With the release of Microsoft Exchange 2000, administrators discovered the ability to create and manage multiple Exchange systems from a centralized location—despite geographic factors, varying connection speeds, and different levels of reliability. While Exchange 2000 has simplified the process of managing multisystem Exchange networks, implementation can still be confusing. In this Daily Feature, we’ll examine the factors you need to consider when deploying multiple Exchange 2000 servers into several locations.
Understanding why you need multiple Exchange servers
In a typical small Active Directory setup, you might have your entire network of servers incorporated into one Windows 2000 Active Directory site. However, you may face a situation where you must support Exchange 2000 at more than one site. Having to support Exchange 2000 at multiple sites can have quite an impact on your network if done improperly. Based on the types of connections you use and their reliability, you might end up having so much Exchange and Active Directory traffic across your slower and more expensive connections that your network becomes effectively blocked.
You’re more likely to achieve the results your organization needs by ensuring that your Exchange site configurations mirror your overall Windows 2000 site configurations. Another factor to consider is the inclusion of multiple domain controllers inside each site along with a global catalog server to help improve network response.
Sites vs. routing groups
To determine where to place sites, Exchange 5.5 looks at the cost you assign for the transportation of information across your connection pathways. Exchange 5.5 bases cost assignments primarily on the assumption that the faster the throughput level, the lower the value assigned as cost. In other words, a phone modem connection of 56K would be considered a high-cost pathway because of the throughput capabilities and its overall reliability. In Exchange 5.5, you administer your network’s usage of these pathways within the Site Connector.
With Microsoft Exchange 2000, “sites” no longer exist. Instead, Exchange 2000 uses routing groups to establish a cost for your multiple connections. Routing groups aid in creating and setting preferred routes of transport for messages, and they control information between your installed Exchange servers. By default, Exchange servers are created and installed inside a common routing group.
So why would you need to establish additional routing groups (sites)? The answer depends on the types of connections you use between your physical network sites. If you have extremely reliable and fast connections for your servers (such as a T-1 or a DSL service) and no other real need to exert control over your messaging transportation, you probably won’t require additional routing groups. On the other hand, if you need to control the messaging protocol and pathway selections, you don’t have reliable, full-time connections between some or all of your servers, or you simply need to account for each piece of traffic that moves across your network, additional routing groups will enable you to balance your usage effectively.
Consider creating routing groups
To demonstrate how creating additional routing groups for your individual site locations would be beneficial to your network’s performance, let’s consider the following example. Imagine you have three Exchange 2000 servers within your organization, and the servers are located in three separate geographical locations. We’ll call the first Exchange server “Server A” and place it on the Internet via a dedicated T-1 connection that’s physically located in your company’s headquarters. Server B connects to the Internet with a DSL service and also communicates with Server C via an ISDN connection between the two offices. Server C establishes an ISDN connection with Server A.
Now, assume that for virus-scanning purposes, all electronic communications must pass through Server A. Based on the costs you assign each method of connection between the Exchange systems, individual routing groups would greatly improve your network’s overall performance. Messages would flow across those links that have the least cost and keep from bottlenecking your network. To establish your servers as members of their own routing groups, you have three choices:
- Routing Group Connector
- SMTP Connector
- X.400 Connector
Enter the Routing Group Connector
Of the three choices, the Routing Group Connector is the preferred method of transporting information between Exchange servers. If you’re familiar with the older Site Connector included in Exchange 5.5 and earlier versions, you’ll recognize many of the same features in the new connector. As with previous versions, you’ll see that you need to specify very few options. By default, SMTP is the protocol that the Routing Group Connector uses to connect between two of your sites, but you can use other protocols to conform to your existing network installation.
The Routing Group Connector allows for the use of bridgehead servers (the actual machines that send and receive the messages) or other defined servers. You can also specify that you don’t want the connector to use bridgehead servers. In the case of the absence of a bridgehead server, the Routing Group Connector uses as many servers as necessary. While this behavior provides you with a level of built-in fault tolerance, it also makes scanning messages for viruses and other tracking requirements more costly. Keep in mind that each Routing Group Connector you create is for transportation from one site to another only, not for two-way communication. Therefore, when you’re defining your Routing Group Connector, let the System Manager automatically set up the additional Routing Group Connector between the destination and source for return communications.
Connecting with other sites
The SMTP connector enables you to exert a finer degree of control over the connections between your sites, but it requires the use of the SMTP protocol. The only exception to this is the case of an Exchange 2000 server communicating with an Exchange 5.5 (or older) server. Because the Exchange 2000 server can’t read the configuration data on the older server, it uses RPC to communicate between the two sites.
You can also use the X.400 Connector to connect your sites and exchange message traffic. Unfortunately, the X.400 Connector can support only one bridgehead server, which can severely affect your ability to move traffic. Like with the Routing Group Connector, X.400 connections use various protocols—such as IPX/SPX and NetBIOS—to establish communications, but they require more specific configuration information to efficiently work at peak performance.
Managing multiple sites
Now that we have multiple sites, how do we put them to use? Once you’ve created your Exchange servers and the routing groups they use to communicate with one another, you need to assign users and their mailboxes on the appropriate server in the correct location for each individual. Because each mailbox is actually a part of Active Directory, you can’t specify a location for the user ID to be created, but you can specify the location of the mailbox for each user, as shown in Figure A.
|You can specify the server each user is a member of based on physical location.|
If a user’s role within the company changes, and the user is moved to another location, you can move the user’s mailbox from one site to another. As you can see in Figure B, you simply select Move Mailbox to modify the network location of the user’s mailbox and account information. Another factor to consider is the creation of Administrative Groups to help you diversify your administration requirements for Exchange 2000. To accomplish this, you simply need to place the appropriate Exchange servers and their associated routing groups into each Administrative Group.
|You can move an individual’s mailbox and account onto servers in different locations.|
Keeping users in the loop
One final thing to keep in mind concerning the use of multiple servers in your enterprise is that you must notify users or local administrators of the name of the server that you’ve placed the user’s account on, especially if your network includes multiple servers in one site location. Another option is to establish a front-end and back-end server scenario, with one server acting as the central location for all users to connect to, including SMTP, POP3, IMAP4, and Web Outlook users. This arrangement would provide one server that would proxy to the appropriate server that houses a user’s mailbox.
Microsoft Exchange 2000 enables you to effectively manage multiple Exchange servers located in separate locations. By incorporating routing groups into each location’s configuration, you can create and maintain preferred paths for your network’s traffic. In this Daily Feature, we examined several of the concerns you can expect to have when deploying Exchange 2000 servers in multiple locations.