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
_______________________________________________
Sip-implementors mailing list
[email protected]
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
