Web OS 10.0 Application GuideChapter 6: Server Load Balancing n 123212777-A, February 2002 Some services require that a series of client requests go to the same real server so that ses-sion-specific state data can be retained between connections. Services of this natureinclude Web search results, multi-page forms that the user fills in, or custom Web-basedapplications typically created using cgi-bin scripts. Connections for these types of ser-vices must be configured as persistent (see Chapter 16, “Persistence”) or must use theminmisses or hash metrics (see “Metrics for Real Server Groups” on page 131). Clients and servers can be connected through the same switch port. Each port in use on theswitch can be configured to process client requests, server traffic, or both. You can enableor disable processing on a port independently for each type of Layer 4 traffic.o Layer 4 client processing: Ports that are configured to process client request trafficprovide address translation from the virtual server IP to the real server IP address.o Layer 4 server processing: Ports that are configured to process server responses to cli-ent requests provide address translation from the real server IP address to the virtualserver IP address. These ports require real servers to be connected to the Web switchdirectly or through a hub, router, or another switch.N OTE – Switch ports configured for Layer 4 client/server processing can simultaneously pro-vide Layer 2 switching and IP routing functions.Consider the following network topology:Figure 6-5 Example Network for Client/Server Port ConfigurationIn Figure 6-5, the switch load balances traffic to a Web server pool and to a Domain NameSystem (DNS) server pool. The switch port connected to the Web server pool (port 2) isasked to perform both server and client processing.Some topologies require special configuration. For example, if clients were added to Switch Bas shown in Figure 6-5, these clients could not access the Web server pool using SLB services,except through a proxy IP address that is configured on port 2 of the Alteon Web switch.Web SwitchRouter DNSServerPoolWebServerPoolInternetCSClient ProcessingServer ProcessingSCClients on the Internetinitiate HTTP sessions whichare load balanced to Web serversWeb servers initiate DNS requestswhich are load balancedto DNS serversSCAB123
