No Speech path when Nortel IP set places call on hold over SIP to 3rd party SIP PBX

[ibeintexas]

Hello all,

The Nortel system is a CS1000E on RLS 5.50J using 1140e, 1120e, i2007 and i2050 sets.

The 3rd party PBX is CIC with Polycom phones.

Problem: When Nortel IP set calls CIC IP extension over SIP VoIP trunks the caller can hear called party with good 2 ways speech. If the Nortel caller places call on hold, then picks call back up, there is no speech path either direction.

Inversely - When the CIC Polycom phone call the Nortel set over same SIP trunks and places Nortel on hold and picks call back up, 2 way speech is still good.

More information about setup:

- CIC PBX only supports G.711 codec, no G.729 or T.38 codecs on CIC PBX.
- Nortel TDM set to CIC over SIP works fine (same test).

Findings:

- When Nortel places CIC on hold, SIP trace shows that RTP from Nortel stops.
- When CIC places Nortel on hold, RTP stays active.

I have a feeling this will require a patch on the Nortel, but looking thru ESPL is not yielding the patch i need.

Please help!

Thanks all!