Exchange 5.x integrated with Internet Information Services (IIS) to a degree, most notably in the way Outlook Web Access relied on IIS to serve the ASP pages that allowed users to access their Exchange mailboxes through the Web. Exchange 2000 Server in some ways increases the integration with IIS, and in others, it appears to reduce it. In this Daily Drill Down, I’ll explore the ways in which Exchange 2000 Server and IIS interact.

Overview of IIS
If you haven’t done much in the way of Web or FTP server configuration or management, you might not be overly familiar with IIS in Windows 2000. IIS plays a very small role in many Windows 2000 tasks, such as user management. So if you spend the majority of your time managing users and domains, you probably have little reason to explore uncharted territory in IIS. Even if you spend some of your time managing Exchange 2000 Server, you might not realize all of the relationships that exist between Exchange 2000 Server and IIS and how much Exchange 2000 Server relies on IIS to provide client services.

Outside the context of Exchange 2000 Server, IIS provides several services under Windows 2000. These services include the following:

  • Web service—The Web service allows Windows 2000 to host Web sites with a broad range of authentication and hosting options. You can host multiple sites per server and even multiple sites per IP address using host headers to differentiate sites. The Web service supports both anonymous access, authenticated access, and secure connections through SSL. Site content can come from a single directory structure on the server, from virtual directories hosted on the server or elsewhere on the LAN, from redirected URLs, or a combination of the three. The Web service offers an excellent degree of control over connections, security, logging, and other site configuration properties.
  • FTP service—You can use the FTP service in IIS to provide standards-based file transfer using the FTP protocol. Like the Web service, the FTP service supports both anonymous and authenticated users, allowing you to use one or both as needed. If necessary, you can limit the number of connections, specify connection timeout, and easily specify user messages, logging options, and other configuration properties. The FTP service in Windows 2000 provides the ability to restart failed transfers, and you can build an FTP site’s directory structure using directories that are both local to the server and located on shared network volumes. Like the Web service, the FTP service can support multiple FTP sites per server.
  • NNTP service—The NNTP service supports the Network News Transfer Protocol (NNTP), which allows you to use IIS to set up your own newsgroup server. You can host public, private, read-only, moderated, and authenticated newsgroups with the NNTP service. The NNTP service supports multiple virtual news servers per physical server.
  • SMTP service—This service supports the Simple Mail Transport Protocol (SMTP), the primary protocol for transferring e-mail across the Internet. The SMTP service included in IIS doesn’t turn Windows 2000 into a full-featured e-mail server but instead allows you to create virtual SMTP servers that forward messages to other servers that do provide full client support, such as for POP3 users.

One of the benefits that IIS offers from an administrator’s perspective is a unified management interface. The IIS console serves as the means of managing all of the IIS services, presenting service properties and controls in a cohesive, uniform way. This makes it possible to manage all of your Web-related services from a single console. With the Microsoft Management Console’s ability to integrate multiple console snap-ins, you can easily create a custom console that incorporates IIS, DNS, DHCP, and the other services that support your Web server. Other more obvious benefits are support for Integrated Windows Authentication (NTLM authentication), HTTP Digest Authentication, and a broad range of other standards and services including SSL, FrontPage Server Extensions, domain- and IP-based access restrictions, custom errors, and more.

Exchange 2000 Server and IIS integration
Exchange 2000 Server integrates more tightly with IIS than does Exchange Server 5.x. The Extensible Storage Engine (ESE) comprises the Exchange database and log files for each message store. (Exchange 2000 Server supports multiple stores.) Below the ESE lies the Exchange 2000 Server Web store, Store.exe, which comprises the store kernel, folder replication, XAPI, and MAPI. Between the store and IIS sits the Exchange Interprocess Communication Layer (ExIPC), which serves as a queuing layer between Exchange 2000 Server and IIS. The ExIPC handles communication between IIS and Exchange through protocol stubs in the store. Traffic for each protocol (including POP3, SMTP, NNTP, IMAP, and HTTP [WebDAV]) travels through its own queue in the ExIPC between IIS and Exchange. By providing asynchronous communication, the ExIPC provides fast, reliable communication between Exchange and IIS.

