I have a couple of minor comments on 5966bis-02: - Section 8
For reasons of efficiency, DNS clients and servers SHOULD transmit the two-octet length field, and the message described by that length field, in a single TCP segment. I suspect we cannot reasonably require this (with a "SHOULD") at the level of DNS client/server implementation since an application cannot always/fully control a specific TCP segment contains how much data: it depends on the state of the TCP connection, specific implementation details of the TCP stack, etc. I suggest rephrasing this as follows (and I guess that was actually what was intended to say here): For reasons of efficiency, DNS clients and servers SHOULD pass the two-octet length field, and the message described by that length field, to the TCP layer at the same time (e.g., in a single write() system call) so it will be more likely that all the data will be transmitted in a single TCP segment. This additionally avoids problems due to some DNS servers being very sensitive to timeout conditions on receiving messages (they may abort a TCP session if the first TCP segment does not contain both the length field and the entire message). - Appendix A TCP does not suffer from UDP's issues with fragmentation. Exactly what does this mean? Is this to say IP fragmentation won't happen for TCP? Or does this mean even if fragmentation occurs TCP is free from the "UDP's issues" (what are they, btw)? My impression from this sentence is that it assumes path MTU discovery is used for TCP and fragmentation should normally not happen for TCP. If this is the intent, I think it will need to explain a bit more, including this particular assumption and why UDP can't benefit from it. If my impression is incorrect, I'd like to understand what it actually tries to say. -- JINMEI, Tatuya _______________________________________________ DNSOP mailing list DNSOP@ietf.org https://www.ietf.org/mailman/listinfo/dnsop
