AudioCodes does it again! They released a new model, the Mediant 9000 today (Lync qualification expected Q1 2014). This is a Pure Session Boarder Controller (E-SBC) that will allow up to 16,000 sessions. This is following the company's release of the Mediant 2600 (600 sessions) in May 2013 and Mediant 4000 (5,000 sessions) released in July 2012. The Mediant 2600 and up can be deployed in a high availability pair to provide uninterrupted service.
The chart below shows the current offerings and SBC session capacity.
I am a big fan of the AudioCodes E-SBC application. I find the user interface easy to understand and configure. AudioCodes has published a document LTRT-54006 Lync 2013 - Mediant E-SBC SIP Trunking Configuration Note Ver. 6.6
and it's a very good jump start on configuring the E-SBC for Lync Server 2013.
Visit the AudioCodes Lync solution catalog to view the models and software version tested.
AudioCodes Mediant Session Border Controllers
AudioCodes Mediant Enhanced Media Gateways
AudioCodes Mediant Survivable Branch Appliances