RFC 2105 (rfc2105) - Page 2 of 13

Cisco Systems' Tag Switching Architecture Overview

RFC 2105           Cisco's Tag Switching Architecture      February 1997


   4.4    Flexible routing (explicit routes)  .....................   9
   5      Tag switching with ATM  .................................   9
   6      Quality of service  .....................................  11
   7      Tag switching migration strategies  .....................  11
   8      Summary  ................................................  12
   9      Security Considerations  ................................  12
   10     Intellectual Property Considerations  ...................  12
   11     Acknowledgments  ........................................  12
   12     Authors' Addresses  .....................................  13

1. Introduction

   Continuous growth of the Internet demands higher bandwidth within the
   Internet Service Providers (ISPs). However, growth of the Internet is
   not the only driving factor for higher bandwidth - demand for higher
   bandwidth also comes from emerging multimedia applications.  Demand
   for higher bandwidth, in turn, requires higher forwarding performance
   (packets per second) by routers, for both multicast and unicast
   traffic.

   The growth of the Internet also demands improved scaling properties
   of the Internet routing system. The ability to contain the volume of
   routing information maintained by individual routers and the ability
   to build a hierarchy of routing knowledge are essential to support a
   high quality, scalable routing system.

   We see the need to improve forwarding performance while at the same
   time adding routing functionality to support multicast, allowing more
   flexible control over how traffic is routed, and providing the
   ability to build a hierarchy of routing knowledge. Moreover, it
   becomes more and more crucial to have a routing system that can
   support graceful evolution to accommodate new and emerging
   requirements.

   Tag switching is a technology that provides an efficient solution to
   these challenges. Tag switching blends the flexibility and rich
   functionality provided by Network Layer routing with the simplicity
   provided by the label swapping forwarding paradigm.  The simplicity
   of the tag switching forwarding paradigm (label swapping) enables
   improved forwarding performance, while maintaining competitive
   price/performance.  By associating a wide range of forwarding
   granularities with a tag, the same forwarding paradigm can be used to
   support a wide variety of routing functions, such as destination-
   based routing, multicast, hierarchy of routing knowledge, and
   flexible routing control. Finally, a combination of simple
   forwarding, a wide range of forwarding granularities, and the ability
   to evolve routing functionality while preserving the same forwarding
   paradigm enables a routing system that can gracefully evolve to



Rekhter, et. al.             Informational