HP Survivable Branch Communication zl Module powered by Microsoft Lync Planning and Design Guide 2011-02

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SBM Overview
SBM Role in a Microsoft UC&C Solution
■ Lync Server Front-End Server or pool of Front-End Servers—The
Front-End Server (or pool of Enterprise Front-End Servers) is responsible
for helping Lync users to reach each other and establish communications.
All Lync users, who are imported from the domain, are assigned to at least
one Front-End server (or pool).
When a Lync user logs in to a client, the client finds its Front-End server
(typically, using DNS services entries stored on the domain DNS server).
The client authenticates using NT LAN Manager (NTLM) or Kerberos
authentication and also checks the server’s digital certificate. If Transport
Layer Security (TLS) is enabled, as it is by default, the client and server
then establish secure, encrypted communications for all future
exchanges.
After authenticating, the client registers the user to the server, indicating
the user’s current location. For this reason, the Front-End Server is called
the user’s registrar. (With Lync, users can also register to a secondary
registrar at another site. The secondary registrar provides backup in case
the primary one fails.)
Front-End Servers track the users that have registered to them and
communicate with each other so that they can maintain the users’ pres-
ence.
A Front-End Server can also act as a Session Initial Protocol (SIP) proxy
server, helping users to establish permitted communications according to
defined voice policies and routing rules. Depending on these policies and
on the services requested, the Front-End Server routes the users’ commu-
nication to the appropriate destination, which might be:
• Another Lync client for calls, instant messages (IMs), application
transfers, or file transfers with other Lync users
• A Mediation Server (box B in the figure) for PSTN calls
• A Conferencing server (box C) for multi-party communications
• An Edge Server (box D) for communications with a remote client
“Communications” on page 1-11 provides a more detailed explanation of
how the SBM’s Front-End Server specifically fulfills these functions.
■ Central management store—The site stores information about its
topology, configuration, and services in a central management store on a
SQL server. This server resides either on a Standard Front-End Server or
on a Back-End Server for an Enterprise server pool. Each Front-End
Server at the site replicates the central management store locally. The
Lync Server Replica Replicator Agent continuously communicates with
the central management store, ensuring that the topology remains up
to date.