Starting with version 4.1 of Cisco Unified CallManager Express, Cisco has introduced support for hardware based multiparty conferencing. This is a great improvement over the default software based conferencing that is also available in CallManager Express. What this means is that Call Manager Express can support up to 32 parties in a Conference call using the G.711 codec and up to 16 parties in a conference Call using the G.729a or G.729ab codecs. This is a great improvement on the 3 party limit of ad-hoc conferencing when using the software based conference feature.
To setup hardware based conferencing resources, we need to make sure we have the appropriate hardware. Cisco Call Manager Express needs DIgital Signal Processors or DSPsf or short. DSPs commonly come in the PVDM2 format that plugs into the motherboard of a Cisco 2800 or 3800 series router or a network module like the NM-HDV2 or NM-HD-2VE.
Types of conferencing available in CallManager Express
Ad-Hoc Conferencing
Ad-hoc commonly invoked by the CONFRN softkey on a phone for an impromptu conference call. Even with hardware conferencing the maximum amout of parties on a IP phone is 8.
Meet Me Conferencing
Previously only available in full blown CallManager. An admin can define a conference directory number that can be given out or a meet-me softkey can be used for users to join into a conference. The conference creator uses the meet me softkey to invoke the conference and has control over the participants. A meet me conference can have up to 32 parties (G.711).
Checklist for setting up harware base muilitparty conferencing in CallManager Express 4.1 and 4.2
Configure Join and Leave Tones for Conferencing, (optional)
Configure SCCP for Cisco Unified CME, (required)
Configure the DSP Farm for Hardware Conferencing, (required)
Associate Cisco Unified CME with a DSP Farm Profile, (required)
Configure Hardware Conferencing on Cisco Unified CME, (required)
Configure Conferencing Extensions, (required)
Configure Conferencing Options for Phones, (required)
Verify Hardware Conferencing on Cisco Unified CME, (optional)
Cisco has prepared a great guide to setting up all of these features at http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme41/htmpconf.pdf