Technology

INTRODUCTION

Both large and small Internet Service Providers (ISPs) constantly face the challenges of adapting their networks to support rapid growth and customer demand for more reliable and differentiated services. Moreover, many carriers found it cost-effective to multiplex Internet traffic as one of many services carried over an ATM core. Recently, the growth of Internet services and Wavelength Division Multiplexing (WDM) technology at the fiber level have provided a viable alternative to ATM for multiplexing multiple services over individual circuits. In addition, the once faster and higher bandwidth ATM switches are being out-performed by Internet backbone routers. Equally important, Multiprotocol Label Switching (MPLS) offers simpler mechanisms for packet-oriented traffic engineering and multiservice functionality with the added benefit of greater scalability. MPLS emerged from the IETF's effort to standardize a number of proprietary multilayer switching solutions that were initially proposed in the mid-1990s. To help you appreciate the importance of MPLS and its impact on the Internet core, the first half of this paper describes the forces that motivated the development and evolution of these different solutions, focusing on the common features and design considerations shared by the different solutions-the complete separation of the control component from the forwarding component and the use of a label-swapping forwarding paradigm.

Perspective

Over the past few years, a number of new technologies have been designed to support Internet Service Providers (ISPs) as they try to keep a step ahead of the Internet's explosive growth. The latest technological advances include Internet backbone routers, new queuing and scheduling algorithms, IPSEC, web-caching services, directory services, and integrated routing/forwarding solutions. While all these technologies are critical for the successful operation and continued growth of the Internet, the evolution of routing functionality is essential if ISPs want to provide support for a new class of revenue-generating customer services.

Multiprotocol Label Switching (MPLS) is the latest step in the evolution of routing/forwarding technology for the core of the Internet. MPLS delivers a solution that seamlessly integrates the control of IP routing with the simplicity of Layer 2 switching. Furthermore, MPLS provides a foundation that supports the deployment of advanced routing services because it solves a number of complex problems:

" MPLS addresses the scalability issues associated with the currently deployed IP-over-ATM overlay model
" MPLS significantly reduces the complexity of network operation.
" MPLS facilitates the delivery of new routing capabilities that enhance conventional IP routing techniques.
" MPLS offers a standards-based solution that promotes multivendor interoperability.

MPLS emerged from the IETF's effort to standardize a set of proprietary multilayer switching solutions that were originally developed in the mid-1990s. To fully understand the essence of MPLS and its role in the Internet, it is valuable to look back and examine the forces that stimulated the development of these proprietary multilayer switching approaches and how they were ultimately integrated into MPLS

Terminology

Forwarding Equivalence Class (FEC):- A group of IP packets which are forwarded in the same manner (e.g. over the same path, with the same forwarding treatment)