RI just completed a quick review of draft-ietf-tram-turn-server-discovery-08. The DNS Service Discovery section is much improved. I have a couple of comments on the revised text: I suggest adding a reference to the IANa "Service Name and Transport Protocol Port Number Registry", http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=Turn, as the source of the service names "turn" and "turns". While the example DNS records for "exampleco TURN Server" are technically correct, they would most likely be generated by the DNS-SD/mDNS library in a server, rather than appearing in a DNS server zone file somewhere. For clarity, it might be better to use the unicast DNS versions of the DNS-SD records by substituting "example.com" for "local". In my opinion, the details in section 5.1 are redundant with and (possibly) not identical to the specification in RFC 6762 and RFC 6763. Specifically, Figure 1 includes a typo; there should be separate A/AAAA query and reply messages. More generally, DNS-SD/mDNS servers may return the SRV, TXT, A and AAAA records in the first reply, as an optimization. I think it would be better, in this document, to specify simply that TURN servers and clients use the message exchanges specified in those RFCs for TURN server discovery. - Ralph
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