Computer Hardware & Networking : (EC) : Chapter 4

                                   NETWORKING TECHNOLOGY

                                                                    by Shivajirao Jadhav , Mumbai

    Marks: 10 (15)

Introduction:

1. Networking is the concept of sharing resources and services. 

2. A network of computers is a group of inter connected systems sharing resources and interacting using a shared communication link. 

3. A network is a set of inter connected systems. The shared resource can be data, a printer, a fax, modem or a service a database or an email system.

Study of transmission lines:

1. The pathways through which individual systems are interconnected in a network are called as transmission media.

2. Transmission media make possible the transmission of electronic signals from one computer to another.

3. Each type of transmission media has special characteristics that make it suitable for specific type of services.

The characteristics of transmission media are-

1. Cost

2. Installation requirement

3. Band width

4. Band usage

5. Attenuation

6. Immunity from electromagnetic interference

Cost: 

1. One major factor in purchase decision of any networking component is cost. 

2. When one tries to opt new technology, it is fastest and it is more expensive. 

3. The Network designer must settle for something which is cheaper and robust.

Installation Requirements: 

1. Some transmission media requires skilled labour to install. 

2. This increases cost of network and it may cause certain delay. 

3. Before installation we need to prepare actual physical layout of network.

Band width: 

1. Band width is a measure of the capacity of a medium to transmit data. 

2. Data transmission rates are bits that can be transmitted per second. 

3. An ethernet LAN can transmit 10 million bits per second and has a band width of 10 megabits per second (Mbps). 

4. Band width of cable also depends on length of cable. A short cable can have greater band width than a long cable. 

Band usage (Base band or Broadband): 

1. There are two transmission modes, base band and broad band transmissions.

2. Base band devotes the entire capacity of the medium to one communication channel.

3. Broad band enables two or more communication channels to share the band width of the communication medium. 

4. Base band is most common mode of operation. Most local area networks (LANS) function in base band mode. 

5. The TV cable coming from antenna or cable provider is a broad band of the cable because each signal is modulated using a separate assigned frequency.

            

Attenuation: 

1. Attenuation is a measure of how much a signal weakens as it travels through a medium. 

2. Attenuation s decides the cable length when signal strength falls below certain limits, then at receiving station noise may appear. 

3. Repeaters are used to regenerate signals.

Electromagnetic Interference (EMI): 

1. Electromagnetic Interference consists of outside electromagnetic noise that distorts the signal in a medium. 

2. Crosstalk is special kind of interference caused by adjacent wires. 

3. Crosstalk occurs when the signal from one wire is picked by another wire. This can, be experienced while talking on phone. 

There are two types of transmission modes, 1. Cable media  2. Wireless media

Cable Media:

There are three types of network cabeling media.

1. Coaxial cable

2. Twisted pair cable

3. Fiber - optic cable

Coaxial cable: 

In this cable there are two conductors sharing a common axis. This cable is shown in figure. 

          

The components of coaxial cable are as follows:

1. A center conductor. This is a solid copper stranded wire. 

2. An outer conductor. This forms a tube surrounding the centre conductor. This onductor is braided wires, metallic foil or both. The outer conductor is called shield. It serves as a ground and protects inner conductor from EMI.

3. An insulator layer. This keeps outer conductor spaced evenly from the inner conductor.

4. A plastic Jacket. This protects cable from damage.

There are two types of coaxial cables:

1. Thin net (Thin, flexible and inexpensive)

2. Thick net (Thick, hard and expensive)

Advantages:

1. It is easy to install and ideal for network connections upto 10 Km.

2. It is robust and difficult to damage

3. Less attenuation

4. Shielding provides better resistance to electromagnetic interference (EMI).

Disadvantages:

1. It more expensive

2. Bandwidth capacity is less

Twisted pair cable: 

This is a popular cable for all new networks. This is a low cost cable. The telephone cable is an example of twisted pair cable. A basic twisted pair cable is shown in figure 

                   

1. It consists of two strands of copper wire twisted together but insulated from each other. 

2. The twisting reduces the sensitivity of the cable to EMI and also reduces the tendency of the cable to radiate radio frequency. 

There are two types of twisted pair cable – 

Shielded twisted - pair (STP) cable and Unshielded twisted - pair (UTP) cable

Shielded twisted - pair (STP) cable: 

1. It consists of one or more twisted pairs of cables enclosed in foil wrap and woven copper shielding. 

2. The shield is connected to the ground portion of the electronic device to which cable is connected. 

3. Ground portion is electrical reference point. A properly grounded shield prevents signals from getting into or out of the cable. 

