Frame Relay Components

A comprehensive look of all the components you need to know about when using Frame Relay. Illustrations and tables provide a crib sheet you'll want to bookmark. From Cisco Press' Network Consultants Handbook.

 By Cisco Press
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Network Consultants Handbook - Frame Relay
by Matthew Castelli

Network Consultants Handbook -- Click here to go to publisher's site

Frame Relay Components
Frame Relay WAN service comprises four primary functional components:

  • Customer premise Frame Relay access device (FRAD)
  • Local access loop to the service provider network
  • Frame Relay switch access port
    Link Management Interface parameters are defined here
  • Frame Relay VC parameters to each end site

Customer Premise FRAD
This device is either a dedicated FRAD, such as a Cisco XXX; or a router, such as a Cisco 26xx Series Router. Figure 15-3 illustrates a typical FRAD implementation.

NOTE:   A router with an integrated CSU/DSU acts as a FRAD/Router.

Figure 15-3: Frame Relay Access Device
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Local Access Loop to the Service Provider Network
Local access loop is the physical wiring that interconnects the customer premise FRAD and the service provider networks Frame Relay switch access port. This local loop is typically a DS0, DS1, NxDS1, DS3 service, or some fraction of DS1/DS3 service (such as Frac-T1).

In telephony, a local loop is the wired connection from a telephone companys central office (CO) in a locality to its customers telephones at homes and businesses. This connection is usually on a pair of copper wires called twisted pair. The local loop system was originally designed for voice transmission only using analog transmission technology on a single voice channel. A modem is used to handle the conversion between analog and digital signals. With the advent of ISDN or digital subscriber line (DSL), the local loop can carry digital signals directly and at a much higher bandwidth than for voice only.

The local loop requires termination into a network interface unit (NIU) at the customer premise, and subsequent connection to the customer DCE device, usually a CSU/DSU. The DTE port of this CSU/DSU provides connectivity to the FRAD/Router. Figure 15-4 illustrates a typical local loop configuration.

Figure 15-4: Frame Relay Local Access Loop
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This article was originally published on Jan 10, 2002
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