Best Practices for WINS Replication

Configuring replication correctly can avert many problems, and doing so enables a group of WINS servers to function more effectively.

Configure Push/Pull Replication Partners

In general, push/pull replication is the simplest and most effective way to ensure full WINS replication between partners. This also ensures that the primary and secondary WINS servers for any particular WINS client are push and pull partners of each other, a requirement for proper WINS functioning in the event of a failure of the primary server of the client.

For most WINS installations, avoid the use of limited replication partnerships (push only or pull only) between WINS servers. In some large enterprise WINS networks, limited replication partnering can effectively support replication over slow network links. However, when you plan limited WINS replication, pay attention to the design and configuration. Each server must still have at least one replication partner, and each slow link that employs a unidirectional link should be balanced by a unidirectional link elsewhere in the network that carries updated entries in the opposite direction.

Use a Hub-and-Spoke Design for WINS Replication and Convergence

Convergence is a critical part of WINS planning. The central question of convergence time for a WINS network design is "How long does it take for a change in WINS data at one WINS server to replicate and appear at other WINS servers on the network?" The answer is the sum of the replication periods from one server to the next over the path containing the longest replication periods. For more information on convergence, see "Detailed Replication Example" in this chapter.

In most cases, the hub-and-spoke model provides a simple and effective planning method for organizations that require full and speedy convergence with minimal administrative intervention. For example, this model works well for organizations with centralized headquarters or a corporate data center (the hub) and several branch offices (the spokes). Also, a second or redundant hub (that is, a second WINS server in the central location) can increase the fault tolerance for WINS.

For an example of a simple hub-and-spoke configuration, see Figure 7.17.

Figure 7.17 A Hub-and-Spoke Deployment of WINS Servers

The convergence time for the system shown in Figure 7.17 is the sum of the two longest convergence times to the hub. For instance, if WINS-B and WINS-D replicate with WINS-A every 30 minutes, and WINS-C and WINS-E are configured to replicate every 4 hours, the convergence time is 8 hours.

Replication Across a Firewall

In some large networks, WINS replication is desirable across a firewall. WINS replication occurs over TCP port 42, so this port must not be blocked on any intervening network device between two WINS replication partners when configuring replication across network firewalls.