Microsoft® Office System White Paper
Enabling a Superior Client Experience with Microsoft Office Outlook2003
Abstract
Microsoft Office Outlook 2003 introduces a number of new features that enable improved information worker productivity in a variety of scenarios. When Outlook 2003 is used as an e-mail client on Exchange Server 2003-based systems, the negative effect of transient issues such as high latency, loss of connectivity, and limited bandwidth are significantly reduced. This paper describes the new features and capabilities that make these improvements possible.
December 2003
The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication.Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication.
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Contents
Executive Summary
Introduction
Messaging Technology Overview
Connection Bandwidth, Latency, and Reliability
Client Connection Types
Outlook 2003 Technology Overview
Cached Exchange Mode
Automatic Conflict Resolution
Remote Procedure Calls over HTTP
MAPI Compression
Buffer Packing
Recommended Settings Based on User Type
Conclusions
For Additional Information
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Enabling a Superior Client Experience with Microsoft Office Outlook 20031
Microsoft® Office System White Paper
Executive Summary
MicrosoftOffice Outlook® 2003 introduces a number of new features that enable improved information worker productivity over a variety of networks. When Outlook 2003 is used as an e-mail client on Microsoft Exchange® Server 2003-based systems, the negative impact of transient issues such as high latency, loss of connectivity, and limited bandwidth are significantly reduced. This paper describes the new features and capabilities of Outlook 2003 that make these improvements possible. Although some of the issues described here are exclusive to Exchange Server 2003, most of the improvements are also relevant to systems running Exchange Server 5.5 and Exchange Server 2000.
In the context of these new capabilities, the final section of this paper provides usage and optimization information for each key feature of Outlook 2003. Finally, the paper concludes by offering specific recommendations for achieving the best client experience in specific userscenarios.
Introduction
Whether information workers are at home, the office, a hotel, or in a taxi, they have a number of methods at their disposal to access the Internet: broadband, dialup, and cellular, to name a few. As a result, they expect to get access to their e-mail messages anytime, anywhere.
Users of previous versions of the Microsoft Outlook messaging and communications client had an array of options for achieving the best e-mail access experience based upon such factors as the connection speed to the server and usage habits. The core decision for these users was whether to use online or offline mode. They used online mode whenever possible to get access to the complete range of Outlook e-mail, calendar, and free/busy information features, to create rules, and so on. When users were offline or hada slow connection to the server, they would use sophisticated combinations of various capabilities in offline mode to achieve a seamless experience.
Microsoft Outlook 2000 and Microsoft Outlook version 2002 went a long way to make it possible for information workers to access rich Outlook functionality no matter where they were.Outlook 2003 goes much fartherby providing substantial improvements to many existing featuresand adding key new features as well.
The driving vision behind Outlook 2003 improvements was to provide a messaging client that would “just work”, regardless of the quality, speed, and reliability of its connection to the Exchange Server computer. For example, Outlook 2003 makes deciding between online mode and offline mode a thing of the past. Information workers can now use a new connection feature called Cached Exchange Mode, which provides users with a superior experience whether they are connected to the network or not. Cached Exchange Mode shields information workers from transient issues such as latency and temporary losses of connectivity, enables them to change seamlessly between connected and non-connected states, and helps them retain full network independent functionality when they are not connected to the network. Users can also change seamlessly between On, Hibernate or Standby power states without shutting down or restarting Outlook 2003.
The key technologies that combine to provide a superior client experience in Outlook 2003 include:
- Cached Exchange Mode
- Network adapter speed awareness
- Improved synchronization efficiency and robustness
- Automatic conflict resolution
- Remote procedure calls (RPC) over HTTP(enables direct Outlook to Exchange Server connection over the Internet)
- Enhancements to personal folder (PST) and offline folder (OST) files
The remainder of this paper discusses these technologies, describes their use, and offers specific recommendations about how to best apply these technologies in different connection scenarios.
Messaging Technology Overview
Before discussing specific improvements to the information workerexperience of Outlook 2003, it is important to understand the improvements that can be madeto any messaging system.
The best way to understand these improvements is to understand how Outlook 2003 uses remote procedure calls (RPCs) to communicate with Exchange Server. Outlook retrieves data differently depending on whether the Outlook client can connect to the Exchange server. The basic types of Outlook-to-Exchange Server communication includes:
- Data Requests.Outlook 2003 requests data from the mailbox to display it for the information worker or to complete an action, which can include:
- Sending e-mail messages
- Switching folders
- Displaying individual items such as e-mail messages, contacts, or appointments
- Displaying reminders
- Using the address book to find names of contacts
- Scheduling meetings
- Processrules.
- Synchronization.Outlook 2003 synchronizesthe information on the local computer with the Exchange Server 2003 computer to:
- Send or receive e-mail messages
- Download the address book.
