User`s guide

XSR User’s Guide 119
7
Configuring Frame Relay
Overview
Frame Relay is a simple, bit-oriented protocol that offers fast-packet
switching for wide-area networking. It combines the statistical multiplexing
and port-sharing features of an X.25 connection with high speed and low
delay to provide high performance and less overhead. Frame Relay organizes
data into variable-length, individually addressed units known as frames
rather than placing them in fixed time slots for delivery over a packet-
switched network where the data channel is occupied only for the duration of
the transmission.
Virtual Circuits
Frame Relay is based on the concept of the Virtual Circuit (VC) - a two-way,
always on, software-defined data path between two ports that acts as a
“private” line in the network. The XSR supports Permanent Virtual Circuits
(PVCs), multiplexing several PVCs in a single Frame Relay port, which
reduces the number of physical connections required to link sites. A Frame
Relay connection can be ordered with multiple PVCs connecting to different
remote site. Refer to Figure 14 for a typical network topology.
DLCIs
The Data Link Connection Identifier (DLCI) is a unique number assigned to a
PVC end point, essentially, the port to which the destination network is
attached. DLCIs can perform data “interleaving” from two or more devices
on a single channel known as statistical multiplexing. Data entering a Frame