23 SepCalls from Lync to Nortel CS1000 over ISDN don’t display caller ID on handset

During a recent Lync 2013 Enterprise Voice roll-out I was configuring interoperability with the legacy Nortel CS1000 PBX. For this, we’d deployed a pair of Sonus SBC 1000 gateways with 2x ISDN PRI ports each. In each gateway, one PRI port was connected to the PSTN and the other PRI port was connected to the CS1000, so these gateways were deployed in an upstream model in front of the PBX.

Calls to all destinations (Lync, the CS1000 and the PSTN) were connecting fine with no media problems, but we did observe that calls from Lync to legacy PBX phones were not displaying the calling number (or caller ID, or CLI, take your pick) on the handset. Tracing this using Sonus LX found that the gateway was configured to pass through the calling and called numbers correctly, so the problem wasn’t immediately apparent:

lync to pbx no CLI

This looked like a case closed “something is wrong with your legacy PBX” problem, but I compared this to calls that were displaying the caller ID properly that were being passed through by the gateway from the PSTN to the CS1000 and found one inconsistency:

lync to pbx successful CLI

I found that for calls where the calling number was being displayed on the Nortel handset correctly had a Screening value of Network Provided. Whereas calls where the calling number was not being displayed on the Nortel handset had a Screening value of User Provided, Not Screened.

To eliminate this inconsistency, I created a new rule in the transformation table for calls from Lync to the CS1000 on the Sonus gateways to match the Calling Number Screening value of Any, and replace the output with a value of Network.

trans rule to fix Lync to PBX CLI

Once this was applied, the LX log reflected the Screening value correctly and the caller ID for calls from Lync to CS1000 started appearing correctly on Nortel handsets.

pstn to pbx successful CLI

This might seem like a minor issue but it was important that we fixed this as it represented a deployment blocker. Without resolving this, users that hadn’t been migrated to Lync yet were confused who was calling when a Lync voice pilot user called them, which would inhibit user adoption of Lync Enterprise Voice. Now the migration of users to Lync voice is 100% seamless and completely transparent. 🙂

2 Responses to “Calls from Lync to Nortel CS1000 over ISDN don’t display caller ID on handset”

  1. Well, actually this is a great solution, and the good thing that the sonus gateway can support such translations, thank you for sharing

  2. Kris says:

    A completely revamped LX 2.0 is out there. Please reach out to your SE to get it. Thanks.

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