Many of the protocols that previously functioned primarily through Exchange Server 5.x are now integrated into Windows 2000 and IIS. Rather than manage these protocols through IIS, however, you manage them through the Exchange System Manager. This is one reason why it might seem that protocol functions have been transferred to Exchange, but those functions still reside firmly in IIS. Only the management of those protocols has changed. For example, rather than configure and control the SMTP or NNTP protocols through the IIS console, you control them through the Exchange System Manager.

Exchange 2000 Server extends the core protocols in Windows 2000 and IIS to provide additional functions and routing capabilities. Let’s take a look at the protocols individually, taking a more detailed look at how they are affected by Exchange 2000 Server.

SMTP is the primary protocol in Exchange 2000 Server for communicating with e-mail clients and other e-mail servers, including other Exchange 2000 servers, and it replaces remote procedure calls (RPC) for that purpose. Switching the primary protocol to SMTP provides greater routing flexibility for your Exchange network and broader interoperability with non-Exchange e-mail servers.

Where SMTP was handled through the Internet Mail Service in Exchange 5.x, SMTP is now integrated in IIS. If you explore IIS prior to installing Exchange 2000 Server, you’ll find that you can create virtual SMTP servers under IIS. These virtual servers function primarily as routing servers, accepting messages from external clients (either on the network or on the Internet) or from Web applications on the server that create messages, such as those created from automated code on a Web site. After you install Exchange 2000 Server, however, you’ll find you can no longer create SMTP virtual servers under IIS, but you can through the Exchange System Manager. SMTP is still a function primarily of IIS but is now managed in the context of Exchange.

POP3 and IMAP4
POP3 and IMAP4 are the two protocols on which the vast majority of e-mail services rely for message retrieval, and both are Internet standards. POP3 has been the most common protocol for several years but is slowly being replaced by IMAP4 as the protocol of choice because of advantages it offers over POP3 in terms of message storage and delivery.

Both the POP3 and IMAP4 protocols are an integral part IIS. Like SMTP, POP3 and IMAP4 are both enhanced by the addition of Exchange 2000 Server. For example, through Exchange 2000 Server, you can create multiple virtual servers for either protocol, each with its own properties, authentication mechanisms, and message storage and delivery options. An important feature for enterprise deployment of POP3 and IMAP4 is the ability Exchange Server provides for building a front-end/back-end service topology. The front-end servers receive POP3 and/or IMAP4 requests and route that traffic to back-end servers where the users’ mailboxes reside. This makes it possible to easily distribute mailboxes across multiple servers while still providing a single namespace and point of access for all users. Exchange 2000 Server also improves IMAP4 with several performance enhancements and new features, such as the ability to store messages in native MIME format, the ability to assign delegate access to folders, and improved message handling.

Although POP3 and IMAP4 are components of IIS, you manage these protocols through the Exchange System Manager. For example, you use the System Manager to create virtual POP3 and IMAP4 servers and to control which of these protocols each user can use to access his or her mailbox. These settings are stored in Active Directory and are applied to IIS through the Exchange System Attendant.

The NNTP protocol, also an Internet standard, is an integral part of IIS. With Windows 2000 and IIS, you can create virtual NNTP servers that function as newsgroup servers. NNTP under IIS provides all of the features you might expect of a newsgroup server. Some of the things you can do with NNTP under IIS include:

  • Creating public and private newsgroups for access from the intranet or the Internet.
  • Allowing users to create and remove newsgroups (subject to their permissions).
  • Providing support for standard newsgroup clients such as Outlook Express and Agent.
  • Creating multiple NNTP virtual servers per physical server.

Installing Exchange 2000 Server affects NNTP under IIS in two primary ways. First, Exchange 2000 Server adds capabilities to NNTP not provided through IIS. Second, Exchange 2000 Server moves the creation and management of NNTP servers from the IIS console to the Exchange System Manager. Without Exchange 2000 Server installed, you create NNTP virtual servers and configure their properties through the IIS console. After installing Exchange 2000 Server, you no longer have the ability to manage NNTP virtual servers in IIS but instead perform that function through the Exchange System Manager.

