Planning for your organization lync server 2010 (rc)

Planning for Your Organization:
Microsoft Lync Server 2010
Published: September 2010

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Contents
Planning for Your Organization....................................................................................................1
Beginning the Planning Process...............................................................................................1
Topology Basics You Must Know Before Planning...................................................................3
Sites......................................................................................................................................3
Server Roles.........................................................................................................................4
Initial Planning Decisions.........................................................................................................7
Deciding Which Clients To Deploy............................................................................................8
Reference Topologies.............................................................................................................10
Reference Topology With Limited High Availability..............................................................10
Reference Topology With High Availability and a Single Data Center.................................12
Reference Topology for Multiple Data Centers....................................................................14

Planning for Your Organization
The topics in this section help you get started with planning your Microsoft Lync Server
2010 communications software deployment.

• Beginning the Planning Process helps you understand how to get started, and how
the planning documentation works with the Microsoft Lync Server 2010, Planning Tool
and Topology Builder.
• Topology Basics You Must Know Before Planning describes the basics of Lync
Server topologies, including sites and server pools. You must understand these concepts
when using the Lync Server 2010, Planning Tool.
• Initial Planning Decisions takes you through the questions you must answer to decide
what workloads and features of Lync Server to deploy.
• Reference Topologies shows three sample topologies that illustrate good topology
design in three typical organization types, and explains the reasoning behind many of the
decisions in designing those topologies.

Beginning the Planning Process
While planning a unified communications deployment may seem intimidating, Microsoft Lync
Server 2010 communications software provides two valuable tools to help you:
• Microsoft Lync Server 2010, Planning Tool is a wizard that interactively asks you a
series of questions about your organization, the Lync Server features you want to enable,
and your capacity planning needs. It then creates a recommended deployment topology
based on your answers, and produces several forms of output to aid your planning and
installation.
• Topology Builder is an installation component of Lync Server 2010. You use
Topology Builder to create, adjust and publish your planned topology. It also validates
your topology before you begin server installations. When you install Lync Server on
individual servers, the servers read the published topology as part of the installation
process, and the installation program deploys the server as directed in the topology.

Lync Server 2010 Planning Tool
The Lync Server 2010, Planning Tool takes your answers to the questions in the tool and
generates a topology based on Lync Server guidelines and best practices. It also provides
several views of a deployment based on your answers. It shows both a global view of all your
sites (that is, including both central sites and branch sites), and detailed views showing the
servers and other components at each site.
Running the Planning Tool does not commit you to any specific deployment or initiate any
processes. In fact, running the Planning Tool even before you have a firm plan in mind can be a

Planning for Your Organization: Microsoft Lync Server 2010
very instructive way to understand the kinds of questions you need to think about in your planning
process.
You can run the Planning Tool multiple times, answering questions differently, and compare the
outcomes. If you have a design you are mostly satisfied with but that you need to make changes
to, you can return to the Planning Tool, load the design, and make the changes. It takes about 15
minutes to complete the Planning Tool once.
After you are completely satisfied, you can use the Export to Topology Builder option to export
your planned topology to an XML file that you can then input to Topology Builder.
You use the Planning Tool only for your initial topology design. After you export the topology to
Topology Builder and begin working with it there, you can no longer use the Planning Tool to
modify your topology.

Lync Server 2010 Topology Builder
Topology Builder takes the XML file provided by the Planning Tool, and displays the topology. You
can then use Topology Builder to make final adjustments such as specifying IP addresses and
fully qualified domain names (FQDN). After you are satisfied, you have Topology Builder validate
the topology, and then, if it passes, you can publish the topology. When you publish the topology,
Lync Server puts the topology into the Central Management store (which is created at this time if
it does not already exist). Then, when you go to install Lync Server on each server in your
deployment, the server reads the topology from the Central Management store and installs itself
to fit into its role in your deployment.
Alternatively, if you are very familiar with Lync Server and need less prescriptive guidance, you
can skip the Planning Tool and use the wizards in Topology Builder for the initial design of your
deployment, as well as for the validation and publishing steps.
Using Topology Builder to plan and publish a topology is a required step. You cannot bypass
Topology Builder and install Lync Server individually on the servers in your deployment. Each
server must read the topology from a validated, published topology in the Central Management
store.

