Re: [sipcore] New Version Notification for draft-sparks-sipcore-refer-explicit-subscription-01

[Christer Holmberg <[e-mail]>]

Hi,

>>>> As a general rule, REFER request may fork.
>>>> But a referrer receives only one response(i.e. Refer-Events-At).
>>>> Does this draft disallow a REFER request to be forked?
>>> No.
>>>
>>> If the REFER forks, it will get responses from each branch of the fork.
>>> The response from each branch will have its own information about 
>>> whether the REFER was accepted on that branch, including its own 
>>> Refer-Events-At URI.
>> In accordance with the following, a successful response for REFER 
>> request is only one.
>>
>> RFC3261
>> 17.1.2.1 Overview of the non-INVITE Transaction
>>
>>     Unlike an INVITE transaction, a non-INVITE transaction has no special
>>     handling for the 2xx response.  The result is that only a single 2xx
>>     response to a non-INVITE is ever delivered to a UAC.
>Wow (slaps forehead) - very good catch. That's the whole reason the immediate NOTIFY in SIP Events exists.
>
>The consequences of that are going to require some time to think through.

I was checking RFC 4488, because you have the same issue there if the immediate NOTIFY is not sent.

RFC 4488 "solves" the problem with the following statement:

	"The "Refer-Sub" header field set to "false" MAY be used by the REFER-
   	Issuer only when the REFER-Issuer can be certain that the REFER
   	request will not be forked."

So, perhaps we could do the same.

Regards.

Christer