Re: [sipcore] draft-roach-sipcore-rfc3265bis-00

["Christer Holmberg" <[e-mail]>]

Hi, 

>>Because method names are one SIP's extension points, proxies don't
inherently know which requests can form dialogs. For example, if a proxy
forks a XYZZY request, how would it know whether to return a 
>>single 200 response or all of them? It has know way of knowing whether
XYZZY is a dialog-forming request.
>
>Because, what does a proxy do if it receives additional 200 responses?
I can't find any text about that in 3261.
>   
>
>It's going to drop them. See RFC 3261, section 16.7, step 5.

Maybe I'm just too blind to find it, but could you copy the text which
says that? :)

In the beginning there is generic text which says that any 2xx response
is forwarded.

Further down there is INVITE specific text, which says that non-2xx
responses are not immedialtly forwarded - instead the choose-the-best
procedures are used.

I see no text saying that additional 2xx responses for non-INVITEs are
dropped. 

------

>>>>That's certainly the intention of 4.3. It's a bit tortured to
imagine 
>>>>that a proxy might be on the path of the NOTIFY without having 
>>>>Record-Routing the SUBSCRIBE. Nonetheless, I'm okay with prohibiting

>>>>Record-Routing a NOTIFY unless you've also Record-Routed the 
>>>>associated SUBSCRIBE; I'll add:
>>>>
>>>>   Proxies that did not add a Record-Route header field to the
>>>>   initial SUBSCRIBE request MUST NOT add a Record-Route header
>>>>   field to any of the associated NOTIFY requests.
>>>>     
>>>>
>>>Don't you need a Proxy-Require option tag for that? 
>>>
>>>Again, a 3261 compliant proxy may Record-Route the SUBSCRIBE, but
that 
>>>doesn't mean it will Record-Route the NOTIFY. It may simply be 
>>>configured to Record-Route all dialog initiation requests.
>>   
>
>For a proxy to have the first clue that SUBSCRIBE is a dialog
initiation request, it has to be aware of the semantics of SUBSCRIBE.
Otherwise, it doesn't know SUBSCRIBE from XYZZY.
>
>And if a proxy is blindly Record-Routing unknown methods, it will
Record-Route the NOTIFY also. 

Doesn't the NOTIFY contain a To tag? The proxy would assume it is an
in-dialog request, so it would not Record-Route it.

What does a stateful proxy do with an in-dialog request it doesn't find
state for, btw?

------

>I've worked with enough implementors to know that there's never enough
accounting for crazy, but the failure you're describing would require a
certain amount of malice: enough understanding to know what 
>SUBSCRIBE means, but a bewildering level of willful ignorance to then
pretend not to understand NOTIFY.

I agree that if the proxy is SUBSCRIBE aware, there should be no
problem.


Regards,

Christer