All performance issues and technologies that have been designed to improve system performance relate in some way to managing or facilitating data requests and synchronizing data with the server. In this context, the next sections describe the key environmental variables of Outlook 2003 use.
Connection Bandwidth, Latency, and Reliability
Before introducing the different server connection scenarios, it is important to distinguish between connection bandwidth, latency, and reliability. When people think about their connection to the server and system performance, they usually think only in terms of connection bandwidth. But connection bandwidthis only part of the performance equation. Latency and reliability are the other major factors.
Latency is the amount of time (including the processing time)that it takes for a request to a server to return to the client. Aninformation worker could have a reasonablyhigh speed connection such as digital subscriber line(DSL) or a cable modem but be geographically located so far from the server that latency becomes a systems performance issue. Other factors that affect latency include the number of routers between server and client computers, the time it takes to process a request on the server (which includes factors such as the capacity and load on the server), and the network load. The influence oflatency can be reduced by decreasing the number of requests made to the server. Cached mode also reduces the influence of latency by decoupling the server requests from the user’s actions. Client PC latency also affects latency to some degree, especially if the client PC is underpowered.
The reliability of a client connection to the Exchange Server computer can have just as much effect on systems performance as bandwidth or latency does. Connectionsthat are interrupted during transmission of e-mail messages can affect network performance. Taken together, connection bandwidth, latency, and reliability are the key network characteristics of any given connection scenario.
Note: Latency and reliability are impacted by network bandwidth. When bandwidth is saturated, latency and error rate increase.
Client Connection Types
Cached Exchange Mode, network adapter speed awareness, and other features combine to reduce the effect that the type of client connection has on the Outlook 2003 user experience. Whether an information workeruses alocal area network (LAN), dialup, or DSL connection, the basic experience of smooth, seamless access will be the same.
However, the Outlook2003 client responds differently to different connection types because they affectthe amount and reliability of data traveling over the wire duringa given period of time. An information worker using Cached Exchange Mode over a dialup connection will be able to create messages even if the connection is dropped. The connection speed and reliability still determine such things as how long it takes to perform the initial synchronization, to send e-mail messages, and so on. Whenthese factors are known, information workers can improve performance in a number of ways. For example, to speed the initial synchronization across a slow network connection of a low-latency network, information workers can specify that Outlook 2003 only copy message headers to the local OST. On a fast network (that is, one with virtually unlimited bandwidth), headers are not much faster than the full e-mail messages. However, headers by themselves are much faster on a lower bandwidth connection. In most cases, Outlook can transition automatically from headers to full e-mail messages. This is detailed in later sections of this paper.
Another reason it is important to understand how the client connects is that there are also some instances whenonline mode still makes sense, and this will be affected by connection type. These instances are described in the “Exceptions” section later in this report,
Key typesof client connectionsinclude:
- Network (LAN/WAN)connections, which are generally high-speed, high-quality, and low-latency. WAN connections vary in speed and latency but are usually high-quality.
- DSL, ISDN, or Cable Modem connections, whichare all much better than traditional dial-upconnections. Latency can still be a factorin these connections, particularly if information workers are geographically distantfrom the system e-mail servers.
- Cellular or Land-Line Modemsaregenerally the slowest connection method. Frequently, the telephone line is not dedicated to a network connection; or, it might serve the dual purpose of serving telephone calls and providing network access.
Note: High speed modems that have superior compression don’t really add any value for the typical user of Outlook messaging and collaboration client or the Outlook Web Access (OWA) client users since they are typically accessing encrypted content. Encrypted content doesn’t benefit from hardware compression on the client.
Outlook 2003 Technology Overview
Outlook 2003 introduces a number of new capabilitiesand improvements to existing technologies. These enhancements include:
- Cached Exchange Mode.Cached Exchange Mode combines the ability of offline mode to shield information workers from transient network issues with the rich feature set of online mode, which delivers a consistently superior user experience. In Cached Exchange Mode, Outlook 2003 works from a local copy of an information worker’s Exchange Server mailbox, stored in an OST file on the information worker’s computer. The Offline Address Book (OAB) is also stored alongside the OST file on the information worker’s computer. The cached mailbox and OAB are updated periodically from the Exchange Server computer.
By caching the information worker’s mailbox and the OAB locally, Outlook 2003 operation avoids dependence on ongoing network connectivity to provide access to user information. Whenever possible, Outlook 2003 synchronizes the offline copy of the mailbox with the server to keep the copies up to date. As a result, even when information workers disconnect from the network or temporarily lose connectivity, they do not have to do anything to ensure they have the most recent data. Furthermore, they do not lose network independent functionality.They can create e-mail messages, look up names in the offline address book, and so on. When they reconnect, Outlook 2003 synchronizes the mailbox seamlessly without intervention.
