Microsoft Ocs/Lync B2Bua (Back-To-Back User Agent); Usage Features And Limitations - Cisco TelePresence Administrator's Manual

Microsoft OCS/Lync B2BUA (back-to-back user
agent)
The Microsoft OCS/Lync back-to-back user agent (B2BUA) on the VCS is used to route SIP calls between
the VCS and a Microsoft Edge Server.
The B2BUA provides interworking between Microsoft ICE (used when MOC / Lync clients communicate
through the Edge Server) and media for communications with standard video endpoints. The B2BUA also
provides call hold, call transfer and Multiway support for calls with OCS/Lync clients, and can share FindMe
presence information with OCS/Lync.
The B2BUA operates between both endpoints of a SIP call and divides the communication channel into two
independent call legs. Unlike a proxy server, the B2BUA maintains complete state for the calls it handles.
Both legs of the call are shown as separate calls on the
The setting up of the B2BUA includes the following tasks:
Configuring and enabling the
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Configuring the transcoders
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through them (this is optional; the B2BUA can still operate without any associated transcoders).
Defining the B2BUA's
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Setting up search rules to route calls with the OCS/Lync domain to the B2BUA — when the B2BUA is
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enabled a non-configurable neighbor zone (named "To Microsoft OCS/Lync server via B2BUA") is
automatically created; this zone must be selected as the target zone of the search rules.
A service restart is sometimes required to enable certain configuration changes to the B2BUA to take effect.
A system alarm will be raised if a service restart is necessary.

Usage features and limitations

The B2BUA has a maximum simultaneous call capability of 50 calls.
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If a call is routed through the B2BUA, the B2BUA always takes the media and always remains in the
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signaling path.
The B2BUA does not consume any calls licenses in addition to the license required by the leg of the call
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between the endpoint and the VCS.
The Enhanced OCS Collaboration key must be installed for the B2BUA to establish calls to OCS/Lync
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clients via a Microsoft Edge Server, and to support encrypted calls.
If all configured transcoders reach their capacity limits, any calls that would normally route via a transcoder
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will not fail; the call will still connect as usual but will not be transcoded.
Bandwidth controls can be applied to the leg of the call between the endpoint and the B2BUA, but cannot
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be applied to the B2BUA to Microsoft OCS/Lync leg of the call. However, as the B2BUA forwards the
media it receives without any manipulation, any bandwidth controls applied to the VCS to B2BUA leg in
effect also controls the B2BUA to OCS/Lync leg implicitly.
As Microsoft Lync Server does not support IPv6, only IPv4 networks can be supported.
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Cisco VCS Administrator Guide (X7.1)
B2BUA for Microsoft OCS/Lync
that may be used by the B2BUA and any
trusted hosts — the devices that may send signaling messages to the B2BUA.
Call status and Call history
communications.
policy rules
Applications
pages.
used to control routing
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