Technical data

ServerIron ADX Advanced Server Load Balancing Guide 95

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Sample configurations

Basic TCS configuration

Figure 21 shows a configuration in which HTTP traffic flows into a Point-of-Presence (POP) from

Remote Access Servers (RASs) and out of the POP to the Internet through a Border Access Router

(BAR). The cache servers are labeled C1, C2, and C3.

FIGURE 21 Basic TCS configuration example

In the most basic setup, HTTP traffic flowing across the ServerIron ADX, in any direction, is

redirected to the cache servers. If a cache server has the requested content, the server returns the

content to the client. If the cache server does not have the content, the cache server goes to the

Internet to get the requested content, then caches the content and sends it to the client.

The client never accesses the Internet directly, unless all the cache servers in the cache group are

unavailable. In that case, traffic flows across the ServerIron ADX at Layer 2 and out to the Internet

in the normal way.

In a transparent caching scheme, the ServerIron ADX acts as the traffic redirector and the cache

servers accept requests for any destination IP address. A cache server that accepts requests for

any IP address are running in promiscuous mode. The client does not have to configure anything on

their web browser. Thus, the caching is “transparent” to the client. It is this transparent

characteristic that sets proxy-based caching and transparent caching apart.

Internet

Border Access Router (BAR)

e3e2

Cache server C1

RAS1

RAS2

RAS3

BAR

Cache server C2

Cache server C3

The BAR connects the clients

(through the ServerIron) to the

Internet.

Remote Access Server (RAS)

The CAR connects the clients

(through the ServerIron) to the

cache servers.