2 link layer protocols of wan, X.25 and lapb, 2 link layer protocols of wan -4 – Nortel Networks 8000 User Manual

Page 34: Link layer protocols of wan

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1 WAN access overview

Nortel Secure Router 8000 Series

Configuration -WAN Access

Interface

Command Line

View

Command

Prompt

LoopBack interface

LoopBack
interface view

Run the

interface
loopback 2
command in the

system view.

[Nortel-LoopBack2]

NULL interface

NULL interface

view

Run the

interface null 0
command in the

system view.

[Nortel-NULLO]

Tunnel interface

Tunnel interface

view

Run the

interface tunnel
0/0/6 command
in the system

view.

[Nortel-Tunnel0/0/6]

ED NOTE

The SR8000 is a centralized device. For the interfaces such as the Mp-group interface, tunnel interface,
and virtual-ethernet interface, the slot number and card number are fixed as 0.

This document describes parameters of the WAN physical interfaces and logical interfaces.

For other functions related to LAN and network layer protocols, refer to other manuals in the

Nortel Secure Router 8000 Series Configuration Guide.

1.1.2 Link layer protocols of WAN

PPP

The link layer provides reliable transmission of data from one site to the other. The link layer

receives packets from the network layer, and then encapsulates packets into frames to deliver
them to the physical layer.

WAN link layer protocols supported by the SR8000 are described as follows.

The Point-to-Point Protocol (PPP) encapsulates an IP datagram over serial links. It supports

the 8-bit asynchronous mode, free of parity check and bit-oriented synchronous link.

PPP includes the Line Control Protocol (LCP) to create, configure, and authenticate the data
links. It also includes the Network Control Protocol (NCP) that is oriented to different

network layer protocols.

The SR8000 also supports the Multi-link Protocol (MP), which binds multiple PPP links

together to provide larger bandwidth.

X.25 and LAPB

X.25 is an interface procedure between the data terminal equipment (DTE) and the data

circuit-terminating equipment (DCE).

X.25 has the following functions:

1-4

Nortel Networks Inc.

Issue 5.3 (30 March 2009)

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