v16.3.0 attribute anycast media CAUTION attribute atmmap media CAUTION attribute atmQOSparms media CAUTION attribute atmTrfcDesc media CAUTION attribute bc_program session NORMAL TS 183 063 R3 ETSI TISPAN Technical Specification TS 183 063 "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); IMS-based IPTV stage 3 specification" attribute bc_service session NORMAL TS 183 063 R3 ETSI TISPAN Technical Specification TS 183 063 "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); IMS-based IPTV stage 3 specification" attribute bc_service_package session NORMAL TS 183 063 R3 ETSI TISPAN Technical Specification TS 183 063 "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); IMS-based IPTV stage 3 specification" attribute bcap session, media INHERIT attribute bcastversion session NORMAL attribute bcob media CAUTION attribute bearerSigIE media CAUTION attribute bearerType media CAUTION attribute bfcpver media TBD attribute bundle-only media NORMAL attribute bw-info media IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 attribute cache media CAUTION attribute calgextmap session, media NORMAL attribute candidate media TRANSPORT attribute capability media CAUTION attribute cat session NORMAL attribute cbrRate media CAUTION attribute ccap session, media IDENTICAL attribute ccc_list session NORMAL 3GPP TS 26.114 v16.3.0 attribute cdsc session, media NORMAL attribute cfw-id media NORMAL attribute chain media CAUTION attribute channel media NORMAL attribute charset session NORMAL attribute charset:iso8895-1 session NORMAL attribute chatroom media TBD attribute clir session, media TBD attribute clkrec media CAUTION attribute cmid media NORMAL attribute cname source NORMAL attribute codecconfig media CAUTION attribute conf media CAUTION attribute confid media TBD attribute connection session, media TRANSPORT attribute content media NORMAL attribute content-desc session, media TBD attribute control session, media CAUTION attribute cpar session, media INHERIT attribute cparmax session, media SPECIAL attribute cparmin session, media SPECIAL attribute cpsSDUsize media CAUTION attribute creq session, media NORMAL attribute cryptex session, media TRANSPORT attribute crypto media TRANSPORT attribute cs-correlation media TBD attribute csup session, media NORMAL attribute curr media CAUTION attribute dccp-port media CAUTION attribute dccp-service-code media CAUTION attribute dcmap media SPECIAL attribute dcsa media SPECIAL attribute depend media IDENTICAL-PER-PT attribute des media CAUTION attribute dsel media CAUTION attribute duplication-delay session, media NORMAL attribute ebuacip media TBD EBU Tech 3368 - Audio Contribution over IP – Profiles attribute ecan media CAUTION attribute ecn-capable-rtp media IDENTICAL attribute eecid media CAUTION attribute end-of-candidates session, media IDENTICAL attribute etag session, media CAUTION attribute extmap session, media SPECIAL attribute extmap-allow-mixed session, media IDENTICAL attribute fec media CAUTION attribute FEC media NORMAL attribute FEC-declaration session, media TBD attribute FEC-OTI-extension session, media TBD attribute fec-repair-flow media SPECIAL attribute fec-source-flow media SPECIAL attribute file-date media, dcsa (msrp) TBD attribute file-disposition media, dcsa (msrp) TBD attribute file-icon media, dcsa (msrp) TBD attribute file-range media, dcsa (msrp) TBD attribute file-selector media, dcsa (msrp) TBD attribute file-transfer-id media, dcsa (msrp) TBD attribute fingerprint session, media TRANSPORT attribute floorctrl media TBD attribute floorid media TBD attribute flute-ch session, media TBD attribute flute-tsi session, media TBD attribute fmtp media, source, dcsa (t140) IDENTICAL-PER-PT attribute framerate media IDENTICAL-PER-PT attribute framesize media CAUTION attribute fsel media CAUTION attribute gc media CAUTION attribute gpmd media TBD ITU-T Rec. V.150.1 ITU-T Rec. V.152 attribute group session NORMAL attribute h248item session, media SPECIAL ITU-T H.248.15 attribute hlang-recv media, dcsa (t140) NORMAL attribute hlang-send media, dcsa (t140) NORMAL attribute icap session, media NORMAL attribute ice-lite session NORMAL attribute ice-mismatch media NORMAL attribute ice-options session NORMAL attribute ice-pacing session NORMAL attribute