WCCPv2 Support for Services Other than HTTP WCCPv2 allows redirection of traffic other than HTTP (TCP port 80 traffic), including a variety of UDP and TCP traffic. WCCPv2 supports the redirection of packets intended for other ports, including those used for proxy-web cache handling, File Transfer Protocol (FTP) caching, FTP proxy handling, web caching for ports other than 80, and Real Audio, video, and telephony applications. To accommodate the various types of services available, WCCPv2 introduced the concept of multiple service groups .
Service information is specified in the WCCP configuration commands using dynamic services identification numbers (such as 98) or a predefined service keyword (such as web-cache ). This information is used to validate that service group members are all using or providing the same service. The content engines in a service group specify traffic to be redirected by protocol (TCP or UDP) and up to eight source or destination ports. Each service group has a priority status assigned to it. The priority of a dynamic service is assigned by the content engine. The priority value is in the range of 0 to 255 where 0 is the lowest priority.
The predefined web-cache service has an assigned priority of 240. WCCPv2 Support for Multiple Devices WCCPv2 allows multiple devices to be attached to a cluster of cache engines. The use of multiple devices in a service group allows for redundancy, interface aggregation, and distribution of the redirection load. WCCPv2 supports up to 32 devices per service group. Each service group is established and maintained independently. WCCPv2 MD5 Security WCCPv2 provides optional authentication that enables you to control which switches and content engines become part of the service group using passwords and the Hashed Message Authentication Code—Message Digest (HMAC MD5) standard.
Shared-secret MD5 one-time authentication (set using the ip wccp password password global configuration command) enables messages to be protected against interception, inspection, and replay. WCCPv2 Web Cache Packet Return If a content engine is unable to provide a requested object it has cached due to error or overload, the content engine will return the request to the device for onward transmission to the originally specified destination server. WCCPv2 provides a check on packets that determines which requests have been returned from the content engine unserviced.
Using this information, the device can then forward the request to the originally targeted server (rather than attempting to resend the request to the content engine cluster). This process provides error handling transparency to clients. Typical reasons why a content engine would reject packets and initiate the packet return feature include the following: • Instances when the content engine is overloaded and has no room to service the packets • Instances when the content engine is filtering for certain conditions that make caching packets counterproductive (for example, when IP authentication has been turned on) Configuring WCCP WCCPv2 Support for Services Other than HTTP Configuring WCCP 5