Chapter 9. Tag Switching Overview

Tag Switching combines the performance and capabilities of Layer 2 (data link layer) switching with the proven scalability of Layer 3 (network layer) routing. It enables service providers to meet challenges brought about by explosive growth and provides the opportunity for differentiated services without necessitating the sacrifice of existing infrastructure. The Tag Switching architecture is remarkable for its flexibility. Data can be transferred over any combination of Layer 2 technologies, support is offered for all Layer 3 protocols, and scaling is possible well beyond anything offered in today's networks.

Specifically, Tag Switching can efficiently enable the delivery of IP services over an ATM switched network. It supports the creation of different routes between a source and a destination on a purely router-based Internet backbone. Service providers who use Tag Switching can save money and increase revenue and productivity.

Tag Switching offers the following benefits:

• IP over ATM scalability—Enables service providers to keep up with Internet growth

• IP services over ATM—Brings Layer 2 benefits to Layer 3, such as traffic engineering capability

• Standards—Supports multivendor solutions

• Architectural flexibility—Offers choice of ATM or router technology, or a mix of both