https://www.infra-repository.org/oiar-2013/index.php?action=history&feed=atom&title=PAT.Access_DistributionPAT.Access Distribution - Revision history2026-05-06T15:12:34ZRevision history for this page on the wikiMediaWiki 1.40.0https://www.infra-repository.org/oiar-2013/index.php?title=PAT.Access_Distribution&diff=546&oldid=prevJan Schoonderbeek: start2012-11-11T23:22:21Z<p>start</p>
<p><b>New page</b></p><div>{{Maturity|3}}<br />
{{Pageheaderbox4PatternType<br />
|PATname=Access Distribution<br />
|summary=Provides smart access to back-end facilities, providing services such as caching, health/capacity based load balancing etc.<br />
|version=0.2<br />
|owner=J.A.H. Schoonderbeek<br />
|sector=Infrastructure Sector Business Support<br />
}}<br />
This facility serves to accept connections from clients (users) and direct them to a facility or application (or to a set of different facilities or applications) that has been realized with multiple instances (so-called "distributed facilities"). The reason to distribute access over multiple instances of a facility/application may be to increase the maximum load that can be handled, or to help business continuity by spreading the facility/application over multiple sites, or both.<br />
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Examples of components used by an Access Distribution realization are a load balancer appliance and a web proxy server.<br />
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Access Distribution facilities are often combined with [[PAT.Access Security|Access Security]] facilities.<br />
{{PAgraphic<br />
|graphic=PAT.Access Distribution.png<br />
|source=Pattern Types.vsd<br />
|size=400px<br />
|title=Access Distribution pattern<br />
}}<br />
{{Pattern Type Composition}}<br />
{{Pattern Type Composition Row<br />
|facility=BT.Distribution<br />
|choice=must<br />
|reason=This facility delivers the core functionality of the pattern.<br />
}}<br />
{{Pattern Type Composition Row<br />
|facility=BT.Caching<br />
|choice=may<br />
|reason=The Access Distribution Pattern is a very good place to implement caching as it can both ease the load on the distributed facilities behind this pattern, and speed up their apparent responsiveness.<br />
}}<br />
{{Pattern Type Composition Row<br />
|facility=BT.Data Scanning<br />
|choice=may<br />
|reason=Distribution may occur not only based on the traffic characteristics ("conventional routing") but also on the content of the traffic ("content based routing"). To this end, the Access Distribution pattern should have access to the data of the traffic that's being distributed, and this Building Block Type offers that access. As an example: this BBT could recognize HTTP headers within network traffic, and direct traffic destined for a particular application to the right application server.<br />
}}<br />
{{Pattern Type Composition Row<br />
|facility=BT.Load Balancing<br />
|choice=may<br />
|reason=Loads may need to be (re)directed either for an even distribution of load on the distributed facilities, or to counter the effect of a failure of a component or facility in the hinterland. In either case, a facility is needed that can provide the Distribution facility with the means to sense the need for load balancing, and consequently make a distribution decision.<br />
}}<br />
{{Pattern Type Composition Row<br />
|facility=BT.Connection Handling<br />
|choice=may<br />
|reason=For a correct distribution of access over distributed facilities, the Distribution facility may need access to session data, which Connection Handling can provide. Furthermore, for a seamless transition of a user session from one part of the distributed facility to another, the session may require special attention (e.g. a "session state database").<br />
}}<br />
{{Table Ending}}<br />
{{Pattern Type Neighbors}}<br />
{{Table Ending}}<br />
{{PATfooter}}</div>Jan Schoonderbeek