computer networking

                                           

                                                     COMPUTER NETWORKING

            Computer network is a collection of computers and other hardware devices so that network users can share hardware, software, data and they can communicate with each other electronically.  Computer networking is connecting a computer with other computers or other devices to enable them to communicate with each other, between:

1. computer devices/equipments

2. transmission media to send/control data/signals

3. communication devices to transmit/send data from

    sources to destinations

4.  softwares

                    TYPE OF NETWORK

v  LAN

v  MAN

v  WAN

v  PAN

1. LAN

• Covers relatively small geographical area. Eg. Home,

schools, office building

• Client/ server network is example of LAN

• Allows file exchange, emails, printer sharing or accessing

the internet.

2. MAN

• Network designed to service a metropolitan area, a city or

a county

• Owned or provided by a city or network provider

• For local people’s access to internet

• Example in Malaysia? 3 network of LAN for Mid Valley City

3. WAN

• network that covers large / broad geographical area

• Ex: telecommunications network that links across metropolitan,

regional, or national boundaries) using private or public network

transports.

• In essence, this mode of telecommunication allows a business to

effectively carry out its daily function regardless of location.

• Internet: world’s largest WAN

NETWORK COMPONENT

1. Hots/End nodes

• Refers to the data source and the data destination.
• Examples:
– Personal computers
– Terminals
– Workstations

– Automatic Teller Machine

2. Transmission media

• For transmitting data and control signals
• Responsible for sending electric or signal through spesific
media. It can be bounded (wired) or unbounded (wireless)

media.

Unbounded (wired)	Bounded (Wireless)
·         Coaxial cable            ·         Twisted pair            ·         Fibre optic	·         Radio signals                 ·         Satellite transmission                 ·         Infrared transmission

3. Network electronic devices

• Responsible to control data from source to destination

• Provide interface between different media transmitter or for

different protocol

• To connect multiple network together or to connect

computer or network to the internet

• Examples:

– Bridges

– Routers

– Multiplexers

– Switches

– Hubs

– Gateways

– Front End Processors

4. Software/Application

• The applications at the end nodes (what is end node?)

normally involves technique and protocols

• The protocol determines the rules and procedure to send

data, terminate data, interpret data, present data and

control mistakes

• Software in the network functions to ensure data is

delivered at respective destination

• to control data transmission

5. Network architecture standard and protocols

• NAS: The blueprint of standards that define:

– How device in a network typically connect

– How the device can communicate

• To ensure interoperability between various

devices and equipment made by different

vendors.

• To enable devices made by different companies to

work or communicate with each other.

Example : TCP/IP, Ethernet (802.3), Wi-Fi

(802.11), WiMAX etc

• Network architecture is the way they are design to

communicate

• 2 types :

1. Client/Server Networks

• Client = computers that request or utilize network

resources

• Server = processing the request by client

• What is network server? Provide access to software, files

etc being shared in the network

• Retrieves file from server: download

• Transfer from client to server : upload

2. Peer to Peer Networks

• No central server

• Have direct access to other devices attached to the

network

• As long as they are declared as ‘shared devices’

• Internet peer to peer: eg. iTunes, Bluetooth between hand

phone.

NETWORK TOPOLOGY

Physical	Logical
Linear bus	Shared media
Star	Token based
Ring
Tree
Mesh

1. Physical topology
• The physical layout of devices on a network.or the way that the devices on a network are arranged     and how they communicate with each other
• The way that the workstations are connected to thenetwork through the actual cables that transmit       data

1. Linear Bus
􀂃 consists of central cable to which all devices are connected
with a terminator at each end.
􀂃 All nodes (file server, workstations, and peripherals) are
connected to the linear cable.
􀂃 Data transmitted through the bus line from one device to
the other
􀂃 Network cannot function when the bus line fails
􀂃 Ethernet and LocalTalk networks use a linear bus topology.
􀂃 The message is transmitted along the cable and is visible
to all computers connected to that cable.

2. Ring
• Each of the systems is connected to its respective
neighbor forming a ring.
• Sometimes called “star-wired network”
• The main difference between the bus and ring is that the
ring topology does not require termination. Because the
systems are connected all together in a loop, there is no
beginning and end point as there is with the bus topology.
• No terminator and no bounce back signal.

3. Star
• All networked devices are connected directly to the
central device (hub) / concentrator
• From central device, all network transmissions are sent
• Data on a star network passes through the hub or
concentrator before continuing to its destination. The hub
or concentrator manages and controls all functions of the
network. It also acts as a repeater for the data flow.

4. A tree (hybrid)
• Can incorporate structures such as ring, star and bus
network in one large network
• It consists of groups of star-configured workstations
connected to a linear bus backbone cable.
• Allow for the expansion of an existing network, and enable
schools to configure a network to meet their needs.

5. Mesh
• Computers have redundant physical connections to one
another
• When the mesh network is a WAN (such as the Internet),
or a LAN that is divided into multiple subnets, routers make
decisions about which of the multiple available paths will
be taken.
• Decide based on which one is the most ‘effective’

2. Logical topology
• how the systems communicate across the physical
topologies
• the way that the signals act on the network media, or the
way that the data passes through the network from one
device to the next without regard to the physical
interconnection of the devices.
• 2 types:

1. Shared media topology

• In a shared media topology, all the systems have the
ability to access the physical layout whenever they need it.
• Advantage : the systems have unrestricted access to the
physical media.
• Disadvantage : Collisions - If two systems send information
out on the wire at the same time, the packets collide and
kill both packets. If add more systems to the network, there
is a greater opportunity for collisions.
• To help reduce the number of collisions, many
networks are broken up into several smaller
networks with the use of switches or hubs, and
each network is then referred to as its own
collision
• Example: Ethernet


2. Token-based topology

• Have a token that travels around the network.
• When a system needs to send out packets, it grabs the
token off of the wire, attaches it to the packets that are
sent, and sends it back out on the wire.
• As the token travels around the network, each system
examines the token.
• When the packets arrive at the destination systems, those
systems copy the information off of the wire and the token
continues its journey until it gets back to the sender.
• When the sender receives the token back, it
pullsthe token off of the wire and sends out a new

empty token to be used by the next machine.
• Advantage : Do not have the same collision problems that
Ethernet-based networks do because of the need to have
possession of the token to communicate.
• Disadvantage : Latency – Because each machine has to
wait until it can use the token, there is often a delay in
when communications actually occur.
• Token-based network are typically configured in physical
ring topology because the token needs to be delivered
back to the originating machine for it to release.
• The ring topology best facilitates this requirement