High-Level Planning Process
We recommend the following general process for using both the documentation and the Planning
Tool to plan your Lync Server deployment
1. Run the Planning Tool to get a sense of the kind of questions you need to think about
as you begin the planning process.
2. Read New Server Features to familiarize yourself with the new features and
requirements in Lync Server 2010.
3. Read the other parts of this section: Topology Basics You Must Know Before
Planning, Initial Planning Decisions, Deciding Which Clients To Deploy, and Reference
Topologies.
4. Now that you are more familiar with Lync Server features and the kinds of questions
that must be answered, run the Planning Tool again and view the resulting topology and
its details.

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5. If there are particular workloads or features you are interested in or need to learn
about, read the appropriate sections of Planning for Lync Server 2010.
6. Run the Planning Tool again. You can start with the deployment you created in step 3
and modify the results, or start over from the beginning.
If needed, run the Planning Tool a third time and repeat until you are satisfied with the output.
7. When you have finalized the topology plan, use the export feature of the Planning
Tool to create an XML file that you can use with Topology Builder. Load that XML into
Topology Builder and add final details such as IP addresses.
8. Before you begin deployment, read Preparing Your Environment and Determining
Your Infrastructure Requirements to familiarize yourself with the prerequisites and
necessary infrastructure for Lync Server. Additionally, be sure you have read all the
sections of Planning for Lync Server 2010 that apply to the workloads and features that
you plan to deploy.

Migrating from Previous Versions
If you are migrating to Lync Server from a previous version, see the Migration documentation for
specific instructions for your migration and deployment.

Topology Basics You Must Know Before Planning
You do not have to be an expert on Microsoft Lync Server 2010 communications software to run
the Microsoft Lync Server 2010, Planning Tool. In fact, running the Lync Server 2010, Planning
Tool multiple times, answering questions differently, and comparing the output is a good way to
learn about Lync Server 2010.
Before you learn about the various components in more depth, you should understand the
following basic aspects of Lync Server topologies.

• Sites
• Server Roles

Sites
In Microsoft Lync Server 2010 communications software, you define sites on your network that
contain Lync Server 2010 components. A site is a set of computers that are well-connected by a
high-speed, low-latency network, such as a single local area network (LAN) or two networks
connected by a high-speed fiber optic network. Note that Lync Server sites are a separate
concept from Active Directory Domain Services (AD DS) sites and Microsoft Exchange Server
sites. Your Lync Server 2010 sites do not have to correspond to your Active Directory Domain
Services (AD DS) sites.

Site Types
Each site is either a central site, which contains at least one Front End pool or Standard Edition
server, or a branch site. Each branch site is associated with exactly one central site, and the

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users at the branch site get most of their Lync Server functionality from the servers at the
associated central site.
Each branch site contains one of the following:
• A survivable branch appliance, which is a new device introduced in Lync Server 2010
that combines a public switched telephone network (PSTN) gateway with some Lync
Server functionality.
• A PSTN gateway and, optionally, a Mediation Server.
A branch office with a resilient wide area network (WAN) link to a central site can use the second
option, a PSTN gateway and optionally a Mediation Server. Branch office sites with less-resilient
links should use a Survivable Branch Appliance, which provide resiliency in times of wide-area
network failures. For example, in a site with a Survivable Branch Appliance deployed, users can
still make and receive Enterprise Voice calls if the WAN connecting the branch site to the central
site is down. For details about the Survivable Branch Appliance and resiliency, see Planning for
Branch-Site Voice Resiliency in the Planning for Enterprise Voice documentation.

Site Topologies
Your deployment must include at least one central site, and can include zero to many branch
sites. Each branch site is affiliated with one central site. The central site provides the Lync Server
2010 services, such as presence and conferencing, that are not located locally at the branch site.

