Configuring Caching Hierarchies

If several proxy servers are serving the network, you can set up a hierarchy of proxy caches. If a proxy server does not find the requested page in its cache, it queries its peers and parents for the information.

The queried peers and parents can then, in turn, query additional peers and parents for the requested information. The origin server is queried as the last resort.

The Novell BorderManager 3.8 proxy server is compatible with other Internet Cache Protocol (ICP)-based proxy servers that exist on the Internet. You can set up these proxy servers as peers (neighbors), parents, or both.

You can configure a CERN hierarchy, a cache hierarchy (ICP), or both. If both are configured, the cache hierarchy takes precedence and the CERN hierarchy is used as a backup. CERN hierarchies have only parents, whereas cache hierarchies have both parents and peers.

To configure a hierarchical cache:

1. In NetWare Administrator, select the Novell BorderManager 3.8 Setup page for the server.

2. From the Application Proxy tab, select the HTTP Proxy service, then click Details.

3. Click the Cache Hierarchy Server tab, then select the Enable Cache Hierarchy Server check box.

4. Specify the following, then click OK:

   • Whether to enable source round-trip time: This parameter is used by the proxy to determine whether to send a request to the parent or to the origin server. The proxy uses the route that returns the shortest round-trip time.
   • Whether to enable ICP ACL: This enables the cache hierarchy or ICP access control on the server.
   • ICP listening port number: The UDP port on which the cache listens for queries from other caches.
   • (After clicking Add) One or more multicast IP addresses for the multicast group list: Multicast addresses on which the cache hierarchy server receives multicast cache hierarchy queries.
   • (After clicking Add) One or more hostnames or IP addresses for the access control list: The hostnames or IP addresses on this list are used to verify whether proxies can send a request. The clients on this list are allowed to send a cache hierarchy request.

5. Click the Cache Hierarchy Client tab, then select the Enable Cache Hierarchy Client check box.

6. Specify the following:

   • Must Only Forward Through Hierarchy: Deselect this option if you want the proxy server to retrieve the requested objects directly from the origin server.
   • Cache Neighbor Timeout value: The number of seconds or minutes the proxy server waits for a response to a cache hierarchy request from another proxy server.

     Do not specify a value if you are configuring a CERN client.

   • (After clicking Add) One or more neighbors for the Neighbors List, with the following information specified:

     Name of the nearest host server neighbor.

     Port number of the neighbor HTTP proxy.

     Port number of the neighbor cache hierarchy client: Do not specify a value if you are configuring a CERN client.

     Type of neighbor: peer, parent, or CERN: Select peer or parent if you are configuring a cache hierarchy client; select CERN if you are configuring a CERN client.

     Priority for each neighbor, from 1 (lowest) to 10 (highest): You can prioritize a set of parents or neighbors. A cache hierarchy client chooses the fastest responding hierarchy cache with the highest priority to service a request. CERN uses pure priority routing without querying.

     Domains that the cache hierarchy client will serve: The default is null, or all neighbors receive all queries. CERN also supports domain routing.

   • (After clicking Add) One or more unicast addresses or names and port numbers for the multicast responder list: This is a list of all acceptable neighbors (unicast) that can respond to a multicast query. This list lets the cache hierarchy client verify that the responses are from a valid neighbor. Do not specify a value if you are configuring a CERN client.

7. Click OK.

8. Click the Cache Hierarchy Routing tab, then specify the following:

   NOTE:  Use cache hierarchy (ICP) routing when the parent cannot contact the origin server.

   • Whether a URL's home site is used as a peer cache (not recommended).
   • (After clicking Add) The local domain name for origin Web servers that are in close proximity: The proxy server prefers to query for a URL that it cannot resolve from these servers instead of from the cache hierarchy.
   • (After clicking Add) One or more stop patterns for which the cache must query the origin Web server directly: Specify patterns for which the delays caused by hierarchical caching are unacceptable, for example, static pages that change frequently.

9. Click OK, then click OK again from the Novell BorderManager 3.8 Setup page.