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Lesson 1: General Overview of Messaging Systems

A new messaging system cannot expect to find an uncultivated market segment. Messaging is one of the most popular network applications, available virtually everywhere. Why should your organization, which most likely has a messaging solution in place, consider Exchange 2000 Server?

This lesson provides basic guidelines for evaluating messaging systems. It will help you if you are considering Exchange 2000 Server. If you have decided to use Exchange 2000 Server, this lesson will give you the confidence that you have made the right choice.

At the end of this lesson, you will be able to:

• Describe the differences between a shared-file and a client/server messaging system.
• Identify the characteristics of modern collaboration systems.

Estimated time to complete this section: 75 minutes

Shared-File Messaging Systems

Shared-file messaging systems maintain a structure of directories and files at a centralized location—usually on a file server. These centralized structures are often called post offices . Every user who wants access to e-mail messaging needs to access a mailbox within a post office. The post office serves as the mailbox repository for multiple users. Typical messaging systems that use shared-file post offices are Microsoft Mail for PC networks and Lotus cc:Mail.

Client Sending and Polling

To send messages, users must write their data into the directories (mailboxes) of the post office. The users on the receiving end recognize the written data as incoming messages. The post office itself is a passive file structure, meaning that the client programs must perform all processing of sending and receiving themselves . To check for new messages, clients must poll the post office at regular intervals (see Figure 1.1).

Figure 1.1 A shared-file messaging system

File Locking

When one client opens common files for writing, these files must be locked to prevent accidents. All other clients must wait until one client has completed its write operation. The more clients that access the same post office, the more often these common files will be locked and all other clients will have to wait. This effect can be worsened if the underlying network operating system is not optimized for fast input/output operations. It is not advisable to create a very large number of mailboxes on one server. Microsoft Mail post offices, for instance, are limited to 500 users.

Table 1.1 lists the general advantages and disadvantages of shared-file messaging systems.

Table 1.1 Advantages and Disadvantages of Shared-File Messaging Systems

Exercise 1: A Simulated Shared-File Messaging System

In this exercise you will evaluate the characteristics of a client sending and polling for e-mail messages. You can simulate client polling when configuring Microsoft Outlook 2000 for offline and remote use. For this purpose, you need to configure a personal folder store (.pst) file, which requires some advanced configuration steps. Follow the steps outlined here; Chapter 8, "Microsoft Outlook 2000 Deployment," and Chapter 9, "MAPI-Based Clients," contain more information about Outlook 2000 and the configuration of messaging services.

To view a multimedia demonstration that displays how to perform this procedure, run the EX1CH1.AVI file from the Exercise_Information\Chapter1 folder on the Supplemental Course Materials CD.

Prerequisites

• Make sure your test environment is prepared according to the descriptions given in the "Getting Started" section of "About This Book."
• Ensure that Exchange 2000 Server is operational and running on BLUESKY-SRV1.
• Log on as Administrator to BLUESKY-WKSTA and make sure you can use Outlook 2000 to work with your mailbox.

To simulate client polling with Microsoft Outlook 2000

1. In Outlook, double-click the Tools menu to display all available menu options, then select Services.
2. In the Services dialog box, click Add to display the Add Service To Profile dialog box.
3. Within this dialog box, from the Available Information Services list, select Personal Folders, and then click OK.
4. In the Create/ Open Personal Folders File dialog box, under File Name , type personal.pst , and then click Open.
5. In the Create Microsoft Personal Folders dialog box, click OK to accept the default settings.
6. Switch to the Delivery property page and under Deliver New Mail To The Following Location, select Personal Folders. Outlook 2000 will now work primarily with the newly configured personal folder store and download incoming messages from the Exchange 2000 Server.
7. Switch back to the Services property page, select Microsoft Exchange Server, and then click Properties.
8. In the Microsoft Exchange Server dialog box, select Manually Control Connection State, as shown in Figure 1.2. Under Default Connection State, select Work Offline And Use Dial-Up Networking.
9. Switch to the Dial-Up Networking tab and select Do Not Dial, Use Existing Connection.
10. Click OK twice to close the dialog boxes.