Server Roles
Each server running Microsoft Lync Server 2010 communications software runs one or more
server roles. A server role is a defined set of Lync Server 2010 functionality provided by that
server. You do not need to deploy all available server roles in your network. Install only the server
roles that contain the functionality that you want.
Even if you are not familiar with server roles in Lync Server, the Microsoft Lync Server 2010,
Planning Tool can guide you to the best solution for the servers you need to deploy, based on the
features that you want. This section provides a brief overview of the server roles and the general
features they provide:
• Front End Server and Back End Server
• A/V Conferencing Server
• Edge Server
• Mediation Server
• Monitoring Server
• Archiving Server
• Director
For most server roles, for scalability and high availability you can deploy pools of multiple servers
all running the same server role. Each server in a pool must run an identical server role or roles.
For some types of pools in Lync Server, you must deploy a load balancer to spread traffic
between the various servers in the pool.

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Standard Edition Server
The Standard Edition server is designed for small organizations, and for pilot projects of large
organizations. It enables many of the features of Lync Server 2010, as well as the necessary
databases, to run on a single server. This enables you to have Lync Server functionality for a
lesser cost, but does not provide a true high-availability solution.
Standard Edition server enables you to use instant messaging (IM), presence, conferencing, and
Enterprise Voice, all running on one server.
For a high-availability solution, use Lync Server 2010 Enterprise Edition.

Front End Server and Back End Server
The Front End Server is the core server role, and runs many basic Lync Server functions. The
Front End Server, along with the Back End Servers that provide the database, are the only server
roles required to be in any Lync Server Enterprise Edition deployment.
A Front End pool is a set of Front End Servers, configured identically, that work together to
provide services for a common group of users. A pool provides scalability and failover capability
your users.
Front End Server includes the following functionality:
• User authentication and registration
• Presence information and contact card exchange
• Address book services and distribution list expansion
• IM functionality, including multi-party IM conferences
• Web conferencing and application sharing (if deployed)
• Application hosting services, for both applications included with Lync Server (for
example, Conferencing Attendant and Response Group application) and third-party
applications
• Application services for application hosting and hosts applications (for example,
Response Group Service, and several others)
Additionally, one Front End pool in the deployment also runs the Central Management Server,
which manages and deploys basic configuration data to all servers running Lync Server 2010.
The Central Management Server also provides Lync Server 2010 Management Shell and file
transfer capabilities.
The Back End Servers are database servers running Microsoft SQL Server that provide the
database services for the Front End pool. You can have a single Back End Server, but a cluster of
two or more servers is recommended for failover. Back End Servers do not run any Lync Server
software. If you already have a SQL Server cluster that you are using for other applications, you
can also use this cluster for Lync Server 2010, if performance allows.
Information stored in the Back End Server databases includes presence information, user’s
contact lists, conferencing data including persistent data about the state of all current
conferences, and conference scheduling data.

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A/V Conferencing Server
A/V Conferencing Server provides A/V conferencing functionality to your deployment. It can be
collocated with Front End Server, or deployed separately as a single server or A/V Conferencing
Server pool.
For details, see Web Conferencing and A/V Conferencing in the Planning for Conferencing
documentation.

Edge Server
Edge Server enables your users to communicate and collaborate with users outside the
organization’s firewalls. These external users can include the organization’s own users who are
currently working offsite, users from federated partner organizations, and outside users who have
been invited to join conferences hosted on your Lync Server deployment. Edge Server also
enables connectivity to public IM connectivity services, including Windows Live, AOL, and Yahoo!.
For details, see the Planning for External User Access documentation.

Mediation Server
Mediation Server is a necessary component for implementing Enterprise Voice and dial-in
conferencing. Mediation Server translates signaling and, in some configurations, media between
your internal Lync Server infrastructure and an Internet Protocol/Public Switched Telephone
Network (IP-PSTN) gateway or a Session Initiation Protocol (SIP) trunk.
For details, see Mediation Server Component in the Planning for Enterprise Voice documentation.

Monitoring Server
Monitoring Server collects data about the quality of your network media, in both Enterprise Voice
calls and A/V conferences. This information can help you provide the best possible media
experience for your users. It also collects call error records (CERs), which you can use to
troubleshoot failed calls. Additionally, it collects usage information in the form of call detail records
(CDRs) about various Lync Server features so that you can calculate return on investment of your
deployment, and plan the future growth of your deployment.
For details, see the Planning for Monitoring documentation.