One of the improvements Exchange 2000 Server makes to NNTP is the ability to pull news feeds from other news servers. An ISP, for example, might use Exchange 2000 Server to create a public newsgroup server for its users for Internet newsgroups. A large company might do the same to make Internet newsgroups available to its employees. By itself, IIS doesn’t provide this capability.

Exchange 2000 Server also changes storage options for NNTP. With IIS, the NNTP service stores newsgroups and messages in folders within the server’s file system. With the addition of Exchange 2000 Server, the NNTP service can also store newsgroups in Exchange public folders, which are housed in the Exchange data store(s). You build the newsgroup hierarchy using virtual directories that point to physical folders in the file system or to public folders in Exchange.

As with POP3 and IMAP4, you can deploy NNTP servers in a front-end/back-end configuration to offer support for a large number of users and provide fault tolerance. Exchange 2000 Server brings several other enhancements to NNTP, including content indexing of public folders and the ability for clients to read and post messages through the Web store.

Outlook Web Access
Another service that shows the tight integration between IIS and Exchange 2000 Server is Outlook Web Access (OWA). Using OWA, clients can connect through a Web browser to their Exchange mailboxes in order to send and receive e-mail messages, manage their schedule and contacts, and access other data that they might otherwise access through Outlook. OWA not only allows Outlook users to work with the mailboxes when they are on the road or don’t have access to their own workstations but also allows users who work from other platforms such as UNIX to access their mailboxes and participate in group scheduling and collaboration.

Microsoft made significant changes to OWA in Exchange 2000 Server. In Exchange Server 5.x, OWA functions primarily through ASP pages hosted under IIS, with the server using MAPI to handle messaging requests. This reliance on ASP places the majority of OWA’s functionality on IIS, rather than Exchange. In Exchange 2000 Server, Microsoft changed OWA’s architecture to shift most of the functionality of OWA from IIS to Exchange. OWA now relies on HTML and DHTML rather than ASP, and simply passes messaging requests to Exchange and then forwards responses back to the user. As such, IIS now functions primarily as a front-end service for OWA, which is integrated as a function of the Exchange Web store. You manage OWA through the Exchange System Manager and use the Active Directory Users And Computers console to enable or disable OWA for users.

Instant messaging
Instant messaging (IM) is another feature of Exchange 2000 Server that integrates with IIS. IM allows users to participate in real-time, text-based chat sessions with other users locally or on the Internet. IM participants use the MSN Instant Messenger client to manage their contact lists and chat with other users. This IM client supports IM sessions on the Internet through non-Exchange IM servers and through Exchange Server IM servers, both local and remote.

Exchange 2000 Server IM uses HTTP over port 80 as its transport mechanism, so IIS is therefore very much an integral component of the IM service. You create virtual IM routing or home servers through the Exchange System Manager, which adds virtual directories to the default Web site on the server (or another Web site, if you choose), which is hosted by IIS. IM would therefore not function without IIS as the underlying transfer mechanism.

Some of the management tasks you perform for IM happen in the Exchange System Manager, while others require you to use the IIS console. For example, you configure authentication and connection limits through the IIS console by setting properties for the Web site and the IM virtual directory. You configure user settings related to IM through the Active Directory Users And Computers console.

Putting it all together
IIS installs as a required core component of the Windows 2000 Server operating system rather than as an optional service you can add to support Web services, as it is in Windows NT. Shifting protocol support from components of Exchange Server to Windows 2000 and IIS offers several benefits including improved performance and greater flexibility. Because IIS functions as the initial point of access for essentially all Exchange communications, you have much more flexibility in designing your Exchange topology. For example, you can now develop a front-end/back-end architecture that lets you use non-Exchange servers as entry points to the Exchange site and use multiple back-end servers to support a much larger number of users than was previously practical and provide better fault tolerance and failover capabilities.

If you are an experienced IIS administrator who also needs to deploy and manage Exchange 2000 Server, you’ll find many of the administrative tasks you previously performed in IIS—setting up Web sites, configuring site properties, and so on—are still applicable. The primary difference is that you’ll perform more of that configuration through the Exchange System Manager and less through the IIS console.