Transcript LAN Software

Data Communications and
Computer Networks: A
Business User’s Approach
Chapter 9
Local Area Networks - Software and
Support Systems
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Last time;
this time
• Internetworking devices
• This time NOS
– What does an OS do?
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Data Communications and Computer Networks
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Introduction
Proper support of a local area network requires hardware,
software, and miscellaneous support devices.
A network operating system is the most important software
component.
Application programs are also required to support users on a
LAN.
Support devices such as hubs, switches, routers, servers,
modems, power supplies, and more are also necessary.
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Network Operation Systems (NOSs)
An operating system manages all applications and resources in a
computer.
A multitasking operating system supports the execution of
multiple processes at one time.
A network operating system is a large, complex program than
manages the resources common on most local area networks.
Besides performing standard operating system functions, a
network operating system is called upon for additional
functions, such as …
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Data Communications and Computer Networks
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Client/Server Systems
A distributed computing system consisting of a server and one
or more clients which request information from the server.
Common examples of client/server systems include the file
server found in a LAN network operating system and a database
server found in many businesses.
A two-tier client/server architecture supports clients directly
connected to server.
A three-tier client/server architecture has clients connected to a
transaction processing monitor which is connected to the server.
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Client/Server Systems
A three-tier client/server architecture has clients connected to a
transaction processing monitor which is connected to the server.
Transaction processing monitor responsible for
Message queuing
Scheduling
Prioritization
Advantages: handle 1000’s of workstations
Disadvantages: increased level of complexity
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Data Flow Through a Client/Server Network
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Network Servers
Where does the NOS reside?
Network servers provide the storage necessary for LAN
software.
They are usually the focal point for the network operating
system.
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Network Servers
•Network servers – from microcomputer to mainframes
•Typically a powerful microcomputer with many
redundant components
•512M to Gig ram
•Large storage harddrives
•High speed microprocessor(s)
•UPS
•SCSI (small computer system interface) – fast transfer of
data between disk drive and computer
•Raid (redundant array of independent disks)
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Network Servers
•Server blades
•Server on a card
•Compact, cheaper
•Hot swappable
•Robust to failure
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Dell’s Server Blade
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Network Operating Systems
Several popular network operating systems currently
exist:
• Novell NetWare versions 3, 4, 5 and 6
• Windows NT and 2000
• Unix
• Linux
•Mac OS/X?
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Novell NetWare
Version 3 - Popular but older version of Novell NetWare. Is no
longer supported by Novell (end of 2000). User logs onto a
particular server. Bindery maintains directory system.
Version 4 - Unlike version 3 this version allows single network
login. Bindery replaced by powerful NDS database.
Version 5 - Allows administrator to use IP protocol instead of
Novell’s proprietary IPX/SPX protocols.
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Data Communications and Computer Networks
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Novell NetWare Version 6
Any client anywhere on the Internet can print and use storage
services from a NetWare 6 server without loading a single byte
of Novell’s Client32 software
Powerful Internet printing services (iPrint) make printing nearly
idiot-proof (user clicks on graphical image of floor plan
showing printers; if user does not have printer driver, it is loaded
automatically in background!)
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Data Communications and Computer Networks
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Novell NetWare Version 6
iFolder – Very effective background application powered by
Apache Web Server to “equalize” the documents in each
system’s My Documents folder with an identical set on the
server.
Volumes can hold 8 terabytes of data in up to 8 trillion files and
can keep 1 million files open concurrently.
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Novell NDS (NetWare Directory Services)
A database that maintains information on, and access to, every
resource on the network, including users, groups of users,
printers, data sets and servers.
Network administrator creates a hierarchical tree structure that
represents the layout of the organization.
Tree structure is composed of organizational units which are
composed of further objects, and leaf objects which are not
composed of further objects.
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Windows NT version 4
User interface based on popular Windows operating system, but
is NOT the same as Windows 98 or Windows Me.
Full service multi-tasking operating system capable of
supporting multiple servers.
NT systems work very well with other Microsoft products.
Questionable if NT can support large systems.
Blue screen of death (BSOD) plagues NT systems.
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Windows NT version 4
Domain
Group of users, servers, and other resources that share
account and security information
May have from 1 to several hundred domains depending on
size of system
Every domain has one and only one primary domain
controller (PDC) (a server)
Centrally manages account information and security
Each domain should have at least one backup domain
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controller (BDC) (a server)
Data Communications and Computer Networks
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Windows NT version 4
Single domain model
Simplest Windows NT domain model
One domain that services every user and resource
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Data Communications and Computer Networks
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Windows NT version 4
Master domain model
Uses a single domain to exert control over user account information
Separate resource domains manage resources such as networked printers
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Windows NT version 4
Multiple master domain model
Uses two or more master domains that are joined in two-way
trusts to manage many resource domains
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Windows 2000
Newest version of Windows NT network operating system.
Specific versions of 2000 designed to support wide variety of
system types:
Windows 2000 Professional - replaces NT Workstation
Windows 2000 Server - replaces Windows NT Server
Windows 2000 Advanced Server – supports up to 8 procs / 8GB
Windows 2000 Datacenter Server - supports up to 32 processors
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and 64GB RAM
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Windows 2000
Biggest change from NT: Active Directory
The AD is the central repository for all objects that make up the
enterprise: domains, organizational units, users, groups,
computers, printers, etc.
