syjc l5 transmission media

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Transmission Media

The path ways through which individualsystems are connected in a network are

called transmission media. it transferselectronic signals that is binary pulses



Characteristics

Cost of media

Installation Requirement

Bandwidth Band Usage(Baseband & Broadband)

Attenuation

Immunity from electromagnetic interference.



Bandwidth

Bandwidth is the measure of the capacity of amedium to transmit data.

Data transmission rate is number of bitstransmitted per second.

Bandwidth of a cable depends of cable length.

A short cable can have greater bandwidth thanlong cables.



Band usage

There are two transmission modes Base band &Broadband transmission.

Base band devotes the entire capacity of mediato one communication channel . It is used inLAN .

Broadband enables two or more communicationchannels to share the bandwidth ofcommunication media .



Attenuation

Attenuation is a measure of how much a signal weakens as it travel through a media .

As signals pass through the medium part ofsignal is absorbed and makes the signal weak.

Repeaters are used to regenerate signals. If thenetwork is to be extended beyond predefinedcable limit repeater is used.



Immunity from electromagnetic

interference.

Electromagnetic interference consists of outsideelectromagnetic noise that distorts the signal in a

medium. EMI is interfering the signals and makes difficult

for computers to decode the signal.



Guided Transmission Media

Twisted Pair

Coaxial cable

Optical fiber



Twisted Pair



Twisted Pair

Twisted pair cable consists of two wires ofconducting material like copper, insulated fromeach other by plastic.

It consists of two or more strands of copper wire twisted together.

This twisting reduces the sensitivity of the cableto EMI(Electromagnetic interference)

It is divided in two types.



Types of Twisted Pair

1) Shielded Twisted pair(STP):

Cable consists of one or more twisted pairs of cables enclosedin a foil wrap and woven copper shielding. The shield isconnected to the ground portion of the electronic device to

which cable is connected. It has capacity of 500 MBPS. Aproperly grounded shield prevents signals from getting into orout of the cable. Metal braid or sheathing that reduces interference

More expensive

Harder to handle (thick, heavy) Expensive than UTP

Less attenuation & EMI is less.

Used in LAN.



Types of Twisted Pair

1) Unshielded Twisted pair(UTP):

Cable does not have a shield into its structure. Telephone systems uses UTP cables.

Ordinary telephone wire Cheapest

Easiest to install

Disadvantage

Can be used for short distance communication

Typical speed of computer data is 1200 bits/seconds.

Suffers from external EM interference



Twisted Pair

Advantages:

1. Cheap

2. Easy to work with

3. Reduces EMI

Disadvantages:

1. They can be used only for short distance

communication2. The speed of computer data is 1200 bits/second



Optical Fibre

The light wave can be efficiently conducted through transparentglass fiber cables known as optical fiber cable.

The center conductor of this cable is a fiber that consists ofhighly refined glass or plastic.

It is designed to transmit light signals with little loss. Fibre is coated with cladding or gel that reflect signals back into

fibre to reduce signal losses. A plastic sheet protects the fibrefrom damage.

These cables can carry much information at a time.

The fibre optical cables are used for optical transformation. This cable has extremely high bandwidth. It has zero sensitivity to EMI and runs over several kilometers.



Optical Fiber

Advantages:

1] High data transfer capacity 1000 MBPS than100 MBPS of co-axial cable.

2] No sensitivity to EMI .

3] Attenuation is very less .

Disadvantages:-

1] It is very costly.

2] Installation is difficult .



Optical Fiber



Coaxial Cable



Coaxial Cable

In coaxial cable there are two conductor sharing acommon axis.

The coaxial cable components are as follows: 1] A center conductor is a solid copper wire . 2] An outer conductor form a tube surrounding the

inner conductor. This is made up of braided wire ,metallic foil or both . The outer conductor is called asshield .

3] An insulator layer keeps outer conductor spacedevenly from the inner conductor.

4] A plastic jacket protects cable from damage .



Types of co-axial cable

A] Thin net:-

Thin , flexible & inexpensive

B] Thick net :- Thick , hard & expensive .



co-axial cable

Advantage:-

1] It is better shielded than the twisted pair cable. So itcan travel longer distance.

2] shield provide better resistance to EMI .

3] Attenuation is less than twisted pair cable.

Disadvantages: -

1] It is expensive . 2] Bandwidth capacity is less than fiber optic cable.



Wireless media

1] Radio waves

2] Micro waves

3] Infrared & millimeter waves



Network topology is the studyof the arrangement or mapping of the elements (links, nodes,etc.) of a network, especially

the physical (real) and logical(virtual) interconnectionsbetween nodes

Network topology



Basic types of topologies

The arrangement or mapping of the elements of anetwork gives rise to certain basic topologies whichmay then be combined to form more complextopologies (hybrid topologies). The most common ofthese basic types of topologies are

BUS

Star

Ring Mesh



Bus Topology



Bus Topology

The type of network topology in which all of thenodes of the network are connected to a commontransmission medium which has exactly twoendpoints (this is the 'bus', which is also

commonly referred to as the backbone, or trunk) –

all data that is transmitted between nodes in thenetwork is transmitted over this commontransmission medium and is able to be received byall nodes.

It is multipoint , broadcast network.



Bus Topology

Advantages:-1. Easy to intall,requires less cabling.

Disadvantages:-

1. Entire network shuts down if there is a break inthe main cable.2. Terminators are required at both ends of the

backbone cable.3. Difficult to identify the problem if the entire

network shuts down.4. Not meant to be used as a stand-alone solution in

a large building.



