Exchange Server 2003 Virtual Servers
Exchange Server 2003 Virtual Servers Overview
Simple Mail Transfer Protocol (SMTP) Virtual Servers
Simple Mail Transfer Protocol (SMTP) is an industry standard protocol used for the Internet. SMTP controls the communication of email messages and the message formats between messaging hosts. SMTP Service Extensions (ESMTP) is an extension of SMTP that enables users to request delivery status notifications on outgoing messages. It also makes it possible for a message size to be defined for inbound ESMTP connections. SMTP and ESMTP require the TCP/IP protocol as the transport means.
The SMTP/ESMTP procedure initially connects to the remote host’s TCP port 25; who in turn replies to the request. SMTP communication is then established and email messages are passed. The commands and responses that have to be used between the SMTP systems to transfer messages are specified at the application layer. The commands are used to initiate the transmission of messages.
Responses are used to acknowledge the receiving of messages.
- Welcome messages are returned by the server to the client.
- The HELO/ EHLO command initiates the session.
- The MAIL FROM command signifies an originator address.
- RCPT TO indicates mail recipients.
- The DATA command starts message transfer.
ESMTP supports the following types of SMTP extensions
- Registered extensions:TheDSN command and SIZE are regarded as registered extensions. The DSN command indicates to the receiving system that a delivery status notification has to be sent back to the transmitting host.
- Unregistered extensions:These commands, such as XEXCH50, have to commence with X which basically signifies that they are not standardized.
The SMTP service has to determine the IP address of the remote host when attempting to create a connection. Active Directory can be used for this purpose by Exchange servers that are part of the same organization. DNS, WINS, and the HOSTS file and LMHOSTS file are name resolution methods supported by Windows 2000 and Windows Server 2003. DNS is typically used for name resolution when communicating with hosts over the Internet. The SMTP service uses the Resolver to contact the local DNS server when needing to retrieve an SMTP host’s IP address. The Resolver is a component of the TCP/IP protocol stack. The local DNS server queries another DNS server when the domain name cannot be resolved locally. The SMTP host’s IP address is then returned to the Resolver and returned to the SMTP service.
Simple Mail Transfer Protocol (SMTP) has the characteristics listed below:
- SMTP can be used to forward mail from one SMTP host to another SMTP host. SMTP cannot deliver mail directly to the client. Mail clients use POP3 or IMAP to receive e-mail. Windows Server 2003 includes the POP3 service for providing clients with mailboxes, and for handling incoming e-mail.
- SMTP enables Internet Information Services (IIS) machines to protect mail servers such as Microsoft Exchange servers from malicious attacks by operating between these servers and Sendmail host at the ISP of the organization.
- SMTP does not provide mailboxes to users, nor does it process incoming e-mail.
- The SMTP service is fully integrated with event and performance monitoring of Windows Server 2003.
When you install the SMTP service on Internet Information Services (IIS), the SMTP directory structure is created, as well as the Default SMTP Virtual Server. Through configuring the Default SMTP Virtual Server, mail can be forwarded to multiple SMTP domains. This eliminates the need to host multiple SMTP virtual servers on one machine to forward mail.
A SMTP virtual server manages one or multiple SMTP domains. SMTP domains are also called service domains. A SMTP domain is a DNS domain that manages messages for delivery. The SMTP domain is automatically the default local domain of the Default SMTP Virtual Server. You can view the default local domain in the IIS Manager. Simply click the SMTP virtual server node in the console tree to display the default domain. A characteristic of the default domain is that you cannot delete it. A SMTP virtual server can only have one default local domain.
In addition to the SMTP default domain, you can create the following domains:
- Alias Domains: If you want to create additional local SMTP domains, you need to create a type of SMTP domain called alias domains. Alias domains are managed by the SMTP virtual server in the same manner as the default domain. In fact, alias domains use the same setting as the default domain.
- Remote Domains: You can also create remote domains to connect to the remote SMTP hosts to which mail is frequently transmitted. You can specify different delivery requirements for each remote domain, specify a predefined delivery route for a remote domain, and you can also specify sub-domains.
Post Office Protocol Version 3 (POP3) Virtual Servers
Post Office Protocol Version 3 (POP3) is a read-only messaging protocol which enables messages to be downloaded from server. POP3 clients include Netscape Navigator Mail, Outlook Express and Eudora. POP users too depend on SMTP to convey messages. SMTP and POP3 hosts can reside on the same server or on separate servers.
The POP3 commands contain a keyword and arguments. A space separates keywords. These commands are not case sensitive. However, only printable ASCII characters can be used. The POP3 responses contain a keyword and status indicator. The POP3 responses have the same ASCII character requirement as the POP3 commands. The positive (+OK) and negative (-ERR) response are existing status indicators.
