Cisco Systems 3130 WCCP Message Exchange

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Cisco Catalyst Blade Switch 3130 for Dell 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 se rv er 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 cl uster ( a series of appli cation en gines) can servic e multiple router s
or switches, as shown Figure 43-1.
Figure43-1 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-ena ble d swit ch by u sin g 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 UD P po rt 2 048 .
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 ea ch othe r.
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
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path tree)
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