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
The site can optionally include these components:
■ Mediation Server—A Mediation Server (or pool of servers) receives SIP
calls that are destined to the PSTN. It translates the Microsoft proprietary
SIP traffic to standard SIP and decrypts TLS traffic. It also translates the
codec, which is the protocol used to encode sound into a digital format.
For example, the Mediation Server can translate between the RTAudio
codec, which Lync clients typically use, and the G.711 (a-law or mu-law)
codec that is understood by most SIP-capable PSTN gateways.
Note Microsoft Lync allows Lync users to bypass the Mediation Server for certain
PSTN gateways. Media Bypass diminishes the load on the Mediation Server
by allowing the media stream to flow directly from the Lync Client to the PSTN
gateway. As a result, you can collocate the Mediation Server with the Front-
End Server, and that server can support more PSTN calls. It is recommended
that you use this feature on an SBM. (See “Media Bypass” on page 2-17 of
Chapter 2: “Design Considerations.”)
■ Audio/Video Conferencing Server—This server handles communica-
tions with more than two parties, including audio-only conferences and
audio and video conferences. (This server is always collocated on Stan-
dard Front-End Servers, but potentially on another server for an Enter-
prise server pool.)
■ Edge Server or pool of Edge Servers—The Edge Servers provide
access to the UC&C solution for off-site (remote) users:
• An Access Edge Server provides basic communications services.
• An Edge Conferencing Server provides the conferencing services.
• Other services are provided as well, such as archiving and monitoring.
Refer to Microsoft documentation for more information about the Lync archi-
tecture and these services.
SBM Role
In previous Microsoft UC&C architectures, branch office users registered to
Front-End Servers at the central office data center. Not only chats, calls, and
conferences with other domain users, but PSTN calls as well, traveled over
the wide area network (WAN) connection between the branch and the data
center. Because that connection often did not provide high availability, users,
who were accustomed to high reliability for PSTN calls from private branch
exchanges (PBXs), sometimes lost the ability to place or receive calls. Or, the
company was forced to use a PBX at the branch office for the PSTN calls.