Web Accumulation Advice Protocol
To affluence burden on chock-full WAN links in networks with abounding hosts, Cisco developed WCCP
to alike the assignment of bend routers and agreeable engines (also accepted as accumulation engines). Content
engines aggregate frequently accessed data, usually HTTP traffic, locally, so that aback hosts access
the aforementioned pages the agreeable can be delivered from the accumulation agent rather than bridge the WAN.
WCCP differs from web proxy operation in that the hosts accessing the agreeable acquire no knowledge
that the agreeable agent is complex in a accustomed transaction.
WCCP works by acceptance bend routers to acquaint with agreeable engines to accomplish anniversary aware
of the other’s attendance and to admittance the router to alter cartage to the agreeable agent as
appropriate. Amount 5-3 shows how WCCP functions amid a router and a agreeable agent when
a user requests a web article application HTTP.
Figure 5-3 WCCP Operations Amid a Router and a Agreeable Engine
The amount shows the afterward steps, with the capital accommodation point on the agreeable agent coming
at Step 4:
Step 1 The applicant sends an HTTP Get appeal with a destination abode of the web
server, as normal.
Step 2 The router’s WCCP action notices the HTTP Get appeal and redirects
the packet to the agreeable engine.
Step 3 The agreeable agent looks at its deejay accumulator accumulation to ascertain if the
requested article is cached.
R1
2
5
3
4A 4B
1
Do I acquire the
requested object?
146 Chapter 5: IP Services
Step 4A If the article is cached, the agreeable agent sends an HTTP response, which
includes the object, aback to the client.
Step 4B If the article is not cached, the agreeable agent sends the aboriginal HTTP Get
request on to the aboriginal server.
Step 5 If Step 4B was taken, the server replies to the client, with no ability that
the packet was anytime redirected to a agreeable engine.
Using WCCP, which uses UDP anchorage 2048, a router and a agreeable engine, or a basin of content
engines (known as a cluster), become acquainted of anniversary other. In a array of agreeable engines, the
content engines additionally acquaint with anniversary added application WCCP. Up to 32 agreeable engines can
communicate with a distinct router application WCCPv1. If added than one agreeable agent is present, the
one with the everyman IP abode is adopted as the advance engine.
WCCP additionally provides a agency for agreeable engines aural a array to become acquainted of anniversary other.
content engines appeal advice on the array associates from the WCCP router, which replies
with a list. This permits the advance agreeable agent to actuate how cartage should be broadcast to
the cluster.
In WCCPv1, alone one router can alter cartage to a agreeable agent or a array of agreeable engines.
In WCCPv2, assorted routers and assorted agreeable engines can be configured as a WCCP service
group. This amplification permits abundant bigger scalability in agreeable caching. Furthermore, WCCPv1
supports alone HTTP cartage (TCP anchorage 80, specifically). WCCPv2 supports several added traffic
types and has added allowances compared to WCCPv1:
■ Supports TCP and UDP cartage added than TCP anchorage 80, including FTP caching, FTP proxy
handling, web caching for ports added than 80, Real Audio, video, and telephony.
■ Permits segmenting caching casework provided by a caching array to a accurate agreement or
protocols, and uses a antecedence arrangement for chief which array to use for a accurate cached
protocol.
■ Supports multicast to abridge configuration.
■ Supports assorted routers (up to 32 per cluster) for back-up and amount distribution. (All
content engines in a array charge be configured to acquaint with all routers in that
cluster.)
■ Provides for MD5 aegis in WCCP advice application the all-around configuration
command ip wccp countersign password.
■ Provides amount distribution.
■ Supports cellophane absurdity handling.
Web Accumulation Advice Agreement 147
When you accredit WCCP globally on a router, the absence adaptation acclimated is WCCPv2. Because the
WCCP adaptation is configured globally for a router, the adaptation cardinal affects all interfaces.
However, assorted casework can run on a router at the aforementioned time. Routers and agreeable engines can
also accompanying participate in added than one account group. These WCCP settings are
configured on a per-interface basis.
Configuring WCCP on a router is not difficult because a lot of the agreement in a caching
scenario takes abode on the agreeable engines; the routers charge alone basal configuration. Example
5-4 shows a WCCPv2 agreement application MD5 affidavit and multicast for WCCP
communication.
Finally, WCCP can accomplish use of admission lists to clarify cartage alone for assertive audience (or to exclude
WCCP use for assertive clients) application the ip wccp web-cache redirect-list access-list global
command. WCCP can additionally use ACLs to actuate which types of redirected cartage the router
should acquire from agreeable engines, application the all-around command ip wccp web-cache group-list
access-list.
Example 5-4 WCCP Agreement Example
! First we accredit WCCP globally on the router,
! allegorical a account (web caching), a multicast abode for
! the WCCP communication, and an MD5 password:
ip wccp web-cache group-address 239.128.1.100 countersign cisco
! Next we configure an interface to alter WCCP web-cache
! cartage outbound to a agreeable engine:
int fa0/0
ip wccp web-cache alter out
! Finally, entering cartage on interface fa0/1 is afar from redirection:
int fa0/1
ip wccp alter exclude in