Network Station - Thin Client Computing - Overview
The objective of this document is to help develop an understanding of a
Server Based Computing/Thin-Client environment using MS Windows NT®
4.0, MS Terminal Server 4.0, Citrix Metaframe, IBM Network Station Manager,
and IBM Network Stations. It provides an overview of the different
components involved in an enterprise Network Computing solution design and
In order to migrate to a server based, or thin client model, three important
factors must be considered: the applications requirements, the server
configuration and the network capacity. The systems integration of
applications, servers, and size/speed of the network is most critical, and
should receive proper analysis and architecting considerations before a
migration begins. Network, or server based computing, isn't just network, or
thin clients, or servers. It is the sound integration of all of those components
after having gained an understanding of the footprint requirements of the
applications and the level of user demand upon the system.
Applications and Capacity Planning
Applications and capacity planning have always been a significant aspect in
the design of any computer system, but it is especially important when
designing a Server-Based Network Computing solution. The traditional
Windows-based distributed computing environment in its simplest form
provides users with an operating system running on the local PC workstation
and access to local and remote applications and network resources. The
computing environment that is provided by Windows Terminal Server is
significantly different. The Windows Terminal Server provides users with the
desktop (operating system), applications, and network resources via remote
network communications between the client, and the WTS.
Capacity planning for the WTS begins by identifying the factors that impact
system performance and how they affect performance. Factors that should be
considered in any capacity planning strategy include the following: WTS
applications, user characteristics, and the network environment. In essence,
you should become familiar with how your applications, users, and network
environment will impact WTS performance.
Know Your Applications
It is important to understand how a particular application will operate on a
WTS. Applications executing on a WTS may react very differently than when
operating in a traditional Windows-based computing environment. Knowing
your application may require asking the following questions: How
graphics-intensive is the application? How much memory does the application
require? How much of the application's memory is shareable between users?
How does the application refresh the screen? Does the application require a
lot of typing? Applications need only be installed once on Terminal Server for
multiple users to have access to them. Thus, upgrading in much easier if
required in the future, the upgrade need only be done once.
Limiting MS-DOS Applications
Take care when deploying applications written for MS-DOS. Standard
MS-DOS applications will require more memory because each application will
spawn its own 16-bit Windows on Windows (WOW) subsystem.
Know Your Users
User usage patterns have a significant impact on WTS performance and
should be considered carefully when designing a capacity planning strategy.
Knowing your user may require asking the following questions: Do your users
leave the applications open? When do users log on? Do the users stay logged
on throughout the day? Are logons evenly distributed throughout the day or
are most logons at a specific time of the day?
Know Your Network
Understanding the network environment is especially important when
designing a WTS solution that involves WAN communications. Because WTS
provides both applications and the desktop to the user, network
communications are very important. Even infrequent network slowdowns can
provide unacceptable performance to WTS users. Knowing your network may
include the following questions: How fast do your users type? Are the
applications graphics-intensive? What is the typical display resolution of your
client workstations? What is the network bandwidth required for a user running
the application?
Server Configuration Considerations
Boot Server (Base Code Server)
The boot server provides the base operating system of the IBM Network
Station (the kernel), all application modules for the native applications such as
the 3270 and 5250 emulators, the NC Navigator browser, etc., the fonts file,
and the Java classes.
Configuration Server
The terminal configuration server provides the terminal based hardware
preferences. These are all the configuration files that set the characteristics of
the terminal (the IBM Network Station) itself, regardless of which user is
actually using it. In other words, this is all the configuration data BEFORE the
user identifies itself by logging into the Network Station.
Authentication Server
The authentication server provides basically all the configuration data that is
specific to a particular user.