In addition to improving the information worker’s experience by using a local copy of the mailbox, Cached Exchange Modedetects network adapter speed to optimize the type and amount of data sent. For example, if Outlook 2003 is configured withOn Slow Connections Download Only Headers, the type and amount of data sent over the connection is changed automatically whenever the connected network adapter speed is lower than 128Kbps.
Note: OAB configuration cannot be controlled from the Send-Receive setting. Automatic OAB downloads are controlled via registry key. Additionally, when in Header mode, Outlook will not perform automatic OAB updates.
- Remote Procedure Calls (RPC) over HTTP.When used with Exchange Server 2003, Outlook 2003 can now connect to the Exchange Server computer from any internet-capable connection. These connections can be made without the inconvenience and overhead associated with using a virtual private network (VPN). These inconveniences include the necessity of initiating the connection and the problem of dropped connections while working within Outlook 2003.
When RPC over HTTP is used, Outlook 2003 tunnels each Messaging API (MAPI) RPC request throughan HTTP/HTTPS connection. This approach gives Outlook 2003 the ability to communicate to the server by using direct HTTP or HTTPS. Using the correct configuration provides a rich client experience to a corporate mailbox server over insecure and unreliable networks such as the Internet. Just like normal connectivity to Exchange from inside a firewall, Outlook use RPC over HTTP will automatically reconnect a dropped HTTP/HTTPS connection to Exchange in the background, preserving the Cached Exchange Mode user experience around connectivity.
- Synchronization Improvements – Synchronization between Outlook 2003 and Exchange Server 2003 is more efficient and robust when Outlook 2003 is deployed. This is especially true when Exchange Server 2003 is part of the system. For example, Microsoft has reduced the number of change notificationsthat appear when the client is in Cached Exchange Mode. This efficiency results in cost savings on pay-by-the-byte networks and generally reduces the amount of time required to complete any synchronization.
Key synchronization improvements include:
- Smart Change Synchronization.When Outlook 2003 performs synchronization at the item level (for example, an individual e-mail message), changes that occur to a message object or any part of the headers can be tracked and only the changed part of the item needs to be re-synchronized with the server. In earlier versions of Outlook, any change would trigger synchronization of the whole item. With the new synchronization in Outlook 2003, if a mobile user synchronizes a large message to a local OST file and then replies to it, the large message no longer has to be re-synchronized with the server because only a portion of the header was changed.
Outlook 2003 treats reply/forward header information and message flags as special attributes to make this possible. When these attributes change, a synchronization of the entire object with the server does not reoccur.
- Incremental Change Synchronization (ICS) Check-pointing.When Outlook 2003 is used to synchronize data against an Exchange Server 2003 computer (not available on older versions of Exchange), an advanced Incremental Change Synchronization (ICS) check-pointing algorithm is used. This approach ensures that data Outlook has already received does not need to be resent if network connectivity is lost during synchronization. Rather, Outlook 2003 will pick up where it left off and continue the synchronization.
Note: Outlook will immediately resume following the last full item download. For instance, if the user has an e-mail message that has a 100MB attachment and the network connection fails while the e-mail is transversing the network, the user will have to re-download the e-mail.
- Skip Bad Items.During fast transfer synchronization, Outlook 2003 will skip and log any bad or malformed items that are found on the server. In previous releases of Outlook, such items would cause the synchronization process to fail.Virus infected items are also excluded if the user is using a supported Virus Scanner that works with Exchange Server 2003 and if it has marked the item as quarantined.
- Pre-Synchronization Reporting.Outlook2003 determines the number and size of items to be synchronized and presents information workerswith a visual notification that describes the synchronization status. This includes the current folder’s total size of data coming down to the client, the number of items and size of each item being downloaded.
- MAPI Compression.MAPI compression inOutlook 2003 and Exchange Server 2003 enables much faster communications than was possible in previous versions. The compression affects the entire message body, including attachments. For example, Microsoft Word documents compress very well through this new MAPI compression mechanism.
- Buffer Packing.When Outlook 2003 and Exchange Server 2003 are used together, buffer packing provides additional efficiency to client and server communications. There is a close relationship between buffer size and compression becausethe Outlook 2003 client can request a data buffer of 32Kb.However, afterthe server has compressed the data, it may be significantly smaller on the wire. Therefore, to accommodate varying compression rates but fully utilize the remaining buffer space, Exchange 2003 includes support for buffer packing. This approach enables the server to keep adding compressed data to the buffer until the buffer is full.
Note: Public Folder access, delegate access, Free/Busy, and data transfer from the client to the server are at 32kb, whereas 96kb is used for synchronization tasks.