[VoiceOps] The peer of my peer is my peer?

Mark Holloway mh at markholloway.com
Tue Jul 13 16:58:13 EDT 2010

I don't experience this with a provider like Level 3, but on our network when one customer has an IP PBX with a SIP Trunk calling another on-net customer with a SIP Trunk, the compatibility lies within those endpoints playing nice with each other or else the call will fail.  An example of this is a customer we had as a field trial with a Toshiba CIX SIP Trunk using G.729 and calling customers on the same SIP network with Adtran TA900's.  The CIX defaults to 40ms packetization with G.729 and the TA900 only supports up to 30ms packetization. When the CIX customer would call the other on-net numbers using TA900's they experienced one-way audio.  We were able to have the customer change the CIX to 20ms.  It's a tricky area and I think it's going to take several more years to iron out all the kinks.. There is just too much interop testing to do between endpoints and providers that unless there are standards set in place, I don't see how these sorts of issues can be avoided 100%.

On Jul 13, 2010, at 1:38 PM, Hiers, David wrote:

> Every so often this issue comes up, and I want to get a read on it from other VOIP resellers...
> Consider a couple of unrelated VOIP resellers that peer with a carrier like L3.  Both can interop with L3 using strict SIP and RTP settings (max forwards, g729 only, 10ms ptime, whatever).  Both are free to select mutually incompatible settings.  For instance, reseller A can chose 729 only, and reseller B can choose 711 only.  L3 will connect both to the PSTN without any trouble.
> Everything is good until they try to call each other.  Then the mutually incompatible settings will break calls or render predicted usage patterns invalid.  Sure, you’re still signaling to a L3 SIP server, but some the information in the SIP/SDP packets that you receive is controlled by the other reseller.
> How often do you see problems related to the peer of your peer?
> David Hiers
> ADP Dealer Services
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