DHCP Server
Dynamic Host Configuration Protocol (DHCP) Server provides the Network
Stations with an IP address. Once a DHCP server responds positively to the
client, giving him an IP address to use for a specified period of time, the client
becomes operational and uses the allocated IP address to communicate on
the network. Using a DHCP server is always the preferred method for a thin
client to get its network configuration data. However, if a DHCP server is not
available or not possible, the Setup utility of the thin client can be used to
enter the required network and boot configuration data into its NVRAM (IBM
Network Stations require additional User Definable Options in the DHCP
RAS Server
Remote access allows you to access remote network resources or access the
main network from a remote location. Windows NT does this through remote
access server service. The remote access server is usually a Windows NT®
4.0 Server with the remotes access server services installed (there are other
remote access server applications available from third party vendors that
maybe used instead of Microsoft's RAS Server).
Primary Domain Controller Server - (PDC)
The domain server that contains the master copy of the security, computer,
and accounts database and that can authenticate workstations. By default,
every NT domain contains at least one NT Server that has been installed as a
Backup Domain Controller Server - (BDC)
A BDC off loads logon authentication from the PDC and provides fault
tolerance in the event that the PDC becomes unavailable. The BDCs receive
automatic updates of the security and user databases from the PDC.
Separation of Servers
Network Architecture and Design Considerations
Generally, you should consider the network infrastructure when deploying
Terminal Server. This step is especially important when you are replacing
legacy systems with Network Stations or personal computers and you must
connect these new systems to the network so they can gain access to
Terminal Server. In most cases effective deployment will depend on careful
planning in a number of areas related to the infrastructure.
When you add any new systems to the network, be sure to include a physical
path to the servers and domains to which they need to gain access. Take a
particular care to configure routers correctly to establish a network path from
the client to the server.
Place all servers running Terminal Server on a backbone for optional
bandwidth usage. Use the highest bandwidth segment available on your
network. For example, do not use a 10-Mbps segment if 100-Mbps segment is
NT Domain
It's important to remember that no single domain design should be considered
"correct." Every organization will have a different architecture to accommodate
different needs and limitations, and you must plan the Terminal Server
deployment accordingly. However, you should keep in mind a few rules when
planning to implement a Terminal Server solution: Terminal Server need not
be in a Windows NT Server domain to function, but without a domain
architecture, users must have separate accounts on every computer running
Terminal Server. This limits scalability and makes it more difficult to administer
groups of users.
Consult your Windows NT documentation for more information on setting up
Windows NT Server domains. Administrators can choose to add attributes that
are specific to Terminal Server to user accounts. This adds a small amount of
information, typically 1 KB or less, to each user's entry in the domain's Security
Accounts Manager (SAM) database. This additional information is not
necessary, but it allows the administrator to exercise additional control over
individual user settings. Every Windows NT Server domain has at least one
server that functions as a domain controller. We strongly recommend that you
not run Terminal Server on any computer that is also a domain controller
because of the resource load that Terminal Server places on the system. Also,
because Terminal Server is designed to perform like Windows NT Workstation
at the end-user level, the system will not assign top priority to critical
domain-level processes such as user account replication, logon requests,
logon script replication, and authentication requests. In addition, domain
controllers cannot be cloned because the security identifiers (SIDs) will be
duplicated across the cloned servers and will therefore be unable to join the
An exception might be a company with no preexisting Windows NT Server
domains that requires only a few servers running Terminal Server. If this
company wants to use global groups to apply user policies and to create user
accounts that can be used across multiple servers, it might be appropriate to
install a server running Terminal Server as a domain controller rather than as a
member server. Small organizations without many users typically use a single
In order for the Network Station to communicate with your servers, you need a
TCP/IP network. If you understand your TCP/IP network, installing and
configuring your Network Station and IBM Network Station Manager program
is much easier.
Dynamic Host Configuration Protocol (DHCP) is also a TCP/IP protocol. DHCP
provides a way for a server to automatically allocate IP addresses and
configuration information without forcing the administrator to record and track
the MAC addresses of the networked computers. DHCP is capable of
assigning either a permanent IP address or a temporary IP address for every
host or Network Station within a predetermined range of IP addresses. It is
also capable of assigning IP addresses either statically or dynamically.