Archiving Server
Archiving Server enables you to archive IM communications and meeting content for compliance
reasons. If you do not have legal compliance concerns, you do not need to deploy Archiving
Server.
For details, see Planning for Archiving.

Director
Directors can authenticate Lync Server user requests, but do not home user accounts, or provide
presence or conferencing services. Directors are most useful in deployments that enable external
user access, where the Director can authenticate requests before sending them on to internal
servers. Directors can also improve performance in organizations with multiple Front End pools.
For details, see Director in the Planning for External User Access documentation.

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Initial Planning Decisions
The first part of the planning process is deciding which Microsoft Lync Server 2010 workloads and
major features you want for your organization.
1. Do you want a physical or virtualized topology? Microsoft Lync Server 2010
supports all workloads and server roles in both physical and virtualized topologies. User
capacity in a virtualized topology is roughly 50 percent of the capacity in a physical
topology. For details, see Running in a Virtualized Environment in the Planning for Other
Features documentation.
2. IM and presence are always enabled. In any Lync Server deployment, the instant
messaging (IM) and presence workload is installed and enabled by default. IM enables
your users to communicate with real-time text messages, and presence enables them to
see the status of other users on the network. A user’s presence status provides
information to help others decide whether they should try to contact the user, and by what
means. For details, see the IM and Presence documentation.
3. Do you want to deploy any modes of conferencing? Conferencing is another core
feature of Lync Server. Several modes of conferencing are supported. You can choose to
deploy all supported types of conferencing, or just some of them. Web conferencing
enables users to see a file, such as a slide deck created with Microsoft PowerPoint
presentation graphics program, that is being presented. Application sharing enables
users to share all or part of their desktop with each other in real time. With A/V
conferencing, users can add audio (and possibly video) to their conferences and peer-to-
peer communications. Dial-in conferencing enables users to use standard PSTN phones
to join the audio portion of conferences hosted at your organization. For details, see the
Conferencing documentation.
4. If you deploy A/V conferencing, you should also monitor the audio quality of
these conferences. Many factors affect the audio and video quality of Lync Server A/V
conferences. By using the A/V quality monitoring features provided by the Monitoring
Server role, you can detect issues that affect media quality, and ensure that your users
have the best possible media experience.
5. Do you want high availability for your IM, presence, and conferencing servers?
If you have only one server at a site providing IM, presence and conferencing features,
your users’ productivity will be greatly affected if that server goes down. By deploying a
pool of multiple servers for these functions, you make it possible for Lync Server to
continue functioning with all of these features intact even if a server goes down.
Additionally, if you have more than 12,500 users at a site, you must deploy a pool to
serve this large number of users. This pool also provides high availability.
6. Do you want to deploy Enterprise Voice? Enterprise Voice is the voice over IP
(VoIP) solution provided by Lync Server. It provides an attractive alternative to traditional
PBX-based telephony. Enterprise Voice enables users to place calls from their computers
by clicking a contact in Outlook or Microsoft Lync 2010. They can place calls over the IP
network from computer to computer, computer to telephone, or telephone to computer.
Users benefit from having all of their communications options-voice, e-mail, IM, and

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conferencing-available and integrated on their computers. For details, see the Planning
for Enterprise Voice documentation.
7. If you deploy Enterprise Voice, you should also monitor the audio quality of
these calls. We recommend you use Monitoring Server to ensure the audio quality of
your Enterprise Voice calls, if you deploy Enterprise Voice.
8. Do you want to deploy Exchange UM? If your organization uses Microsoft
Exchange Server for its email services, you can deploy the Exchange Unified Messaging
(UM) features of both Microsoft Exchange and Lync Server to enhance communications
capabilities for your users. Exchange UM features include enabling users to receive
voicemail notices and listen to voicemail within their Microsoft Exchange mailbox, to
access their Microsoft Exchange mailboxes using a telephone, and to receive faxes in
their Microsoft Exchange mailboxes.
9. Do you need to archive IM content or meeting content for compliance
purposes? If your organization has to archive IM content or meeting content for
compliance purposes, you can deploy an Archiving Server.
10. Do you want to enable your users to communicate and collaborate with
external users? Enabling communication and collaboration with external users can
increase your return on investment in Lync Server. This enables your organization’s own
users to benefit from Lync Server features even when they are working outside your
organization’s firewalls. You can also federate with your partner or customer
organizations that run Lync Server. By doing so, your users and federated partner users
can easily send and receive IM messages, invite each other to meetings, and see each
other’s presence. Additionally, your users can use an email message to invite specific
outside users to online meetings they organize.
11. Do you have branch offices in your organization? If your organization has branch
offices, Lync Server 2010 supports a variety of ways to support them and ensure their
resiliency for voice and other features. In particular, at a branch office that does not have
a resilient WAN link to a datacenter, you can install a Survivable Branch Appliance to
maintain Enterprise Voice support should the wide area network (WAN) link go down. For
details, see Enhanced Voice Resiliency in Central Sites and Branch Offices in the Getting
Started documentation.

