[dns-operations] Using all the addresses of every name server? (Was: ANY efforts at taking additional responses more compact?

Paul Vixie paul at redbarn.org
Mon Sep 12 16:36:16 UTC 2016

Viktor Dukhovni wrote:
> ... These days a name with a single address is often multiple machines, and
> conversely multiple addresses under a single name are often in fact
> multiple machines.

multiple machines can in fact be well-expressed by individual NS RRs, so 
there is no need to redefine other encodings to suit this purpose.

> I would not recommend imputing any shared state across multiple
> addresses associated with a given name.  ...

that ship has already sailed, so, the expectation must remain reasonable.

> In Postfix (an example with which I happen to be familiar), there
> is no distinction between 20 (equal preference) MX hosts with a
> single address each, and one MX host with twenty addresses.  However,
> by default at most 10 connection attempts and at most 2 SMTP sessions
> (SMTP transactions over completed TCP connections) are made per delivery.
> Postfix does not waste scarce resources to try every address of snowshoe
> spammer domains with large pools of MX hosts.

postfix is free to behave this way. a new multihome specification would 
even be free to recommend behaving this way. but the older way of 
interpreting multiple addresses in an RRset must remain reasonable, and 
any recommendation toward changing it must account for the installed base.

P Vixie

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