[SIPForum-discussion] Query on SIP re-invite

[Paul Kyzivat]

On 3/31/16 1:07 PM, Neelakantan, Neel wrote:
>
> -----Original Message-----
> From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Paul Kyzivat
> Sent: Tuesday, March 29, 2016 2:44 PM
> To: discussion at sipforum.org
> Subject: Re: [SIPForum-discussion] Query on SIP re-invite
>
> On 3/22/16 10:24 AM, Serrano, Angel (CCI-Atlanta) wrote:
>> Reinvites  also occurs  after the initial invite,  when the application server sends a challenge to the invite with a 401 unauthorized.
>
> While that is *another* INVITE, it is not a *re*INVITE.
>
> A Re-INVITE occurs within the dialog established by an initial INVITE.
> When an initial INVITE is challenged with 401 it has failed, and there is no dialog. The subsequent INVITE starts over.
>
> 	Thanks,
> 	Paul
>
> [Neel] It is true, but most implementation chooses to maintain the dialog fields, and this probably lead many to think that an INVITE after challenge is Re-INVITE.

The difference is that in this case the UAS doesn't establish any dialog 
state. The following INVITE (probably another try, this time with 
credentials) is entirely separate.

The distinction is subtle. But if your stack treats it as a re-INVITE 
then you may run into some anomalies. (I would have to think awhile to 
figure out what they might be.) So you should take care to build your 
stack to treat the case properly.

> Also on an established Dialog, mid call, there can be 401 response.  In that case it is not another INVITE.

Yes. In this case the INVITE that gets a 401 response and the following 
one responding to the challenge are both re-INVITEs.

	Thanks,
	Paul

> Thanks,
> Neel.
>
>> Also after the registration timer expires.  Sip is well documented,  RFCs are a great resource.
>>
>> COX
>> ----------------------------------------------------------------------
>> --------------------------------
>> Angel Serrano
>> Premise Technologies
>> 404-269-8093 (Office)
>> 470-658-7571 (Cell)
>> 6305 Peachtree Dunwoody Road, Atlanta, GA. 30328 Visit the MyAxis
>> page: TechOps  Please don't print this e-mail unless you really need
>> to do so.
>>
>>
>> -----Original Message-----
>> From: discussion-bounces at sipforum.org
>> [mailto:discussion-bounces at sipforum.org] On Behalf Of qcorba
>> Sent: Thursday, March 17, 2016 3:23 AM
>> To: Sathya <thinksathya at gmail.com>
>> Cc: discussion at sipforum.org
>> Subject: Re: [SIPForum-discussion] Query on SIP re-invite
>>
>> Examples can be found in the following documents:
>> 1. rfc3665
>> 2. https://tools.ietf.org/html/draft-mule-sip-t38callflows-00
>>
>> On 3/15/16, Sathya <thinksathya at gmail.com> wrote:
>>> Hello experts,
>>>
>>> I am new to this and have a doubt regarding sip reinvite. It may be
>>> discussed earlier but need your help on understanding on what
>>> scenarios the sip re-invite is used in call flow.
>>>
>>> Thanks
>>> Sathya
>>>
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