Lecture 1: Network Operating Systems (NOS)
An Introduction
Abubaker Sasi, Ph.D.
E-mail/ Abubaker.sasi@gmail.com
ISA Server / كلية تقنيات الحاسوب بالزاوية 2
What is an Operating System?
• 2 kinds of a
software
– Application
Software
• Word processors,
database manager,
compiler, web
browser
– System Software
• Operating system
itself
• Bridges between the
hardware and users
Functions of Operating Systems (OS)
Resource management
• Memory management
• Device management
– Printer
– Hard drive
– display
• Process management
• Processor management (CPU time )
Operating Systems (OS) : Examples
Operating Systems: Examples
Examples of popular modern operating systems include:
Android, BSD, iOS, Windows Phone,
Linux, OS X, QNX,
Microsoft Windows, and IBM z/OS.
All these examples, except Windows, Windows Phone and z/OS,
share roots in UNIX.
Operating Systems
An operating system (OS) is software that manages
computer hardware and software resources and provides
common services for computer programs.
Operating systems form an essential component of the
system software in a computer system. Application
programs usually require an operating system to function.
Time-sharing operating systems schedule tasks for
efficient use of the system.
Operating Systems
For hardware functions such as input and output and memory
allocation, the operating system acts as an intermediary
between programs and the computer hardware, although the
application code is usually executed directly by the hardware
and will frequently make a system call to an OS function or be
interrupted by it.
Operating systems can be found on almost any device that
contains a computer—from cellular phones and video game
consoles to supercomputers and web servers.
Networks Operating Systems
Network operating system refers to software that implements
an operating system of some kind that is oriented to computer
networking.
For example, one that runs on a server and enables the server to
manage data, users, groups, security, applications, and other
networking functions.
The network operating system is designed to allow shared file
and printer access among multiple computers in a network,
typically a local area network (LAN), a private network or to other
networks.
Networks Operating Systems: Where to use?
NOS can be used in:
Routers, switches and hardware firewall.
PCs in Peer-to-peer networks
Client-server Architicture
Routers NOSs
Network operating systems can be embedded in a router or hardware
firewall that operates the functions in the network layer (layer 3) of the
OSI model.
Examples:
JUNOS, used in routers and switches from Juniper Networks,
Cisco IOS (formerly "Cisco Internetwork Operating System").
Linux, in distributions like Openwrt and DD-WRT which run on low-cost platforms
such as the Linksys WRT54G.
Peer-to-Peer and Clint/server NOSs
Peer-to-Peer NOSs
In a peer-to-peer network operating system users are allowed to share resources and
files located on their computers and access shared resources from others. This
system is not based with having a file server or centralized management source. A
peer-to-peer network sets all connected computers equal; they all share the same
abilities to use resources available on the network.
Examples:
AppleShare used for networking connecting Apple products.
Windows for Workgroups used for networking peer-to-peer windows computers.
Advantages
Ease of setup
Less hardware needed, no server needs to be purchased.
Disadvantages
No central location for storage.
Lack of security that a client/server type offers.
Client/Server NOSs
Network operating systems can be based on a client/server
architecture in which a server enables multiple clients to share
resources.
Client/server network operating systems allow the network to
centralize functions and applications in one or more dedicated
file servers.
The server is the center of the system, allowing access to
resources and instituting security.
The network operating system provides the mechanism to
integrate all the components on a network to allow multiple
users to simultaneously share the same resources regardless of
physical location.
Client/Server NOSs
Examples:
Novell NetWare
Windows Server
Advantages
Centralized servers are more stable.
Security is provided through the server.
New technology and hardware can be easily integrated into the system.
Servers are able to be accessed remotely from different locations and types of
systems.
Disadvantages
Cost of buying and running a server are high.
Dependence on a central location for operation.
Requires regular maintenance and updates.
