Enterasys Networks X-PeditionTM manual DTEs, DCEs

Overview

Figure 9-1 Frame Relay Network Topology

DLCIs

New York

Minneapolis

Frame Relay

(Packet Switching Network)

DLCIs

Boston Toronto

From the perspective of the OSI reference model, Frame Relay is a high-performance WAN protocol suite operating at the physical and data link layers (1 and 2). Starting from a source site, variable-length packets are switched between various network segments until the destination is reached.

Devices attached to a FR WAN fall into two categories: Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE).

DTEs

A DTE is a network end station, either the ultimate source or destination of data through a FR network. A FR device can be a router, bridge, terminal or PC. For example, the XSR acts as a DTE originating or terminating device.

As a source device, a DTE encapsulates data in a FR frame and transmits. As a destination device, a DTE de-encapsulates FR data (strips the FR “header” from the packet) leaving only user IP data. The frame-relayintf-type dte command assigns the device to the port.

DCEs

A DCE is an internetwork switching device located at your service provider’s premises. DCEs provide network clocking and the switches which actually transmit data across the WAN. In most cases, these are packet switches.

The connection between a DTE device and a DCE device consists of both physical- and link-layer components. The physical component defines mechanical, electrical, functional, and procedural specifications of the connection between the devices while the link-layer component defines the protocol that establishes the connection between the DTE and the DCE.

9-2 Configuring Frame Relay