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

Wed Nov 21 11:35:25 UTC 2007

Hi Steve,

>>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? 
You can keep any value.
This is how it works
In Response to Regiater in 2XX,If the Contact header does not have an
"expires" parameter, the valueof the Expires header field is taken. 
If  neither is there, the expiration time specified in the  request by
default, is used.

HTH,
Sreeram.

________________________________

From: Steve [mailto:sg1009 at gmail.com] 
Sent: Wednesday, November 21, 2007 4:42 PM
To: Sreeram Kanumuri (WT01 - TES-Mobility & Carrier Infrastructure)
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Expires and Contact;expires for
Microsoft SIP client compatibility

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Expires which would be superseded by the individual address.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
<mailto: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
<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 <mailto: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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