Web OS 10.0 Application Guide414 n Chapter 15: Content Intelligent Switching 212777-A, February 2002Content Precedence LookupThe Layer 7 Precedence Lookup feature in Web OS allows you to give precedence to one Layer7 parameter over another and selectively decide which parameter should be analyzed first.The Content Precedence Lookup feature allows you to combine up to two Layer 7 load balanc-ing mechanisms. You can specify which types of Layer 7 content to examine, the order inwhich they are examined, and a logical operator (and/or) for their evaluation.The following Layer 7 content types can be specified: URL SLB HTTP Host Cookie Browsers (User agent) URL hash Header hashUsing the above content types with the and and or operators, the Web switch is configured torefine HTTP-based server load balancing multiple times on a single client HTTP request inorder to bind it to an appropriate server. Typically, when you combine two content types withan operator (and/or), URL hash and Header hash are used in combination with Host, Cookie,or Browser content types.For example, the following types of load balancing can be configured using the Content Prece-dence Lookup feature: Virtual host and/or URL-based load balancing Cookie persistence and URL-based load balancing Cookie load balancing and/or URL-based load balancing Cookie persistence and HTTP SLB together in the same service Multiple HTTP SLB process type on the same serviceN OTE – Cookie persistence can also be combined with the Layer 7 content types. For moreinformation on cookie persistence, see Chapter 16, “Persistence.”For example, the Content Precedence Lookup feature can be used in the following scenarios: If the client request is sent without a cookie and if no HTTP SLB is configured, then theswitch binds the request to the real server using normal SLB. If the client request is sent without a cookie, but HTTP SLB is configured on the switch,then the request is bound to real server based on HTTP SLB. If the client request is sent with a cookie, and a real server associated to the cookie isfound in the local session table, then the request will stay bound to that real server.
