Subject: Re: Negotiation of session-expires refresh timer

From: John Hearty <[email-masked]>
Date: Fri, 19 Feb 1999 09:07 -0600 (CST)

>> 
>> >But, if the UAC doesn't understand the session timer, the UAC gets the
>> >400 response, tries again (without the timer header, of course), which
>> >generates another 400 response, and so on.
>> 
>> The SIP spec states for 4xx responses that "The client SHOULD NOT retry
>> the same request without modification..."  It seems to me UACs should
>> have a minimum requirement to understand _all_ 4xx responses for the
>> supported SIP version, whether or not they can support the appropriate
>> modified re-try request, or if they don't understand the 4xx response,
>> don't retry the Invite.
>
>I don't think clients should be required to understand all 4xx responses
>- thats the point of having a hierarchical error namespace.

Good point.

>
>You are correct, though (thanks for the info) that they won't retry the
>request. But, this means no call gets made. This means that these
>forceful proxies will not complete any calls for
>non-expiration-supporting clients - seems bad for business...

Well, I was just thinking that if we allow some UACs to make calls
without the timer, that defeats the whole purpose of this draft, in
that some calls may remain forever active in the stateful proxy's state
tables if the proxy misses a BYE or it never gets sent.  I suppose
it would be a business/engineering decision.

John Hearty
MCI Worldcom