Re: [DNSOP] Spencer Dawkins' Discuss on draft-ietf-dnsop-session-signal-12: (with DISCUSS and COMMENT)

[Benjamin Kaduk <[e-mail]>]

On Thu, Jul 26, 2018 at 09:33:20PM -0700, Spencer Dawkins wrote:
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
[snip]
> 
> This next one is well within the "Spencer wouldn't have done it this way, but
> Spencer's not the working group, or the IETF" range, but
> 
>   However, in the typical case a server will not know in advance
>    whether a client supports DSO, so in general, unless it is known in
>    advance by other means that a client does support DSO, a server MUST
>    NOT initiate DSO request messages or DSO unacknowledged messages
>    until a DSO Session has been mutually established by at least one
>    successful DSO request/response exchange initiated by the client, as
>    described below.  Similarly, unless it is known in advance by other
>    means that a server does support DSO, a client MUST NOT initiate DSO
>    unacknowledged messages until after a DSO Session has been mutually
>    established.
> 
> seems fragile, especially in environments where clients can come and go, and
> servers may be addressed using anycast (so I knew in advance that the four
> servers at that anycast address supported DSO, but somebody installed a fifth
> server that does not). Is that unlikely to be a problem?

Note that the client is only prohibted from using "unacknowledged"
(one-shot) messages -- it can send always normal requests and use the
presence of a reply to determine server support, on this connection.
So this seems like a pretty vanilla "client initiates" thing, if I
understand correctly.

-Benjamin

[snip]