Integration with Internet Information Services 5

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When Windows 2000 is installed, the base version of SMTP is installed. Network News Transfer Protocol (NNTP) may also be installed when Windows 2000 is installed, but it must be selected manually. In Windows NT 4 and Internet Information Server (IIS) 4, these services were part of IIS.

Because these protocols are now basically transport stacks for the operating system, Windows 2000 no longer relies on RPCs. For instance, it is possible to have Active Directory information replicated over SMTP rather than RPCs.

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An RPC allows an application to execute code that resides on a remote machine. RPC-based applications use the network to transport the request. The client computer issues a call to "stub code" that takes the place of a local procedure. The stub code uses both communication and data conversion utilities to execute the request within the memory of the remote computer. Because RPC uses the network for its transport, TCP handshakes must be established for each new RPC between two machines, which results in high overhead on the network. RPC also requires permanent, high-bandwidth connectivity to ensure that the TCP connection can stay active. Compare this to SMTP, under which commands can be passed between servers in the form of messages. SMTP is thus more tolerant of lower-bandwidth environments and as a result is a better protocol over which to conduct server overhead functions, such as directory replication.

Given the ability to exploit Active Directory information via traditional Internet protocols, such as HTTP (and the improved version, WebDAV)and SMTP, as well as via Outlook Web Access (OWA), Web-based applications will become more popular, especially in environments where the work force is distributed but the information is centralized.

In addition, because IIS is now installed as part of the operating system and can run the transport protocols independently, the ability to host the protocols on different servers allows you to design an Exchange 2000 topology that will scale into the millions of users. Using a bank of front end and back end servers, Exchange 2000 can work with any size of installed base. For example, you can design your Exchange 2000 server topology with a bank of front end servers that allow non-MAPI clients, such as HTTP clients, to connect to virtual IP-addressable front end servers while storing messages and collaboration data on separate back end servers.

The protocols shipped with Exchange 2000 Server, such as SMTP and NNTP, lead to services such as OWA, instant messaging, and data conferencing. These protocols and services are discussed in the sections that follow.

Instant Messaging

Instant messaging allows users to see presence information for other users (that is, which people are online, out of the office, or not receiving calls) and lets users communicate instantly when an immediate response is necessary. The interface is lightweight, and it is designed for ad hoc communication. The major difference between instant messaging and e-mail is that instant messages are not stored in the Exchange 2000 store; after a message has disappeared from the screen, it is gone forever.

Instant messaging uses DNS and Active Directory to locate the home server for a user. It also supports front end/back end configurations for scalability into the tens of thousands of users. Instant messaging is hosted via virtual servers and realms. Virtual servers group users by e-mail address, and one physical server can host multiple virtual servers. Realms map an e-mail address (for example, research.microsoft.com) to a virtual server that is designated through a URL, such as http://im.research.microsoft.com.

A user principal name, such as [e-mail] will be translated by Exchange into a URL, such as http://im.research.microsoft.com/aliases/benglish. To learn more about instant messaging, see Chapter 19.

Data Conferencing

When more than two users need to collaborate in real time, they can use data conferencing. This powerful tool enables information to be exchanged through a shared clipboard, file transfer, a shared whiteboard, chat, audio, and video in real time. This service is T.120 compliant, meaning that any T.120 client can interoperate with a data conferencing server. The server is H.323 compliant. Audio and video streaming is accomplished through IP multicast technologies.

Exchange 2000 Server installs two Windows 2000 services to enable conferencing. The first is the Microsoft Exchange Conferencing Management Service. This service manages the virtual resource mailboxes and conference profiles. In addition, it routes clients to the appropriate server when they join the conference.

The second service is the Microsoft Exchange Data Conference Service. This is the hosting service for the conference session. It implements the T.120-compliant conference bridge (known as a multipoint conferencing unit, or MCU). Although a single Conferencing Management Service normally manages the conference facilities for an entire site, scaling can be achieved by deploying multiple MCUs. Each Exchange 2000 server can host exactly one MCU.

Simple Mail Transport Protocol

Exchange 2000 Server relies entirely on the Windows 2000 operating system to provide SMTP services. During the installation of Exchange 2000 Server, the IIS SMTP protocol is extended to include additional command verbs that enable link state routing and other advanced features. In addition, an advanced queuing engine and an enhanced message categorization agent are installed. For more information on the SMTP protocol, see Chapter 17.

Network News Transfer Protocol

NNTP, used by Exchange 2000 Server to access newsgroups, is part of Internet Information Services 5 and Windows 2000. Exchange 2000 does not extend or modify this protocol when it is installed.