Question about Codecs in Unity / Trunks

[demerson111]

Our phone system transitioned from SCCP to SIP fairly recently, and we have had numerous issues ever since. Once such issue is that call forwarding is not working properly when trying to dial from Unity.

A basic rundown of our system is this:

• Two main offices
• West - holds all publishers
• East - holds subscribers
• several smaller branch offices throughout country
• Two SIP trunks - East/west coast - each connected to CUBE respectively - connected through MPLS

Before I get into too much details on this specific situation, I wanted to ask as a general rule- does a Unity Connection SIP Trunk have to use 711ulaw and only 711 as its codec, or can I set it up to allow for g.729 also? The calls are dropping because we have a call handler that is dialing an internal extension which it reaches just fine, but if the extension is forwarded to a cell phone, the carrier tries to renegotiate the call as g.729, and the call will briefly pop up on the user's cell phone, then drop immediately. I realize there are a number of factors between A to B, but wanted to ask this generalized question before going further.

Also, does anyone know how to write SIP normalization scripts which could fix this problem? I am not an engineer, so my UC experience doesn't go that deep, so I could use any and all experienced engineers suggestions - I can post more detailed traces as needed- thanks

Dave

[hsood]

Hi,

Q- Does a Unity Connection SIP Trunk have to use 711ulaw and only 711 as its codec, or can I set it up to allow for g.729 also?

A- It can do both. You can configure under Telephony Integration >> Port Group >> Advertised Codec Settings.

If the call has not been picked up by the cell phone user yet, it is highly unlikely a codec issue as SDP does not play a part till the time call has been picked up.

Issue lies somewhere in the call control indeed i.e. signalling as per your description.

Please rate if useful.

Regards,

Hitesh

[demerson111]

Thank you Hitesh, I haven't posted back recently because an engineer was able to resolve the problem of codec negotiation between Unity to carrier by implementing a transcoder. I went through in Unity and checked the settings you mentioned, and everything looks good there. The reason I originally mentioned codecs is because a trace revealed the call was originally negotiated between Unity and the carrier to accept either g.711 or g.729, but even before the call recipient would get a chance to answer, his or her phone would do like half a ring, then immediately disconnect, with the caller hearing "The wireless member you are trying to reach is unavailable" or "The number you dialed is not a working number, please check the number and dial again". A trace was showing that the carrier would renegotiate prior to establishing a session that it would only accept g.711.

I am having a separate issue with call forwarding now, that has nothing to do with Unity, but is behaving in a similar fashion (ie. an outside caller will dial a desk phone that is forwarded, it will ring less than once, then drop). I believe it is dial-peer related now. The scope of this problem is a little larger than I thought. If anyone is interested in tackling this one, I can post the traces/trunk configs...