> Hello Thomas,
>
> I'm just returning from vacation and catching up, but it seems
> to me that the packet size issue could become important if we
> expect that the DNS will return many AAAA, A, etc. records
> for some FQDNs. Are there any limits on the number of RRs
> per FQDN that may be stored in the DNS?
No. Theoretically you can fall all the way back to using
a zone transfer to get the data you want if it is too big
for a single DNS/TCP message.
There have been a number of proposals to allow a multi-message
DNS/TCP response regardless of query type. AXFR/IXFR should
not have been a special cases.
> And, is EDNS0
> essential to support query responses when the size would
> exceed 512 bytes?
Essential. No. Highly desirable. Yes. EDNS's larger UDP
size is to try to reduce the number of times a client will
have to fall back to TCP.
> Thanks - Fred
> [EMAIL PROTECTED]
>
> Thomas Narten wrote:
>
> >>>If I
> >>>am correct, then, what would be the problem with listing EDNS0
> >>>as a SHOULD? =20
> >>>
> >>>
> >
> >
> >
> >>None significant I can think of, though I'd like to hear other opinions.=20
> >>
> >>
> >
> >Perhaps the question to ask is whether support of EDNS0 is needed to
> >make IPv6 work well enough. The thing that EDNS0 fixes that is of
> >relevance here is the small packet size problem. In DNS, packets are
> >restricted (by default) to be 512 bytes. With IPv6's bigger addresses,
> >packet overflows are more likely to happen. If we expect this is going
> >to be a problem, then the right thing to do is recommend use of EDNS0,
> >even if it isn't widely deployed yet (and for ipv4, the packet size is
> >less of an issue, hence less motivation/need for it there).
> >
> >Thomas
> >
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>
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
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