Enterasys Matrix DFE-Gold Series Configuration Guide 23-1
23

Transparent Web Cache Balancing Configuration

ThischapterdescribestheTransparentWebCacheBalancing(TWCB)commandsandhowtouse
them.

Understanding Transparent Web Cache Balancing (TWCB)

TransparentWebCacheBalancing(TWCB)providesforthestoringoffrequentlyaccessedweb
objectsonacacheoflocalservers.EachHTTPrequestistransparentlyredirectedbytheNSeries
routertoaconfiguredcacheserver.Whenauserfirstaccessesawebobjectthatobjectisstoredon
acacheserver.Eachsubsequentrequestfortheobjectusesthiscachedobject.Webcachingallows
multipleuserstoaccesswebobjectsstoredonlocalcacheserverswithamuchfasterresponsetime
thanaccessingthesameobjectsoveraninternetconnectionorthroughadefaultgateway.Thiscan
alsoresultinsubstantialcostsavingsbyreducingtheinternetbandwidthusage.
TheNSeriesrouterdoesnotactasacacheforwebobjects;rather,itredirectsHTTPrequeststo
localserversonwhichwebobjects��arecached.Thecacheserversshouldhaveawebbasedproxy
cacherunning.TheSquidapplicationisanexampleofawebbasedproxycache.
ImplementingaTWCBconfigurationrequiresuserstoconfigurearoutednetworkwithIP
interfacesthatallowtheNSeriesroutertosendrequestsfortheinternettothecorrectweb
cachingdevice.
TherearefiveaspectstoTWCBconfiguration:
• Createtheserverfarmsthatwillcachethewebobjects.Aserverfarmismadeupof1ormore
cacheservers.
•SpecifytheenduserswhoseHTTPrequestswillorwillnotberedirectedtothecacheservers.
Thisstepisoptional.Ifnohostsareconfigured,thefirmwareredirectsallHTTPrequests.
•SpecifythewebsitehoststhatwillnottakepartinTWCB.
• Createawebcachethattheserverfarmswillbeassociatedwith.
•ApplythecachingpolicytoanoutboundinterfacetoredirectHTTPtrafficonthatinterfaceto
thecacheservers.
Figure 231providesanexampleofaTWCBconfigurationoverview.Thewebcacheismadeupof
serverfarmswhichlogicallygrouponeormorecacheservers.Inourexample,Cache1isthename
ofthewebcache.Itismadeupoftwoserverfarms:s2Serversands1Servers.Thes1Serverserver
Router: Unless otherwise specified, the commands covered in this chapter can be executed only
when the device is in router mode. For details on how to enable router configuration modes, refer to
Enabling Router Configuration Modes on page 2-103.
Note: An Enterasys Feature Guide document that contains a complete discussion on TWCB
configuration exists at the following Enterasys web site: http://www.enterasys.com/support/
manuals/