[asterisk-dev] Call numbers in IAX2 media frames

[Russell Bryant]

Tim Panton wrote:
> I'd look _very_ carefully at the way that transfer works, since in the 
> current model the mini-frame packets
> get to keep their numbers but if it were the other way around you'd have 
> to change them in mid flow.

Ah, interesting point.  However, I still don't see this as a problem.  There is 
a call number information element that is sent with a TXREQ message that 
contains the destination call number on the peer that the media would then be 
sent to.

> It also allows you to use the same matching code on mini-frames and 
> fullframes since
> both contain the same data in the first 2 bytes (apart from the top bit).
> Actually we don't do this - Java doesn't lend it self that that sort of 
> brutality :-)

Right, but splitting that up is not any kind of measurable performance hit. 
Also, it's only helpful for the code that gets the source IP address out of the 
frame.  There is a lot more work to do after that in which they differ.

Like I said before, there are definitely compatibility issues in regards to this 
proposed change.  I'm trying to figure out if it could still work.  :)

> In our implementation we have a two level optimization, first we use the 
> source IP address
> to select the peer we expect to talk to. We then hash into a table of 
> active calls (local to the peer)
> which are indexed on the call number.

I assume you meant source IP address and port number.  But, wouldn't it be nice 
to just immediately have the local call number to identify the call?  That way, 
you would completely eliminate the step in that process of matching the peer.

-- 
Russell Bryant
Software Engineer
Digium, Inc.
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