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Architecture Components
This section explores the major components of desktop architectures, their applicability to varying user contexts, and some elements of component design and scaling. The four major components of the desktop environment are client devices, application integration solutions, services and servers, and software. The following diagram shows a typical heterogeneous customer environment containing many of these elements, which are in the following sections.
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FIGURE 1
Desktop Environment Components
Client Devices
The range of potential client devices has grown in recent years, and desktop or mobile users have a wide choice of interfaces to their business and personal productivity applications. There is also an emerging trend for organizations to adopt a thin-client strategy to manage and reduce their TCO. This section examines client device options (both thick and thin) and gives guidelines on how to select an appropriate device for specific user groups.
Sun Ray Ultra-Thin Clients
The Sun Ray ultra-thin client consists primarily of the hardware and firmware required to present the output associated with a user's desktop session onto an integrated or detached display device (either CRT or LCD) and to accept user input in the form of keystrokes and mouse movements. The actual processing for the user's session takes place on an associated server that is running the Sun Ray ultra-thin client server software and provides the CPU, memory, and storage resources needed by the user.
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FIGURE 2 Sun
Ray Ultra-Thin Client Architecture
The Sun Ray ultra-thin client moves desktop processing back into the data center or local server cabinet, providing for scalability, resilience, and centralized storage and backup. The other significant feature of the Sun Ray ultra-thin client is the ability to relocate sessions between devices. This feature is dependent on the association between a user and a Java Card technology, which carries a unique token used by the server software to identify the session. At present, this session mobility feature is limited to devices attached to servers in the same physical location, but in the future, it will extend to devices located anywhere on an enterprise's WAN.
The Sun Ray ultra-thin client requires bandwidth of around 1 megabit per second between itself and the server. This requirement is likely to be reduced with future versions of the Sun Ray ultra-thin client software and firmware.
Benefits of the Sun Ray ultra-thin client include:
Long lifetime due to the simplicity of construction
Low power consumption and reduced cooling requirements
Reduced help desk intervention to solve user misconfiguration, operating system problems, and disk crashes
Ease of installation and reconfiguration
Session mobility
Continuity of service
Availability or suitability
With fewer components, the Sun Ray 1 ultra-thin clients have fewer failures and are supplied with a five-year warranty.
The Sun Ray ultra-thin client receives its identity (that is, its IP address) from a server after the client is powered on. Therefore, the client can be installed or relocated by unskilled staff or by end users.
This is a convenient feature for collaborative workers, mobile users, and users who want to deliver presentations.
Drawbacks of the Sun Ray ultra-thin client include:
The client is dependent on server and network resilience.
Currently, the Sun Ray ultra-thin client is not available or suitable for small offices (fewer than five users) or home offices until bandwidth requirements have been reduced. This situation is scheduled to change with the next release of the server software, sometime in the middle of 2004.
Windows-Based Terminal Clients
A solution that has been deployed by many organizations to deliver applications to users is to install a simplified (that is, thin-client) device known generically as a Windows-based terminal. The Windows-based terminal solution seems to provide many of the benefits of the Sun Ray ultra-thin client solution without needing to install a server layer (other than Windows application servers). It usually contains a limited software set (operating system, Citrix or Remote Display Protocol [RDP] client, and browser) in firmware, plus local memory and processor, but no local storage facility. Therefore, the Windows-based terminal solution is potentially more reliable than conventional PCs.
Benefits of a Windows-based terminal solution include:
Reduced complexity and longer working life than thick client systems
Easy installation and configuration
Reduced help desk intervention to solve user misconfiguration, operating system problems, and disk crashes
Drawbacks of Windows-based terminals, as compared to the Sun Ray ultra-thin client, include:
Client device is somewhat more complex
Vulnerability to theft
Limited capability for session mobility
No native access to Solaris OS and/or Linux-based applications
The lifetime might be shorter than the Sun Ray ultra-thin client.