Ring Topology



Ring Topology

The type of network topology in which each ofthe nodes of the network is connected to twoother nodes in the network and with the first

and last nodes being connected to each other,forming a ring – all data that is transmittedbetween nodes in the network travels from onenode to the next node in a circular manner and

the data generally flows in a single directiononly.



Ring Topology

Advantages :

1. Easier to Mange than a Bus Network2. Handles high volume of traffic3. Only two connections are required to change if

we want to add or delete a device.Disadvantage:1. If one computer has goes down then network

goes down.2. Message sent to one device , it passes through

all the devices, so takes long time to reach thedestination.

3. Break in the cable can disable the network.



Star Topology



Star Topology

The type of network topology in which each ofthe nodes of the network is connected to acentral node with a point-to-point link in thecentral node being the 'hub‘ or ‘switch’ and thenodes that are attached to the central node .Alldata that is transmitted between nodes in thenetwork is transmitted to this central node, which is usually some type of device that then

retransmits the data to some or all of the othernodes in the network, although the central nodemay also be a simple common connection point.



Star Topology

Advantages:-

Easy to manage .

Easy to locate problems (cable/workstations)

More expensive , requires more hardware. Easy to install.

It is robust i.e if one link fails, only that link getsaffected other links are active.

Disadvantage: If the central HUB fails , the entire network goes

down.



Mesh Topology



Mesh Topology

A network setup where each computer and network device isinterconnected with one another, allowing for mosttransmissions to be distributed, even if one of the connectionsgo down. This topology is not commonly used for mostcomputer networks as it is difficult and expensive to have

redundant connection to every computer. However, thistopology is commonly used for wireless networks. Below is a

visual example of a simple computer setup on a network using amesh topology.

• Every device has dedicated point to point link to every other

device.

• The link carries data between the two devices it connects.•Used for network having large number of nodes .



Mesh Topology Advantages:

1. Data can be transmitted from different devices simultaneously. This topology can withstand high traffic.

2. Even if one of the components fails there is always an alternative

present. So data transfer doesn’t get affected.

3. Expansion and modification in topology can be done without

disrupting other nodes.4. Maintains privacy or security. It provides very fast response time.

Disadvantages:

1. Overall cost of this network is very high as compared to other

network topologies.

2. Set-up and maintenance of this topology is very difficult. Evenadministration of the network is tough.



Hub : It is a central computer used usually in start topology. Messages arepassed from 1 node to another through hubs. It also performs routing of allmessages. Some times it works as switch , which established connectionbetween nodes. Its types are :

Passive Hubs : It doesn’t contain electronic components and nor it does

any processing on data. It just pass es signal from nodes to node. Theyare used in small network where distance between the nodes is small. They are inexpensive and easy to install

Active Hubs: They contain electronic components which amplify theresignals flowing from 1 node to another . As they amplify the signaldistance between the nodes can be increased. They are more costly thanpassive Hubs

Intelligent Hubs: They are advanced sctive hubs. They can supportmultiple communication media(Twisted & Optical),multiple speed andmultiple protocols. They also provide basic bridging and routingtechniques.



A router is the inter network connectivitydevice used to inter connect two or moreindependent networks. Router is a combination

of hard ware and software. The hardware can bea network server , a separate computer or aspecial black box.

Router are used: A) to divide a big network intosmall networks called subnets. B) to connect asmall network to big network like LAN to

WAN.

Router



It expands network length. If the network is tobe used beyond pre defined limit repeater isused. Repeater can be of both types. The first

type is amplifying the entire signal, while thesecond type where repeaters creates an exactduplicate of signal known as signal regenerating

repeaters.

REPEATERS



If computer is used for internet or Emailcommunication then MODEM is required.MODEM is a technique of using a telephoneline for digital communication.

Full form of MODEM is ModulatorDemodulator.

Applications of MODEM: 1) Fax communications

2)Chat communications

3)Email communication 4)Internet browsing

MODEM



These are the set of rules for communication. Aprotocol is a special set of rules that enablecommunication between two computers. The

commonly used protocols are TransmissionControl (TCP/IP), File Transfer Protocol(FTP), and Hypertext Transfer Protocol

(HTTP).The format of packet in a type ofprotocol specifies the following informationsuch as:

Protocols

Header Data Trailer



Header(Start of packet):It specifies source anddestination address.

Message(Data): This part of packet containsactual data or information.

Trailer: In this part of packet, ending

information is transmitted like error checkingand correction information. When this packet istransmitted during the transmission, message

may get damaged or loosed due to seriousreasons, for this purpose this information is sentin the trailer part.



There are different international standard atdifferent levels:

a) TCP/IP(Transmission control protocol andInternet Protocol). B)UDP(User DataProtocols)

ARP(Address Resolution Protocols) ICMP(Internet Control Message Protocols)

Internet Protocol: The Internet protocol was

developed by United States Department ofDefense to interconnect educational instituteand government installations.

TCP/IP Protocols:1) Hardware or physical

A M h d



When more than one node try to use

transmission media it results in collision. Tominimize or avoid collisions there are certainmethods called access methods. There are three

techniques: 1) Contention: Contention means to struggle,

nodes are struggling for accessing media. This is

more useful in LANS. In contention basednetwork each node is observing media beforetransmitting. There are two methods known ascarrier sensing and carrier detecting.

Access Methods



3)Token Passing: As explained in token ringarchitecture it is forming a ring and circulatingtoken known as frame to each node. If node isready at the moment when it has token itoccupies media to transmit or receive. After itpasses token to the next node in the ring.

Access Methods

syjc l5 transmission media

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