Cisco Catalyst 3120 User Manual

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Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
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Chapter43 Configuring Web Cache Services By Using WCCP
Understanding WCCP
When an application engine receives a request, it attempts to service it from its own local cache. If the
requested information is not present, the application engine sends a separate request to the end server to
retrieve the requested information. After receiving the requested information, the application engine
forwards it to the requesting client and also caches it to fulfill future requests.
With WCCP, the application-engine cluster (a series of application engines) can service multiple routers
or switches, as shown Figure 43-1.
Figure 43-1 Cisco Cache Engine and WCCP Network Configuration
WCCP Message Exchange
This sequence of events describes the WCCP message exchange:
1. The application engines send their IP addresses to the WCCP-enabled switch by using WCCP,
signaling their presence through a Here I am message. The switch and application engines
communicate to each other through a control channel based on UDP port 2048.
2. The WCCP-enabled switch uses the application engine IP information to create a cluster view (a list
of application engines in the cluster). This view is sent through an I see you message to each
application engine in the cluster, essentially making all the application engines aware of each other.
A stable view is established after the membership of the cluster remains the same for a certain
amount of time.
3. When a stable view is established, the application engine in the cluster with the lowest IP address is
elected as the designated application engine.
Router A
Source
Receiver
Router C
RP
Router B
Shared tre
e
from RP
S
ource tree
(shortest
path tree)
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Cisco Catalyst 3120 Specifications

General

Brand	Cisco
Model	Catalyst 3120
Category	Switch
Language	English