Nortel Networks has gone bankrupt, and is selling bits and pieces to Nokia Siemens. I'm not sure if the CS2K is one of those pieces.
Nortel has a lot of really smart people. It's difficult to change from charging $16M for a telephone switch servicing 100,000 lines in 1997 (which is what they charged BellSouth for the DMS100 in my home town) to the current marketplace.
There are interesting engineering and technical questions that arise when a company does this. People have long complained about Nortel's support for the CS2K. At least one carrier is rumored to have stopped provisioning new subscribers on their Nortel CS2K as soon as the bankruptcy was announced.
If you need a modern alternative to the CS2K, what are the choices? There are plenty, but a few front-runners:
MetaSwitch is the first to come to mind because CS2K users often have copious TDM and SS7 interconnections. The MetaSwitch platform can definitely do this, Class-5 and Class-4/tandem type features.
- BroadSoft may be a fine choice if you were using the CS2K primarily for Class-5-like features, and you have some other way of interconnecting SIP to the PSTN.
- Alcatel-Lucent has the old Telica Plexus 9000 platform (not to be confused with the Plexus 8000). I think the name-of-the-month is the "Alcatel-Lucent Network Gateway". It's a nice box, but somewhat difficult to troubleshoot. (Especially if you don't have the super-secret list of debug commands and logging that you can run on the individual CPU and VSM cards.) Still, if you're looking for solid SIP-to-PSTN interworking, it's a good option to consider.
- Taqua has a platform worth considering.
- You might consider Cisco because of the PGW or BTS10200. These come across as pretty weak players, compared to other folks in this list. If you're interconnecting the VoIP world with the PSTN, then you can use AS5400s and have great joy. (Just be sure you add access-lists to control the paths SIP can take. IOS will accept a call from anybody!)