Nortel Networks WEB OS 212777 - Manual (Page 394)

Web OS 10.0 Application Guide
394 n Chapter 15: Content Intelligent Switching
212777-A, February 2002
Content Intelligent Web Cache Redirection
Web OS allows you to redirect Web cache requests based on different HTTP header information,
such as “Host:” header or “User-Agent” for browser-smart load balancing. For more information
on layer 4 Web cache redirection, see
Chapter 8, “Application Redirection .”
The No Cache/Cache Control for Web Cache Redirection (WCR) feature in Web OS allows
you to off load the processing of non-cacheable content from cache servers by sending only
appropriate requests to the cache server farm. When a Cache-Control header is present in a
HTTP 1.1 request, it indicates a client's special request with respect to caching, such as to guar-
antee up-to-date data from the origin server. If this feature (Cache-Control: no cache directive)
is enabled, HTTP 1.1 GET requests are forwarded directly to the origin servers.
N OTE – The term origin server refers to the server originally specified in the request.
The HTTP 1.0 Pragma: no-cache header is equivalent to the HTTP 1.1 Cache-Con-
trol header. By enabling the Pragma: no-cache header, requests are forwarded to the ori-
gin server.
N OTE – For WCR, at any given time one HTTP header is supported globally for the entire
switch.
This section discusses the following types of Web cache redirection:
n
“URL-Based Web Cache Redirection” on page 395
n
“HTTP Header-Based Web Cache Redirection” on page 403
n
“Browser-Based Web Cache Redirection” on page 405
n
“URL Hashing for Web Cache Redirection” on page 406
n
“Layer 7 RTSP Streaming Cache Redirection” on page 409