ice-pwd session, media TRANSPORT attribute ice-ufrag session, media TRANSPORT attribute identity session NORMAL attribute ike-setup session, media IDENTICAL attribute imageattr media IDENTICAL-PER-PT attribute inactive session, media, dcsa (t140), dcsa (msrp) NORMAL attribute ipbcp session SPECIAL ITU-T Recommendation Q.1970, "BICC IP bearer control protocol" (07/2001) attribute isup_usi media CAUTION attribute key-mgmt session, media IDENTICAL attribute keywds session NORMAL attribute label media NORMAL attribute lang session, media NORMAL attribute lcfg media SPECIAL attribute lij media CAUTION attribute loopback media NORMAL attribute loopback-mirror media NORMAL attribute loopback-source media NORMAL attribute max-message-size media CAUTION attribute max-size media, dcsa (msrp) TBD attribute maxmptime media TBD ITU-T Recommendation V.152 "Procedures for supporting voice-band data over IP networks", September 2010 attribute maxprate session, media SPECIAL attribute maxptime media IDENTICAL-PER-PT attribute mbms-flowid media CAUTION attribute mbms-mode session, media CAUTION attribute mbms-repair session, media CAUTION attribute mediaclk session, media, source NORMAL attribute mfcap session, media IDENTICAL-PER-PT attribute mid media NORMAL attribute mscap session, media INHERIT attribute msid media NORMAL attribute msrp-cema media, dcsa (msrp) TBD attribute mtag session, media CAUTION attribute multicast-rtcp session, media IDENTICAL attribute omcap session, media NORMAL attribute omr-codecs media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-m-att media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-m-bw media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-m-cksum media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-s-att media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-s-bw media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute omr-s-cksum media NORMAL TS 24.229 v10.7.0 table 7.5.2 attribute onewaySel media CAUTION attribute orient media NORMAL attribute orient:landscape media NORMAL attribute orient:portrait media NORMAL attribute orient:seascape media NORMAL attribute path media, dcsa (msrp) TBD attribute pcfg media SPECIAL attribute phone-context session, media TBD attribute pmft media TBD ITU-T Recommendation V.152 "Procedures for supporting voice-band data over IP networks", September 2010 attribute portmapping-req media CAUTION attribute predefined_ROI media IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 attribute previous-ssrc source NORMAL attribute profileDesc media CAUTION attribute prtfl media CAUTION attribute PSCid session NORMAL TS 183 063 R3 ETSI TISPAN Technical Specification TS 183 063 "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); IMS-based IPTV stage 3 specification" attribute psk-fingerprint session, media IDENTICAL attribute ptime media IDENTICAL-PER-PT attribute Q763-INN session, media TBD attribute Q763-nature session, media TBD attribute Q763-plan session, media TBD attribute qos-mech-recv session, media TRANSPORT attribute qos-mech-send session, media TRANSPORT attribute qosClass media CAUTION attribute quality media NORMAL attribute rams-updates media CAUTION attribute range session, media CAUTION attribute record session, media TBD attribute recordpref session, media TBD attribute recvonly session, media, dcsa (t140), dcsa (msrp) NORMAL attribute remote-candidates media TRANSPORT attribute repair-window media SPECIAL attribute require session, media TBD attribute resource media NORMAL attribute rid media SPECIAL attribute rmcap session, media IDENTICAL-PER-PT attribute rtcp media TRANSPORT attribute rtcp-fb media IDENTICAL-PER-PT attribute rtcp-idms media NORMAL attribute rtcp-mux media IDENTICAL attribute rtcp-mux-only media IDENTICAL attribute rtcp-rgrp session, media IDENTICAL attribute rtcp-rsize media IDENTICAL attribute rtcp-unicast media IDENTICAL attribute rtcp-xr session, media NORMAL attribute rtpmap media IDENTICAL-PER-PT attribute rtpred1 media CAUTION attribute rtpred2 media CAUTION attribute rtsp-ice-d-m session TBD attribute rtt-mixer media NORMAL RFC9071, Section 2.3 attribute sbc media CAUTION attribute sctp-port media CAUTION attribute sdplang session, media NORMAL attribute secondary-realm media