    

    Figure 1.2 Configuring Outlook 2000 for offline usage

11. In Outlook, from the File menu, select Exit And Log Off.

    At this point you have successfully configured Outlook 2000 for offline usage.

12. Start Outlook 2000 again. The client will start offline and a notification message may be displayed, informing you that the location messages are delivered to has changed, in which case you need to click No to prevent the removal of your shortcuts.
13. Create a new message and type Recipient@Domain-Not-Valid.com as the recipient address.
14. Specify a subject line and enter some message text, then click Send.

    At this point, notice that your test message remains in your Outbox and is not sent to the server, as shown in Figure 1.3.

15. Because you did not configure a polling interval, messages will not leave your Outbox until you manually connect to the server. You can accomplish this using Send on the Tools menu.

    

    Figure 1.3 Messages remain in Outbox until Outlook 2000 works online

16. The recipient address specified does not exist; therefore, the system should return a nondelivery notification. However, you are not aware that a new message is awaiting your attention, because new messages are not discovered automatically.
17. To poll for new messages, from the Tools menu, point to Send/Receive, and then select Microsoft Exchange Server.

    At this point, Outlook checks for new messages and downloads the nondelivery report that was generated automatically as a response to your test message sent to a nonexistent recipient, as shown in Figure 1.4. This indicates that messages are only received after the next polling interval.

    

    Figure 1.4 Messages are received after the next polling interval

Exercise Summary

The preceding experiment illustrates one of the most important disadvantages of shared-file messaging systems. Messages may be waiting, yet the recipients will not be aware of them until the clients are polling their message repositories. Even system processes, such as message transfer agents , which transfer messages between post offices, can be seen completely as clients (see Figure 1.1). These systems also do not recognize new messages until they perform their next polling. Consequently, message delivery in shared-file messaging systems is generally slow. To increase delivery performance, you would have to decrease the polling interval on all client systems, which in turn increases the network load. To make matters worse , polling always happens at regular intervals, even if there are no new messages to retrieve.

Client/Server Messaging Systems

Overcoming the limits of the passive post office structure requires active server components or services. These active services interact with the clients and will process the client requests to return the results only (see Figure 1.5). The client program only has to inform the server, "Here is a message for you. Please deliver it to Paul," and the server services will take care of that request. After completion, the server services return only the result to the client: "Done. Looking forward to servicing you again soon." The client does not need to perform the actual server-side processing, access any file server resources directly, or poll the server anymore because the active server services are able to contact the client themselves when new messages arrive : "Hey, aren't you Paul's Outlook client? Here's a new message for you."

Figure 1.5 A client/server messaging system

Hardware Resources

In a client/server messaging system, the bulk of the work is shifted to the active server. This requires more powerful and expensive server hardware than what is needed by a shared-file-based messaging system. To give an example, it is very common to install Exchange 2000 Server on dual-processor machines, with at least 256 MB of RAM and a well-designed high-performance Small Computer System Interface (SCSI) disk system. You might go along with less, yet the more the better.

Table 1.2 lists the advantages and disadvantages of client/server messaging systems.

Table 1.2 Advantages and Disadvantages of Client/Server Messaging Systems

Exercise 2: Testing the Performance of a Client/Server Messaging System

In this exercise you will use Outlook 2000 online and compare the resulting performance to the outcome of Exercise 1. This will emphasize the reasons to decide in favor of a powerful client/server messaging system, such as Exchange 2000 Server, for your environment.

To view a multimedia demonstration that displays how to perform this procedure, run the EX2CH1.AVI file from the \Exercise_Information\Chapter1 folder on the Supplemental Course Materials CD.

Prerequisites

• Complete Exercise 1, in the previous lesson.
• Outlook 2000 is started and you are currently working offline according to the resulting configuration of Exercise 1.

To configure Microsoft Outlook 2000 for online usage and compare the results with the outcome of Exercise 1

1. From the Tools menu, select Services.
2. In the Services dialog box, from the list of installed services, select Personal Folders, and click Remove.
3. A message box appears telling you that you are about to remove the default message store. Click Yes.
4. Select the Microsoft Exchange Server service from the list of installed services, and then click Properties.
5. In the dialog box that appears, under Default Connection State, select Connect With The Network, as shown in Figure 1.6.

