4. Interworking of AVP, SAVP, AVPF, and SAVPF Entities

The SAVPF profile defined in this document is a combination of the SAVP profile [4] and the AVPF profile [3] (which in turn is an extension of the RTP profile as defined in RFC 3551 [2]).

SAVP and SAVPF use SRTP [4] to achieve security. AVP and AVPF use plain RTP [1] and hence do not provide security (unless external security mechanisms are applied as discussed in Section 9.1 of RFC 3550 [1]). SRTP and RTP are not meant to interoperate; the respective protocol entities are not supposed to be part of the same RTP session. Hence, AVP and AVPF on one side and SAVP and SAVPF on the other MUST NOT be mixed.

RTP entities using the SAVP and the SAVPF profiles MAY be mixed in a single RTP session. The interworking considerations defined in Section 5 of RFC 4585 [3] apply.