Windows NT TCP/IP Network Administration

Other Services

Two services that are used on many Windows NT TCP/IP networks are DHCP configuration servers and mail servers. The purpose of these services and the protocols they are built on is discussed in Chapter 3. In this section we investigate what information must be passed to the users so that the client systems can be successfully configured, and how the network administrator determines that information.

Planning Your Mail System

The TCP/IP protocol suite defines the tools you need to create a reliable, flexible electronic mail system. Servers improve reliability. It is possible to create a peer-to-peer TCP/IP email network in which every end system directly sends and receives its own mail. However, relying on every system to deliver and collect the mail requires that every system be properly administered and consistently up and running. This isn’t practical, because many small systems are off-line for large portions of the day. Most networks use servers so that only a few systems need to be properly configured and operational for the mail to go through.

The terminology that describes email servers is confusing because all of the server functions usually occur in one computer, and all of the terms are used interchangeably to refer to that system. In this text we differentiate between these functions, but we expect you will do all of these tasks on one system. We use this term in the following manner:

mail server

The mail server collects incoming mail for other computers on the network. It supports POP so that users can read their mail when they are ready.

A mail relay is a host that forwards mail between internal systems and from internal systems to remote hosts. Mail relays allow internal systems to have simple mail configurations because only the relay host needs to have software to handle special mail addressing schemes and aliases.

A mail gateway is a system that forwards email between dissimilar systems. You don’t need a gateway to go from one Internet host to another because both systems use SMTP.

The mail server is the most important component of a reliable system because it eliminates reliance on the user’s system. A centrally controlled, professionally operated server collects the mail regardless of whether or not the end system is operational.

The relay host also contributes to the reliability of the email system. If mail cannot be immediately delivered by the relay host, it is queued and processed later. An end system also queues mail, but if it is shut down no attempts can be made to deliver queued mail until the system is back online. The mail server and the mail relay are operated 24 hours a day.

The design of most TCP/IP email networks is based on the following guidelines:

• Use a mail server to collect mail, and POP to deliver the mail.

• Use a mail relay host to forward mail. Implement a simplified email address scheme on the relay host.

• Standardize on TCP/IP and SMTP.

• Standardize on MIME for binary attachments. Avoid proprietary attachment schemes; they just cause confusion when the users of Brand X email cannot read attachments received from Brand Y.

For their client configurations, provide the users with the hostname and IP address of the mail server (i.e., the POP server) and the mail relay. The mail server will also require a username and password for each person.

DHCP Server Planning

If you use a DHCP server you don’t need to communicate any configuration information to Windows 95 or Windows NT users. By default, those systems use DHCP and they locate the DHCP server automatically. You still need to do the various planning exercises described in this chapter, but you don’t need to communicate the information developed from these plans to the user. Instead you use the information yourself to configure the DHCP server.

However, not all of the systems on your network will run Windows 95 or Windows NT. For those systems on your network that can run DHCP client software but don’t run it by default, tell the administrators of those systems to enable DHCP. You will want to use DHCP to the greatest extent possible to simplify the installation and to minimize configuration error. For those systems that cannot run DHCP, you will have to provide the user with the necessary configuration information by some other means.