TRANSPORT TS 24.229 v10.7.0 table 7.5.2 attribute sendonly session, media, dcsa (t140), dcsa (msrp) NORMAL attribute sendrecv session, media, dcsa (t140), dcsa (msrp) NORMAL attribute sescap session CAUTION attribute setup session, media, dcsa (msrp) TRANSPORT attribute silenceSupp media CAUTION attribute simulcast media NORMAL attribute source-filter session, media IDENTICAL attribute sqn session, media NORMAL attribute SRTPAuthentication media TBD attribute SRTPROCTxRate media TBD attribute ssrc media NORMAL attribute ssrc-group media NORMAL attribute stc media CAUTION attribute stkmstream session, media NORMAL attribute structure media CAUTION attribute suspended session, media TBD NENA STA-010.2-2016 attribute T38FaxFillBitRemoval media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxMaxBuffer media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxMaxDatagram media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxMaxIFP media TBD ITU-T Recommendation T.38 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxRateManagement media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxTranscodingJBIG media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxTranscodingMMR media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxUdpEC media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxUdpECDepth media TBD ITU-T Recommendation T.38 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxUdpFECMaxSpan media TBD ITU-T Recommendation T.38 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38FaxVersion media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38MaxBitRate media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38ModemType media TBD ITU-T Recommendation T.38 Annex D, 'SIP/SDP Call Establishment Procedures', September 2010 attribute T38VendorInfo media TBD ITU-T Recommendation T.38 Amendment 2 Annex D, 'SIP/SDP Call Establishment Procedures', February 2000, July 2005. attribute tcap session, media INHERIT attribute tls-id media IDENTICAL attribute tool session NORMAL attribute tra-att session, media NORMAL attribute tra-bw session, media NORMAL attribute tra-contact session, media NORMAL attribute tra-m-line media NORMAL attribute tra-media-line-number session NORMAL attribute tra-SCTP-association media NORMAL attribute ts-refclk session, media, source NORMAL attribute type session NORMAL attribute type:H332 session NORMAL ITU Recommendation H.332 attribute type:broadcast session NORMAL attribute type:meeting session NORMAL attribute type:moderated session NORMAL attribute type:test session NORMAL attribute uiLayer1_Prot media CAUTION attribute upcc media CAUTION attribute userid media TBD attribute v3cfmtp session, media NORMAL attribute vbd (OBSOLETE) media TBD ITU-T Recommendation V.152 "Procedures for supporting voice-band data over IP networks", September 2010 attribute visited-realm media TRANSPORT TS 24.229 v10.7.0 table 7.5.2 attribute vndpar session, media TBD ITU-T Rec. V.150.1 ITU-T Rec. V.152 attribute vsel media CAUTION attribute websocket-uri media CAUTION attribute X-decbyterate media CAUTION attribute X-initpostdecbufperiod media CAUTION attribute X-initpredecbufperiod media CAUTION attribute X-predecbufsize media CAUTION attribute zrtp-hash media TRANSPORT historic; use fmtp as per Specification Required Christer Holmberg content slides Presentation slides NORMAL content speaker Image from the speaker NORMAL content sl Sign language NORMAL content main Main media stream NORMAL content alt Alternative media stream NORMAL content g.3gpp.cat Stream associated with the 3GPP Customized Alerting Ringtone (CAT) service NORMAL 3GPP TS 24.182 v11.2.0 content g.3gpp.crs Stream associated with the 3GPP Customized Ringing Signal (CRS) service NORMAL 3GPP TS 24.183 v9.10.0 annex E content g.3gpp.announcement-no-confirmation Stream associated with video announcement service without user confirmation NORMAL 3GPP TS 24.229 Standards Action Lip Synchronization LS NORMAL Flow Identification FID NORMAL Single Reservation flow SRF NORMAL Alternative Network Address Types ANAT CAUTION Forward Error Correction (Deprecated) FEC NORMAL Forward Error Correction FR FEC-FR NORMAL Composite Session CS NORMAL Decoding Dependency DDP NORMAL Duplication DUP NORMAL Splice SPLICE TBD