A Domain Name server is a server whose responsibility it is to keep track of
host names and IP addresses. Having an administrator manually update a list
of names and addresses might be manageable in a very small environment
with a somewhat low rate of change, but it quickly becomes unmanageable in
large networks and in networks that have a number of mobile workers who
move quickly from one location to another and need to retain the same name,
yet have a different address every day or every week, or whatever might be
the case. This is why a facility is required to allow a dynamic update to the list
of names and addresses maintained by a Domain Name Server.
You can configure Terminal Server so that clients can connect to it using
Windows Internet Naming Service (WINS). If you select this method for name
resolution, you must register all running Terminal Servers with the primary and
backup WINS servers.
Remote Access
Terminal Server can provide remote users with access to applications that
would otherwise be unusable because of poor performance across dial-up
connections (the screen, mouse, and keyboard information sent by Terminal
Server typically uses less bandwidth than an application that must be
downloaded and then run locally on a remote user's machine).
Flash Boot
The flash memory card support enables the use of a PCMCIA flash memory
card to boot the IBM Network Station. Since the IBM Network Station has no
disk storage devices, all the software required to make it operational must be
loaded from a server. In environments where there is no local server,
transferring megabytes of code over a network can take several minutes. In
order to reduce the time needed to boot in these environments, the Network
Station operating system and applications can be stored on a flash memory
card. The flash memory cards supported are from a select subset of PCMCIA
Series D type II cards (listed in the PRPQ documentation) and may be
purchased from several third party vendors.
In addition to individual Network Stations each being able to boot from their
own flash card, the offering also provides the capability for several Network
Stations to boot from one Network Station which contains a flash memory
card. This additional function is called "peer boot" or "buddy boot".
System Software
What is a Windows applications server? A Windows application server is a
machine that executes Windows applications on behalf of clients that cannot
run these same applications on their own processor. The client does not have
to be a network computer, or an X-station, but it can be any machine, even
one capable of executing Windows applications itself. A typical case for
example might be an old PC, with a slow processor and limited local storage
capacity. This PC might be adequate to run a 3270 emulator for example,
which requires little local storage and processing power but once in a while it
needs to execute an application that require a fast processor and large files.
In that case, the PC can take advantage of a Windows application server and
connect to the server when this application needs to be executed. This is also
a good way to reduce the maintenance associated with these applications by
making them available on a server; therefore, when it is time to upgrade these
applications, it can more easily be done by upgrading a few servers rather
than a much larger number of PCs.
Terminal Server system diagram
Microsoft® Windows NT® Terminal Server Edition, or WTS, Microsoft®
Windows NT® Server 4.0, Terminal Server Edition is an extension of the
Windows NT product line that provides support for remote access by using
thin client software that runs on a new class of Windows-based terminals and
on desktop systems running under 16-bit and 32-bit Windows. Terminal Server
allows users to run both the Windows desktop operating system and
Windows-based applications directly off the server, extending the scaleable
Windows family and providing users of low-cost terminal devices and legacy
hardware with access to the latest Windows NT based technology and the
latest Windows-based applications. Terminal Server has three parts. The
server itself is a new edition of Microsoft® Windows NT Server 4.0 with the
ability to host multiple, simultaneous client sessions. Remote Desktop Protocol
(RDP) is the protocol that allows a super-thin client to communicate with
Terminal Server over a network. Terminal Server Client is a super-thin client
application that connects to Terminal Server from a Windows-based terminal,
Microsoft® Windows for Work groups 3.11, Microsoft® Windows 95 or
Windows 98, or Windows NT®.
Citrix MetaFrame / WinFrame
Citrix MetaFrame is thin-client/server system software for Microsoft®'s
Windows NT® Server 4.0, Terminal Server Edition. Citrix MetaFrame system
software, which incorporates Citrix's Independent Computing Architecture
(ICA), provides a complete thin-client/server computing solution for multi-user
NT 4.0 environments.
