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Issue #3: Use of incompatible payload type for RTP codecs Category Implementation of an older specification Description The RTP payload type 2 was assigned to G.721 and later assigned to its successor G.726-32 in the RFC 1890. But when in the RFC 3551 deprecated the RFC 1890, the RTP static payload type 2 was marked as reserved. Despite this clarity in the specification, SIP servers/end-clients use static type 2 for G.726. Implications This can result in a codec negotiation failure, despite both the SIP end-clients supporting common formats.
Instance #1 Pbxnsip proxy version 2.0.0 uses the static payload type 2 rather than assigning a dynamic payload type for G.726. Packet traces / Call-flows Packet trace Fixes / Workarounds None. References 1. RFC3551: RTP Profile for Audio and Video Conferences with Minimal Control (www.ietf.org/rfc/rfc3551.txt) 2. RFC1890: RTP Profile for Audio and Video Conferences with Minimal Control (www.ietf.org/rfc/rfc1890.txt) 3. Discussion on the Pbxnsip forum (http://forum.pbxnsip.com/index.php?showtopic=87)