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Chapter 5
Reverse Proxy and HTTP Redirects
Delivering content in geographically dispersed areas
Traffic Server can be used in reverse proxy mode to accelerate origin servers that provide content to
geographically dispersed areas. Caches can be easier to manage and more cost-effective than replicating data.
For example, Traffic Server can be used as a mirror site on the far side of a trans-Atlantic link to serve users
without having to fetch the request and content across expensive international connections. Unlike replication,
where hardware must be configured to replicate all data and to handle peak capacity, Traffic Server
dynamically adjusts to best utilize the serving and storing capacity of the hardware. Also, Traffic Server is
designed to keep content fresh automatically, therefore eliminating the complexity of updating remote origin
servers.
Providing security for an origin server
Traffic Server can be used in reverse proxy mode to provide security for an origin server. If you have an origin
server that contains sensitive information that you want to keep secure inside your firewall, you can use a
Traffic Server outside the firewall as a reverse proxy for that origin server. When outside clients try to access
the origin server, their requests go to Traffic Server instead. If the desired content is not sensitive, it can be
served from the cache. If the content is sensitive and not cacheable, Traffic Server obtains the content from
the origin server (the firewall allows only Traffic Server access to the origin server). The sensitive content
resides on the origin server, safely inside the firewall.
How does reverse proxy caching work?
When a browser makes a request, it normally sends that request directly to the origin server. When Traffic
Server is in reverse proxy mode, it must intercept the request for that origin server.
This is done by setting up the DNS entry for the origin server (the origin server’s advertised hostname) to
resolve to the Traffic Server’s IP address. When Traffic Server is configured as the origin server, the browser
will connect to Traffic Server rather than the origin server.
The way that Traffic Server receives and processes requests for content in reverse proxy mode differs
according to protocol. For information about using and configuring reverse proxy for HTTP requests, refer to
HTTP Reverse Proxy‚ on page 35
. For information about using and configuring reverse proxy for FTP
requests, refer to
FTP Reverse Proxy‚ on page 39
.
Figure 5-1. Traffic Server as reverse proxy for a pair of origin servers
NOTE
The origin server’s hostname and its advertised hostname cannot be the same or there
would be a DNS conflict.
server
we
b
server
we
b
real.janes_books.com
Traffic Server serves
documents on behalf of
real.janes_books.com
and
big.server.net
requests for
www.janes_books.com
and jazz.flute.org
resolve to
virtual IP of Traffic Server
world wide web
big.server.net
hosts jazz.flute.org
Traffic
Server