Deciding Which Clients To Deploy
Microsoft Lync Server 2010 communications software supports several types of client software
that you can deploy to your organization’s users, including computer-installed client software,
web-based clients, and mobile devices. This topic outlines the different clients that you can use.
For a detailed comparison of the features provided by different clients, see Client Comparison
Tables in the Planning for Clients and Devices documentation.

Microsoft Lync 2010
Microsoft Lync 2010 is the default client for Lync Server 2010 meetings. Features include
presence, contact management, instant messaging (IM), telephony, and greatly enhanced
conferencing.

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To implement the manager/delegate scenario with Lync 2010, both manager and delegate need
to install and use Lync 2010.

Microsoft Lync 2010 Attendee
Microsoft Lync 2010 Attendee is a rich conferencing client that allows users without Lync 2010
installed to fully participate in Lync Server 2010 meetings. Lync 2010 Attendee can be installed on
a per-user basis, so you can choose to selectively deploy this client during migration, or you can
allow users to download and install it as needed.
For details about how to control the conferencing client choices that appear on the online meeting
join page, see the “Configuring the Meeting Join Web Page” section in Migration Considerations
for Meetings topic in the Planning for Clients and Devices documentation.

Microsoft Lync Web App
Microsoft Lync Web App is a web-based conferencing client that supports most Lync 2010
collaboration and sharing features, as well as presenter meeting controls and dial-in and dial-out
voice conferencing.
For users who do not have Lync 2010 installed, you can offer this conferencing option when it
isn’t practical or possible to install Lync 2010 Attendee
For details about how to control which client options appear on the meeting join page, see the
“Configuring the Meeting Join Web Page” section in Migration Considerations for Meetings topic
in the Planning for Clients and Devices documentation.

Microsoft Lync Server 2010 Attendant
Microsoft Lync 2010 Attendant is an integrated call management application that enables a
receptionist to manage multiple conversations at once through rapid call handling, IM, and on-
screen routing.
Lync 2010 Attendant no longer supports the manager/delegate scenario. Both manager and
delegate must have Lync 2010 installed to access these features.

Microsoft Lync 2010 Mobile
Microsoft Lync 2010 Mobile provides IM, enhanced presence, and telephony for users in your
organization who are connecting from a smartphone or a phone running a Professional edition of
Windows Mobile.

Microsoft Lync 2010 Phone Edition
Microsoft Lync 2010 Phone Edition is software that runs on intelligent Internet Protocol (IP)
phones (for example, USB-attached phones), and supports placing and receiving calls, enhanced
presence, and client audio capabilities for conferences.

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Online Meeting Add-in for Microsoft Lync 2010
The Online Meeting Add-in for Microsoft Lync 2010 supports meeting management from within
Outlook. This software is installed automatically with Lync 2010.

Reference Topologies
The ideal Microsoft Lync Server 2010 communications software topology depends on your
organization’s size, the workloads you want to deploy, and your preferences for high availability
versus cost of investment.
The following topics outline three reference topologies, including the reasoning behind many of
the decisions that drive the requirements for each topology.

