Chapter 3 -- Understanding Exchange 2000 Server Routing Architecture

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Chapter 3

One of the most significant differences between Microsoft Exchange Server 5.5 and Microsoft Exchange 2000 Server lies in the basic architecture of an Exchange system. The message routing topology in Exchange Server 5.5 is based on sites. A site is a logical grouping of servers that enjoy permanent, high-bandwidth connectivity. Architecturally, each site defines three distinct boundaries: the boundary for single-hop routing, the administrative unit, and a namespace hierarchy in the directory structure.

In Exchange 2000, these three boundaries have been separated into individual elements. Single-hop routing is defined by a routing group, the unit of administration is defined by the administrative group, and the namespace hierarchy exists in the Active Directory directory service in the form of a domain. This architecture gives administrators much more flexibility in determining how Exchange 2000 Server is administered because administrative assignments can be divided along functions and activities rather than geography.

This chapter focuses on the routing architecture used in Exchange 2000 Server. It describes what routing groups are, how to plan and name them, how they connect, and how link state information works to provide better message routing than Exchange 5.5 Server. We'll also look at the transport architecture and introduce some of the new architectural features.