5.1 Tag Switching Overview

5.1 Tag Switching Overview

In Chapter 1 we saw that there were many motivations behind the development of the various label switching approaches, such as additional routing functionality, improved scalability of the routing system, better forwarding performance, and more flexibility of the routing system. However, the one that has been most widely appreciated is the easiest to understand: performance. The idea is simple: provide the functionality of a router (IP forwarding) with the performance (and cost) of an ATM switch.

The design goals of Tag Switching are rather broad. In particular, Tag Switching has focused on adding functionality (such as explicit routes) and improving scalability (e.g., through the use of a hierarchy of routing knowledge), as the following sections will illustrate. Moreover, Tag Switching aims at being link layer independent, thus allowing operation over virtually any media type, not just ATM. High performance is just one among many goals for Tag Switching.

Tag Switching can be implemented in a variety of devices, such as routers or ATM switches. Implementing Tag Switching on routers doesn?t require hardware modifications to the routers, although one certainly could provide specialized hardware support for high performance Tag Switching forwarding. Implementing Tag Switching on ATM switches doesn?t require any modifications to the hardware used by these switches (although Tag Switching could benefit from certain hardware modifications, as we?ll describe below); support for Tag Switching on ATM switches can be achieved purely by upgrading software.

A Tag Switching network consists of Tag Edge Routers, and Tag...

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Switching in IP Networks: IP Switching, Tag Switching, & Related Technologies

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5.1 Tag Switching Overview

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