[SIPForum-discussion] what is the diffrence b/w a transaction, session , dialog

[malaya.kishore at wipro.com]

Hi Vikas,

In a normal call flow

UAC                                  UAS
INVITE-------------------------->
Trying<--------------------------
180<---------------------------
200ok<-------------------------
ACK---------------------------->
BYE<----------------------------
200OK------------------------->
--------------------------------------------------------------------
Dialog:
--------------------------------------------------------------------
When UAC sends INVITE to UAS, it contains From-tag and Call-ID in the
Message.

In response UAC receives 200 OK, and in 200 OK, To-tag will be present.

* In SIP the From-tag, To-tag, Call-ID makes a Dialog.

So when there is a successful INVITE and its response, then a Dialog is
established.

* A Dialog is a sequence of Transactions.
--------------------------------------------------------------------
--------------------------------------------------------------------
Transaction
--------------------------------------------------------------------
Every Request and its corresponding Responses makes a Transaction
Eg:
Transaction x: REGISTER and 200 OK
Transaction y: Bye and 200 OK


In case of INVITE, Transaction is as follows:
If UAC receives a successful response that is 200 OK for the INVITE it
sends then the transaction includes ACK.

That is 
Transaction is: INVITE---- 1xx responses -- 200 OK --- ACK

In case UAC receives a non Success response (anything other than 2xx)
transaction doesnot include ACK.

That is
Transaction is: INVITE --- a non 200 response
And ACK will be another transaction.

* In SIP Transaction is identified by the "CSeq number" in a Dialog
--------------------------------------------------------------------


--------------------------------------------------------------------
Session
--------------------------------------------------------------------
With every INVITE -- 200 OK -- ACK, a session is established, that is
the two clients have a session to exchange media. That's a session.
--------------------------------------------------------------------

Hope it's clear. 


Kind Regards,
Kishore





-----Original Message-----
From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of VG
Sent: Saturday, June 06, 2009 10:23 AM
To: nitin kapoor
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] what is the diffrence b/w a
transaction,session , dialog

Thanks Nitin for this valuable information.

May u please specify with an example like :

In a normal call flow

UAC                                  UAS
INVITE-------------------------->
Trying<--------------------------
180<---------------------------
200ok<-------------------------
ACK---------------------------->
BYE<----------------------------
200OK------------------------->


Which is transaction, dialog and session. It will be much more clear.

Thanks & Regards,
VG
On Sat, Jun 6, 2009 at 5:36 AM, nitin kapoor<nitinkapoorr at gmail.com>
wrote:
>
> Hello Vikas,
>
> Below is the bit explanation of dialog, transaction & session.
>
> Dailog:
>
> Dialog is a peer-to-peer relationship between two user agents. It
represents
> a context that facilitates the sequencing of messages between the user
> agents and proper routing of requests between both of them.
>
>
>
> Transaction:
>
> Transaction is a request sent by a client transaction (using the
transport
> layer) to a server transaction, along with all responses to that
request
> sent from the server transaction back to the client. Any task that a
user
> agent client (UAC) accomplishes takes place using a series of
transactions.
>
>
>
> Session:
>
> A session refers to all the connections that a single client might
make to a
> server in the course of viewing any pages associated with a given
> application. Sessions are specific to both the individual user and the
> application. As a result, every user of an application has a separate
> session and has access to a separate set of session variables.
>
>
>
> Thanks,
>
> Nitin Kapoor
>
>
>
> 2009/6/5 VG <vikasraigupta at gmail.com>
>>
>> Hi,
>>
>> I m confused with these three things :
>> transaction
>> session
>> dialog
>>
>> Please specify me with an example.
>>
>> Thanks & Regards,
>> VG
>> _______________________________________________
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>
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