Enterasys Networks Security Router X-PeditionTM - Manual (Page 210)

Overview
9-2 Configuring Frame Relay
Figure 9-1 Frame Relay Network Topology
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-relay intf-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.
New York
Toronto
Minneapolis
Frame Relay
(Packet Switching Network)
DLCIs
DLCIs
Boston