Frame Relay is a telecommunication
service designed for cost-efficient data transmission
for intermittent traffic between Local Area
Networks (LANs)
and between end-points in a Wide Area Network
(WAN). Frame relay puts
data in a variable-size unit called a frame and leaves
any necessary error correction (retransmission of data)
up to the end-points, which speeds up overall data transmission.
For most services, the network provides a Permanent
Virtual Circuit (PVC),
which means that the customer sees a continuous, dedicated
connection without having to pay for a full-time leased
line, while the service provider figures out the route
each frame travels to its destination and can charge
based on usage. An enterprise can select a level of
service quality - prioritizing some frames and making
others less important. Frame Relay
is provided on fractional T-1 or full T-carrier system
carriers. Frame relay complements and provides a mid-range
service between ISDN, which offers bandwidth at 128
Kbps, and Asynchronous Transfer Mode (ATM),
which operates in somewhat similar fashion to frame
relay but at speeds from 155.520 Mbps or 622.080 Mbps.
Frame Relay is based on the older X.25
packet-switching technology which was designed for transmitting
analog data such as voice conversations. |
|
Unlike X.25 which was designed for analog signals, frame
relay is a fast packet technology, which means that
the protocol does not attempt to correct errors.
When an error is detected in a frame, it is simply "dropped."
(thrown away). The end points are responsible for detecting
and retransmitting dropped frames. (However, the incidence
of error in digital networks is extraordinarily small
relative to analog networks.)
Frame Relay is often used to connect
local area networks with major backbones as well as
on public wide area networks and also in private network
environments with leased lines over T-1 lines. It requires
a dedicated connection during the transmission period.
It's not ideally suited for voice or video transmission,
which requires a steady flow of transmissions. However,
under certain circumstances, it is used for voice and
video transmission.
Frame Relay relays packets at the Data
Link layer of the Open Systems Interconnection
(OSI) model rather than
at the Network layer. A frame can incorporate packets
from different protocols such as Ethernet and X.25.
It is variable in size and can be as large as a thousand
bytes or more. |
