IBM SC30-3681-08 manual Using Frame Relay Interfaces, Frame Relay Overview, 387, Shutdown

Chapter 30. Using Frame Relay Interfaces

This chapter describes how to use the Frame Relay interface and includes the following sections:

v ªFrame Relay Overviewº

v ªFrame Relay Network Managementº on page 395

v ªFrame Relay Data Ratesº on page 396

v ªCircuit Congestionº on page 399

v ªBandwidth Reservation over Frame Relayº on page 402

v ªDisplaying the Frame Relay Con®guration Promptº on page 402

v ªFrame Relay Basic Con®guration Procedureº on page 402

v ªEnabling Frame Relay PVC Managementº on page 403

v ªEnabling Frame Relay SVC Managementº on page 404

Frame Relay Overview

The Frame Relay (FR) protocol is a method of transmitting internetworking packets

by combining the packet switching and port sharing of X.25 with the high speed and

low delay of time division multiplexing (TDM) circuit switching. FR allows you to

connect multiple LANs to a single high-speed (1.54 Mbps) WAN link with multiple

point-to-point virtualcircuits (VCs). FR offers the following features:

v High throughput and low delay. Utilizing the core aspects (error detection,

addressing, and synchronization) of the Link Access Protocol, D-Channel (LAPD)

datalink protocol, FR eliminates all network layer (Layer 3) processing. By using

only the core aspects, FR reduces the delay of processing each frame.

v Congestion detection. Upon receiving Backward Explicit Congestion Noti®cation

(BECN) or a Forward Explicit Congestion Noti®cation (FECN), the router initiates

a controlled slowdown of traffic, thereby avoiding a complete FR network

shutdown.

The router can also initiate a slowdown of traffic when it receives a Consolidated

Link Layer Management (CLLM) congestion message. CLLM is an optional part

of the Frame Relay standards that provides additional management information

about the operation of the frame relay network to attaching DTEs.

v Circuit access and control. As the router dynamically learns about the availability

of non-con®gured circuits (orphan circuits), you can control access to those new

circuits.

v Network management option. As your network requires, the FR protocol can

operate with or without a local network management interface.

v Multiplexing protocols. Using one VC to pass multiple protocols.

v Data compression that supports the FRF.9 standard. See Using the Data

Compression Subsystem in Using and Con®guring Featuresfor details.

v Data encryption using a proprietary encryption scheme. See Overview of

Encryption in Using and Con®guring Featuresfor details.

FR provides no error correction or retransmission function. To provide error±free

end-to-end transmission of data, FR relies on the intelligence of the host devices.

© Copyright IBM Corp. 1994, 1998 387