                                    

Unshielded twisted - pair (UTP) cable: 

1. This cable does not have a braided shield into its structure. 

2. The characteristics of UTP are similar to STP. Only difference is in attenuation and EMI. 

3. Telephone systems commonly use UTP cable. 

4. In some networks UTP cable is used. Now use of UTP in LAN is increasing. 

5. UTP cable is available in 5 grades or categories.

           

     

Comparison between UTP and STP:

UTP cable	STP Cable
It consists of a number of twisted pairs with plastic jacket	It also consists of number of pairs but shell usually aluminium or polyester between jacket and pairs.
Inexpensive and easy to install	Expensive than UTP and difficult to install.
Bandwidth capacity is from 1 to 100 Mbps upto 100 meters.	It is 155 Mbps upto 100 meters.
More attenuation and sensitive to EMI.	Less attenuation and EMI.
Used in telephone system.	STP is used in LAN
Maximum number of nodes 1024.	Maximum number of nodes is 270.

Comparison between twisted pair cable and coaxial cable:

Twisted pair cable	Coaxial cable
It consists of pair of wires or more pairs  of two twisted copper wires	It is cable with solid copper at centre of cable
It is inexpensive medium	It is less expensive medium
Attenuation is more	Attenuation is less
Bandwidth capacity is from 1 to 100 Mbps	Bandwidth is upto 500Mbps
It can be used only for short distance communication	It is used in network

Fiber optic cable:

1. In every way, fiber optic cable is ideal cable for data transmission. 

2. This cable has extremely high bandwidth. 

3. It has no problem with EMI and cable runs over several kilometers. 

4. The two disadvantages are cost and installation difficult. 

5. Now a days, it is often installed into buildings by telephone companies. 

                               

6. The center conductor of fiber optic cable is a fiber that consists of highly refined glass or plastic. 

7. It is designed to transmit light signals with little loss. 

8. The fiber is coated with cladding or a gel that reflects signals back into fiber to reduce signal loss. 

9. A plastic sheath protects the fiber from damage. 

The characteristics/advantages of fiber optic cable:

1. Cost: It is expensive as compared to coaxial and twisted pair cable.

2. Installation: It requires greater skill for installation. It gets damaged if bended sharply. The cable cannot be stretched.

3. Capacity: It supports high data rates (upto 200000 Mbps) even with long run cable.

4. Attenuation: It is much less than copper cables.

5. EMI: As fiber optic cable does not use electric signals to transmit data, therefore they are free from EMI.

Comparison between coaxial cable and fiber optic cable:

Coaxial cable	Fiber optic cable
Low cost	Expensive
Installation is cheap and easy	It requires skilled installation, hence costly
Sensitive to EMI	Not sensitive to EMI
Attenuation is more	Attenuation is less

Unbounded or wireless media:

Radio waves:

1. Radio waves are easy to generate. They can travel long distance and can penetrate buildings easily. Hence, radio waves are widely used for both indoor and outdoor purposes.

2. Radio waves travel in all directions in the free space so that there is no need to place the receiver or transmitter along a direct line of sight.

3. As radio waves covers large distance, interference between users is a problem. For this reason government license is necessary to transmit radio waves.

4. Radio communication having major drawback that it may be disturbed by rains, bounces back from obstacles. It offers low bandwidth for data communication.  

Microwaves:

1. Microwaves travels in straight line. For microwaves transmitting and receiving antennas should be accurately align. 

2. Since, microwaves travel in straight lines, for longer distances periodic repeaters are necessary.

3. Unlike radio waves, microwaves can not penetrate buildings.

Infrared and millimeter waves:

1. These waves are widely used for short range communication.

2. The remote control used in television, V.C.Rs. etc. all used infrared communication.

3. They are relatively directional, cheap and easy to generate. 

4. Major drawback of these waves is that they can not pass through solid objects.

5. Infrared system does not interfere other infrared system operating in adjacent room. So no government license is necessary.

Network Types and Topologies:

Computer Networks:

Computer network is an interconnected collection of system of computers capable of sharing resources and services. 

 The main advantages of computer network:

1. Network provides resource sharing.

2. It provides exchange of information and software.

3. It provides high reliability by using other machine if one machine fails in the network like military banking, air and traffic control.

4. Access to any file or data.

5. Finally the system is saving money by network only.

Types of networks:

    1. WAN. 2. MAN 3. LAN

Wide Area Network (WAN):

1. Large networks such as those that cover a complete country or state are called as ‘Wide

Area Networks'. e.g long distance telephone systems. 

2. These networks use cables of various types for their interconnection.  In many systems cases, radio links using microwave relay stations or satellite are used. 

