Re: Query related to Expires header with value 0 in INVITE

Hi All

IMO the UAS should response 487 when it receives INVITE with "Expires = 0"
andalso as I know the ETSI test case suggests  "UAS should response 487 when
it receives INVITE with "Expires = 0" "

Thanks
Samman/孙永光(SunYongGuang)
MSN:[email protected] <MSN%[email protected]>

2008-12-11



2008/12/4 Neelakantan Balasubramanian <[email protected]>

>  See below.
>
>
>
> *From:* [email protected] [mailto:[email protected]] *On Behalf Of *Anita
> Tailor
> *Sent:* Tuesday, December 02, 2008 5:10 AM
> *To:* [email protected]
> *Subject:* [Sip] Query related to Expires header with value 0 in INVITE
>
>
>
> Hi All,
>
>
>
> I have some queries related to expires header in SIP message.
>
>
>
> *RFC 3261 Section 20.19***
>
> *" The value of this field is an integral number of seconds (in decimal)
>    between 0 and (2**32)-1, measured from the receipt of the request"*
>
>
>
> Does this mean 0 is a valid value of Expires header ? I am confused because
> of "between" word here as meaning might different if "from 0 to  (2**32)-1"
> have used.
>
>
>
> >>> It doesn't look like properly.  See  RFC 3261 Section 13.2.1
>
>
>
>    The UAC MAY add an Expires header field (Section 20.19) to limit the
>
>    validity of the invitation.  If the time indicated in the Expires
>
>    header field is reached and no final answer for the INVITE has been
>
>    received, the UAC core SHOULD generate a CANCEL request for the
>
>    INVITE, as per Section 9.
>
>
>
> So, immediately after INVITE, the UAC should generate CANCEL.  But it has
> to wait until it gets some response.
>
>
>
> Section 9.1
>
>
>
>    If no provisional response has been received, the CANCEL request MUST
>
>    NOT be sent; rather, the client MUST wait for the arrival of a
>
>    provisional response before sending the request.
>
>
>
> Does Expires value in INVITE is modified by intermittent SIP entities
> before it reaches to its destination?
>
>
>
> Proxies do not modify headers present in the request it receives.  See
> section 16.6.
>
>
>
> If yes, then what should be UAS behavior when it receives INVITE with value
> 0 in Expires header ? Should UAS respond with 487 ?
>
>
>
>
>
> *Section 13.1.1 [1]*
>
> *  "If the request is an INVITE that contains an Expires header
>  field, the UAS core sets a timer for the number of seconds
>  indicated in the header field value.  When the timer fires, the
>  invitation is considered to be expired.  If the invitation
>  expires before the UAS has generated a final response, a 487
>  (Request Terminated) response SHOULD be generated."*
>
>
>
> So the UAS should generate a 487 right away.
>
>
>
> Thanks in Advance
>
> Anita
>
>
>
>
>
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