A Windows-based terminal client might contain desirable components, such as flash and conventional memory, which might make the unit more vulnerable to theft.
Windows Desktop Clients
Traditional desktop systems based on the Intel x86 architecture and the Microsoft operating software have been the clients of choice in many organizations for a number of years. They offer independent processing power to the user and the capability to install a wide range of personal productivity and line-of-business applications that meet the individual needs of the user. A typical enterprise today has more than 1,000 different PC-based applications running on its desktop client systems.
One of the primary drawbacks of these systems is that the IT organization is expected to refresh the hardware and operating software on a frequent basis. The terms of Microsoft's Software Assurance program and the ability of hardware manufacturers to frequently upgrade equipment specifications mean that many users are compelled to refresh their software, at most, every three or four years. For each such refresh, the IT organization (whether in-house or outsourced) will spend many months requalifying the applications that run on the client estate on the updated hardware and/or software platform.
Linux Clients
As the open source movement gains support in the computer industry, it has become increasingly evident that there is a potential market, particularly among cost-sensitive organizations, for Linux desktop systems. Some popular Linux distributions now contain a number of packages that supply the needs of the desktop user. For example, Sun has recently announced a Java Desktop System that includes StarOffice, GNOME, and other open source software packages.
It is now feasible to replicate many or most of the generic facilities provided by traditional desktop clients on a Linux system. A potential desktop client offering should contain the components described in the following table.
TABLE 2 Sun Java Desktop System Components
|
Component |
Product |
|
Operating system and CPU architecture |
Linux with an x86 CPU architecture or the Solaris OS with a SPARC_ processor |
|
Windows manager |
GNOME 2 |
|
Office productivity |
StarOffice software suite |
|
Internet browser |
Mozilla 1.x |
|
Mail and calendar client |
Ximian Evolution |
|
Windows emulator |
WINE or Codeweaver's CrossOver Office |
|
Integration clients |
Citrix ICA, Tarantella AIP, and/or RDP |
The potential benefits of a Linux desktop solution are:
Lower TCO compared with Windows clients due to significantly lower software license costs
Longer refresh cycles
The Linux desktop solution can use lower specification hardware; therefore, it extends the life of the current estate.
Improved performance compared with Windows desktops
The drawbacks of a Linux desktop solution are:
Not all of the Windows applications are available to the user through WINE or RDP and ICA.
Linux skills are be required for at least some IT staff, and users require retraining, even though the GNOME look and feel can be made very similar to Windows.
Macintosh Desktops
There is a significant interest in the maintenance of support for the Apple Macintosh product set, particularly among users of special graphical and publishing applications that are developed specifically for this platform. These users can be integrated into an overall desktop architecture in a number of ways:
Mac OS 9 and OS X clients exist for UNIX_ printing (for instance, the common UNIX printing system known as CUPS) and SAMBA and NFS file sharing (see "File Services" on page 21).
A variety of Mac OS email clients are also available (for example, the native Apple mail client, Mozilla, Netscape™, or Eudora).
Several office productivity suites exist for Apple users, including Microsoft Office and a port of OpenOffice 1.0 (the open source version of the StarOffice 6.0 software).
For more information, see:
Personal Digital Assistants and Mobile Devices
The number of Personal Digital Assistants (PDAs) and mobile devices has proliferated considerably in the last four or five years. The options range from sophisticated mobile phones, such as the recently introduced third generation (3G) handsets, to full-featured PDAs that are, in effect, reduced-footprint PCs, complete with an operating system, productivity and business applications, and browser. Currently, there is no single standard operating system or software stack for such devices. The options available in the marketplace include:
Java technology-based solutions
PDAs based on variants of the PALM operating system, such as Palm, Handspring, and Sony
PDAs that run on Win CE or PocketPC
Generally, these are mobile phones, PDAs, and some gaming devices. These operate the Java Virtual Machine (JVM™) software and a selection of services most likely corresponding to one of the profiles defined by the Java Community Process (for example, the Mobile Information Device Profile, or MIDP). These devices generally run a number of standard productivity applications such as simple word processors, spreadsheet applications, calendars, and email clients, and they are capable of provisioning and executing Java applications, such as games, on a pay-per-use basis.