POP3 sessions move through the following states:
- Authorization state: This state occurs when the welcome message of the server is received following the client establishing a connection to TCP port 110. User account information is transmitted to the server in the Authorization state.
- Transaction state: The Transaction state is reached after the user is successfully validated. A user is now able to access email messages. Transmitting the QUIT command to the server disconnects the session.
- Update state: In the Update state, the POP3 server transmits a goodbye message to the client. The TCP/IP connection is removed.
Internet Mail Access Protocol Version 4 (IMAP4) Virtual Servers
Internet Mail Access Protocol Version 4 (IMAP4) is an Internet protocol that enables access to various server based messaging folders. The IMAP4 commands contain a tag, keyword and arguments. A space separates keywords. These commands are not case sensitive. Only printable ASCII characters can be utilized. The server utilizes the tag to determine the command that a response is associated to.
IMAP4 sessions move through the following states:
- Non Authenticated state: This state occurs when an IMAP4 client connects to TCP port 143 at the server. At this state, the client has to provide the necessary authentication information.
- Authenticated state: The Authenticated state is reached after the client logs on through the LOGIN command. The client can use the SELECT command to select a folder from the mailbox. Other commands that can be used are the STORE command and FETCH command.
- Selected state: The Selected state occurs when users utilize their IMAP4 clients.
- Logout state: The Logout state occurs when the client sends the LOGOUT command to the server. The server sends a goodbye message and ends the connection.
Network News Transfer Protocol
(NNTP) virtual serversThrough the NNTP service, you can implement private news servers to host discussion groups, or you can implement public news servers to provide customer support and help resources to Internet users. You can specify that users need to be authenticated to both read and post to items to newsgroups, or you can allow access to everybody. The NNTP service can also integrate with the Windows Indexing Service for indexing of newsgroup content. It is also fully integrated with event and performance monitoring of Windows Server 2003.
Newsgroups basically represent the context of discussions in the same manner that public folders do. Articles in newsgroups symbolize bits and pieces of discussions. Articles are replicated to each instance of a particular newsgroup over USENET. Newsfeeds are needed for newsgroup replication. Exchange supports newsreader applications through the Windows extended NNTP service. A newsreader can communicate through NNTP. It is basically a client program that can be utilized to read articles.
The following types of NNTP data transfer exist:
- Pull Feed: Here, the local host starts the connection to the remote server, and then pulls the information. With pull feeds, it is possible to specify the newsgroups.
- Push Feed: With Push feed, theremote host starts the connection and then pushes the information to the local hosts
With NNTP communication, newsreader applications start a connection to TCP port 119 to create a session. A welcome message is transmitted by the NNTP server to the client. Next, the client and the host communicate NNTP commands and responses. An NNTP command contains keywords and arguments. Only printable ASCII characters can be utilized.
Hypertext Transfer Protocol(HTTP) Virtual Servers
Hypertext Transfer Protocol (HTTP) is a data mechanism of the World Wide Web. Microsoft Internet Explorer and Netscape Navigator are regarded as HTTP compliant clients. When transferring data, the HTTP compliant client has to connect to an HTTP server. The World Wide Web Publishing Service of Windows 2000 Server and Windows Server 2003 is a HTTP/Web server. The Web browser by default connects to the TCP port 80 of the server.
The browser has to provide a uniform resource identifier (URI) to inform the Web server of the document that should be returned. A URI is also referred to as a shortcut, URL or Web address. A URL finds a resource through its location on the network, while a uniform resource name (URN) finds a resource through its globally unique distinguished name. WebDAV, an extension of HTTP1.1, defines headers and content types for the management of resource properties on the server. WebDAV also encompasses the manipulation of namespaces, locking of resources, creation of resource collections and the encoding of data elements in XML or the HTTP headers. Items in the Web Storage System can be accessed using the WebDAV protocol. Folders and messages have a corresponding URL. The Web Storage System depends on content classes to connect items with associated forms. To use Web forms, browsers have support to HTML 3.2 or above.
HTTP virtual servers and WebDAV provides the following functions when used in Exchange Server 2003:
- Document access: Enables users to access and modify documents, and move or copy files.
- E-mail access: HTTP virtual servers and WebDAV provide the following capabilities for users:
- Access mailboxes
- Access messages
- Delete messages on the server
- Move and copy e-mail on the server
- Alert when new messages are received.
- Application access: Because HTTP and WebDAV are application layer protocols that utilize a unique Uniform Resource Locator (URL) to access mailboxes, it can be used to enable custom applications to obtain data from the Information Store.
