Push to talk and unicast

[Matt Domnick]

I have call manager behind Cisco Firewall Service modules that do not support multicast.

The phones are secured by an ACL and are not behind the FWSM.

In this config, will push to talk work?

Are multicasts streams limited to the phones themselves?

Is it a unicast stream between the phone and CM server that sets up the push to talk session?

Thanks.

[William Bell]

Matt,

By "push to talk" I assume you are referring to a one-to-many paging application. CUCM does not have a native paging solution. It requires a third party application. The approach used by third party applications may vary by platform. For most solutions, the stream from the page originator is unicast to a software based media engine. This engine then multicasts the stream.

Different vendors have different solutions to deal with pockets of unicast in the environment. Generically speaking, the solutions involve one media engine/agent doing a unicast stream to another agent, which then multicasts on a local LAN.

Since the stream is multicast and the RTP media is encoded using non-proprietary standards, you aren't limited to streaming to Cisco IP phones. You just need an endpoint that can be instructed to receive a media stream on a specific mcast group and port.

I am oversimplifying things a bit. I don't want to get into specifics withouth knowing more about the environment.

HTH.

-Bill (http://ucguerrilla.com)