   

   Figure 1.6 Configuring Outlook 2000 for online operation

6. Click OK twice to close the Services dialog box.
7. From the File menu, click Exit And Log Off to close Outlook 2000. It is necessary to reconnect to Exchange 2000 Server explicitly.
8. Start Outlook 2000 again. Your Outlook 2000 client should be switched back to the normal, online connection mode.
9. From the Tools menu, select Services to display the Services dialog box.
10. Select the Delivery property page and, under Deliver New Mail To The Following Location, select Mailbox - <User Name>.
11. Click OK to close the Services dialog box.
12. From the File menu, select Exit And Log Off (it is necessary to close Outlook to activate the new location for messages).
13. Start Outlook 2000 again and create a new message.
14. Type Recipient@Domain-Not-Valid.com as the recipient address.
15. Specify a subject line and enter some message text, then click Send.

    At this point, you should notice that the message leaves your Outbox immediately and that a nondelivery report is returned in a relatively short period of time, as shown in Figure 1.7.

    

    Figure 1.7 Sending and receiving messages takes only seconds

Exercise Summary

Exchange 2000 Server is strictly a Windows 2000 Server system comprising various active Windows 2000 services, which are typically launched when the operating system starts. Examples are the Microsoft Exchange System Attendant and the Microsoft Exchange Information Store. It is the Information Store that handles message processing on behalf of client programs. This service assists the clients in sending and receiving messages and accessing public folders. You can read more about the purpose and tasks of the Exchange 2000 Server services in Chapter 3, "Microsoft Exchange 2000 Server Architecture."

Collaboration/Groupware Systems

Your future messaging system should have capabilities beyond plain messaging. It should provide you with powerful workgroup and workflow capabilities. It should be a collaboration or groupware system that allows your users to interact efficiently , find and share information conveniently, publish information quickly, and track how information is used. Even better, automated processes on the active server can deliver information to you when the system determines it may be helpful or relevant.

Collaboration Solutions

Outlook 2000 provides numerous items you can customize easily (Appointments, Tasks, Journal, and Contacts). Basically, you only need to place the desired standard module in a public folder and your work is done. It is really that easy. In Chapter 21, "Microsoft Outlook Forms Environment," you will learn how to customize Outlook's standard modules.

The following are types of collaboration solutions based on Exchange 2000 Server and Outlook 2000:

• Discussion groups. The repository of a discussion group is a public folder, where users can post and share information using a standard or customized post form. It is also possible to post responses to existing contributions in the public folder. A threaded conversation view allows users to view the history of responses to a particular discussion.
• Instant collaboration. Solutions of this type rely on built-in Outlook 2000 modules to realize collaboration solutions with minimal configuration and development effort.
• Reference systems. A reference system stores unstructured data of any kind, such as e-mail messages, graphic images, URLs, voice mail messages, and Microsoft Office or other documents. A user manual consisting of numerous Microsoft Word documents placed together in a public folder is a good example of a reference system. Exchange 2000 Server includes built-in content indexing for high-speed, accurate full-text searches, which makes this system an ideal document management platform.
• Routing systems. Routing solutions pass information to individual users in sequence or to a group of users simultaneously . Exercise 3 illustrates a simple routing scenario. Exchange 2000 Server's extensive routing engine and capabilities are covered in more detail in Chapter 24, "Workgroup and Workflow Technologies."
• Tracking systems. Tracking solutions keep a history of the usage of information and are most useful for data that is constantly updated. Using a tracking solution, for instance, you can track who currently is reviewing a particular document, who reviewed the document already, and whether the reviewer(s) approved or made changes to the document. Tracking systems are often implemented in conjunction with workflow solutions.
• Real-time collaboration. Real-time collaboration provides services that enable you to schedule, create, administer, join, and track online sessions and conferences. Exchange 2000 Conferencing Server supports data and video conferencing and Exchange 2000 Server's Instant Messaging platform allows you to detect the presence of other users on the network and communicate with them in real time. In addition, Exchange 2000 supports multiuser chat environments, where users can interact with each other using chat conversation channels.
• Microsoft Web Storage System. Web Storage System solutions represent a new and exciting technology that combines data repositories of various types, such as the folder system of Exchange 2000 Server, the file system of Windows 2000 Server, and Web-based resources, and presents them as a single place for storing information. You can access all information through URLs in any Web browser, in Outlook, or any Internet-based e-mail client, as well as Windows Explorer.