Using Exchange virtual servers in a Clustered Environment
The Exchange Server 2003 virtual servers can use the clustering services and technologies of the following Windows editions:
- Windows Server 2003 Enterprise Edition
- Windows Server 2003 Datacenter Edition
The specific clustering features and services used by Exchange Server 2003 are listed here:
- Resource DLLs provides the means for Cluster Service to communicate with the Exchange services supported in the cluster.
- Resources are hardware and software components of the cluster. Services and applications in the cluster are called resources. Resources in the cluster are added to Cluster Groups to create Exchange virtual servers.
- A resource group contains all resources needed for a specific application. Each resource group has an IP address and network name which are unique. Resources that are dependent on another resource must reside in the same group, and on the same node.
- Exchange Virtual Server; refers to the resource group which holds the resources needed by Exchange to function as a clustered implementation:
- Exchange Services
- IP Address
- NetBIOS name of server.
You can use either of these methods to place Exchange 2003 virtual servers in a cluster:
- New installation method: Requires all Exchange 2003 preparation tasks to be completed before deploying Exchange 2003 in the cluster.
- Post First Server method: Here, the Exchange services and user mailboxes are deployed to the cluster after the Exchange 2003 environment is installed and running.
- Coexistence method: Here the Exchange 2003 clusters and existing Exchange 2003 server coexist in the same environment.
Before you install Exchange Server 2003 on a cluster node, you have to install the following Windows services:
- Simple Mail Transfer Protocol (SMTP) service
- Network News Transfer Protocol (NNTP) service
- World Wide Web service
- Microsoft ASP.NET
- Microsoft .NET Framework
Using Exchange virtual servers in a Network Load Balancing (NLB) Environment
Windows Network Load Balancing (NLB) is a clustering technology that provides high availability and scalability. With NLB, client requests are load balanced according to the configured load balancing parameters. Servers in the NLB cluster can be configured to share the processing load of client requests.
To ensure high performance, NLB uses a distributed filtering algorithm to match incoming client requests to the NLB servers in the cluster when making load balancing decisions. The NLB cluster can automatically detect when one server has a failure, and can then reroute traffic requests to the other servers in the cluster which are online. This leads to enhanced availability for mission-critical applications.
The servers in a NLB cluster send heartbeat messages to determine the state of the cluster. Each heartbeat message contains information on the state of the NLB cluster, information on the configuration of the cluster, and information on port rules.
Exchange Virtual Server Installation Requirements
The basic resource requirements for an Exchange virtual server are listed here:
- Static IP address
- Network Name
- At least one dedicated physical disk for shared storage
- Exchange 2003 Server System Attendant resource
Windows Server 2003 provides three of the above mentioned resources:
- Static IP address
- Network Name
- Physical disk for shared storage
Exchange Server 2003 provides one of the above mentioned resources:
- The Exchange System Attendant resource that enables a number of additional Exchange dependency resources.
When you create the Exchange System Attendant resource, the Exchange System Attendant creates the Exchange Server 2003 virtual server resources listed here:
- Exchange HTTP Virtual Service Instance
- Exchange Information Store Instance
- Exchange Message Transfer Agent Instance
- Exchange MS Search Instance
- Exchange Routing Service Instance
- SMTP Virtual Server Instance
The Exchange Server 2003 components and associated dependencies are listed below:
- System Attendant component; manages how resources are created and deleted in the Exchange virtual servers. Associated dependencies include:
- Network name resource
- Shared disk resource
- Exchange store component; provides the public folder storage and mailbox storage. Associated dependency:
- System Attendant resource
- SMTP component; provides e-mail transport and delivery services. Associated dependency:
- System Attendant resource
- POP3 component; provides e-mail access for POP3 clients. Associated dependency:
- System Attendant resource
- IMAP4 component; provides e-mail access for IMAP clients. Associated dependency:
- System Attendant resource
- HTTP component; provides access to Exchange mailboxes and to public folders. Associated dependency:
- System Attendant resource
- Message Transfer Agent (MTA) component; provides interoperability with Exchange Server 5.5 and also provides communication with X.400 systems. Associated dependency:
- System Attendant resource
- Exchange MS Search Instance component; provides content indexing for the Exchange virtual servers. Associated dependency:
- System Attendant resource
- Routing Service component; creates link state tables. Associated dependency:
- System Attendant resource
How to enable default disabled services
The following services are disabled by default on the Exchange server and therefore need to be enabled:
- IMAP4 service
- NNTP service
- POP3 service
To configure the IMAP4 service to start automatically on the Exchange server:
- Open the Services console.
- Right-click Microsoft Exchange IMAP4 and select Properties from the shortcut menu.
- The Exchange IMAP4 Properties dialog box opens.
- In the Startup Type drop-down list box, select the Automatic option.
- Click the Apply button.
- Click the Start button.
- Click OK.
To configure the NNTP service to start automatically on the Exchange server:
- Open the Services console.
- Right-click Microsoft Exchange NNTP and select Properties from the shortcut menu.
- The Exchange NNTP Properties dialog box opens.
- In the Startup Type drop-down list box, select the Automatic option.
- Click the Apply button.
- Click the Start button.
- Click OK.
To configure the POP3 service to start automatically on the Exchange server:
- Open the Services console.
- Right-click Microsoft Exchange POP3 and select Properties from the shortcut menu.
- The Exchange POP3 Properties dialog box opens.
- In the Startup Type drop-down list box, select the Automatic option.
- Click the Apply button.
- Click the Start button.
- Click OK.
How to determine whether the Exchange virtual servers have started
To start the IMAP4 virtual server:
- Open Exchange System Manager
- Navigate to Default IMAP4 Virtual Server.
- Right-click Default IMAP4 Virtual Server:
- The IMAP4 virtual server has started if the Start option is unavailable and the Stop option is available.
- If the IMAP4 virtual server has not started, select the Start option from the shortcut menu.
To start the NNTP virtual server:
- Open Exchange System Manager.
- Navigate to Default NNTP Virtual Server.
- Right-click Default NNTP Virtual Server:
- The NNTP virtual server has started if the Start option is unavailable and the Stop option is available.
- If the NNTP virtual server has not started, select the Start option from the shortcut menu.
To start the POP3 virtual server:
- Open Exchange System Manager.
- Navigate to Default POP3 Virtual Server.
- Right-click Default POP3 Virtual Server:
- The POP3 virtual server has started if the Start option is unavailable and the Stop option is available.
- If the POP3 virtual server has not started, select the Start option from the shortcut menu.
How to assign IP addresses for Exchange virtual servers
To assign the IP address for the IMAP4 virtual server:
- Open Exchange System Manager.
- Navigate to Default IMAP4 Virtual Server.
- Right-click Default IMAP4 Virtual Server and select Pause from the shortcut menu.
- Right-click Default IMAP4 Virtual Server and now select Properties from the shortcut menu.
- In the IP Address drop-down list box, click the IP address of the Local Area Connection.
- To view the virtual server configuration, click the Advanced button.
- Click OK.
- Click OK in the Properties dialog box of the IMAP4 virtual server.
- Right-click Default IMAP4 Virtual Server and select Pause from the shortcut menu.
To assign the IP address for the NNTP virtual server:
- Open Exchange System Manager
- Navigate to Default NNTP Virtual Server.
- Right-click Default NNTP Virtual Server and select Pause from the shortcut menu.
- Right-click Default NNTP Virtual Server and now select Properties from the shortcut menu.
- In the IP Address drop-down list box, click the IP address.
- To view the virtual server configuration, click the Advanced button.
- Click OK.
- Click OK in the Properties dialog box of the NNTP virtual server.
- Right-click Default NNTP Virtual Server and select Pause from the shortcut menu.
To assign the IP address for the POP3 virtual server:
- Open Exchange System Manager
- Navigate to Default POP3 Virtual Server.
- Right-click Default POP3 Virtual Server and select Pause from the shortcut menu.
- Right-click Default POP3 Virtual Server and now select Properties from the shortcut menu.
- In the IP Address drop-down list box, click the IP address.
- To view the virtual server configuration, click the Advanced button.
- Click OK.
- Click OK in the Properties dialog box of the POP3 virtual server.
- Right-click Default POP3 Virtual Server and select Pause from the shortcut menu.
To assign the IP address for the SMTP virtual server:
- Open Exchange System Manager
- Navigate to Default SMTP Virtual Server.
- Right-click Default SMTP Virtual Server and select Pause from the shortcut menu.
- Right-click Default SMTP Virtual Server and now select Properties from the shortcut menu.
- In the IP Address drop-down list box, click the IP address.
- To view the virtual server configuration, click the Advanced button.
- Click OK.
- Click OK in the Properties dialog box of the SMTP virtual server.
- Right-click Default SMTP Virtual Server and select Pause from the shortcut menu.
To assign the IP address for the HTTP virtual server
- Open IIS Manager.
- Navigate to Default Web Site.
- Right-click Default Web Site and select Properties from the shortcut menu.
- Click the Web Site tab.
- In the IP Address drop-down list box, click the IP address of Local Area Connection.
- Click OK.
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