Cisco Cisco Expressway Maintenance Manual
Microsoft Lync B2BUA
The Microsoft Lync back-to-back user agent (Lync B2BUA) on the Expressway is used to route SIP calls
between the Expressway and a Microsoft Lync Server.
between the Expressway and a Microsoft Lync Server.
It provides interworking between Microsoft ICE (used by Lync clients) and media for communications with
standard video endpoints. It also provides call hold and call transfer support for calls with Lync clients.
standard video endpoints. It also provides call hold and call transfer support for calls with Lync clients.
The setting up of the Lync B2BUA includes the following tasks:
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used to control routing
through them (this is optional and are typically only used with Lync 2010).
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— the devices that may send signaling messages to the B2BUA.
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Setting up search rules to route calls to the Lync domain via the B2BUA — when the B2BUA is enabled a
non-configurable neighbor zone (named "To Microsoft Lync server via B2BUA") is automatically
created; this zone must be selected as the target zone of the search rules.
non-configurable neighbor zone (named "To Microsoft 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 Lync B2BUA to take
effect. A system alarm is raised if a service restart is necessary.
effect. A system alarm is raised if a service restart is necessary.
Microsoft Lync 2010
The Microsoft Interoperability option key must be installed to enable encrypted calls to and from Microsoft
Lync 2010 Server (for both native SIP calls and calls interworked from H.323). It is also required by the
B2BUA when establishing ICE calls to Lync 2010 clients.
Lync 2010 Server (for both native SIP calls and calls interworked from H.323). It is also required by the
B2BUA when establishing ICE calls to Lync 2010 clients.
The B2BUA can use the Cisco AM GW to transcode between standard codecs (such as H.264) and
Microsoft RT Video and RT Audio to allow high definition calls between Microsoft Lync 2010 clients and
Cisco endpoints.
Microsoft RT Video and RT Audio to allow high definition calls between Microsoft Lync 2010 clients and
Cisco endpoints.
Microsoft Lync 2013
The B2BUA provides interworking between standard H.264 AVC and Lync 2013's H.264UC SVC codec.
You can still configure the B2BUA to use Cisco AM GW transcoders with Lync 2013, but it is not necessary
and we recommend that they are not deployed with Lync 2013.
You can still configure the B2BUA to use Cisco AM GW transcoders with Lync 2013, but it is not necessary
and we recommend that they are not deployed with Lync 2013.
Lync 2013 no longer supports H.263, so X8.1 or later software is required to interoperate successfully with
Lync 2013.
Lync 2013.
The Microsoft Interoperability option key is required for all types of communication with Lync 2013.
Usage features and limitations
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The Lync B2BUA has a maximum simultaneous call capability of 100 calls (for all system sizes, including
Large systems); however, calls that use transcoder resources count as 2 calls.
Large systems); however, calls that use transcoder resources count as 2 calls.
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If a call is routed through the Lync B2BUA, the B2BUA always takes the media and always remains in the
signaling path. The call component that is routed through the B2BUA can be identified in the call history
details as having a component type of Microsoft Lync B2BUA.
signaling path. The call component that is routed through the B2BUA can be identified in the call history
details as having a component type of Microsoft Lync B2BUA.
Cisco Expressway Administrator Guide (X8.2)
Page 180 of 378
Applications
B2BUA (back-to-back user agent) overview