User`s guide

XSR User’s Guide 121
Chapter 7 Frame Relay Features
Configuring Frame Relay
DTEs
A DTE is a network end station, either the ultimate source or destination of
data through a Frame Relay network. A Frame Relay 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 Frame Relay frame and
transmits. As a destination device, a DTE de-encapsulates Frame Relay data
(strips the Frame Relay “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.
Frame Relay Features
The XSR supports the following Frame Relay features:
 The router acts as a DTE device in the UNI (User Network Interface)
interface, supporting Frame Relay PVC connections. DCE
functionality is not supported.
 10-bit DLCI addressing using a 2-byte DLCI header. 3- and 4-byte
DLCI headers are not supported.
 Rate enforcement (CIR) with automatic rate fallback via
traffic/adaptive shaping when the network is congested.
Automatically restores to normal rates when congestion is removed.
 Congestion control by Backward Explicit Congestion Notification
(BECN). The XSR does not send packets with the BECN bit set.
 The three standard LMIs: ILMI (FRF1.1) ANSI Annex D, CCITT
Annex A. Also supported: Auto LMI detect and None.