TCS with reverse proxy relieves clients who have configured their web browsers to point to a proxy server from the need to reconfigure their browsers. When you configure the ServerIron ADX for this feature, the ServerIron ADX performs TCS for clients whose browsers do use a proxy and for clients whose browsers do not use a proxy:
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For clients whose browsers do not use a proxy, the ServerIron ADX performs transparent TCS,using the normal hash mechanism to map requests to a cache server based on the source and destination information in the mask and the IP address of the requested site.
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For clients whose browsers use a proxy, the ServerIron ADX load balances the requests acrossthe cache servers. The clients are served transparently by a virtual IP address (VIP) that you configure on the ServerIron ADX with the same IP address as the proxy. Although this is different from the hash mechanism used for transparent TCS, the results for the client are exactly the same. The ServerIron ADX sends the request to a cache server that either has the requested content and sends it back to the client or does not have the requested content but quickly obtains it from the Internet, then sends it back to the client. In addition, the hash mechanism not only distributes traffic, but also ensures that duplication of content is
minimized. The hash mechanism minimizes duplication by ensuring that a particular website is always cached on the same cache server.
In either case, the ServerIron ADX provides the requested content to the client.
Figure 27 shows an example of a TCS configuration in which some clients have browsers
configured to use a proxy while other clients’ browsers are not thus configured.
As shown in the figure, some clients’ web browsers are configured to use proxy IP address 10.157.22.2, while other client’s web browsers are not configured to use a proxy server. You can configure the ServerIron ADX to satisfy both sets of clients.
Sample configurations
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FIGURE 27 Example Proxy Server Cache Load Balancing Configuration
Follow the steps given below to configure Proxy Server Cache Load Balancing.
1. Add the cache servers as customary, using the server cache-name <string> <ip-addr> command.
2. Add the HTTP ports and configure port-specific health check parameters at the Cache Server level, using the port http | <num> commands.
3. Create the proxy virtual IP address (VIP) and bind the HTTP ports of the cache servers to the VIP. Use the server virtual-name-or-ip <string> <ip-addr> and bind… commands.
4. Add the cache servers to a cache group using the server cache-group 1 command.
Sample configurations
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NOTE
If you have already configured your cache servers and cache group, you do not need to change their configuration. You only need to add the VIP for the proxy and bind the HTTP ports to it, then save the changes.
To configure the ServerIron ADX for the example shown in Figure 27 on page 110, enter the
following commands on the ServerIron ADX.
NOTE
This example shows commands that are valid on the ServerIron ADX device only when it is running the Layer 3 router image.
ServerIronADX(config)#server port 4199 ServerIronADX(config-port-4199)#tcp ServerIronADX(config-port-4199)#exit ServerIronADX(config)#server port 8080 ServerIronADX(config-port-8080)#tcp ServerIronADX(config-port-8080)#exit
The commands above add port profiles for the two HTTP ports in this example that are using port numbers other than the well-known port 80: 4199 and 8080. The tcp command at each port’s configuration level is required. If you do not identify the ports as TCP ports, the ServerIron ADX assumes the ports are UDP ports and thus does not use an appropriate health check for the ports. You do not need to add a port profile for port 80, since that is the well-known HTTP port.
ServerIronADX(config)#server cache-name Cache-Server1 10.157.22.26 ServerIronADX(config-Cache-Server1)#port 4199
ServerIronADX(config-Cache-Server1)#port 8080 ServerIronADX(config-Cache-Server1)#port http ServerIronADX(config-Cache-Server1)#exit
ServerIronADX(config)#server cache-name Cache-Server2 10.157.22.27 ServerIronADX(config-Cache-Server2)#port 4199
ServerIronADX(config-Cache-Server2)#port 8080 ServerIronADX(config-Cache-Server2)#port http ServerIronADX(config-Cache-Server2)#exit
The commands above add cache servers Cache-Server1 and Cache-Server2. The port commands add the HTTP ports to the cache servers. This example does not include optional modification of the HTTP health check parameters for specific servers. For information about customizing an HTTP health check for a specific server.
ServerIronADX(config)#server virtual-name-or-ip Proxy 10.157.22.2 ServerIronADX(config-vs-Proxy)#port 4199 sticky
ServerIronADX(config-vs-Proxy)#port 8080 sticky
ServerIronADX(config-vs-Proxy)#bind 4199 Cache-Server1 4199 Cache-Server2 4199 ServerIronADX(config-vs-Proxy)#bind 8080 Cache-Server1 8080 Cache-Server2 8080 ServerIronADX(config-vs-Proxy)#exit
The commands above configure a virtual IP address (VIP) to take the place of the Proxy IP address to which some of the client browsers are directing their web requests. The IP address specified with the server virtual-name-or-ip command is the IP address that is configured as the proxy on some clients’ web browsers. The port 4199 sticky and port 8080 sticky commands add the ports and also make them “sticky”. When a port is sticky, once a client session is established on the port, the ServerIron ADX’s load balancing mechanism (used for the proxy) sends subsequent packets in the same session to the same cache server. The sticky parameter is not required in this configuration but it can streamline cache performance by keeping client sessions on the same cache servers.
High availability designs with TCS
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The bind commands create table entries in the ServerIron ADX that associate the cache servers and their HTTP ports with the Proxy VIP.
ServerIronADX(config)#server cache-group 1
ServerIronADX(config-tc-1)#cache-name Cache-Server1 ServerIronADX(config-tc-1)#cache-name Cache-Server2 ServerIronADX(config-tc-1)#write mem
The commands above add the cache servers to a cache group, then save the configuration changes to the ServerIron ADX’s startup-config file.