Media bundling BUNDLE NORMAL CLUE-controlled "m=" line CLUE NORMAL V3C grouping V3C NORMAL First Come First Served with permanent, stable, and publically accessible document. ack Positive acknowledgement IDENTICAL-PER-PT app Application-defined parameter SPECIAL ccm Codec Control Commands and Indications IDENTICAL-PER-PT nack Negative Acknowledgement IDENTICAL-PER-PT trr-int Minimal receiver report interval IDENTICAL-PER-PT 3gpp-roi-arbitrary Video region-of-interest (ROI) arbitrarily selected by the endpoint IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 3gpp-roi-predefined Video region-of-interest (ROI) pre-defined by the sender and selected by the endpoint IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 3gpp-delay-budget Available or requested delay budget specified in milliseconds IDENTICAL-PER-PT 3GPP TS 26.114 v16.3.0 3gpp-viewport Viewport feedback for viewport-dependent 360-degree video IDENTICAL-PER-PT 3GPP TS 26.114 First Come First Served with a permanent, stable, and publically accessible document sli Slice Loss Indication nack IDENTICAL-PER-PT pli Picture Loss Indication nack IDENTICAL-PER-PT rpsi Reference Picture Selection Indication ack, nack IDENTICAL-PER-PT app Application layer feedback ack, nack SPECIAL rai Rapid Acquisition Indication nack IDENTICAL-PER-PT tllei Transport-Layer Third-Party Loss Early Indication nack IDENTICAL-PER-PT pslei Payload-Specific Third-Party Loss Early Indication nack IDENTICAL-PER-PT ecn Explicit Congestion Notification nack IDENTICAL ccfb Congestion Control Feedback ack IDENTICAL-PER-PT Specification Required Stephan Wenger lay Layered decoding dependency IDENTICAL-PER-PT mdc Multi descriptive decoding dependency IDENTICAL-PER-PT Specification Required Bo Burman callerid Caller ID TBD uuie User-User Information Element TBD dtmf Dual-tone Multi-Frequency TBD external External TBD Standards Action FID Flow Identification NORMAL FEC Forward Error Correction NORMAL FEC-FR Forward Error Correction FR NORMAL DUP Duplication NORMAL Specification Required Magnus Westerlund This registry of the key management protocol identifier, KMPID, has a name space that is shared between the SDP "key-mgmt" attribute and RTSP header "keymgmt". mikey Multimedia Internet KEYing IDENTICAL Specification Required Stephan Wenger fir Full Intra Request Command ccm IDENTICAL-PER-PT tmmbr Temporary Maximum Media Stream Bit Rate ccm IDENTICAL-PER-PT tstr Temporal-Spatial Trade-off ccm IDENTICAL-PER-PT vbcm H.271 video back channel messages ccm IDENTICAL-PER-PT pause Media Pause/Resume ccm TBD lrr Layer Refresh Request Command ccm IDENTICAL-PER-PT Specification Required Christer Holmberg rsvp TRANSPORT nsis TRANSPORT IETF Review cap-v0 NORMAL med-v0 NORMAL bcap-v0 NORMAL ccap-v0 NORMAL icap-v0 NORMAL IETF Review a Attribute Configuration b Bandwidth c Connection Data i Title m Media Configuration mt Media Type pt Payload Type Number Mapping t Transport Protocol Configuration Specification Required Magnus Westerlund ntp Network Time Protocol NORMAL RFC7273, section 4 ptp Precision Time Protocol NORMAL RFC7273, section 4 gps Global Positioning System NORMAL RFC7273, section 4 gal Galileo NORMAL RFC7273, section 4 glonass Global Navigation Satellite System NORMAL RFC7273, section 4 local Local Clock NORMAL RFC7273, section 4 private Private Clock NORMAL RFC7273, section 4 Specification Required Magnus Westerlund sender Asynchronously Generated Media Clock NORMAL RFC7273, section 5 direct Direct-Referenced Media Clock NORMAL RFC7273, section 5 IEEE1722 IEEE1722 Media Stream Identifier NORMAL RFC7273, section 5 Standards Action NORMAL CAUTION IDENTICAL TRANSPORT SUM INHERIT IDENTICAL-PER-PT SPECIAL TBD First Come First Served webrtc-datachannel IESG Specification Required Adam Roach pt max-width max-height max-fps max-fs max-br max-pps max-bpp depend Specification Required Christer Holmberg 3GPP Specifications Manager mailto:3gppContact&etsi.org 2017-06-16 Brian Rosen mailto:br&brianrosen.net 2016-10-11 Dongwook Kim mailto:dongwook.kim&etsi.org 2026-01-15 Felix Poulin, EBU-FNS Coordinator mailto:poulin&ebu.ch 2016-11-17 Ozgur Oyman mailto:ozgur.oyman&intel.com 2019-11-06 Simão Campos-Neto mailto:simao.campos&itu.int 2019-07-30 Sonia Compans mailto:Sonia.Compans&etsi.org 2010-11-24