Subject: [Sip] Reg. refresher param in 2xx response

From: Harbhanu <[email-masked]>
Date: Tue, 18 May 2010 14:18:31 +0530

As per 4028, for the following case UAS MUST specify the refresher parameter
in 2xx response.

UAC ----INV ----> supported=timer, SE=90-----> UAS

UAC <----2XX INV -- SE=90- ---------------- UAS

[Section-9, page-16]

The UAS MUST set the value of the refresher parameter in the Session-Expires
header field in the 2xx response.

But IMO when UE sends response for INVITE and it adds Session-Expires but
doesn't specify the refresher parameter.

Then in this case UAC can safely assume that, either the UAS doesn't support
session-timer or it doesn't want to act as a 'refresher'.

So instead of sending a BYE UAC MAY treat this as a buggy/naive UE & hence
"UAC" SHOULD act as 'refresher'.

Please share your opinion. Thanks!

Regards,

Harbhanu

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---

From: Brett Tate <[email-masked]>
Date: Tue, 18 May 2010 05:16:14 -0700

If 2xx's session-expires doesn't contain the mandatory refresher parameter, it is likely because interworking with an old implementation of the draft:
http://tools.ietf.org/wg/sip/draft-ietf-sip-session-timer/

The refresher parameter was added within version 5 of the draft.

Per RFC4028, it is an abnormal situation; I don't recall the RFC indicating how to act within the abnormal situation.  Thus you can however you want.

From: [email-masked] [mailto:[email-masked]] On Behalf Of Harbhanu
Sent: Tuesday, May 18, 2010 4:49 AM
To: [email-masked]
Subject: [Sip] Reg. refresher param in 2xx response

As per 4028, for the following case UAS MUST specify the refresher parameter in 2xx response.

[Section-9, page-16]

The UAS MUST set the value of the refresher parameter in the Session-Expires header field in the 2xx response.

But IMO when UE sends response for INVITE and it adds Session-Expires but doesn't specify the refresher parameter.
Then in this case UAC can safely assume that, either the UAS doesn't support session-timer or it doesn't want to act as a 'refresher'.

So instead of sending a BYE UAC MAY treat this as a buggy/naive UE & hence "UAC" SHOULD act as 'refresher'.

Regards,
Harbhanu

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This e-mail and attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient's) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!

---

From: Harbhanu <[email-masked]>
Date: Tue, 18 May 2010 19:38:55 +0530

Precisely, IMO too RFC doesn't specify UAC behavior for this situation.

So, we think that in order to have a better error tolerance or say
flexibility, this behavior SHOULD be fine.

So can anybody suggest/highlight any scenario/use-case wherein this
'tolerance' might prove otherwise? :-)

Also, please specify if you are aware of its handling in any of the
commercial implementations.

Thanks again!!

Regards,

Harbhanu

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From: Brett Tate [mailto:[email-masked]] 
Sent: Tuesday, May 18, 2010 5:46 PM
To: Harbhanu; [email-masked]
Subject: RE: [Sip] Reg. refresher param in 2xx response

If 2xx's session-expires doesn't contain the mandatory refresher parameter,
it is likely because interworking with an old implementation of the draft:

Per RFC4028, it is an abnormal situation; I don't recall the RFC indicating
how to act within the abnormal situation.  Thus you can however you want.

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Harbhanu
Sent: Tuesday, May 18, 2010 4:49 AM
To: [email-masked]
Subject: [Sip] Reg. refresher param in 2xx response

[Section-9, page-16]

Regards,

Harbhanu

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From: "Kevin P. Fleming" <[email-masked]>
Date: Wed, 19 May 2010 11:28:16 -0500

On 05/18/2010 09:08 AM, Harbhanu wrote:
> Precisely, IMO too RFC doesn’t specify UAC behavior for this situation.

That is generally the case; RFCs can't possibly define how an
implementation should behave when interacting with a non-conforming
implementation, because there are an infinite number of ways to be
non-conformant.

-- 
Kevin P. Fleming
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