Exercise 3: Setting Up a Corporate Phone Book for Business Contacts

In this exercise you will take a first glance at the extensive collaboration capabilities of Exchange 2000 Server. The following procedure suggests a public phone book for business contacts. You will set up the repository as a moderated resource according to the process illustrated in Figure 1.8.

To view a multimedia demonstration that displays how to perform this procedure, run the EX3CH1.AVI file from the \Exercise_Information\Chapter1 folder on the Supplemental Course Materials CD.

Prerequisites

• Make sure you have completed Exercise 2 and Outlook 2000 is working online.
• Perform the following steps on BLUESKY-WKSTA.

Figure 1.8 A collaboration example using a moderated public folder

To set up a public phone book for business contacts

1. In Outlook 2000, from the File menu, point to Folder, and then select New Folder to display the Create New Folder dialog box.
2. In the Create New Folder dialog box, under Name, type Business Contacts .
3. Under Folder Contains, select Contact Items.
4. Under Select Where To Place The Folder, expand the Public Folders tree, select All Public Folders, and then click OK.
5. If a dialog box appears asking you whether you want to create a shortcut on your Outlook Bar, click Yes.
6. On the Outlook Bar, click My Shortcuts to display the list of your shortcuts, which also shows an icon named Business Contacts.
7. Right-click Business Contacts, and then select Properties.
8. Switch to the Administration property page, and then click Moderated Folder.
9. Activate the Set Folder Up As A Moderated Folder check box, and then click To to select Carl Titmouse as the folder moderator.
10. Activate the Reply To New Items With check box.
11. Under Moderators, click Add, and specify the user selected in Step 9 again (Carl Titmouse).
12. Click OK twice.

    At this point, you have set up the public contact repository and specified a folder moderator, as shown in Figure 1.9.

    

    Figure 1.9 Specifying a folder moderator

13. Open the public folder Business Contacts by clicking on its shortcut using the left mouse button.
14. Double-click in the empty right pane to create a new contact object.
15. Type a contact name (for instance, Mr. Frederick Fly ) and a telephone number, and then click Save And Close.
16. When you are entering the phone number, a Location Information dialog box may appear asking you for information regarding the country/region system settings. Enter the information according to your location. If, subsequently, a Modem Properties dialog box appears, click OK again.
17. A Check Phone Number dialog box will appear asking you for country information and an area code for the phone number specified. Verify the information, and then click OK.

    At this point, the new object does not appear in your public folder yet. Instead you have received a standard notification that your submission has been received and is reviewed. Open your inbox to read the response from Business Contacts, as shown in Figure 1.10.

    

    Figure 1.10 A standard response from the Business Contacts folder

18. Log off from Outlook 2000 and Windows 2000 and then log on as Carl Titmouse (the public folder moderator). Then, start Outlook 2000 and connect to the mailbox of Carl Titmouse. Note that the object created during the previous steps is awaiting your attention.
19. Double-click on the object, verify the correctness of the information, and then from the File menu, select Move To Folder.
20. In the Move Item To dialog box, open the Public Folders tree, then All Public Folders, and then double-click Business Contacts to move the object back into the public folder. If another item is opened automatically, close it again.
21. In the right Outlook pane, click Inbox (the button available on the top-left of the list of messages), open Public Folders, then open All Public Folders, and then select Business Contacts.

    At this point, your contact object is publicly available. Optionally, you may log off and back on as Administrator to verify the result, as shown in Figure 1.11.

    

    Figure 1.11 Moving an item into a public folder

Exercise Summary

Exchange 2000 Server provides an excellent set of workgroup and workflow features. Following the steps just outlined, you created an instant collaboration solution with basic routing capabilities in which users contribute new information, which is then forwarded automatically to a central moderator for approval. After approval, the information is made available to all users in the organization. A moderator can guarantee that only valid information is published. You can read more about public folders and their configuration in Chapter 17, "Public Folder Management."