Parent Caching 53Layer 4 redirection device. All Web traffic arriving from client machines tothe LAN port of the Webcache is directed into the caching software. Allnon-Web traffic is automatically sent back out onto the network via theWAN port. Cache misses are automatically redirected from the LAN portto the WAN port.For further information, see “Configuring Inline Cache Mode” onpage 118.Advantages You do not have to add new devices to your network. Therefore it iseasy to try out the Webcache in your network. No configuration of the Web browser on each client machine isneeded because all network traffic goes through the Webcache.Disadvantages The Webcache is a single point of failure; if it fails, the entire networkbecomes inaccessible. All incoming and outgoing network traffic is handled by the softwarebuilt into the Webcache. The peak packet rate that can be sustained istherefore lower than using a Layer 4 device, resulting in reducedperformance.Parent Caching Parent Caching allows you to explicitly configure a hierarchy ofWebcaches within your network. Web requests from client machines thatare not fulfilled by a child Webcache (cache misses) can be routed toparent Webcaches instead of the origin Web server. If a parent Webcachehas the requested content, it serves it back to the child Webcache, whichin turn caches and serves it back to the client machines.For further information, see “Configuring Parent Caching” on page 119.You can configure a child Webcache to use parent caching regardless ofwhich deployment mode it is currently operating in. The child Webcacheuses the TCP port number that you configure for the parent Webcache tosend its requests.Any compliant HTTP proxy cache can be used as a parent Webcache. Theparent Webcache does not have to be a 3Com SuperStack 3 Webcache.dua1611-5aaa04.book Page 53 Friday, November 29, 2002 8:56 PM