• Reference Topology With Limited High Availability
• Reference Topology With High Availability and a Single Data Center
• Reference Topology for Multiple Data Centers

Reference Topology With Limited High Availability
The reference topology with limited high availability is for an organization that wants to deploy
Microsoft Lync Server 2010 communications software functionality at a minimum cost. Typically,
the specific topology shown in the following diagram is recommended for organizations with 5,000
or fewer users, although you can support additional users by adding additional Standard Edition
servers.

Note:
All capacity and performance numbers in this section pertain only to the Microsoft Lync
Server 2010 (Release Candidate) release, and are subject to change in future releases.

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Reference topology with limited high availability

• Active Directory Deployment All Lync Server deployments reside in a single
Active Directory forest. For this topology, the customer has Lync Server deployed in the
child domain, retail.contoso.com.
• Voice Pilot The organization using the exact topology shown in this diagram is
currently running a pilot program of the Enterprise Voice feature of Lync Server. Some
users are using Lync Server as their sole voice solution.
If they go on to fully deploy Enterprise Voice and remove the PBX system, they should
provide high availability for their voice solution by deploying a second Standard Edition server
or moving to a Front End pool. A single Standard Edition topology as shown in this diagram is
recommended only if you are not deploying Enterprise Voice in a production environment.
Because being able to make calls is mission critical for almost every organization, you should
provide high availability if you use Enterprise Voice as your telephone solution.
• Another Standard Edition Server Can Be Added A single Standard Edition server
can support up to 5,000 users. If you want to accommodate more users or provide some
high availability capability for Enterprise Voice (at a minimum cost), you could add
another Standard Edition server to this topology.
For a true high availability solution, you should deploy Enterprise Edition and deploy a Front
End pool. Although having two Standard Edition Servers would maintain Enterprise Voice
functionality should one of these servers go down, a Front End pool provides much better
continuity of service for other Lync Server features.

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• Branch Site Survivability This organization is running the Enterprise Voice pilot
with some branch site users as well. The branch office does not have a reliable wide area
network (WAN) link to the central site, so a Survivable Branch Appliance is deployed
there. With this deployed, if the WAN link goes down users at the branch site can still
make calls, receive calls from both PSTN users and other Enterprise Voice users, and
have peer-to-peer instant messaging and application sharing sessions.
• Edge Server Recommended Although deploying an Edge Server is not required
for internal instant messaging (IM), presence and conferencing, it is recommended even
for small deployments. You can maximize your Lync Server investment by deploying an
Edge Server to provide service to users currently outside your organization’s firewalls.
The benefits include the following:
• Your organization’s own users can use Lync Server functionality, if they are
working from home or are out on the road.
• Your users can invite outside users to participate in meetings.
• If you have a partner, vendor or customer organization that also uses Lync
Server, you can form a federated relationship with that organization. Your Lync
Server deployment would then recognize users from that federated organization,
leading to better collaboration.
• Your users can exchange instant messages with users of public IM services,
including any or all of the following: Windows Live, AOL, and Yahoo!, as well as
XMPP-based providers and servers, such as Google Talk and Jabber. A separate
license might be required for public IM connectivity with Windows Live, AOL, and
Yahoo!

Reference Topology With High Availability and a Single Data Center
The reference topology with high availability and a single data center is designed for a small-to-
medium size organization with one central site. The exact topology in the following diagram is for
an organization of 15,000 users. Typically, the type of topology shown in the following diagram is
recommended for organizations with 5,000 to 30,000 users, but it can support over 30,000 users.

Note:
Server 2010 (Release Candidate) release, and are subject to change in future releases.

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Reference topology with high availability and a single data center

