Overview

In this chapter we examine the label switching approach known as IP Switching. An individual device that implements the IP Switching architecture is, of course, an IP Switch. As noted previously, we use these terms specifically to describe the approach developed by Ipsilon, even though they are sometimes used generically elsewhere.

One of the significant innovations of the Ipsilon approach to label switching was to define not only a label distribution protocol (which all approaches do) but also a switch management protocol. This protocol, known as GSMP (General Switch Management Protocol), allows an ATM switch to be controlled by an IP Switch controller and thus turned into an IP Switch. This protocol takes the separation of control and forwarding, discussed in Section 2.1, to its logical conclusion: it enables control and forwarding to reside in separate physical boxes connected by a link, over which GSMP runs.

GSMP provides a range of technical, business, and economic benefits. In particular, at the time that Ipsilon was founded, ATM switches with capacities of around 2.5 Gb/sec (16 OC-3) were becoming commodity items, in the sense that they were being manufactured by many vendors and were differentiated more by price than by features. In such an environment, an approach that could turn any vendor s ATM switch into something with the capabilities of a router with only a modest increase in total cost was likely to have considerable market appeal. This is exactly what GSMP enabled Ipsilon to do.

GSMP is a...