Choosing a WCCP transmission method

Transmission methods between WCCP routers and appliances

NetCache supports both unicast and multicast transmission between WCCP routers and appliances. If your WCCP routers are configured for WCCP multicast, you can configure WCCP service groups for multicast transmission between WCCP routers and appliances. Unicast and multicast are defined as follows:

With unicast transmission, communication occurs between one host and another, in this case, between a WCCP router and an appliance.
With multicast transmission, multiple hosts can listen for transmission from one host. For example, all transmissions from a appliance for a service group configured for multicast are detected by all devices listening to the multicast address for that service group.

The advantages of using multicast transmission between members of a service group are as follows:

Use of multicast significantly reduces network traffic.
Less configuration is required in NetCache.
With unicast transmission, you must explicitly identify WCCP routers with which the appliance interacts. If a router is later removed from the network, you must remove the router's IP address from the NetCache configuration.

Network Appliance recommends that you select one transmission scheme for your WCCP transparency deployment--either unicast or multicast--to simplify configuration and management.

Configuration requirements for multicast

Configuration requirements for multicast transmission are as follows:

If you want a WCCP router to handle multicast service groups, you must enable the router for multicast. (Most WCCP routers support multicast. See your Cisco documentation for information about how to configure routers for multicast.)
Parameters for each service group, including the transmission method, must match in the service group configuration on all routers and appliances that will handle that service group.
For each WCCP service group that you configure in NetCache, provide a multicast IP address. A multicast IP address does not have to be unique among service groups.

If you are using WCCP multicast transmission, Network Appliance recommends that you deploy the appliance on the same subnet as the WCCP router.. Thus, you can limit multicast transmissions to one subnet. Otherwise, you must enable general multicast transmission on all the routers between the appliance and the WCCP router.

Note
A WCCP router configured for multicast transmission can handle both multicast service groups and unicast service groups.