Avaya Configuring Frame Relay Services Bedienungsanleitung PDF herunterladen (Seite 33)

Frame Relay Overview

117376-C Rev. 00

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Frame relay assumes that networks use transmission lines with low error rates,

such as digital transmission media. Consequently, frame relay provides only basic

error detection with no error recovery. This minimizes the processing required for

each packet, allowing frame relay networks to operate at high speeds with few

network delays.

Because frame relay performs only basic error checking, end stations running

upper-layer protocols such as Internet Protocol (IP) are responsible for resending

packets that did not transmit correctly the first time.

Permanent Virtual Circuits

A permanent virtual circuit (PVC) is a dedicated logical path that connects two

devices over a network. Once configured, a PVC is always available to the

connected devices; a PVC does not require setup before data can travel across the

network, nor a disconnect after. Since many PVCs can coexist, devices can share

the bandwidth of the transmission line.

Switched Virtual Circuits

A switched virtual circuit (SVC) is a logical path that is established on an

as-needed basis. That is, an SVC exists only when there is data to transfer. SVCs

can connect any two points on a network without the requirement that the provider

preconfigure virtual circuits (VCs).

SVCs can provide an alternative to a large network infrastructure, potentially

resulting in cost savings for networks with infrequent communications between

sites. SVCs can also provide an easy and relatively inexpensive solution for

disaster recovery. Costs associated with having a redundant PVC are eliminated.

In addition, you can prepare an SVC network for disaster recovery by performing

incremental backups to a mirror-image database on a remote server.

In addition to cost savings, SVCs provide other benefits. When frame relay

networks using global addressing approach a thousand sites, they run out of data

link connection identifiers (DLCIs). SVCs enable you to manage connectivity on

the basis of use rather than permanent connections. Using SVCs also simplifies

network administration because you do not have to preconfigure network

topologies and support moves, adds and changes, as with PVCs. This can be a

significant benefit in large, highly meshed networks.

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Avaya Configuring Frame Relay Services Bedienungsanleitung Seite 33