These devices tend to have more capacity than phone handsets and carry a larger range of built-in applications. Some (for instance, the latest Palm products) ship with the JVM software to facilitate dynamic application provisioning.
Basically, these are subsets of the Microsoft Windows operating system family that provide a potential platform for ports of the many Windows-based applications.
Given the wide variety of clients available, most IT organizations will probably look to identify a least common denominator solution that will enable the support for the widest variety of client devices. Some of the architecture decisions that designers need to examine are:
Integration with office productivity suites
Email and data synchronization
Choice of integration software layer for delivery of server-based applications (for example, Tarantella, Citrix, or other)
Both Microsoft Office 11 and the StarOffice 7 software will provide compatibility with some, but not all, PDA office personal productivity applications.
Emerging standards such as SyncML might assist in simplifying the options for achieving synchronization between handheld devices and enterprise mail message stores. For more information about SyncML, see: http://www.openmobilealliance.org
Citrix appears to support more native client types than Tarantella, but both products have the capability to deliver to an HTML browser, provided that an appropriate Java VM is present (see "Application Integration Solutions" on page 18).
UNIX Workstations
There is still a considerable installed base of technical workstations based on RISC processors and various flavors of UNIX. The SPARC workstation with the Solaris OS holds the greatest market share in this sector, but systems produced by Hewlett-Packard (PA-RISC/HP-UX), IBM (POWER/AIX), and Silicon Graphics (MIPS/IRIX) are still in use, as well as even older similar workstations. For many of these users, there is a requirement to interoperate with and use office productivity applications, Internet browsers, and other applications. In most cases, the only feasible option is to install open source equivalents, as most of these have been ported to the more popular variations of UNIX. Finally, Tarantella and Citrix clients exist for most UNIX variations. These modules can be used to deliver applications that are served from a Windows system.
Application Integration Solutions
Windows Terminal Services (WTS) is a facility that was first provided by Microsoft as an add-on to Windows NT 4, and subsequently, it has been delivered as an inherent component of Windows server operating systems (Windows 2000 Server and Windows 2003 Server). WTS delivers a presentation layer service to suitably equipped client devices through Microsoft's RDP. In this context, a suitably equipped client could be a PC running Windows ME or XP, or it could be a system that emulates the RDP client such as Tarantella Enterprise 3 or WinConnect S.
A variant solution used by many organizations is to install Citrix MetaFrame on the Windows server to deliver applications to devices, such as a Windows-based terminal or a traditional desktop PC with Citrix client software. Citrix MetaFrame runs on a Windows server in parallel with the WTS functionality, but it has some lower level hooks into the operating system that bypass WTS and overcome some of its limitations. Regardless of whether WTS, RDP, or Citrix is the delivery mechanism of choice, the user will have to pay for additional Microsoft licenses, known as Client Access Licenses, for each concurrent client device or system.
There are several contenders in the marketplace that can be used to deliver Microsoft Windows applications to heterogeneous client systems (for example, Tarantella Enterprise 3, Citrix MetaFrame, ThinSoft's WinConnect, and Rdesktop). The following table compares the attributes of these products.
