ietf
[Top] [All Lists]

RE: Last Call: draft-lawrence-sipforum-user-agent-config (Session Initiation Protocol (SIP) User Agent Configuration) to Informational RFC

2010-04-08 15:51:46
On Thu, 2010-04-08 at 15:15 -0400, Hadriel Kaplan wrote:

-----Original Message-----
From: Scott Lawrence [mailto:xmlscott(_at_)gmail(_dot_)com]
Sent: Thursday, April 08, 2010 9:37 AM
To: Hadriel Kaplan

Well, one could argue that a provider could cause the returned SIP url
for the change notice subscription to be one for which there is no
routing (return 'Link: <sip:devnull.example.org>').  By the rules, the
UA would periodically make a DNS request to try to find it, but would be
allowed to use the configuration data.  Silly, but allowed.

Right, but the since that would make it an "unknown validity" config,
and the requirements do not mandate any UA to *use* an "unknown
validity" config... do you see a problem?

The requirements explicitly allow the UA to use an "unknown validity"
configuration.  I don't think it would be appropriate to put in a MUST
that says the UA should use any configuration data response - the data
may be in the wrong format, corrupt, or have any other problem, so that
would just lead to a different argument.

Instead of getting into an unknown-behavior state, why don't you
simply allow the HTTP response to NOT have a Link header, or define a
NULL URI to use - and then state that it means there is no
Subscription service and the UA MUST consider the HTTP-based config
valid?

No one is going to be forced to use any of this specification.  If you
don't want the features it provides (automatic initial configuration
with prompt updates), then don't use it.

So we should go define another profile which is a textual copy of this
one, but changes two sentences??  Is that really good for SIP or the
SIP-Forum?

At the risk of repeating myself, I want to make sure that one reason for
using SUBSCRIBE/NOTIFY for the change notices is clear:  there is no
other existing standard way to address a specific User Agent.  

Right, I understand that you have no other way to do X.  Fine, so
specify how to do X.  Don't mandate that X be used with Y, when Y does
not depend on X to function properly, and X is not trivial.

Perhaps our fundamental disagreement is whether or not having a prompt
way to reconfigure a UA is a requirement.  When the SIP Forum chartered
this work, it was agreed that that was requirement (and I certainly
think it is).  I think that a configuration mechanism that does not
allow for updates under the control of the service won't be successful.

Could we allow the Configuration Service to omit the Link?  Obviously,
we could.  I think that would materially reduce the utility of the
protocol and would be a bad idea.  Clearly we differ on that.


_______________________________________________
Ietf mailing list
Ietf(_at_)ietf(_dot_)org
https://www.ietf.org/mailman/listinfo/ietf

<Prev in Thread] Current Thread [Next in Thread>