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Peer to
peer and client server models:-
Peer-to-Peer Networks
A peer-to-peer network allows two or more PCs to pool their resources together. Individual resources like disk drives, CD-ROM drives, and even printers are transformed into shared, collective resources that are accessible from every PC.
Unlike client-server networks, where network information
is stored on a centralized file server PC and made available to tens,
hundreds, or thousands client PCs, the information stored across
peer-to-peer networks is uniquely decentralized.
Because
peer-to-peer PCs have their own hard disk drives that are accessible by
all computers, each PC acts as both a client (information requestor) and a
server (information provider). A peer-to-peer network can be built with
either 10BaseT cabling and a hub or with a thin coax backbone. 10BaseT is
best for small workgroups of 16 or fewer users that don't span long
distances, or for workgroups that have one or more portable computers that
may be disconnected from the network from time to time.
After the networking hardware has been installed, a peer-to-peer network software package must be installed onto all of the PCs. Such a package allows information to be transferred back and forth between the PCs, hard disks, and other devices when users request it. Popular peer-to-peer NOS software includes
Most NOSs allow each peer-to-peer user to determine
which resources will be available for use by other users. Specific hard &
floppy disk drives, directories or files, printers, and other resources
can be attached or detached from the network via software. When one user's
disk has been configured so that it is "sharable", it will usually appear
as a new drive to the other users.
In other words, if user A has
an A and C drive on his computer, and user B configures his entire C drive
as sharable, user A will suddenly have an A, C, and D drive (user A's D
drive is actually user B's C drive). Directories work in a similar
fashion. If user A has an A & C drive, and user B configures his
"C:\WINDOWS" and "C:\DOS" directories as sharable, user A may suddenly
have an A, C, D, and E
drive (user A's D is user B's C:\WINDOWS, and E is user B's C:\DOS). Did you get all of that?
Because drives can be easily shared between peer-to-peer PCs, applications only need to be installed on one computer--not two or three. If users have one copy of Microsoft Word, for example, it can be installed on user A's computer--and still used by user B.
The advantages of peer-to-peer over client-server NOSs include:
No need for a network administrator
Network is
fast/inexpensive to setup & maintain
Each PC can make backup
copies of its data to other PCs for security. By far the easiest type of
network to build, peer-to-peer is perfect for both home and office use.
Client-Server Networks
In a client-server environment like Windows NT or Novell
NetWare, files are stored on a centralized, high speed file server PC that
is made available to client PCs. Network access speeds are usually faster
than those found on peer-to-peer networks, which is reasonable given the
vast numbers of clients that this architecture can support. Nearly all
network services like printing and electronic mail are routed through the
file server, which allows networking tasks to be tracked. Inefficient
network segments can be reworked to make them faster, and users'
activities can be closely monitored.
Public data and applications
are stored on the file server, where they are run from client PCs'
locations, which makes upgrading software a simple task--network
administrators can simply upgrade the applications stored on the file
server, rather than having to physically upgrade each client PC.
In the client-server diagram below, the client PCs are
shown to be separate and subordinate to the file server. The clients'
primary applications and files are stored in a common location.
File servers are often set up so that each user on the network has access
to his or her "own" directory, along with a range of "public" directories
where applications are stored. If the two clients below want to
communicate with each other, they must go through the file server to do
it.
A message from one client to another is first sent to the file
server, where it is then routed to its destination. With tens or hundreds
of client PCs, a file server is the only way to manage the often complex
and simultaneous operations that large networks require.
Mainframe model
All users work on terminals which are connected to the mainframe - they are the front end. The mainframe computer does all the processing - it is the back end.
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