[SIPForum-discussion] Possible responses to 180 Ringing Messages

[Rudra Kant Kanth]

Thanks Srinivas,
You may well be correct here. I hadn't thought of the UPDATE message. My
Bad.

Can you help me with a trace here. I would like to see how the traces would
like like in such a case.

Regards,
Rudra

On Thu, Jan 5, 2012 at 12:24 PM, Banda, Srinivas (Srinivas) <
sribanda at avaya.com> wrote:

> Hi Rudra,****
>
> ** **
>
> *But assuming the question is re-framed as what all are possible next
> messages after a 180 Ringing, THEN among the options, we can have a CANCEL
> coming in as well. If still I have to choose a 3rd option then, I would
> choose an INVITE as my last option. The reason for choosing INVITE and not
> BYE as my answer is that(based on my gut feeling):- in an event a user
> decides to drop the call, he has to send a CANCEL. However, if the user
> decides to change any of the entries in the INVITE headers (say contacts,
> or codecs etc), it has to come up to the far-end client in form of INVITE
> only.*
>
> ** **
>
> I completely disagree with the above analysis:****
>
> How does a UA sends another INVITE,  without getting the final response to
> the Initial INVITE?****
>
> In this case if the UA wants to change(codec etc) he has to Send the
> UPDATE not the INVITE message.****
>
> ** **
>
> Regards****
>
> Srinivas****
>
> ** **
>
> ** **
>
> *From:* discussion-bounces at sipforum.org [mailto:
> discussion-bounces at sipforum.org] *On Behalf Of *Rudra Kant Kanth
> *Sent:* Saturday, December 17, 2011 11:01 PM
> *To:* AMIT ANAND
> *Cc:* discussion at sipforum.org
>
> *Subject:* Re: [SIPForum-discussion] Possible responses to 180 Ringing
> Messages****
>
> ** **
>
> Hi Amit and Albert,****
>
> ** **
>
> I have seen situations where 180 Ringing is followed up with PRACK as
> reliable acknowledgement to the 180 Ringing. ****
>
> ** **
>
> Though by default, the 180 Ringing doesn't need acknowledgement of
> successful receipt by the far-end. However, when there is a "*required: 100
> rel*" parameter in the 180 Ringing, then that 180 Ringing needs to be
> acknowledged for successful receipt and thus a PRACK is sent by the UAS,
> for which the client sends back 200 OK. However, in more generic cases, a
> 180 Ringing would have 100 rel in the supported format.****
>
> ** **
>
> Thus,****
>
> PRACK is the ONLY VALID "RESPONSE" in this case. As Amit stated, all the
> options were actually REQUESTS only.****
>
> But assuming the question is re-framed as what all are possible next
> messages after a 180 Ringing, THEN among the options, we can have a CANCEL
> coming in as well. If still I have to choose a 3rd option then, I would
> choose an INVITE as my last option. The reason for choosing INVITE and not
> BYE as my answer is that(based on my gut feeling):- in an event a user
> decides to drop the call, he has to send a CANCEL. However, if the user
> decides to change any of the entries in the INVITE headers (say contacts,
> or codecs etc), it has to come up to the far-end client in form of INVITE
> only.****
>
> ** **
>
> OK, another thing is that in race-conditions, you will also find a BYE
> being sent in a CANCEL request call, but, this BYE HAS TO FOLLOW THE
> CANCEL. It will never come before the CANCEL.****
>
> ** **
>
> So, PRACK, CANCEL and INVITE.****
>
> ** **
>
> Regards,****
>
> Rudra****
>
> ** **
>
> ** **
>
> On Wed, Dec 14, 2011 at 11:44 AM, AMIT ANAND <amiit.anand at gmail.com>
> wrote:****
>
> Hi Albert,
>
> Where did you get this question?
>
> If i were on your place i would say non of these,
>
> These all are requests and ideally there could be no response to a
> response.
>
> Except ACK any of other four can come in a call flow after 180.
>
> Cheers
> Amit
>
>
> ****
>
> On Fri, Dec 9, 2011 at 6:53 AM, Albert Etsebeth <umbrualbert at gmail.com>
> wrote:****
>
> Hi All****
>
> ** **
>
> I got this question in a exam, and its been driving me mad.****
>
> ** **
>
> Question:"what are valid responses to 180 ringing" (Choose 3)****
>
> ** **
>
> Options:PRACK / ACK / BYE /CANCEL /INVITE ****
>
> ** **
>
> In my opinion there is only 2, PRACK and CANCEL****
>
> ** **
>
> Thanks****
>
> ** **
>
> umbru****
>
> ** **
>
> ** **
>
>
> _______________________________________________
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>
>
>
>
> --
> Thanks
> Amit Anand
>
> _______________________________________________
> This is the SIP Forum discussion mailing list
> TO UNSUBSCRIBE, or edit your delivery options, please visit
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> Post to the list at discussion at sipforum.org****
>
> ** **
>
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