The
Structure of Network Operating Systems
by
Matthew
Martin
An important feature of networking
is the independence of the networking hardware (LAN network cards, etc.)
from the networking software. In the past some companies, such as IBM and
Digital, tried to tie networking schemes to specific operating systems. These
attempts failed because their competitors drove international and open standards
that became popular. One of the most popular schemes is Ethernet, which works
independent of the hardware and operating systems used, as long as it follows
the agreed protocols for Ethernet.
Contents
Protocols
A networking protocol is a scheme that agrees the manner
in which data is packaged, sent and accounted for across a network. Vendors
(companies) and industry committees develop the agreements and individual
companies write software that conforms to the standards agreed. Usually they
do not get it right first time, and there follows several rounds of re-development
before a satisfactory implementation of the protocol is achieved.
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Functions of LAN Software
- The
sharing of resources (printers, hard disks, communication links) across
a network.
- Making
distant resources appear local.
- Network
Operating System (OS) uses layers of software that follow the protocols
(rules) for formatting data, addressing, reliable transmission of data across
the network.
- Networking
software performs the same functions regardless of the OS being used.
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What is a Network Operating System?
A network OS is a collection of different software, each
performing different functions. Some of this software acts as servers of some
computers and as clients on other computers. Today many OSs include networking
functions as an integral part of the OS but the functionality is still distinct.
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Clients
A computer that uses network resources (rather than providing
them) is called a client. The network resources that the client uses are provided
by one or more servers. It is possible for any computer on a network to act
as some type of server. A client PC that shares some of its files or a printer
across the network is acting also acting
as a server. Thus there is an overlap between computers that are clients and
those that are servers.
Some important features about clients:
Redirection Software
Redirection software makes network resources look like
they are local to the client. This makes the provision of network resources
transparent to the user. For example, a network drive that exists on a server
is visible to the user on a client workstation as a drive E: that can be accessed
as if it is a local drive.
OS modules in the client include
the redirection software, which redirects certain requests and keyboard inputs
out across the network through the network adapter instead of being dealt
with locally.
Transport Layer Software
Networking software in the client redirects output from
the client to the network adapter and out across the network. The software
that does this has three parts:
- Application Program Interface (API),
- Network communication that follows a specific protocol,
- Drivers that are specific top the network (LAN) adapter.
An Application Program Interface (API) is a specification
describing how application programs interact with the disk operating system
or network operating system.
Netware Shell:
Microsoft Redirector:
by
Matthew Martin
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