TABLE 3 Windows Terminal Services Software Comparison
|
Attribute |
ThinSoft |
Tarantella |
Citrix |
Rdesktop |
|
RDP version supported |
5.2 |
4.0 |
N/A |
4.0 |
|
Max Colors1 |
16 million |
256 |
16 million |
256 |
|
Sound Support* |
Yes |
No |
Yes |
No |
|
Local printer support |
Yes |
Yes |
Yes |
No |
|
Local disk access |
Yes |
No |
Yes |
No |
|
Local communication port access |
Yes |
No |
Yes |
No |
|
Requires middleware2 |
No |
Yes |
Yes |
No |
|
Client GUI |
Yes |
Yes |
Yes |
No |
|
Support for UNIX servers |
No |
Yes |
No |
No |
|
Support for z/OS and OS/400 |
No |
Yes |
No |
No |
|
Support for browser access |
No |
Yes |
Yes |
No |
|
Command line options |
Yes |
Yes |
Yes |
Yes |
|
Technical support |
Yes |
Yes |
Yes |
No |
|
Requires MS licenses |
Yes |
Yes |
Yes |
Yes |
|
Cost per client3 |
$99.00 |
$250.00 |
$349.00 |
Free |
RDP 5.0 and 4.0 do not support sound or 24-bit color. This limitation also applies to Tarantella (which relies on RDP), but it is overcome by Citrix, which bypasses the RDP mechanism to deliver these features to its clients. This situation changed with the release of Windows 2003 Server and RDP 5.2. These new products mean that RDP clients are able to provide the features that most users need.
In summary, users with mixed Windows, UNIX, and Linux environments should evaluate Tarantella and Rdesktop. Users who primarily access Windows applications should evaluate Citrix and WinConnect S.
When considering a possible move to thin-client solutions based on WTS and RDP or Citrix ICA, it is important to understand that there is a considerable amount of work involved in ensuring that the organization's many (typically, more than 1,000) Windows applications can successfully be delivered through the proposed integration layer. Generally speaking, Windows applications fall into three main categories:
Applications such as Microsoft Office and terminal emulators that are designed to work with or are already known to be compatible with WTS.
Applications that have not been integrated and/or tested
Applications that cannot be integrated with WTS
These applications can be delivered by using Tarantella or Citrix with no further effort.
Many applications are potentially WTS compatible, but they have not been integrated and tested in such a configuration. Allow at least two to three days for each application.
Some applications—thankfully, a minority—can never be integrated with WTS, particularly old 16-bit programs and software that assumes that it has sole ownership of the hardware. For these applications, the obvious choices are retirement, replacement, or relocation to a legacy fat-client system that will be retained and supported for a limited user population.
For thin-client delivery, additional design considerations are the allocation of applications to servers and the location of servers. There is an obvious design and cost trade-off between colocating all of the application servers into one or two data centers (which requires adequate network bandwidth), as opposed to a wider set of locations. Within the data center, there is also a set of decisions that need to be made about how applications are to be distributed. For instance, should each server provide all of the applications, or will groups of servers specialize in advertising sets of application services?
A final consideration for service delivery to all clients is the degree of integration between presentation layer software products and portal servers. For example, Tarantella is closely integrated with the Sun™ ONE Portal Server software, such that Tarantella-mediated applications can be built into and selected from a portal generated home page.
A Tarantella, Solaris OS, and StarOffice software benchmark is available at:
http://www.tarantella.com/whitepapers
You should also read the following Sun BluePrints OnLine articles:
"Sizing Sun Ray Servers Running Windows Applications with SunPCi IIpro Coprocessor Cards" (November 2001)
"Supporting Microsoft Windows 2000 Server Applications from Sun Enterprise Servers" (June 2001)
Services and Servers
This section looks at the variety of services that should be provided to the desktop user and the servers that can provide them. For each service, some of the architectural requirements relating to performance and resilience is also examined.
File Services
There are two main methods by which file storage services can be provided to users of thin (or thick) client systems: Network File System (NFS) and Common Internet File System (CIFS). NFS is a long established protocol used by UNIX systems to distribute file systems across a network, enabling users of heterogeneous clients to remotely mount directories (subject to security settings) from a file server, as though they were components of the local file system. CIFS is the latest of Microsoft's file networking protocols and is used primarily by Windows clients to mount server file systems as additional drives on their own system.
