The consolidated edge topology is appropriate for small organizations.

In the consolidated edge topology, all three edge server roles (Access Edge Server, Web Conferencing Edge Server, and A/V Edge Server) are collocated on a single physical computer.

This topology offers:

• Reduced server cost.
  
• Ease of deployment and administration.
  

This topology does not:

• Scale easily.
  
• Provide load balancing.
  
• Provide high availability.
  

  Note:
  To avoid port conflicts when running all server roles on a single computer, use a different IP address for each server role.

The following figure illustrates the consolidated edge topology.

Figure 1. Consolidated edge topology

The single-site edge topology is appropriate for medium to large organizations.

In the single-site edge topology:

• The Access Edge Server and Web Conferencing Edge Server are collocated on a single physical computer.
  
• The A/V Edge Server is installed on a separated dedicated computer.
  

This topology is recommended because it offers:

• Flexibility.
  
• Efficient bandwidth utilization (because the A/V Edge Server, which uses the most bandwidth, is on a separate computer).
  
• The fewest number of computers to manage.
  

This topology does not:

• Scale easily.
  
• Provide load balancing.
  
• Provide high availability.
  

The following figure illustrates the single-site edge topology.

Figure 2. Single-site Edge topology

The scaled single-site edge topology is appropriate for large organizations.

This topology is recommended because it:

• Provides load balancing.
  
• Provides high availability
  
• Scales easily.
  

The scaled single-site edge topology is the single-site edge topology scaled out in the following ways:

• A load balancer is connected to two or more computers, with Access Edge Server and Web Conferencing Edge Server collocated on each computer.
  
• Another load balancer is connected to two or more separate computers, each of which serves as an A/V Edge Server.
  

The following figure illustrates the scaled single-site edge topology.

Figure 3. Scaled single-site edge topology

The remote-site edge topology supports multiple sites and is appropriate for organizations with remote sites that are geographically dispersed and are connected by using a WAN.

In the multiple-site edge topology using a remote site, you integrate remote locations into a scaled topology by deploying:

• The scaled topology in your data center (as specified in the scaled single-site edge topology).
  
• Local A/V Conferencing and Web Conferencing Edge Servers and a local Standard Edition server or pool in each remote location.
  

In this topology, traffic from remote or federated users in the remote location travels across the WAN only to contact the Access Edge Server for authentication and instant messaging and presence, which incurs lower bandwidth cost. The Access Edge Server returns the local pool or Standard Edition server for users at the remote site, and the pool or server points the user to the local A/V or Web Conferencing Edge Server. A/V traffic and traffic from the Web Conferencing Server remain local, which results in a better user experience and lower bandwidth usage of the WAN.

In a remote site topology, you can have one or more stand-alone Web Conferencing Edge Servers but only a single A/V Edge Server. If you need more than one A/V Edge Server, use the scaled remote site topology for the A/V Edge Servers.

Note:
If you want to add more than one Web Conferencing Edge Server in a remote site, we recommend load balancing them, as described in the scaled remote edge topology section.

The following figure illustrates a remote site topology in multiple-site edge deployment.

Figure 4. Multiple-site edge topology with remote site

In the remote office, you can also scale the edge topology to provide high availability for external access. In a scaled edge topology of a remote office, one or more A/V Edge Servers are deployed on dedicated servers and Web Conferencing Edge Servers are deployed on separate dedicated computers. All edge servers are connected to a hardware load balancer.

As a variation to the multiple-site edge topology, if you have large remote sites or want to enable high availability in these sites, you can scale the topology in the remote sites by load-balancing your Web Conferencing Edge Servers and your A/V Edge Servers in a topology similar to Figure 5.

Figure 5. Scaled Remote-site Edge Topology

When you deploy an Access Edge Server, you can connect it to your internal network components in either of the following ways:

• Connecting directly to an internal server or Enterprise pool.
  
• Using a Director. A Director is optional but is strongly recommended in all topologies that involve connections across the Internet, especially those that support remote users. The Director is an Office Communications Server 2007 Standard Edition server or Enterprise pool that does not host users but that, as a member of an Active Directory domain, has access to Active Directory for purposes of authenticating remote users and routing traffic to the appropriate server or Enterprise pool. By authenticating inbound SIP traffic from remote users, the Director helps insulate home servers and Enterprise pools from potentially malicious traffic, while relieving them of the overhead of performing authentication.
  

You can deploy either a single Director as a Standard Edition server or Enterprise pool or as an array of Standard Edition servers behind a load balancer that function as a Director. In a large deployment with significant external traffic, an Enterprise pool Director or Standard Edition array Director with a load balancer provides a significant improvement in performance.

However you decide to connect to internal servers, ensure that you should only have one inbound MTLS listener configured on your Director (or your Front End Servers if you are not using a Director). This is the default configuration, which is recommended. If you have more than one listener configured on your Director (or your Front End Servers if you are not using a Director), all other listeners besides the default connection (MTLS on port 5061) must be configured to use TLS or TCP. Having more than one MTLS listener can result in problems communicating with external users and attending external conferences. If you have a requirement for more than one MTLS listener, verify that the port numbers corresponding to each MTLS listener are open on the internal firewall for communication between the Access Edge Server and Director ((or your Front End Servers if you are not using a Director).