- Enterasys Security Router User's Guide

XSR User’s Guide 13-1

Configuring ADSL

This chapter details the background, features, implementation and configuration of Asymmetric

Digital Subscriber Line (ADSL) on the XSR.

Overview

ADSL (Asymmetric Digital Subscriber Line) is a technology for transmitting digital information at

a high bandwidth over existing phone lines. Unlike regular dialup phone service, ADSL provides

continuously available, “always on” service.

ADSL is asymmetric in that it uses most of the channel to transmit downstream to the user and a

smaller part of the channel to receive information from the user. ADSL simultaneously

accommodates analog (voice) information on the same line.

Features

The following ADSL features are supported on the XSR:

• NIM hardware identification via an on-card EEPROM

• ADSL line operation over POTS and ISDN circuits

• ADSL data framing format ATM Frame UNI (FUNI)

• OAM cells: AIS, RDI, CC, Loopback over F4 and F5 flows

• Up to 30 ATM permanent virtual circuits (PVCs)

• ATM UBR traffic class

• ATM Adaptation Layers 0 and 5

• PDU encapsulation types:

– PPPoE - Point-to-Point Protocol over Ethernet (RFC-2516)

– PPPoA - Point-to-Point Protocol over ATM)

– IPoA - Routed IP over ATM (RFC-2684)

• Response to inverse ARP requests

• Maintenance of SNMP interface and Interface Stack Tables

• “Dying Gasp” support to perform an orderly shutdown and report an outage to your DSLAM

Figure 13-1, shown below, illustrates the three “flavors” of ADSL the XSR supports and the path

ADSL traffic follows through various encapsulation layers as defined by the pertinent RFCs.