3. Along with voice communication, data communication is also possible in telephone networks if modems are used. 

Metropolitan Area Network (MAN):

1. A medium-sized network is called as ‘Metropolitan Area Network’ 

2. eg a local cable TV company picks up programs from a satellite and rebroadcasts them via a system of coaxial cables to subscribers.

3. Here each home is node and communication is only one way.

Local Area Network (LAN):

1. Smaller networks are called 'Local Area Networks'.  Most LANS have 10 to 100 connections. In LAN, the nodes or users are usually computers or terminals. 

2. Many PC users can time share the system. Users can share expensive peripherals such as printers, hard disks and modems. 

3. One computer in network is set up as controller. Such unit is called server. LAN also permits software and data sharing.

4. LANs permit users to talk with one another directly or through mail. LANs can inter connected to other systems. 

Access methods of networking:

An access method is a set of rules governing how network nodes shares the transmission medium. There are three types of access methods.

1. Contention: It means that the computers are contending for use of transmission medium. In contention, any computer in network can transmit at at any time (first come first served)

2. Polling: In polling base system, there is a device called controller to poll other device on network to see whether they are ready to transmit or receive data.

3. Token passing: It utilizes a frame called a token, which circulates the network. A computer that needs to transmit must wait until it receives the token. When computer receives token, it is permitted to transmit. When computing completes transmitting, it passes the token to next station. 

Network Topologies:

A topology defines the arrangement of nodes, cables and connectivity d devices that make up the network. There are two categories -

1. Physical topology

2. Logical topology

Physical topology describes actual layout of the network transmission media. It defines the way the network looks.

Logical topology describes the logical pathway a sign follows as it passes among the network nodes. It defines the data passes among the nodes.

Physical and Logical topologies can take several forms.

The most common are:

1. Bus topologies

2. Ring topologies

3. STAR topologies

4. Mesh topology

BUS topologies: 

1. In A bus physical topology, all devices are connected to a common, shared cable. This shared cable is called backbone of network. A bus physical topology is shown in figure.

                        

2. The bus topology is suited for networks that use contention - based access method. Most bus networks broadcast sign in both directions on the backbone cable. 

3. This enables all devices to receive signals directly. Some buses are unidirectional and signals travel only in one direction and can reach only down stream devices. 

4. A terminator is placed at end to prevent signals from reflecting back.

Advantages:

1. The bus system is much faster.

2. The bus topology can be extended with sub branches to form another topology.

3. Breakdown of any failure node does not affect other node’s communication

4. Bus topology is widely used in LAN network. 

Ring topology: 

1. Ring topologies are wired in a circle. Each node is connected to its neighbor on either side, and data passes around the ring in one direction only. It is shown in figure.

2. Each device incorporates a receiver and transmitter and serves as a repeater that passes the signal onto the next device in the ring.

3. Ring topologies are suited for token passing access methods. The token passes around the ring, and the only node that hold the token can transmit data.

4. Ring physical topologies are rare. This topology is always implemented as a logical topology.

                             

Advantages:

1. Cable failure affects limited users.

2. Each node has equal access speed to ring.

3. Equal access for all users.

Disadvantages:

1. Costly wiring is required.

2. Expensive adapter cards.

3. Difficult connections.

Star topologies: 

1. In star topologies all devices are connected to a central hub. This is shown in figure.

                                      

2. The hub receives signals from other network devices and routes the signals to the proper destination. 

Mesh topology:

1. A mesh topology is a hybrid model. It incorporates all topologies. Mesh topology is shown in figure.

                  

2. In mesh, every device is connected to every other device. This increases fault tolerance but involves extra work. 

3. If media break, data transfer can take alternative routes, Cabeling is complicate here.

Network architectures:

1. Ethernet: It is local area network technology. It is used in single building. Ethernet devices can have a few hundred meters of cable between them. Ethernet network transmit data in small units called frames. Each frame contains source address as well as destination address, which identifies recipient and sender of message.

2. Token ring network: It was originally developed by IBM. Token ring uses token passing architecture. The topology is STAR..Each token ring network device is connected to central concentrator, called multistation access unit. Token passing networks moves a small frame called token around the network.

Protocols:

1. A protocol can be defined as a standard set of rules to be followed by all computers wanting to talk to each other. 

2. Therefore, different types of computers running different types of the data operating systems can communicate easily. 

3.  Protocols that use connectionless delivery place of data on network and assume it easily will get through. 

4. These are more fast but unreliable. Connection-oriented protocols are more reliable and slower. 

Types of protocols:

TCP/IP (Transmission Control Protocol/Internet Protocol) Protocol: This is the protocol used by Internet. TCP/IP includes the specifications that identify individual computers and that enable computers to exchange data. They also include rules for several categories of application programs so programs that run on different kinds of computers can talk to one another.  For example, someone using that a Macintosh computer can exchange data with a UNIX computer on Internet.

