Internet Routing Architectures, Second Edition

Controlling IGP Expansion

One of the ways in which administrators push their networks to the limit is by letting them grow in such a way that the IGP will be hard to manage. Whether the IGP is as outdated as RIP version 1 or as advanced as Open Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (IS-IS), the issue of scalability will arise. So far, this chapter has discussed route reflectors and confederations as ways of managing IBGP growth. A scalable way of managing IGP expansion is to segment the AS into multiple regions, each running a single, distinct IGP. The individual regions, in turn, must be connected via BGP. With this design, the stability of one region would not affect the stability of another.

What criteria ...