Understanding Your Current Network Environment


Topic Last Modified: 2005-05-06

Before you design your Exchange messaging system, you need to understand the physical and logical aspects of your current environment. From a physical standpoint, your design depends on the type and integrity of your network infrastructure. These factors influence how you deploy Exchange, where you place servers, and the expected user experience. From a logical standpoint, Exchange 2003 depends on the Active Directory® directory service for its services, so your existing Active Directory framework must be sound. In fact, it is highly recommended that you design your Active Directory framework with Exchange in mind.

An Active Directory infrastructure must be in place before you deploy Exchange 2003. When designing Active Directory, you should understand how Exchange considerations affect your design.

This section describes various aspects of the network infrastructure and Active Directory framework that you should assess when planning an Exchange messaging system. For a checklist that outlines the physical and logical factors you should consider when assessing your current environment, see "Checklist for Evaluating Your Current Environment."

The Microsoft Exchange Server Best Practices Analyzer Tool automatically examines your network and determines if the configuration is set according to Microsoft best practices for an Exchange deployment. For more information, see the Microsoft Exchange Server Best Practices Analyzer Tool (http://go.microsoft.com/fwlink/?LinkId=34707).

One of the first things you should do is build a complete picture of the existing physical network so you can determine how well your existing infrastructure supports Exchange. Going through this process can help you identify any needs for upgrades to the existing LAN or WAN. Start with a simple representation of the entire network to identify locations of offices and the connections between them, and then build in more detail, as illustrated by the following figure:

Start with a simple representation of your network infrastructure


To obtain a detailed picture of the LAN and WAN configuration, it is recommended that you diagram all site locations, connection types, and network topologies (such as bus, token ring, or star). Include the locations of firewalls and perimeter networks. Your assessment should also include a thorough inventory of the hardware that currently makes up your network infrastructure, including stand-alone and clustered servers, routers, and switches. Also note all data center logistics, including rack space, cabling, and power supplies. "Checklist for Evaluating Your Current Environment" lists specific items you examine during this assessment.

In general, you should assess your network infrastructure from the following perspectives:

  • Geographical considerations

  • Bandwidth and latency

  • Current usage

  • Current messaging system

These areas are discussed in the following sections.

After you map the locations of buildings, campuses, and branch offices, determine the types of network connections to each site, as well as the placement of routers and switches. A thorough understanding of this infrastructure can help you determine the number of Exchange routing groups you need, as well as the servers that will constitute each routing group. You also need to know the incoming and outgoing messaging points, including messages to servers within an Exchange organization and servers outside the Exchange messaging system.

A key consideration for planning your messaging system is the total amount of data that can be transmitted over the network in a given amount of time. This quantity is determined by a combination of bandwidth and latency. Bandwidth is the speed of transmission over a network connection in kilobits per second. Latency refers to the amount of time it takes in milliseconds to transfer data from one point to another. Both of these factors combine to determine the amount of data that can be transmitted in a certain amount of time over the network. The product of these two factors directly affects user perception of how long it takes to process a transaction.

When evaluating your network connections, you need to evaluate bandwidth and latency, recognizing that although some types of network connections can maximize bandwidth, they may increase latency. For example, a satellite connection may offer high bandwidth, but latency may suffer when compared to ground connections such as frame relay or dial-up Integrated Services Digital Network (ISDN).

When mapping site locations and connections, determine the type and speed of network connectivity, and factor in the amount of latency introduced due to distances between sites. You may need to recommend network upgrades as part of the project.

The current usage of the network is another key consideration. Examine network usage from all angles, including use by applications and users. Along with identifying the current applications that use the network, consider the impact of future projects or initiatives. You need to plan for the additional impact that future applications will have on the network.

An extremely important consideration when assessing current usage is the network load at peak times. To determine user load on the network, look at the number of users in the various sites as well as their patterns of use.

In general, if a site has more than ten users and is connected by low-bandwidth, high-latency network connections, the site should work in offline mode. Sites connected by low-bandwidth, high-latency network connections benefit from upgrading to Windows Server 2003, Exchange 2003, and Outlook 2003, because they may be able to use the full features of Cached Exchange Mode in Outlook 2003.

During planning, you should ask the following questions about your current messaging system:

  • What impact does your current messaging system have on your network?

  • Are you currently running an earlier version of Exchange? If so, are you running Exchange 5.5, Exchange 2000, or both versions in mixed mode?

During planning you should determine the impact of your current messaging system on your network. To simulate the usage of your current messaging system, use load-simulation tools such as Microsoft Exchange Server Load Simulation Tool (LoadSim.exe) and the Exchange Stress and Performance (ESP) tool. LoadSim simulates the effect of high usage by Outlook MAPI clients and helps you customize the Outlook profiles you want to use during testing. ESP simulates the effect of high usage by non-MAPI clients, such as Post Office Protocol (POP), Internet Message Access Protocol (IMAP), Simple Mail Transfer Protocol (SMTP), and Outlook Web Access 2003. You can also use ESP to simulate load in an architecture that incorporates front-end servers.

The method you follow for upgrading from an existing Exchange messaging system to Exchange 2003 depends on whether you are running Exchange 5.5 or Exchange 2000. If you are currently running Exchange 5.5 on Windows NT® Server version 4.0, you need to plan for moving user accounts to Active Directory and synchronizing directory information. Exchange 5.5 has its own directory service, whereas Exchange 2003 relies on Active Directory for its directory services. In your project plan, you need to build in a method for synchronizing the two directories. You may also need to plan for a period of coexistence until you can move entirely to Exchange 2003 and Active Directory. If you are running Exchange 2000 or a mixed Exchange 5.5 and Exchange 2000 environment, upgrading to Exchange 2003 is straightforward if Active Directory is already updated with current directory information. For this reason, you need to carefully examine the state of your directory information. For more information about how to plan your deployment path from Exchange 5.5 to Exchange 2003, see "Planning Your Deployment Path."

If you are currently running Exchange 5.5, another factor to consider is using Exchange 2003 with Outlook 2003 Cached Exchange Mode feature to host more users per server, thereby reducing the number of Exchange servers you need. For more information about Cached Exchange Mode, see "Understanding Versions of Exchange, Windows, and Outlook."