Load Balancers
Microsoft Office Communications Server 2007 and Microsoft Office Communications Server 2007 R2 will reach end of support on January 9, 2018. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.
A hardware load balancer is required in an Enterprise pool with more than one Enterprise Edition Server. A load balancer is not required for a Standard Edition Server or a single Enterprise Edition Front End Server. A load balancer is recommended, though not required, for arrays of Office Communications Server 2007 Edge Servers or Directors. The load balancer performs the critical role of delivering scalability and high availability across multiple servers connected to a centralized database on the Office Communications Server, Back-End Database. Only one load balancer is required, but you can optionally create two logical load balancers—one for the Front End Servers and one for the Web Components Server—if you deploy Enterprise Edition in an expanded configuration.
If you want to employ two logical load balancers, you can configure two virtual IP (VIP) addresses on one physical load balancer or you can configure two separate physical load balancers. In either case, you must create one load balancer FQDN for the Front End Servers to use and another load balancer FQDN for the Web Components Server to use.
Prerequisites for a Load Balancer Connecting to a Pool
Before configuring a load balancer to connect to the Office Communications Server Enterprise pool, you must configure the following:
A static IP address for servers within your pool.
For each server within the pool, a certificate issued for server authentication by a certification authority in the pools local domain.
A VIP address and a DNS record for the load balancer.
Test users created and SIP-enabled in the pool.
Install root certificate from the CA in the domain (or trusted CA) on client computers.
Log on to all servers in the pool using TLS to ensure certificates are working.
Load Balancer Requirements
A load balancer for the Office Communications Server Enterprise pool must meet the following requirements:
Must expose a VIP Address through ARP (Address Resolution Protocol).
The VIP must have a single DNS entry, called Pool FQDN.
The VIP must be a static IP address.
Must allow multiple ports to be opened on the same VIP. Specifically, it must expose the ports described in Table 35.
Table 35 Required Ports on the Load Balancer Virtual IP Addresses
| Ports Required | Virtual IP (if you have more than one logical load balancer) | Port Use |
|---|---|---|
5060 |
Load balancer VIP used by the Front End Servers |
SIP communication |
5061 |
Load balancer VIP used by the Front End Servers |
SIP communication over TLS |
135 |
Load balancer VIP used by the Front End Servers |
To move users from a pool and other remote DCOM-based operations |
443 |
Load balancer VIP used by the Front End Servers |
HTTPS traffic to the pool URLs |
444 |
Load balancer VIP used by the Web components |
Communication between the focus (Office Communications Server component that manages conference state) and the conferencing servers |
The load balancer must provide TCP-level affinity. This means that the load balancer must ensure that TCP connections can be established with one Office Communications Server in the pool and all traffic on that connection destined for that same Office Communications Server.
The load balancer must provide a configurable TCP idle-timeout interval with a maximum value greater than or equal to the minimum of the REGISTER refresh or SIP Keep-Alive interval of 30 minutes.
The load balancer should support a rich set of metrics (round robin, least connections, weighted, and so forth). A weighted least connections-based load balancing mechanism is recommended for the load balancer. This means that the load balancer will rank all Office Communications Servers based on the weight assigned to them and the number of outstanding connections. This rank will then be used to pick the Office Communications Server to be used for the next connection request.
The load balancer must be able to detect Office Communications Server availability by establishing TCP connections to either port 5060 or 5061, depending on which is active (often called a heartbeat or monitor). The polling interval must be a configurable value with a minimum value of at least five seconds. The load balancer must not select an Office Communications Server that shuts down until a successful TCP connection (heartbeat) can be established again.
Every Office Communications Server must have exactly one network adapter. Multihoming an Office Communications Server is not supported.
The network adapter must have exactly one static IP address. This IP address will be used for the incoming load-balanced traffic.
The computer must have a registered FQDN. The IP address registered for this FQDN must be publicly accessible from within the enterprise.
The load balancer must allow for adding and removing servers to the pool without shutting down.
The load balancer must be NAT (network address translation) capable.
When you configure the load balancer, you will need to request the relevant network and DNS administrator for a VIP (virtual IP) address for the load balancer, as well as a static IP address for every server that you plan to deploy in the Enterprise pool.
Supported Load Balancer Configurations
Most load balancers can be configured to operate in either SNAT (source network address translation) mode or DNAT (destination network address translation) mode. To ensure maximum availability of the pool, you should configure the load balancer to operate in SNAT mode if possible.
If a load balancer for a pool is configured to operate in DNAT mode, connections from member servers in the pool will be redirected to the local host. Redirecting connections to the local host is necessary so that the pool can operate in DNAT mode, but it can adversely affect the availability of the pool.
When you deploy Office Communications Server, setup requires you to specify whether the load balancer is operating in SNAT mode or DNAT mode. After your Office Communications Servers are installed, it is recommended that you do not change this setting on either the server or the load balancer.