Tanmay Zargar wrote:
> Hello,
> I need some help regarding the transport layer of a SIP server.
>
> Consider the following scenario :
>
> The transport layer successively receives a number of messages for a
> *particular connection* (messages from the same client)
> in some order - say INVITE followed by a CANCEL. (Actually this situation
> of an INVITE followed immediately by an CANCEL is
> not valid since the UA that has sent the INVITE, cannot send a CANCEL, or
> for that matter any request, without first
> receiving either a provisional or a final response from the proxy. But we
> can assume that a rogue UA could do this.)
There are sevearl places in the network where messages can be reordered
- in a router, or in an end system using multi-threaded handlers as you
describe. Whichever place it occurs, the protocol needs to handle it,
and it does. The exact problem you describe - misordering of INVITE and
CANCEL, is handled in the specification already. Other misordering
issues are handled in a similar way.
Now, if you are concerned about elements that violate the specification,
so that order is not preserved, well, I don't see why it matters that
you reorder messages that a rogue proxy sends in violation of the
specification.
-Jonathan R.
--
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Avenue
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
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