Both solutions can be provided and supported by Solaris OS and Linux servers. NFS is a standard operating system component for these servers, and CIFS can be delivered by an open source project known as SAMBA (the name derives from Server Message Block—the underlying protocol used by CIFS and its predecessors). The decision as to which file service to employ is partly dependent on the organization's familiarity with the underlying technologies and the requirements of their users. Some pointers are outlined below:
UNIX and Linux clients can access both NFS servers and SAMBA servers (with smbclient).
Windows clients will find it easier to access SAMBA servers, although Windows-based NFS clients are available.
Users who have implemented Active Directory (see "User Authentication Services on page 23) will be able to integrate the latest version of SAMBA 3.x into an Active Directory (AD) forest as a domain server. NFS servers will not be recognized by AD.
CPU requirements for NFS file severs are not typically onerous. One estimate suggests that a typical user generates one to two file system events per second and consumes on average around 0.2 MHz of CPU capacity. A 400-MHz CPU should, in principle, be able to support 2,000 concurrent clients. Memory requirements are also fairly minimal. Around 1 megabyte per concurrent user will suffice unless particularly large data volumes are involved. A more significant issue is the bandwidth required.
Bandwidth needs to be sized so that the peak data volumes expected can be delivered with some margin of safety. For example, if each of 1,000 users will generate 40 megabytes of data traffic during the peak hour of the day, you should configure at least two 100-megabits per second connections to ensure an ample safety margin (the average throughput will be 90 megabits per second with a peak of around 210 megabits per second). It is important to ensure that sufficient disk capacity is provided in a resilient format, such as RAID 1 or RAID 5, and that this disk space is split across a reasonable number of spindles for improved I/O performance.
Print Services
Print services are typically provided by the same software and the same servers as file services. There is a choice of printer hardware configuration, with four main solutions being available in most cases:
Linux and Solaris OS printers
Windows printers
LAN printers
Sun Ray ultra-thin client devices
The queues for these printers are managed by the server to which they are attached.
Many organizations prefer to have their printers attached to Windows servers, even where the majority of their applications are not Windows-based. In this case, the print queues are on the Windows server.
Some printers have built-in networking capability and manageable elements. They can exist as a standalone device. In this case, the associated printer queues can be on any server and might exist on several servers concurrently.
Printers can be attached to the USB ports found on Sun Ray ultra-thin client device. The print queue for such printers is on the Sun Ray ultra-thin client server, which currently holds the session for the device.
The selection of the printer configuration is mainly a matter of individual choice. At one time, there was some preference for Windows printer servers because of a shortage of printer drivers for other platforms. This situation has changed, however, with the advent of networked printers and the greater availability of drivers. Some of the guidelines for file services are also applicable to print servers. Most notably is that UNIX and Linux clients will have some difficulty accessing Windows-attached printers.
Administration of printers is often a time-consuming task for IT organizations. It is advisable to try to ensure consistency in the naming of printers and printer queues across the organizations. For the Solaris OS-attached servers, it is possible to create scripts that can identify the physically closest printer automatically.
Limited information is available on how to size print servers as distinct from file servers. Probably the most important consideration is the locality of the server with respect to the queue of the printer the server holds. It is generally not recommended to attach high-volume graphical printers to a server by using a low-bandwidth WAN connection.
An additional consideration is the amount of disk space required for holding spool files (that is, queued files awaiting output to a physical printer). The required space will be implementation-dependent and will be significant if many large print files are produced or if printers are removed from service (for example, for maintenance).
User Authentication Services
There are at least four currently available and widely used services that enable users to authenticate themselves and that can be used to give or withhold access to system resources, applications, other services, and physical devices:
Lightweight Directory Access Protocol (LDAP)
NT domain controllers
Active Directory
Novell directory service
LDAP is an open standard (defined by IETF RFC 3377) that is widely found on UNIX and Linux systems.