• Active Directory Deployment All Microsoft Lync Server 2010 communications
software deployments reside in a single Active Directory forest. For this topology, the
customer has Lync Server deployed in the child domain, retail.contoso.com.
• To Accommodate More Users, Add More Front End Servers The exact topology
in this diagram has two Front End Servers, so it supports up to 16,000 users. If you have
a single central site and more users, you can simply add Front End Servers to the pool.
One Front End pool can have as many as 10 servers, so a single Front End pool at a
single site can support up to 80,000 users.
However, the single site topology can support even more users by adding another Front End
pool to the site. To support these extra users, you need to add only one additional Front End
pool (that is, just one pool each of A/V Conferencing Servers, Edge Servers, and Directors
are sufficient, although more servers may need to be added to these pools).
• A/V Conferencing Can Be Collocated in Smaller Organizations If this
organization has 10,000 or fewer users, you could decide to collocate A/V Conferencing
Services with the Front End pool, instead of deploying a separate A/V Conferencing pool.
For organizations with 10,000 or more users, collocating these services is not
recommended for performance reasons.
• Monitoring Server Database Options In this topology, the Monitoring Server is
using the same pair of database servers that the Front End pool uses. A topology in
which the Monitoring Server has its own database servers is also supported.
• High Availability for All Server Pools In this example organization with 15,000
users, just one Director server, Edge Server and A/V Conferencing server would be
sufficient for performance. However, there are pools of two servers of each type deployed
to provide high availability for each feature.

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• Branch Site Deployment Options The organization in this topology has Enterprise
Voice deployed as their voice solution. Branch Site 1 does not have a resilient wide area
network (WAN) link to the central site, so it has a Survivable Branch Appliance deployed
to provide telephone service in case the WAN link to the central site goes down. Branch
Site 2 however has a resilient WAN link, so only a public switched telephone network
(PSTN) gateway is needed. The PSTN gateway deployed there supports media bypass,
so no Mediation Server is needed at Branch Site B. For details about deciding what to
install at a branch site, see Branch Site Voice Resilience.
• DNS Load Balancing The Front End pool, Edge Server pool, and the Director pool
have DNS load balancing for SIP traffic deployed. This eliminates the need for hardware
load balancers for Edge Servers, and significantly lessens the setup and maintenance of
the hardware load balancers for the other pools, as the hardware load balancers are
needed only for HTTP traffic. For details about DNS load balancing, see DNS Load
Balancing in the Planning for Other Features documentation.
• Exchange UM Deployment This reference topology includes an Exchange Unified
Messaging (UM) Server, which runs Microsoft Exchange Server, not Lync Server. The
Exchange UM routing functionality for Lync Server runs on the Front End pool.
For details about Exchange UM, see On-Premises Exchange Unified Messaging Integration
and Hosted Exchange Unified Messaging Integration in the Planning for Enterprise Voice
documentation.
• Edge Servers Recommended Although deploying an Edge Server is not required,
it is recommended for any size of deployment. You can maximize your Lync Server
investment by deploying an Edge Server to provide service to users currently outside
your organization’s firewalls. The benefits include the following:
• Your organization’s own users can use Lync Server functionality, if they are
working from home or are out on the road.
• Your users can invite outside users to participate in meetings.
• If you have a partner, vendor or customer organization that also uses Lync
Server, you can form a federated relationship with that organization. Your Lync
Server deployment would then recognize users from that federated organization,
leading to better collaboration.
• Your users can exchange instant messages with users of public instant
messaging (IM) services (including Windows Live, AOL, and Yahoo!) and XMPP-
based providers and servers (for example, Google Talk and Jabber). A separate
license might be required for public IM connectivity with Windows Live, AOL, and
Yahoo!

Reference Topology for Multiple Data Centers
The reference topology for multiple data centers is for any size of organization with more than
one central site. The exact topology in the following diagram is for an organization of 70,000
users, with 40,000 users at Central Site A and 30,000 at Central Site B. The type of topology
shown in this diagram can accommodate organizations with any number of users.

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Note:
Server 2010 Release Candidate) release, and are subject to change in future releases.
This topology is shown in multiple diagrams, with an overview first followed by detailed views of
the central sites.

Overview of the reference topology for multiple data centers

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Reference topology for multiple data centers: Detailed view of Central Site A

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Reference topology for multiple data centers: Detailed view of Central Site B

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Reference topology for multiple data centers: Detailed view of Central Site C

