Section F: News cache configuration scenario

About this scenario  

In this news cache configuration scenario, an ISP provides both Web service and news service to its customers. The ISP has a data center with multiple NetCache appliances, each of which is dedicated to either Web caching or news caching. The news server is at the data center.

The ISP has a number of POPs (points of presence), each of which has a NetCache appliance. For simplicity, this scenario shows only two POPs. One POP has a dedicated news cache, and the other POP has a NetCache appliance that is both a news cache and a Web cache. The scenario demonstrates the configuration differences in both deployments.

What is included in the configuration examples  

The configuration examples focus on the NNTP configuration options that would be set on each NetCache appliance. However, the example of the NetCache appliance that is both a news cache and a Web cache also includes options necessary to send Web request cache misses to the data center, and a few other options that you would use with Web caching but not with news caching.

Note
The configuration examples assume that you have completed the tasks required to identify the NetCache appliance to the network, such as specifying an IP address, a host name, and DNS.

Deployment illustrated  

The following illustration shows the deployment of NetCache appliances at the POPs and data center.

Method chosen for client access to the news caches  

The NetCache appliances at the POPs are configured for transparent proxying so that users do not have to configure their browsers to use the NetCache appliance service. At each POP, an L4 switch is deployed in front of the NetCache appliance to pass NNTP traffic (at POP 1) or HTTP and NNTP traffic (at POP 2) transparently to the appliance deployed at that POP.

The ISP advertises just one IP address for the news service. All users of this ISP are given the same host name to use for the news service. DNS is set up so that requests are routed to the closest POP. The reason for such a DNS configuration is that if users move, they can use the same host name for news even though they are dialing into a different POP.

Failover strategy  

The failover strategy for this scenario is as follows:

• Two news caches are deployed at the data center so that news service is still available if one news cache goes down. If both news caches go down, however, news service will be unavailable.
• An L4 switch pair is deployed in failover mode in front of the news caches at the data center. If one switch fails, the other switch ensures connectivity to the news caches.
• Two Web caches are deployed at the data center so that Web caching service is still available if one Web cache goes down. If both Web caches go down, the switch passes Web requests directly to the Internet.
• An L4 switch pair is deployed in failover mode in front of the Web caches at the data center. If one switch fails, the other switch ensures connectivity to the Web caches.

  Note
  The switch is not configured to pass Web requests to the news cache and vice versa if all caches of one type go down. The reason is that the Web caches are not configured for news caching and the news caches are not configured for Web caching.

Configuration of the news cache at
POP 1  

The NetCache appliance at POP 1 is set up as a news cache, with caching behavior, logging, authentication, and transparency options configured. The following table shows the options that were configured for this NetCache appliance.

Configuration of the news cache and Web cache at POP 2  

The NetCache appliance at POP 2 is set up as a Web cache and a news cache. For the Web cache, the transparency, clustering, access control, and Web filtering options are configured. For the news cache, the transparency, logging, and authentication options are configured. The options that were configured for the news cache setup are the same as those discussed in Configuration of the news cache at POP 1. The following table shows the options that were configured for the Web cache setup on this NetCache appliance.

Additional features configured on the POP 2 NetCache appliance  

The POP 2 NetCache appliance is both a Web cache and a news cache; therefore, some of the options configured for the POP 2 NetCache appliance are not shown for the POP 1 NetCache appliance. Some of the additional features are as follows:

• The NetCache appliance logical settings for hierarchies and clusters are not applicable to news caches. However, it is necessary to set up a cluster parent for the POP 2 NetCache appliance so that HTTP, FTP, Gopher, and tunnel requests that are cache misses at POP 2 can be sent to the Web caches at the data center.
• SmartFilter is enabled for Web caching at POP 2 to control access to URLs by category. SmartFilter is not applicable to news caching.

Configuration of news caches at the data center  

At the data center, two NetCache appliances (C1.ISP.com and C2.ISP.com) are set up as news caches. Distributed caching cannot be set up on the news caches; therefore, failover and load balancing can be achieved by configuring the L4 switch pair that is in front of these NetCache appliances.

The following table shows the options that were configured for these NetCache appliances.

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Part No. 210-00369
File: news17.htm
Last updated: 11/12/02 12:13:58