Network Scalability by Design

While choosing the right hardware for a network is critical, more is involved
in building a scalable network than simply buying routers with redundant
components and a few orders of magnitude more performance than is
immediately needed. As important as hardware selection is, it’s only about
one-third of the task of building a scalable network. The remaining
two-thirds of the task comprise the logical design of the network.

Designing a scalable transport network or adding scalability to an
existing design can be accomplished by scaling intradomain routing, by
scaling interdomain routing, and by engineering transit traffic through
the use of Multiprotocol Label Switching (MPLS). Chapter 12 details the IGP
mechanisms that allow the network to grow without putting service or
connectivity at risk. Chapter 13 addresses methods of
controlling domain-external traffic. This chapter ties the two concepts
together to provide a big-picture look at scaling networks.

Scaling BGP for High Availability

Any discussion of scaling interdomain routing is, by default, a discussion of BGP
scalability mechanisms. This section builds on the Internal BGP (IBGP) configuration basics described in
Chapter 13 to show how a
simple intelligent route reflection scheme can allow a network to expand
or contract to scale as needed.

Note

As explained in Chapter 13, for networks with high availability requirements the authors strongly recommend scaling using route reflection with clusters instead …