These controllers were introduced as components of Windows NT. Each primary domain controller (PDC) holds authentication details (for example, name and password) for resources in its domain and might enter into trust relationships with other domain controllers. This solution is still widely used, as many users have not yet decided when or whether to upgrade to AD.
Active Directory (AD) was first introduced with Windows 2000 Server and is further enhanced in Windows 2003 Server. It extends the concept of domains into a forest of security trees that have a central repository of authentication data, but can delegate some administrative tasks to lower level controllers. AD claims to be LDAP-compatible, but the LDAP integration with AD, as shipped in Windows 2000, presented some challenges. With the release of Windows Server 2003, LDAP integration with AD has been improved.
Novell directory service (NDS) has been in existence in various forms for many years. It is not directly compatible with LDAP or AD, but it can be integrated with either of them with some difficulty. NDS still has a significant user base, but most users anticipate moving to AD or LDAP in the future.
The authentication service is a difficult choice for organizations. In general, users of NDS and NT domain services are looking to migrate to LDAP or AD because they recognize that their current solutions will not be supported indefinitely. Those enterprises that plan to participate in future Web services delivery will also need to build software stacks based on a more contemporary identity services solution.
The move to either AD or LDAP is not without some difficulty because there is a need to migrate user and resource details to the new solution. As a general recommendation, the needs of users who have mainly (or solely) Windows application servers and are committed to the Microsoft proprietary .NET stack will be best served by migrating to, or continuing to use, the AD service. Other users will be better enabled to retain flexibility and openness by the adoption, or continued use, of LDAP-based authentication services.
For users who have both AD and LDAP solutions, there are several meta-directory products that can permit two-way integration between these two authentication servers.
Mail and Messaging Services
In recent years, there has been rapid growth in the use of email and, more recently, instant messaging services. These services are typically provided by a client-server software combination. The possible client solutions (which is discussed in "Software Components on page 27) communicate with servers that handle message storage and transfer by using one of several standard protocols such as IMAP4, POP3, webmail, or the proprietary MAPI interface, which is specific to Microsoft environments. Although Microsoft Exchange (which supports MAPI clients) has the largest share of the corporate email market, it offers a number of challenges for users who plan to evolve with the product:
Users who upgrade to Exchange Server 2000 also have to implement AD services—a reasonably complex project for most organizations.
Exchange users are locked into a fairly expensive and proprietary software product with costly upgrade plans.
Exchange architectures generally involve a proliferation of small or medium servers that have a relatively high TCO because of their associated management costs.
Support for HTML (webmail), IMAP4, POP3, and LDAP open standards
Integration with a selection of antivirus and SPAM prevention products and significant built-in SPAM prevention mechanisms
Integration with a variety of voice mail systems to provide a unified messaging solution
Support for Simple Authentication and Security Layer (SASL), which permits the use of several different authentication mechanisms through an extensible security interface
Extensibility and manageability, along with significantly lower TCO than Microsoft Exchange
Support for instant messaging for users who need to implement an internal message exchange for conferences, alerts, chat, and news, as opposed to depending on a public network such as AOL or Yahoo
A number of alternative solutions exist, including IBM Notes, Openwave Mail, Oracle Collaboration Suite, and Sun™ ONE Messaging Server. A viable candidate product will have most, or all, of the following characteristics:
Calendar Services
The next web-based interactive application expected to become widespread is the calendar. Like email, the e-calendar will become another ubiquitous collaborative application, as people experience the benefits of sharing calendar information and using online interactive scheduling to manage their time, coordinate with family and friends, and track changes to work schedules. The recent ratification of new Internet standards for calendars has been a catalyst in moving calendars and scheduling into mainstream Internet activities. Today, iCalendar (RFC 2445) describes a standard schema for calendar objects on the Internet. The iTIP standard (RFC 2446) describes how to use iCalendar objects to perform common scheduling tasks such as publishing an event or inviting someone to a meeting. The iMIP standard (RFC 2447) describes how the iTIP scheduling operations can be performed over email. The CAP standard (which is work in progress by the Calendaring and Scheduling Working Group of the Internet Engineering Task Force) will provide a real-time access protocol for client applications to talk with calendar servers.
