Re: [Sip] INFO message belongs only to INVITE dialog usage?

[Dean Willis <[e-mail]>]

On May 31, 2007, at 4:19 AM, Nina Garaca wrote:

> Hi all,
>
> I have read rfc2976 - The SIP INFO Method, but I haven't really  
> understood that INFO message belongs only to INVITE dialog usage,  
> which however draft-ietf-sipping-dialogusage-04 claims in its part  
> 5.3:
>
>
>      5.3. Matching requests to usages
>
>
>
>   For many mid-dialog requests, identifying the usage they belong  
> to is
>   obvious.  A dialog can have at most one invite usage, so any INVITE,
>   UPDATE, PRACK, ACK, CANCEL, BYE, or INFO requests belong to it.
>
> So my, question is:
>    Can INFO message  belong to other usages, besides INVITE, such  
> are  SUBSCRIBE  or REFER?
>


There was IIRC no intent in the writing of RFC 2976 to restrict INFO  
to occurring within an INVITE dialog usage. So it could technically  
be used outside of one, including in non-dialog cases.

However, RFC 2976 is considered to be somewhat underspecified, and so  
far the only place we've further specified its usage is in the  
context of transporting binary data for telephony protocol tunelling.  
We have a standing consensus to NOT use it for arbitrary data at this  
time. If we were to start using it, we'd need to do something like  
the event-packages model for INFO. So don't use it, and you won't  
have to deal with this . . .


--
Dean


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