On Tuesday, November 7 2017, "Aman" wrote to "sip-implementors" saying:
> Hi All, > > Is sending the crypto attribute to secure the RTP with the media line > saying "RTP/AVP" is correct way to demonstrate remote end point to choose > if they want to have a secure RTP or non-secure RTP as per the RFC 4568? This is known as "opportunistic SRTP". It has been fairly common practice for over a decade, but is only now being formally standardized by the IETF. See https://tools.ietf.org/html/draft-ietf-mmusic-opportunistic-negotiation-01 and https://tools.ietf.org/html/draft-ietf-sipbrandy-osrtp-02 for the current work (the latter also includes some discussion of the history), and https://tools.ietf.org/html/draft-kaplan-mmusic-best-effort-srtp-01 for the original proposal from 2006. > I mean is following a correct SDP offer, > > v=0 > o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5 > s=SDP Seminar > i=A Seminar on the session description protocol > u=http://www.example.com/seminars/sdp.pdf > e=j....@example.com (Jane Doe) > c=IN IP4 161.44.17.12/127 > t=2873397496 2873404696 > m=video 51372 RTP/AVP 31 > a=crypto:1 AES_CM_128_HMAC_SHA1_80 > inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 > m=audio 49170 RTP/AVP 0 > a=crypto:1 AES_CM_128_HMAC_SHA1_32 > inline:NzB4d1BINUAvLEw6UzF3WSJ+PSdFcGdUJShpX1Zj|2^20|1:32 > m=application 32416 udp wb > a=orient:portrait > > If yes, so answerer can decide if they want to have a secure RTP or not. > > but as per RFC 4568 section 6, it is not, but I have seen some call-agents > sending offer as above. > > ... > > SRTP security descriptions MUST only be used with the SRTP transport > (e.g., "RTP/SAVP" or "RTP/SAVPF"). The following specifies security > descriptions for the "RTP/SAVP" profile, defined in [RFC3711 > <https://tools.ietf.org/html/rfc3711>]. > However, it is expected that other secure RTP profiles (e.g., > "RTP/SAVPF") can use the same descriptions, which are in accordance > with the SRTP protocol specification [RFC3711 > <https://tools.ietf.org/html/rfc3711>]. > > ... -- Jonathan Lennox len...@cs.columbia.edu _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