Sun Ray Ultra-Thin Client Servers
Sun Ray ultra-thin client servers are Solaris OS-based systems that run the Sun Ray ultra-thin client server software. This software is currently in its second major revision (2.0) and provides support for Hot Desk Protocol, which delivers frame buffers to Sun Ray ultra-thin client devices and transmits mouse clicks and keystrokes to the servers. These servers are essential to the operation of Sun Ray ultra-thin client devices because they provide the CPU and memory resources for user sessions.
Version 2.0 of the server software enables the Sun Ray ultra-thin client device to coexist in networks that have other DHCP servers present. Version 1.3 of the server software could not coexist in such a network. Version 2.0 also provides for the optional encryption of data traveling between the server and the client. The key for this encryption is currently hard-wired into the server software.
There is no simple guideline for the ratio between Sun Ray ultra-thin client devices and server resources required to support them. Guidelines provided by the Sun Ray ultra-thin client engineering group suggest that each UltraSPARC_ III CPU can support 25 concurrent Sun Ray ultra-thin clients. Such a guideline, however, ignores other software that is running on the server and user interaction with the server. In a real world situation, the typical user might be running a Tarantella or Citrix native client to present Windows applications and might also be accessing an Internet browser and an office productivity tool (for example, the StarOffice Office Suite), running on the same or a different server. Experience in the field suggests that some of these tools might require frequent screen refreshes caused by user interaction or, in the case of the Internet browser, caused by Shockwave animations or streaming video. Some additional guidelines to consider are:
Always use a server with at least two CPUs whenever possible.
Base a pilot or proof of concept implementation on the server platform that is expected to be used in a more complete roll-out.
If the users are going to access the Internet from their devices, consider installing a copy of the browser on each Sun Ray ultra-thin client server.
This avoids the situation in which a single thread spins on a CPU and locks out other Sun Ray ultra-thin clients. A thread is a section of executable code that is recognized by the operating system as a executable entity in its own right.
This enables you to determine the resources required per user more accurately, assuming that the application set under test is representative of the production environment.
This might reduce the additional traffic and processing overhead caused by users browsing dynamic pages through an intermediate layer such as Tarantella or Citrix.
Memory usage per user will vary depending on the applications in use. General figures vary between 40 and 100 megabytes per user, in addition to 64 megabytes shared system memory. In a typical Sun Ray ultra-thin client server configuration, the operating system is mirrored across two disks. Sufficient swap space should be provided to allow for inactive sessions. The quantity of the inactive sessions is dependent on user work patterns and Sun Ray ultra-thin client server software security settings. The inactive sessions will have a footprint of 40 to 100 megabytes each.
Software Components
This section covers the various software components that make up the software stack for most users. It identifies alternative products and solutions that are available and gives some pointers on selecting appropriate products.
Office Productivity
Although Microsoft Office has been the market leader for a number of years, there has been a significant user reaction to recent changes in Microsoft's licensing policies that appear to be moving toward the concept of software rental and, at the same time, to be forcing users to update their products on a frequent basis. In this environment, the advent of Sun's StarOffice Office Suite (and the associated OpenOffice open source project) has been welcomed by many organizations.
