Deterministic Routing: Routing is no longer determined by link state. Because of this, it is
easier for an administrator to understand and predict the path a message takes.
Direct Connections: Exchange attempts a direct connection to the destination server. It is no
longer necessary to route the message through a series of hops.
Exactly how does transport select the route a message will take? Exchange Server 2007 follows some
simple rules:
The route is selected based on lowest cost only.
Bifurcation, the process of breaking the message into copies for multiple recipients with different
destinations, is delayed as long as possible.
It attempts direct delivery unless message flow is controlled by other means, such as a Hub site.
It relies on IP networks to provide redundancy at the network layer.
Note that in coexistence with legacy Exchange, there are additional considerations about connector
restrictions. Exchange Server 2007 ignores most restrictions on Routing Group Connectors. These restrictions
are discussed later in this chapter in the section on coexistence with Exchange 2003.
The process starts when the user clicks Send; the Microsoft Exchange Mail Submission service notifies an
available Hub Transport server in the same Active Directory site. If the Hub Transport role is co - located
on the mailbox server it will always be chosen.
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