Frame Relay
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OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
Alcatel-Lucent
FRAME RELAY OVERVIEW
FR is a WAN protocol that operates at the physical and data-link layers of the OSI
reference model. This protocol was originally designed for use across ISDN
interfaces but today it is used over a variety of other network interfaces as well.
The following sections provide an overview of the FR encapsulation:
• “Frame Relay Devices”
• “Frame Relay Virtual Circuits”
• “Frame Relay Network Deployments”
FRAME RELAY DEVICES
Devices attached to a FR WAN fall into two general categories:
• DTE - These are considered to be the terminating equipment for a specific
network and typically located on the customer premises.
• DCE - These are carrier-owned internetworking devices. The purpose of DCE
equipment is to provide clocking and switching services in a network.
FRAME RELAY VIRTUAL CIRCUITS
FR provides connection-oriented data-link layer communication. This means that
a defined connection exists between each pair of devices and that each such
connection is associated with a connection identifier. This service is implemented
by using the FR virtual circuit, which is essentially a logical connection created
between two DTEs. A virtual circuit provides for a bi-directional communication
path between one DTE device and another, and is uniquely identified by a DLCI.
Virtual circuits are of two types:
• Switched Virtual Circuits (SVC) - These are temporary connections used in
situations requiring only sporadic data transfer between DTE devices across FR
network. The actual deployment of SVCs is minimal in today's FR network.
• Permanent Virtual Circuits (PVC) - These are permanently established
connections that are used for frequent and consistent data transfers between DTE
devices across a FR network.
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