[SIPForum-discussion] HELP

[reeti sharma]

Hi Ganesh....




On Fri, May 16, 2008 at 2:09 PM, Ganesh Bhattathiri <
ganesh_bhattathiri at persistent.co.in> wrote:

>  Hi
>
   I think u take dialog slightly wrong.... Let we take ur example that " If
UAC sends a request..."

   When UAC sends and request, two possible cases can occur(in case of no
error):
   1) either UAC recieve positive final response (i.e. 2xx series) or
   2) UAC may recive negative final response (i.e. 3456xx series) in case if
UAS is not willing to accept the request or request get rejected via some
other reason (you can go thru the rfc 3261)

Here important is that : in 1st case dialog comes into picture, while in
second case it simply the transaction.

Now in brief : when a UAC recive any 2xx response with "to" tag, then dialog
will be established.
if in provisional responses "to" tag is present then also we can make an
early dialog, which will be confirmed only if any 2xx response will recive.


Now ur transaction part :
transaction is the pairing of related request and its corresponding
response.
For example: If  UAC sends the INVITE and get back 2xx response then INVITE
+ 2xx makes a transaction pair.
if UAC sends INVITE then and get negative final response i.e. 3456xx in case
INVITE + 3456xx + ACK makes the transaction pair.

As per rfc 3261 rules ACK is not consider the part of transaction in case of
2xx respone, while it is consider as the part of tarnsaction for any other
response.

I suggest you to once go thru the rfc 3261 sections which are dedicated to
transaction, it will help you to clear your basic doubts.


>   Regards
>
Reeti...

>
>
  Can somebody tell me the difference between Dialog and session and
> transaction?
>
>
>
> First let me tell you what I thought it was.
>
>
>
> If there is a UAC and UAS, If UAC sends a request and gets a non-100
> response back the whole process is knows as a dialog
>
> And from the point of first request to the ACK sent for BYE it is  a
> session.
>
>
>
> Now if what I have said above is right then how would you differentiate a
> request sent outside the dialog? As in doesn't that also get a response back
> could that not be a non-100 response?
>
>
>
> Can Someone help me get this confusion cleared?
>
>
>
> Thanks again
>
>
>
> Ganesh
>
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-- 
Cheer!
Reeeet.....
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