Re: [Sip] namespaces in RFC 4411, 4412 and draft-ietf-sip-rph-new-namespaces-00

[Dale.Worley at comcast.net]

   From: "Attila Sipos" <attila.sipos at vegastream.com>

   Are namespaces just a way to group together different users across
   different DNS domains?

   What if a.com is using namespaces "dsn-000000" to "dsn-000009"
   and b.com is using the same namespaces?
   Then if A at a.com calls B at b.com, wouldn't the namespaces interfere?

   What looks after or checks the namespaces?
   Is it that a proxy knows what everyone's namespace should be?
   So if someone wants to do "UA Preemption" and tries to use a resource
   priority level higher than they should have, then will the domain's
   proxy downgrade it back to the correct permitted level?

The primary thing is that resource-priority namespaces are registered
with IANA (RFC 4412, section 3.1).

Within any administrative domain, if it processes resource-priorities
at all, it will generally sanitize any incoming SIP messages to match
the policy of the domain.  As a default, this means that it is going
to strip any resource-priority identification.  Above that, it may
respect resource-priority identification if the domain has a suitable
working relationsip with the terminal or domain from which the message
is entering -- but that relationship will explicitly or implicitly
define how the resource-priority identifications will be preserved or
transformed at the boundary.

This is pretty much how *any* priority-identification system has to be
operated.

Dale


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