Frame Relay
is a high-speed packet switching protocol used in wide area networks
(WANs). Providing a granular service of up to DS3 speed (45 Mbps), it
has become popular for LAN to LAN connections across remote distances,
and services are offered by most major carriers.
Frame relay (FR) is much faster than X.25, the first packet-switched
WAN standard, because frame relay was designed for reliable circuits
and performs less error detection . Frame relay does not process the
packets; it relays them from the switch's input port to the output
port, hence the name.
The Frame Relay frame is
transmitted to its destination by way of virtual circuits (logical
paths from an originating point in the network) to a destination point.
Virtual circuits may be permanent (PVCs) or switched (SVCs). PVCs are
set up administratively by the network manager for a dedicated
point-to-point connection; SVCs are set up on a call-by-call basis.
Frame Relay is an example
of a packet-switched technology. Packet-switched networks enable end
stations to dynamically share the network medium and the available
bandwidth. The following two techniques are used in packet-switching
technology:
-
Variable-length packets
-
Statistical
multiplexing
Variable-length packets are
used for more efficient and flexible data transfers. These packets are
switched between the various segments in the network until the
destination is reached.
Statistical multiplexing
techniques control network access in a packet-switched network. The
advantage of this technique is that it accommodates more flexibility
and more efficient use of bandwidth. Most of today's popular LANs, such
as Ethernet and Token Ring, are packet-switched networks.
Advantages of
Frame Relay:
Frame Relay offers an
attractive alternative to both dedicated lines and X.25 networks for
connecting LANs to bridges and routers. The success of the Frame Relay
protocol is based on the following two underlying factors:
-
Because virtual
circuits consume bandwidth only when they transport data, many virtual
circuits can exist simultaneously across a given transmission line. In
addition, each device can use more of the bandwidth as necessary, and
thus operate at higher speeds.
-
The improved
reliability of communication lines and increased error-handling
sophistication at end stations allows the Frame Relay protocol to
discard erroneous frames and thus eliminate time-consuming
error-handling processing.
Frame Relay
Resources:
Cisco Frame Relay Tutorial
Frame
relay protocol
Frame Relay FAQ
Frame
Relay Overview
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