I have been selected as the General Area Review Team (Gen-ART) reviewer for this draft (for background on Gen-ART, please see http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html). Please resolve these comments along with any other Last Call comments you may receive. Document: draft-ietf-avt-rtp-and-rtcp-mux-05.txt Reviewer: David Black Review Date: 16 July 2007 IETF LC End Date: 17 July 2007 Summary: This draft is on the right track, but has open issues, described in the review. Comments: The draft is generally in good shape, although one needs to be an RTP expert to understand all the details. The only "open issue" is the missing instructions to IANA for RTCP packet type registration - from a technical standpoint, this is a nit, but getting it right is of sufficient importance to avoidance of future restrictions RTP/RTCP multiplexing that I've flagged it as an open issue. Everything else in this review is an editorial comment, although the absence of the explanation of the mechanics of the RTP/RTCP conflicts makes that section of the draft difficult to read. Section 1 talks about NAT (Network Address Translation) as a motivation, but the real motivation appears to be NAPT (Network Address Port Translation). This ought to be discussed, and I strongly suggest an Informative reference to RFC 3022. The term "NAT pinhole" also needs to be explained here to connect the problems caused by two UDP ports to NAPT usage, and it may be useful to mention firewall pinholes as a related issue. Section 4 should explain the mechanics of the RTP/RTCP conflict: - The RTCP PT is bits 8-15. - The RTP PT is bits 9-15. - RTP uses bit 8 in that word for a M (Marker) bit that may be on or off. The latter item is the cause for needing to check for whether the RTCP PT conflicts with either the RTP PT or the RTP PT + 128. The last 2 paragraphs in Section 4 before the final Note in that section need attention: - The paragraph on registration of new RTCP packet types needs to instruct IANA on what rules to enforce. The use of "SHOULD" in the current text is not sufficient, instead this needs to be restated as instructions to IANA on how to assign RTCP packet types and noted in the IANA considerations section. - In this text in the second paragraph: Given these constraints, it is RECOMMENDED to follow the guidelines in the RTP/AVP profile [7] for the choice of RTP payload type values, Insert the word "dynamic" between "the choice of" and "RTP payload type values" for clarity. Thanks, --David ---------------------------------------------------- David L. Black, Senior Technologist EMC Corporation, 176 South St., Hopkinton, MA 01748 +1 (508) 293-7953 FAX: +1 (508) 293-7786 black_david@xxxxxxx Mobile: +1 (978) 394-7754 ---------------------------------------------------- _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf