Summary
Microsoft Lync Server 2010 is the next generation of Microsoft Office Communications Server. Lync Server 2010 provides real-time communication for audio and video conferencing, instant messaging, file transfer.

Lync Server helps small businesses take advantage of advanced telecommunication technology at a reduced cost.
Lync Server 2010 includes three built-in tools to manage a Lync Server deployment. This article introduces one of those tools: Lync Server Topology Builder. It also discusses how to use the Topology Builder tool to create a topology in a Lync Server deployment.
"Topology" refers to network topology. A network topology is how a computer network is structured. Typically, "topology" refers to the layout of physical devices, such as servers, client computers, hubs and routers, and other hardware devices.

Lync Server helps small businesses take advantage of advanced telecommunication technology at a reduced cost.
Lync Server 2010 includes three built-in tools to manage a Lync Server deployment. This article introduces one of those tools: Lync Server Topology Builder. It also discusses how to use the Topology Builder tool to create a topology in a Lync Server deployment.
"Topology" refers to network topology. A network topology is how a computer network is structured. Typically, "topology" refers to the layout of physical devices, such as servers, client computers, hubs and routers, and other hardware devices.More Information
Lync Server Topology Builder
Topology Builder is a wizard that helps you setup Lync Server 2010 on servers at your business. You use Topology Builder to create, edit, and validate the Lync Server topology before you install Lync Server 2010 on any servers in your organization.
You do not have to be an Administrator or be a member of a special group to define a topology in Topology Builder.
When you start Topology Builder, you are prompted to choose the location where you want to load the current configuration. The choices are (Screen shot for the choices is listed below):

You will be prompted for a location to save the configuration file. This location can be on the local computer, network share, or on removable media such as a thumb drive.
A previous configuration will be overwritten if you save the new configuration file with the same name in the same location as an existing file.
After you save the configuration file, you will define the primary Session Initiation Protocol (SIP) domain and then any additional supported domains (Screen shot for this step is listed below):
SIP is an Internet Engineering Task Force (IETF) defined protocol used to control communications sessions.

On the Define the first site page, type a name and a description for the first site in the deployment (Screen shot for this step is listed below):

On the Specify site details page, type the location information for the site. After you click Next, click to select the Open the New Front End Wizard when this wizard closes check box, and then click Finish.
Topology Builder is a wizard that helps you setup Lync Server 2010 on servers at your business. You use Topology Builder to create, edit, and validate the Lync Server topology before you install Lync Server 2010 on any servers in your organization.
You do not have to be an Administrator or be a member of a special group to define a topology in Topology Builder.When you start Topology Builder, you are prompted to choose the location where you want to load the current configuration. The choices are (Screen shot for the choices is listed below):
- Download topology from existing deployment - Choose this option if you have already configured a topology and created the Central Management store (CMS).
- Open topology from a local file - Choose this option if you want to edit an existing configuration, but have not created a CMS.
- New topology - Choose this option if you want to create a new topology.

You will be prompted for a location to save the configuration file. This location can be on the local computer, network share, or on removable media such as a thumb drive.
A previous configuration will be overwritten if you save the new configuration file with the same name in the same location as an existing file.After you save the configuration file, you will define the primary Session Initiation Protocol (SIP) domain and then any additional supported domains (Screen shot for this step is listed below):
SIP is an Internet Engineering Task Force (IETF) defined protocol used to control communications sessions. 
On the Define the first site page, type a name and a description for the first site in the deployment (Screen shot for this step is listed below):

On the Specify site details page, type the location information for the site. After you click Next, click to select the Open the New Front End Wizard when this wizard closes check box, and then click Finish.
References
After you create a Lync Server topology, you have to create a Front End pool. For information about how to define and configure a Front End pool, visit the following TechNet website:
http://technet.microsoft.com/en-us/library/gg398538.aspx
http://technet.microsoft.com/en-us/library/gg398538.aspx