Chapter 1 - Introduction

Abstract

The Internet at the highest level consists of a number of Autonomous Systems (ASs) interconnected together. Each AS is basically a Network Service Providers (NSP), such as AT &T or Deutsche Telekom. Each AS has its own customers such as many residential users are customers of AT&T or Verizon. Usually, the network operators would start with Interior Gateway Protocol (IGP) and this practice is called IGP traffic engineering. Multi-Protocol Label Switching (MPLS) traffic engineering allows the use of multiple paths with different IGP metrics for load sharing. This kind of intradomain traffic engineering is transparent to the outside world. In the metro, there are three groups of users, residential, enterprises, and data centers. The first two groups are content users while the third are the content providers. Residential users are connected via Digital Subscriber Line (DSL) or cable modem or Passive Optical Network (PON). The access devices, such as the DSL Access Multiplexer (DSLAMs), are connected by an aggregation network to the Central Office. The aggregation network usually has two levels of devices, with the first-level devices in the Local Exchange Office and the second-level devices in the Central Office.