Roughly based on X.500 spec, creates a hierarchical tree
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Windows 2000
At the top of the hierarchical model is a single forest of one or
more trees, which must contain at least one (root) domain,
which must contain at least one organizational unit (OU), and
several other containers. (See next slide)
Recommended size limitation of 1 million objects per domain,
but lab tests have hit 10 million objects without failure
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Windows 2000
The domain has basically remained the same, but now you can
have parent and child domains
The parent and all its child domains are defined as a single
domain tree, with multiple trees in the same AD a forest
Domains are named in accordance with the Internet’s DNS
standard RFCs 1034 and 1035
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Data Communications and Computer Networks
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Windows 2000
For example, the root domain in a tree could be called
bigcompany.com
The marketing child domain could be mktg.bigcompany.com,
and the production child domain could be prod.bigcompany.com
As in NT, you can create Trusts between parent and child
domains. Only with 2000 the trust can be transitive
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Windows 2000
Many still agree that Windows 2000 has a way to go to catch up
to NetWare with regards to simplicity of administration.
Nonetheless, NetWare has dropped below 20% of the market
while Windows continues to climb (>50%)
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Unix
Older but very popular multitasking operating system capable of
supporting network operations.
First operating system written in the language C.
Very stable system capable of supporting large operations.
Numerous versions available from different vendors.
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Linux
Operating system based on the principles of Unix.
Most versions available for free or very small price.
Very stable multitasking system.
When incorporated with other free software products, such as
the Apache Web Server and Atipa’s BlueBird network
management software, this system becomes extremely cost
effective.
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Data Communications and Computer Networks
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Network Software: Utilities, Tools, and
Applications
In order to support a network operating system, may also need:
• Utilities
• Internet software
• Programming tools
• Applications
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Utilities
Five of the more common groups of network utility software
include:
• Anti-virus software
• Backup software
• Crash protection software
• Remote access software
• Uninstall software
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Internet Server Software
Software necessary to support the server side of Internet
connections.
Retrieves web pages and other documents when asked to by a
client workstation.
Can interface with a database program allowing users to store
and retrieve data via the Internet.
Necessary with commercial Internet applications.
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Data Communications and Computer Networks
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Programming Tools
Software environments that allow programmers to create
programs.
Includes software tools such as compilers and interpreters.
Software also allows individuals to edit, debug and test
programs.
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Data Communications and Computer Networks
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Application Software
Software programs that allow a user to perform common
computer-based functions:
• Database software
• Desktop publishing software
• Office suites, which integrate a collection of office
productivity tools.
• Standalone spreadsheet, word processing, and presentation
software.
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Software Licensing Agreements
Virtually every commercial software program comes with a
specific license agreement.
Most licensing agreements specify the following conditions:
• Software installation and use
• Network installation
• Back-up copies
• Decompilation
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Decompilation
Decompilation is the reverse process of compilation i.e. creating high level language code
from machine/assembly language code. At the basic level, it just requires to understand
the machine/assembly code and rewrite it into a high level language, but things are not
as simple as they seem, particularly when it comes to implementing a decompiler. There
are many situations when decompilation can be used...
• To recover lost source code. You may have written a program for which you only have
the executable now (or you got the exe of a program you wrote long back, from
someone else!). If you want to have the source for such a program, you can use
decompilation to recover it. In all rights, you are the owner of the program, so nobody is
going to question you.
• Just as stated above, applications written long back for a legacy computer may not have
the source code now, and you may need to port it to a new platform. Either you have to
rewrite the application from the scratch, or use decompilation to understand the working
of the application and write it again.
• Say you have code written in some language for which you cant find a compiler today!
If you have the executable, just decompile it and rewrite the logic in the language of
your choice today.
• To discover the internals of someone else's program (like what algorithm they have
used...)
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Software Licensing Agreements
Most licensing agreements also specify the following
conditions:
• Rental statement
• Upgrade availabilities
• Copyright restrictions
• Maintenance agreements
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Data Communications and Computer Networks
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Software Licensing Agreements
Most licensing agreements come in one of the following forms:
• Single user single station license
• Single user multiple station license
• Interactive user license
• Network server license
• Site license
• Corporate license
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Data Communications and Computer Networks
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LAN Support Devices
Other devices necessary for the proper support of a LAN:
• Uninterruptable power supplies (UPS)
• Tape drives
• Printers
• Media converters
• Workstations (including thin client workstations)
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Data Communications and Computer Networks
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LAN Software In Action: Selecting an
NOS
Hannah asks the following questions:
What are the primary uses (applications) of the current system?
Would the primary uses of the system change if a particular
NOS was installed?
How would the choice of a particular NOS affect maintenance
and support?
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Data Communications and Computer Networks
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LAN Software In Action: Selecting an
NOS
Are finances an issue in the selection of a NOS?
Does the existing system have any unusual hardware or software
that might influence the NOS choice?
Will the network be located in a single location or in multiple
locations?
Are there any political pressures to select a particular NOS?
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What did we learn?
• Not that many NOS’s available
• Cost can be a serious issue
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