Web OS 10.0 Application GuideChapter 12: Global Server Load Balancing n 305212777-A, February 2002Table 12-5 explains the packet -flow process in detail. In this example, the initial DNS requestfrom the client reaches Site 2, but Site 2 has no available services.How IP Proxy WorksFigure 12-4 shows examples of two GSLB sites deployed in California and Denver. The appli-cations being load balanced are HTTP and POP3. Any request that cannot be serviced locallyis sent to the peer site. HTTP requests are sent to the peer site using HTTP Redirect. Any otherapplication request will be sent to the peer site using the IP proxy feature.Figure 12-4 POP3 Request Fulfilled via IP ProxyTable 12-5 HTTP Versus Non-HTTP RedirectsSite 2 Web switch Site 1 Web switchHTTP application(built-in redirection)1a. Client DNS request reaches Site 2.Resources are unavailable at Site 2.Site 2 sends a response to Client with Site 1’svirtual server IP address.1b. Client resends request to Site 1.Resources are available at Site 1.Site 1 completes TCP three-way handshake withclient.Non-HTTP application(no redirection)2a. Client DNS request reaches Site 2.Resources are unavailable at Site 2.Site 2 sends a request to Site 1 with Site 2’sproxy IP address as the source IP address andthe virtual server IP address of Site 1 as the des-tination IP address.2b. Site 1 processes the client proxy IP request.Resources are available at Site 1.Site 1 returns request to proxy IP port on Site 2.Site 2 completes the three-way handshake withClient.Proxy IP Address174.14.70.4Proxy Disabled ForLocal Real ServersProxy Enabled ForRemote ServerInternetCalifornia Site #1174.14.70.X NetworkAB CDProxy IP Address200.200.200.4Proxy Disabled ForLocal Real Servers200.200.200.X NetworkHTTP/POP3Local Servers200.200.200.2200.200.200.3Remote Server174.14.70.1Web SwitchVirtual Server200.200.200.1Denver: Site #2HTTP/POP3Local Servers174.14.70.2174.14.70.3Remote Server200.200.200.1Virtual Server174.14.70.1Service requests are always served bylocal real servers if available.If local real servers cannot service the request,the remote server is used via proxy.Web SwitchProxy Enabled ForRemote Server
