The Mediation Server role in Lync Server
2010 is responsible for providing voice features to end users that
allow them to connect with the Public Switched Telephone Network (PSTN)
or another PBX. The Mediation Server provides a number of benefits to a Lync Server 2010 deployment that are discussed in greater detail throughout this section.
Perhaps one of the biggest improvements in Lync is
the fact that the Mediation Server can now be collocated with a Front
End Server, reducing the number of servers required in a deployment.
Enterprise Voice
Enterprise Voice on a basic level is referred to as
the feature that allows Lync endpoints to place and receive phone calls
through the PSTN. Enterprise Voice differs from many other IP PBX
vendors by providing a rich user interface that allows the end user to
control advanced call functionality with only a few clicks. Comparable
solutions from other vendors require logging in to separate systems or
assistance from an administrator to accomplish the same task that an
end-user can do in Lync Server 2010.
Users can forward calls to a mobile phone or
alternative number with a click and even have the calls forwarded based
on working hours defined in Outlook. Delegates can answer calls on
behalf of a manager, and teams can route calls to each other easily.
Presence is also integrated with Enterprise Voice so that users can
have calls sent directly to voice mail if their presence is Do Not
Disturb.
Media Bypass
Media Bypass allows Lync endpoints to communicate
directly with an IP/PSTN gateway or SIP trunking provider. This feature
is a big reason collocation of the Mediation Server with the Front End
service is now supported. Instead of having the Mediation Server
transcode every PSTN audio call from RTAudio to the G.711 codec, the
Lync endpoints can send G.711 audio directly to an IP/PSTN gateway,
bypassing Mediation Server entirely. This not only cuts down on the
processing required for the Mediation Server, it also improves call
quality by removing an additional hop and potential latency.
Call Admission Control
Call Admission Control functionality is another
welcome feature in Lync Server 2010 that gives the administrator much
more control over how voice and video are routed in the network. Lync
Server 2010 provides Call Admission Control by defining network regions
and bandwidth available between different sites. Administrators can
limit both the total amount of bandwidth used for voice and video
between sites and the bandwidth limit for each individual session. When
a Lync client attempts to make a call, both endpoints check the
bandwidth policy to verify the call can be placed. These limits enable
organizations to protect a WAN link from becoming oversaturated and
providing a poor end-user experience.
What happens when these limits are reached is also
configurable by the organization. The first option attempted routes the
call across the Internet using Edge Servers. PSTN rerouting can be used
to automatically place the call through an IP/PSTN gateway instead of traversing
the WAN link. Policies might also be assigned to users who allow them
to override the bandwidth policy and still make a successful call.
Enhanced 911
Enhanced emergency services in Lync Server 2010
allow an emergency call to automatically provide location information
to a dispatcher. Lync Server 2010 maintains a location information
database consisting of subnet, switch, port, and wireless access points
within an organization. These objects are then associated with a
specific address and floor or suite number. When Lync endpoints are
signed in, they can automatically detect the location based on this
data. When users are outside of the organization and a location cannot
be determined, users can enter a location and address manually. They
can also be prohibited from making phone calls until a location is
provided.
Tip
It is important to note that Lync cannot natively
transmit the E-911 information to a dispatcher. The location data is
actually sent first to a third-party emergency service routing provider
web service that delivers the information to dispatchers.
Remote Survivability
Another big improvement in Lync Server 2010 is that
remote sites can sustain the loss of a WAN connection. This is
accomplished by provisioning a survivable branch appliance or
survivable branch server in locations that do not have Front End
services deployed. If a WAN link outage occurs and the branch can no
longer access the Front End pool, the users remain signed in to the
Lync endpoints and can still place and receive PSTN phone calls.
The survivable branch appliances that are produced
by third-party Microsoft partners come in a variety of formats and
capacities. The setup process for each varies slightly, but most of the
configuration can be completed by an administrator in a central site.
Tip
When the appliance arrives at a branch, a technician
with basic skills should be able to physically cable the appliance and
run through a simple setup wizard to complete the installation.
Response Groups
Response Groups are a feature carried forward from
OCS 2007 R2 with quite a few improvements. Response Groups enable
organizations to create groups of call agents that belong to queues.
Callers reach these queues by navigating a workflow that can be as
simple as being routed to different agents based on the time of day.
Workflows can also be more interactive and ask the callers a number of
questions before routing calls to a queue.
With the Lync Server Management Shell, the
depth of a workflow is unlimited and completely flexible. This should
enable organizations to leverage Response Groups in a way that
meets their needs, as different as those might be from one business to
the next. Custom audio prompts can be uploaded for the questions, or
the native text-to-speech capabilities can be used so that
administrators simply need to type a question into a text field.
