[Asterisk-Users] SIP and DSL Bandwidth queries.

[John Todd]

>Here is my setup
>
>7960(A)--Firewall/PAT--dsl---------Internet--------dsl--Firewall/NAT---7960(B)
>                                     |     |
>                                     |     |
>7960(C)--NAT--cable-----------------      -----dsl -- Asterisk
>
>(A) can communicate with (C) only when C is configured with 
>canreinvite=no. The call gets dropped in few seconds if canreinvite 
>is set to yes for C.
>(A) and (B) can communicate fine when both sides have canreinvite=yes.
>
>Since (C) is not working with canreinvite, traffic goes thru 
>Asterisk server. This brings the Dsl connection to asterisk to a 
>crawl. It is so bad that even a idle ssh connection gets 
>disconnected.
>
>Is it possible to configure C so that reinvite works. If not what 
>kind of a bandwidth should I have for Asterisk server. Currently it 
>has a upload of 128K.
>
>The codec currently getting used is ULAW. Even if I configure 7960's 
>to use g729, show sip channel reports as using ULAW.
>
>Thanks,
>==ratnakar

If you are moving your traffic from behind a NAT, your Asterisk 
server must have a G.729 license to terminate the traffic, since 
Asterisk must be the media proxy for the stream.  As you are 
connecting endpoints together that are behind NAT, you would need 
multiple G.729 licenses - one for every device that would be 
concurrently talking to the Asterisk server.  I do not believe that 
it is possible to configure C so that reinvite works, though I would 
be interested in how you do it if you are able to make that function 
without Asterisk being a media channel proxy (quasi-border session 
controller.)

You should have at least 56kbps for G.729, in my experience, unless 
you have no other traffic on the end legs of the diagram.  G.729 uses 
less than 32kbps during normal circumstances, but other TCP traffic 
needs to squeeze in  (as you have discovered.)  Your Asterisk server 
will of course need to have N*(leg bandwidth) capacity, where N is 
the number of legs active at any one time.

JT