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Hi,
the Call-ID is unique for each SIP Request. Even though the on a same
session if you are going to use multiple requests (like invite ,subscribe
options .. etc ) you have to generate the a new call id for each request.
In your case when you received a BY E that dialog is completed. The next
Invite request starts a new Dialog so you can;t use the old Call-ID.
Refer the RFC 3261 Section 20.8 for more details.
In the old RFC the proxy is using the call-id to maintain the transaction
,but as per the RFC 3261 both Call-ID and Tags are used to maintain the
transactions...
Regds
Balaji.C
"Giancarlo Murino" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
11/03/2006 02:30 PM
To
<[email protected]>
cc
Subject
[Sip-implementors] Rules about Call ID, From tag and To tag
Hi,
I have a trouble about Call Id, From tag and To tag. On a Web site I read:
Call-ID is so called call identifier. It must be a unique string that
identifies a call. A call consists of one or more dialogsi. Multiple user
agents may respond to a request when a proxy along the path forks the
request. Each user agent that sends a 2xx establishes a separate dialog
with
the caller. All such dialogs are part of the same call and have the same
Call-ID.
>From tag is generated by the caller and it uniquely identifies the dialog
in
the caller's user agent. To tag is generated by a callee and it uniquely
identifies, just like From tag, the dialog in the callee's user agent.
This hierarchical dialog identifier is necessary because a single call
invitation can create several dialogs and caller must be able to
distinguish
them.
So, if I have understood, if there are parallel dialogs (as in forking
case)
I have to use the same Call-Id , but different to tag and from tag,
because
such dialogs are part of the same call. But if I have two sequencial
dialogs
like in the following flow:
------------->INVITE (start first dialog)
<------------- OK
--------------> BYE (end first dialog)
------------->INVITE (start second dialog)
<------------- OK
--------------> BYE (end second dialog)
Are they a part of the same call, or they belong to two different calls?
According to the definition of call (a call is a group of one or more
dialogs), I think they are a part of the same call. So, must they share
the same Call-ID? If they aren't a part of the same call, why?
Giancarlo_______________________________________________
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