MetaFrame provides value-added functionality for all types of Windows clients
including Windows 95, Windows CE, Windows NT® Workstation, Windows for
Work groups and Windows 3.x systems. MetaFrame also supports
non-Windows clients including DOS, UNIX, Mac OS, Java and OS/2 Warp and
a broad range of client hardware including legacy PCs, Pentium PCs,
Windows-based terminals, network computers, wireless devices and
information appliances.
MetaFrame connects users to the network through standard telephone lines,
WAN links (T1, T3, 56Kb, X.25), broadband connections (ISDN, Frame Relay,
ATM), wireless connections, corporate intranets and the Internet. MetaFrame
supports popular LAN and WAN protocols including TCP/IP, IPX, SPX,
NetBIOS, and direct asynchronous connections. WinFrame is the predecessor
to MetaFrame and is based on Windows NT® 3.51 platform. Both WinFrame
and MetaFrame are supported with the IBM Network Stations.
NCD WinCenter
NCD WinCenter for MetaFrame is an add-on product for enterprises using
Microsoft® Windows NT® 4.0, Terminal Server Edition and Citrix MetaFrame.
Highlights: Integrates security between NT and UNIX systems using NIS
Optional NFS package to share files with UNIX servers Cut-and-paste
between UNIX and Microsoft® applications Supports UNIX workstation floppy
drives NCD WinCenter for MetaFrame uses the open systems X Protocol for
display presentation so no additional desktop software needs to be installed
on your UNIX workstations. This approach offers optional performance (for
both UNIX and Windows applications) because it frees the UNIX desktop from
locally running Windows emulation software, and gives your Windows
applications a dedicated server.
IBM Network Station Manager - NSM
IBM Network Station Manager for Windows NT® Server 4.0 provides central
client management for all (or to specifically designated) IBM Network Stations.
These IBM Network Stations can be connected to a LAN or a WAN in which a
PC Server (Boot Server or Base Code Server) running the IBM Network Station
Manager code is an addressable node. Implement the IBM Network Station
Manager for Windows NT® Server 4.0 software to take advantage of
leading-edge application technologies such as Corporate intranets, the
Internet, and Java With IBM Network Stations, you can access applications
resident on attached PC Servers and on other servers on the network (for
instance, AS/400 ®, RS/6000, S/390 ®, and other systems) and to the myriad
number of servers on the Internet as well.
The data and applications do not reside on the IBM Network Station. As
access to applications is required by the IBM Network Station, the IBM
Network Station Manager for Windows NT® Server 4.0 downloads the
required code from the PC Server. Supported application access software
includes 5250, 3270, X-terminal, NC Navigator, the IBM Network Station
Browser, and Java running either within the Web Browser or within the IBM
Network Station Java Virtual Machine.
The Boot Server may reside on one of the following platforms: PC Server,
AS/400, RS/6000 and S/390. This document will only cover a PC based Boot
Server implementation using MS Windows NT® 4.0.
We recommend that you install NSM on a Stand Alone Server. The current
version of NSM for NT is Release 3.04.
Thin Client Devices
There are three IBM Network Station models. All IBM Network Station models
are designed to: access multiple servers (IBM and others), run Windows
applications via multi-user implementations of Windows NT, support 3270 and
5250 terminal applications and work with applications on AIX and UNIX
servers using X-Windows server support.
Model 100
The Series 100 is an ideal desktop solution for users in multiple-server
environments who need to access a variety of business applications even on
different platforms. Organizations aiming to provide terminal users more
access to contemporary business applications and e-mail at their desktops.
Model 300
The IBM Network Station Series 300 is the Internet network computer. It's the
option for corporate Intranet and Internet access. It is the ideal solution when
your desktop-computing focus extends beyond mainline business applications
and data presentation. The Model 300 is ideal when users spend a lot of time
on your corporate Intranet or the Internet.
Model 1000
The IBM Network Station Series 1000 is the Java network computer. The IBM
Network Station Series 1000 offers robust support for running business-critical
applications and personal productivity tools that take advantage of Java. This
IBM Network Station lets you run Java Applets and applications directly on the
Network Station.
Document ID: ROSN-46BN5B
Copyright © 1998 IBM Corporation
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