End-to-End DSL Architectures

Integrated Routing and Bridging (IRB)

This section describes the protocol stack, connectivity, IP addressing considerations, and advantages and disadvantages of an end-to-end ADSL architecture using IRB based on RFC 2684 bridging. Early ADSL deployments used bridging, and some older networks still use it, although more-sophisticated architecture designs are quickly replacing IRB.

IRB Overview

RFC 2684 IRB permits subscriber-to-subscriber communication, but broadcasts must be (and almost always are) limited. This configuration step prevents either inadvertent or intentional flooding of a bridged network with bandwidth-consuming networking traffic such as unnecessary Address Resolution Protocol (ARP) requests for IP addresses. However, certain ...