Subject: RE: [Sip] RE: [Sip-implementors] another problem related to multiple call legs at UAC

From: "Zmolek, Andrew (Andrew)" <[email-masked]>
Date: Mon, 25 Jun 2001 16:42:51 -0600

>> Another thing  Section 5.2 of bis 03.txt also says that
>> "A proxy client generates a CANCEL request for branches without
>>    a final response after it has forked a request and 
>> receives a 2xx or
>>    6xx response from one of the branches. "
>> Whereas section 17.4, pg. 122 says that
>> "After receiving a 2xx, the server MAY terminate all other
>>              pending requests by sending a CANCEL request"
>> 
>> Note that there is no "MAY" in section 5.2.
>
> These need to be consistent. Honestly, it should probably be a SHOULD
as
> opposed to a MAY in both places. Anyone object to me changing that?

Given that we already have a product that provides this kind of forking
across both the PBX and PSTN environments and whose default behavior is
to bridge all the parties that accept the call, it seems natural that we
would want to extend this to provide the same capability in the SIP
world, and perhaps extend this in other ways. Therefore, I strongly
object to the use of "SHOULD" here in place of "MAY" and suggest that if
alternative wording is required, something like the following be used:

"After receiving a 2xx, the server SHOULD either (1) drop all other
pending requests by sending a CANCEL request or (2) bridge or otherwise
provide an alternative service to each branch connection that responds
with a 2XX." 

Note that "terminate" has a specific meaning in the voice world which is
not consistent with CANCEL as the text now reads. Call termination is
the completion of a process that starts with call origination, and while
I know we don't want to replicate the PSTN world, we would do well not
to muddy the terminology we share by equating termination with something
more akin to tear-down. 

--Andy Zmolek
    Technology & Standards Engineer
      CTO Standards
        Avaya Inc.

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