A feature set comparison of Microsoft Office and StarOffice is online at:
http://wwws.sun.com/software/star/staroffice/6.0/compare/
StarOffice and OpenOffice are now viable alternatives for organizations that are cost-sensitive and/or that do not want to participate in Microsoft's Software Assurance program. The main benefits of StarOffice 6.1 (OpenOffice 1.1) are:
Low licensing and support costs
Improved Microsoft file format compatibility
Native XML file formats
PDF export facility
Users who might be less suited to StarOffice might choose to stay with Microsoft Office for the following reasons:
Large numbers of embedded VBA macros (although these might need to be modified for compatibility with future Microsoft Office releases)
Significant presence of ISV applications that integrate with Microsoft Office
Frequent interchange of documents with external Microsoft Office users
No sizing data is currently available for StarOffice served from a UNIX or Linux server, but a sizing guide is expected some time in the future. The minimum supported configurations for StarOffice clients is online at:
http://wwws.sun.com/software/star/staroffice/6.0/techfaq.html
Internet Browser
Traditionally, two contenders for the role of Internet or Intranet browser have been available: Internet Explorer and Netscape Communicator. A number of other contenders (for example, Mozilla, Opera, and Safari) have appeared recently, however, of which the leading offering is possibly the Mozilla open source project (on which Netscape 7 is based). There are also issues surrounding browser support on mobile devices—many of which are not based on the Microsoft operating software.
For home users and users who need access to a wide variety of multimedia content from the Internet, Internet Explorer remains the most viable choice due to its support of ActiveX controls and integration with a large number of plug-ins. However, there is still a strong linkage between Internet Explorer and the underlying Windows operating system, such that users need to upgrade to later versions of Windows to take advantage of future browser enhancements (other than the frequent security fixes issued by Microsoft).
Users who have limited Internet requirements, who are using a browser primarily for business purposes, or who have a mixed desktop client environment (which appears to be a growing community), might be better suited to the Mozilla or Netscape product, which also provide an open source mail client.
Window Managers
The choice of a window manager is almost a religious or philosophical debate among the more knowledgeable. For other users, it is a matter of indifference (or zero choice). The four main contemporary contenders are:
Windows XP (and its predecessors and successors)
CDE
KDE
GNOME 2
Generally, Windows XP is agreed to be friendly and usable. As a consequence of its widespread use among home and educational users, it is understood by a very wide audience.
CDE was the default desktop environment for the Solaris OS (and therefore for the Sun Ray ultra-thin client). It has a slightly old-fashioned look and feel, and it is likely to be displaced by its successors: KDE and GNOME 2.
KDE is becoming the window manager of choice for more technically oriented Linux users due to its more modern look and feel, flexibility, and range of configuration options.
GNOME 2 is the latest version of an open source project. It is not as flexible as KDE, but it has attractive graphics and can be configured with a skin, which gives it the appearance (and functionality) of Windows XP. GNOME 2 is probably the best choice for users with XP experience who are migrating to UNIX or Linux platforms.
Mail and Calendar Clients
As with other elements of the software stack, the choice of mail and calendar clients depends on the user's system environment and acceptance of open source software.
The choice is essentially between a Microsoft defacto standard and open source equivalents. The main contenders are:
Outlook and Outlook Express
Ximian Evolution
Weblicon Calmena
Mozilla and Netscape
These clients were designed to integrate with Exchange servers that provide both mail and calendar services. They have been targeted by many email-attached viruses that have been able to exploit a variety of security vulnerabilities.
This client is based on an open source project and integrates with a number of backends (for example, Exchange or IMAP and iCalendar-based servers, such as the Sun ONE Messaging Server and Sun™ ONE Calendar Server software). Ximian Express has a look and feel very similar to Outlook, and it incorporates Personal Information Manager (PIM) functionality (as does the full Outlook product). Ximian Evolution is not supported on Windows platforms. It runs only on UNIX or Linux platforms.
This client runs on a variety of platforms (for example, Windows, UNIX, and Linux) and integrates with either Exchange or IMAP4 and iCalendar servers. Weblicon Calmena has more limited functionality than Evolution and does not emulate the appearance of Outlook. However, it is a reasonable choice for organizations that want to displace Microsoft totally and that have a variety of client platforms.
These open source clients provide a useful mail client that integrates with IMAP4 servers and provides limited folder management. They are available for most operating platforms.