[SIPForum-discussion] difference between INFO and OPTIONS method?

[Eric Burger]

And for the second question: please, please, please read RFC 3261, the
defining document for SIP.  Or, go buy SIP Demystified. Or go buy SIP:
Understanding the Session Initiation Protocol.

You would see that OPTIONS is totally orthogonal to mid-call signaling.

What might not be obvious is that INFO as it is today is a poor choice for
mid-call signaling.

To your last question: think about it.  ³How do I do something before I can
do something?² has the answer already there.

On 12/7/07 1:29 PM, "Andrea Puddu" <androjoker at hotmail.com> wrote:

> I answer to first question (correct me if I am wrong):
> 
>   CANCEL request is sent when response to INVITE message is not received. If
> this INVITE request is lost and UA may still send a CANCEL request. Is this
> possible? Can CANCEL request be sent without sending an INVITE message?
> 
> A CANCEL request can be sent if the 200 OK to the INVITE request has not been
> received yet from the Caller. Otherwise you have to send a BYE request.
> Furthermore I guess that if you send a CANCEL not related to an INVITE you
> will probably receive a "
> 481 Call/Transaction Does Not Exist" message. _In fact which Call-ID do you
> mean to use? It has to be the same of the INVITE request. Just try.
> 
> 
> Andrea
> 
> 
> 
>> 
>> Date: Fri, 7 Dec 2007 15:09:33 +0000
>> From: nidhi_jain6680 at yahoo.co.in
>> To: discussion at sipforum.org
>> Subject: [SIPForum-discussion] difference between INFO and OPTIONS method?
>> 
>> Hello, 
>> 
>>         CANCEL request is sent when response to INVITE message is not
>> received. If 
>> this INVITE request is lost and UA may still send a CANCEL request. Is this
>> possible? Can CANCEL request be sent without sending an INVITE message?
>> 
>>         What is the basic difference between INFO and OPTIONS method? can
>> OPTIONS 
>> used for mid-call signalling?
>> 
>>         Why is ACK request required? Is it just to avoid retransmission of
>> response 
>> message. This could be done even by starting the media transmission.
>> 
>>         How are DTMF digits sent before the session setup?
>> 
>> Please reply. 
>> 
>> Thank you. 
>>   
>> 
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