Exchange Server 2003 Services Dependencies
Microsoft Exchange Server 2003 is a client/server messaging system in which active server processes interact with client processes. You can view these server processes in the Services tool, which you can find in the Administrative Tools program group. In Microsoft Windows terminology, a server process is called a service. Most Exchange Server services have a name that starts with Microsoft Exchange. The Microsoft Exchange Information Store service is a good example.
In a client/server system, the majority of processing is performed directly on the server. Server services accept requests and data from clients, process the requests, store the data, and return the processing results to the clients. Microsoft Office Outlook is a client—a messaging client. The primary task of a messaging client is to provide a user interface so that a user can interact with the messaging system in an intuitive way. Exchange System Manager is also a client. This client provides administrators with an interface with which to manage an Exchange Server 2003 organization. Furthermore, the server services themselves are clients to other server services. For example, the Simple Mail Transfer Protocol (SMTP) service must communicate with the Exchange Information Store service to access e-mail messages on a server running Exchange Server. Each service in Exchange Server 2003 has a dedicated purpose. All services must interact with each other and with the services provided by the operating system to function together as a messaging platform.
To understand Exchange Server 2003 as a client/server system, you must be aware of the following components, their dependencies, and their interactions:
Service Control Manager and Windows services architecture Service Control Manager (SCM) is at the core of the Windows services architecture, because it is the central component that manages all Windows services and device drivers that run on Windows. SCM enables you to control a service, but you cannot control a device driver. For example, Service Control Manager starts device drivers in a well-defined order, according to their dependency trees, but you cannot stop device drivers. However, you can start or stop Windows services in the Services tool from the Administrative Tools program group. When you use the Services tool, you interact with the SCM process.
Operating system services The operating system provides a number of necessary services, such as Remote Procedure Call (RPC) service and NTLM Security Support Provider.
Internet Information Services Internet Information Services (IIS) is an important process that must be running on every server running Exchange 2003 Server. Exchange Server 2003 adds POP3 and IMAP4 services to IIS and extends the SMTP service, the Network News Transfer Protocol (NNTP) service, and World Wide Web service.
Core Exchange services In order to perform as a messaging system, Exchange Server 2003 contains several services that are not part of the operating system or IIS. The core services in Exchange Server 2003 are those services that must run on every Exchange server. This section introduces all core services in detail.
Additional Exchange services Exchange Server 2003 can be configured to handle specific tasks. For example, you can use Exchange Server 2003 to implement a dedicated mailbox server or a dedicated bridgehead server. Depending on the server role, additional Exchange services may be required, such as messaging connectors. Exchange services that are required only in specific situations are considered additional services.
This section provides an overview of operating system and Exchange-specific services that are required to run a fully functional server running Exchange Server 2003. It is assumed that you are familiar with the Microsoft Windows Server 2003 platform, networking services, and Active Directory, as well as Exchange Server 2003 administration concepts. For additional information about Windows Server 2003, see the Windows Server 2003 Technology Centers. For additional information about Exchange Server 2003 administration, see the Exchange Server 2003 Administration Guide.