• Active Directory Deployment All Microsoft Lync Server 2010 communications
software deployments reside in a single Active Directory forest. For this topology, the
customer has Lync Server deployed in two child domains, retail.contoso.com and
manufacturing.contoso.com.
• To Accommodate More Users, Add More Front End Servers The organization in
this diagram has five Front End Servers at Central Site A (for 40,000 users), and four
Front End Servers at Central Site B (for 30,000 users). If either site needs to
accommodate more users, you can simply add Front End Servers to the pool at that site.
One Front End pool can have as many as 10 servers, so a single Front End pool at a
single site can support up to 80,000 users.
However, each site can support even more users by adding another Front End pool to the
site. To support these extra users, you need to add only one additional Front End pool (that
is, just single pools at each site of A/V Conferencing Servers, Edge Servers, and Directors
are sufficient, although more servers may need to be added to these pools).
• Using Standard Edition Server at a Branch Site Aside from its use in Lync Server,
this organization considers Site C as a branch site because it has only 600 employees.
However, the users there have many A/V conferences among themselves. If it was

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deployed in Lync Server as a branch site, the media for these conferences would run
across the wide area network (WAN) to and from a central site with A/V Conferencing
Server installed. To avoid this potential performance problem, they have installed a
Standard Edition server at this site, which will host these conferences. And because a
Standard Edition server is installed there, Lync Server by definition considers it a central
site, and it is treated as such in Topology Builder and the Planning Tool.
As long as the users at this site have a pool in another site set as their backup registrar pool,
they will have high availability for Enterprise Voice—voice support will fail over to the backup
registrar site automatically. For a more complete high availability solution at this site, you
could deploy a second Standard Edition server there.
Although Site C is considered a central site, you do not have to deploy Edge Servers there. In
this example, Site C will use the Edge Servers deployed at Site A.
• Monitoring Server and Archiving Server Collocation This organization deploys
both Monitoring Server and Archiving Server. For organizations that deploy both, we
recommend that you collocate them to save server investment. One Monitoring Server
can support up to 100,000 users, and one Archiving Server can support up to 300,000
users.
Note that you need to deploy Monitoring Server and Archiving Server in only one central site.
If the link between the two central sites goes down, the Message Queuing (also known as
MSMQ) technology used by both Monitoring Server and Archiving Server helps preserve data
while the link is down.
In this topology, Monitoring Server and Archiving Server use a separate database server than
any Front End pool.. Topologies in which the Monitoring Server and Archiving Server share
the same database servers as the Front End pool are also supported, although on large
deployments such as this, separate database servers are recommended for performance.
• Branch Site Deployment Options The organization in this topology has Enterprise
Voice deployed as their voice solution. Branch Sites 1 and 3 do not have a resilient WAN
link to the central site, so they have Survivable Branch Appliances deployed to provide
telephone service in case the WAN link to the central site goes down. Branch Site 2
however has a resilient WAN link, so you need only a public switched telephone network
(PSTN) gateway. The PSTN gateway deployed there supports media bypass, so no
Mediation Server is needed at Branch Site B. For details about deciding what to install at
a branch site, see Planning for Branch-Site Voice Resiliency in the Planning for
Enterprise Voice documentation.
• SIP Trunking and Mediation Server Notice that at Site A, Mediation Server is not
collocated with the Front End Servers. This is because sites that use SIP trunking must
deploy Mediation Server in a separate pool from the Front End Servers. In all other
instances, we recommend you collocate Mediation Server with Front End Server.
• DNS Load Balancing The Front End pool, Edge Server pool, and the Director pool
have DNS load balancing for SIP traffic deployed. This eliminates the need for hardware
load balancers for Edge Servers, and significantly decreases the amount of time you
have to spend on the setup and maintenance of the hardware load balancers for the
other pools, as the hardware load balancers are needed only for HTTP traffic. For details

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about DNS load balancing, see DNS Load Balancing in the Planning for Other Features
documentation.
• Exchange UM Deployment Lync Server 2010 works with both on-premise
deployments of Exchange Unified Messaging (UM) and hosted Exchange UM. Central
Site A includes an Exchange Unified Messaging (UM) Server, which runs Microsoft
Exchange Server, not Lync Server. The Exchange UM functionality for Lync Server runs
on the Front End pool.
Central Site B uses hosted Exchange, so the Exchange UM Server functionality is also
hosted.
For details about Exchange UM, see On-Premises Exchange Unified Messaging Integration
and Hosted Exchange Unified Messaging Integration in the Planning for Enterprise Voice
documentation.

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