Deployment considerations

Strategies for client access to your NetCache appliances

You can set up client access to a Web cache in the following ways:

Through transparent proxying--for HTTP and FTP requests only
Through a nontransparent client access
You would need to manually configure client browsers to point directly to one of the following:
- A NetCache appliance
- A device such as a Server Load Balancer (SLB) that is in front of the NetCache appliances and is configured to be aware of the NetCache appliances
- An automatic proxy configuration file

See Chapter 2, Strategies for Client Access to NetCache.

Determining how many Web caches you need

No one formula exists to determine the number of Web caches that you need. Your Network Appliance sales engineer can help you determine the number of caches that are appropriate for your organization, weighing factors such as the following:

Size of your organization, the number of branch offices the organization, and the distance between branch offices
The number of Web requests that you expect would be sent to a particular NetCache appliance
Whether you want the same NetCache appliance to handle traffic of multiple protocols
You can configure a NetCache appliance to operate in more than one mode--for example, as a Web cache and a news cache. However, if you expect your Web cache to handle a substantial load, for example, the volume of an ISP data center, Network Appliance recommends that you dedicate a NetCache appliance to Web caching. By doing so, you avoid conflicts between different software programs, and performance and reliability are better.
Whether you can afford to have Web service unavailable, that is, whether you need a failover strategy
You might, for example, want to plan for one Web cache in addition to the number you think you need to handle the Web traffic. That way, if one Web cache goes down, the remaining Web caches can still handle the volume of traffic. If you are deploying transparent proxying with an L4 switch, you might consider deploying a switch failover pair in case a switch fails.

If your NetCache appliance is behind a firewall

If your Web cache is behind a firewall, you might have to configure NetCache to enable it to send requests through the firewall, depending on the type of firewall you have.

Type of firewall	On the streaming media cache
Transparent	No explicit configuration is necessary to pass requests through the firewall
Nontransparent, running as a proxy	You must include the firewall in the cache hierarchy of the streaming media cache.

For more information about NetCache operation with firewalls, see Chapter 9, NetCache Deployment with Firewalls.