[SIPForum-discussion] Expires and Contact; expires for Microsoft SIP client compatibility

[Steve]

Thanks Sreeram,

I suppose the only issue would be if the PBX wanted to give each contact
address a different 'expires'. With both it would then have a general
Expires which would be superseded by the individual address.

I can't see the PBX 'offering' different expiry per contact but the contact
being registered to the PBX (in the REGISTER) might offer different times.
This would mean the SIP stack would still have to support individual
Contact;expires I believe?

So what should the PBX return to the UA, if the UA has for example:
REGISTER UA to PBX
Contact: <sip:257 at 192.168.1.90:5060>;expires=52
Contact: <sip:258 at 192.168.1.90:5060>;expires=53
Contact: <sip:259 at 192.168.1.90:5060>;expires=54

200 OK (REGISTER)
Contact: <sip:257 at 192.168.1.90:5060>;expires=52
Contact: <sip:258 at 192.168.1.90:5060>;expires=53
Contact: <sip:259 at 192.168.1.90:5060>;expires=54
Expires: - ????? Just default to the first contact expires time perhaps?

In theory the UA will never look at the 'Expires' (in this scenario) but if
I am to place it in all responses what value should I use? I could take the
lowest from the contact;expires or perhaps just return my own preferred
value?

Steve

On 21/11/2007, sreeram.kanumuri at wipro.com <sreeram.kanumuri at wipro.com>
wrote:
>
>
> Steve,
>
> You can have both 'expires' and 'Expires' in the same response.
> It checks for the expires in the contact header,
> If this expires is not there in contact,the value in the Expires field
> is taken.
>
>
> I don't see any problem in your case.
> You can have 'expires' or 'Expires' not a problem. But the preference
> will be given as I mentioned.
>
> HTH,
> Sreeram.
>
> -----Original Message-----
> From: discussion-bounces at sipforum.org
> [mailto:discussion-bounces at sipforum.org] On Behalf Of Steve
> Sent: Wednesday, November 21, 2007 2:47 PM
> To: discussion at sipforum.org
> Subject: [SIPForum-discussion] Expires and Contact;expires for Microsoft
> SIP client compatibility
>
> Hi group,
>
> This is my first message, so I hope I'm all good with this....
>
> My question is the validity and repercussions of implementing the
> 'Expires' header field.
>
> The RFC3261 to me implies that Expires covers all Contact
> (per-binding) addresses are the same time-out. Would it be acceptable to
> have both 'expires' and 'Expires' in the same response to cover any
> incompatibilities?
>
> Steve
>
> Background:
> I'm integrating our office PBX with GSM + WiFi handsets. In this
> particular case the Windows Mobile 6 handsets which use the Microsoft
> RTC 1.5.
>
> I have found that the PBX cuts off calls after the SIP registration
> times out because of the incompatibility in negotiation.
>
> The Windows RTC client used in WM6 reacts to the 'Expires header field'
> value and not the 'Contact; expires=' value. E.g.
>
> Real response (;expires=52):
> Message Header
> Contact: <sip:258 at 192.168.1.90:5060>;expires=52
> From: <sip:258 at 192.168.1.146>;tag=f7c498be3c;epid=877e4564ac
> To: <sip:258 at 192.168.1.146>;tag=329214850
> Call-ID: 000070c4000018188079efd4ed25c801
> CSeq: 2 REGISTER
> Server: AspireML-GE 07.02/2.1
> Via: SIP/2.0/UDP 192.168.1.90:5060;branch=z9hG4bK23b877d934-1
> Content-Length: 0
>
> My Emulated response that the device honours (Expires: 52):
> Message Header
> Contact: <sip:258 at 192.168.1.90:5060>
> From: <sip:258 at 192.168.1.146>;tag=f7c498be3c;epid=877e4564ac
> To: <sip:258 at 192.168.1.146>;tag=329214850
> Call-ID: 000070c4000018188079efd4ed25c801
> Expires: 52
> CSeq: 2 REGISTER
> Server: AspireML-GE 07.02/2.1
> Via: SIP/2.0/UDP 192.168.1.90:5060;branch=z9hG4bK23b877d934-1
> Content-Length: 0
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