 Internet protocol: IP is connectionless protocol. It is fast but unreliable. It provides source and destination addressing and routing.

Transmission Control Protocol: TCP is connection-oriented, so it provides more reliable delivery. TCP is responsible for message fragmentation and reassembly. It uses a sequencing function to ensure that the packets are reassembled in correct order.

Hyper Text Transfer Protocol (HTTP): This is a protocol that World Wide Web clients and servers use to communicate. A hypertext document is a specially encoded file that uses HTML. This language allows a documents author to embed hypertext links (hyperlinks) in the document. HTTP and hyperlinks are the foundations of the WWW.

Introduction to Connectivity Devices: 

Modem:

1. Computers store digital data, while telephone lines can only transfer analog data. If a computer is to be connected to internet through telephone, then it must convert digit data to analog data before transmitting the computer signals.

2. Converting one signal form to another form is called modulation and reconverting it to original form is called as demodulation.

3. Modem is modulator/demodulator. Modem is used to connect computer to internet.

4. Modems convert digital data to analog data and vice-a-versa.

5. They have two advantages:

(i) Modem allows higher speed of transmission on any given analog line.

(ii)  Modem reduces effect of noise and distortion.

6. Modems a are classified into two categories according to transmission method:

Asynchronous modems

Synchronous modems

Hubs:

1. Hubs are devices commonly used to connect segments of a LAN. 

2. The hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets

3. Hub is a connecting device in which cables can be connected without soldering wires.

4.  It manages the cabling in the network and sends signal to the other components of the network.

5. Hubs are of three types:

(i) Active hub (ii) Passive hub (iii) Switching hub

The active hub interconnects network and also amplifies the signal received apart from splitting and retransmitting it to the destination. This hub contains electronic circuits.

Passive hub only splits and transmits signals received and it can not amplify it. This do not contain any electronic component.

Switching hub are quickly routes the signals between ports of hubs. It can be used in place of router.

. 

Repeater:

1. A repeater is a hardware device used to extend range of network cabling.

2. A repeater reshapes and amplifies the signal from one port to another.

3. A backbone cable runs vertical up in the building and a repeater is used to attach an Ethernet segment running in each floor of the office to the backbone cable.

4. It simply regenerates the signal.

5. This device is inexpensive and simple. .

6. Separate power supply is needed for repeaters.

               

Routers:

1. Routers are internetwork connectivity devices. A router is a networking device that forwards data packets between computer networks. 

                         

2. The most familiar type of routers are home and small office routers that simply pass IP packets between the home computers and the Internet. 

3. Broadcast routers can be used to connect two different computers or to connect two computers to the Internet.

4. Wireless routers connect to your modem and create a wireless signal in your home or office. So, any computer within range can connect to your wireless router and use your broadband Internet for free. The only way to keep anyone from connecting to your system is to secure your router.

5. Routers can also be used to divide large, busy LANs into smaller segments.

6. Routers are also employed to connect LAN to wide area network (WAN).

7. Routers are of two types – 1. Static routers 2. Dynamic routers 

Questions

Marks wise Questions: 1M(2), 3M(1), 4M(1), 6M(1)

1. Fill in the blanks with given alternatives.

1. --------- cable is ideal for connecting between two buildings.

(i) UTP (ii) STP (iii) Coaxial (iv) Fiber optic

2. The transmission rate of fiber optic cable is ----------.

(i) 10Mbps (ii) 25Mbps (iii) 100Mbps (iv) 500Mbps

3.  --------converts digital data to analog form and vice a versa.

(i) Modem (ii) Repeater (iii0 Router (iv) Hub

4. In ------- topologies all devices are connected to a central point of server or hub.

(i) Bus (ii) Star (iii) Ring (iv) Mesh

5. A -------- is a hardware device used to extend range of network cabling. OR

6. If the network is to extended beyond cable limit ------ is used.

(i) Modem (ii) Repeater (iii) Router (iv) Modem

7. A standard set of rules to be followed by all computers to be connected in network is called as ---------.

(i) Interface (ii) Protocol (iii) Topology (iv) Network

8. ---------- cable has highest sensitivity to electromagnetic interference (EMI)

(i) STP (ii) UTP (iii) Coaxial (iv) Fiber optic

9. --------- cable is ideal for network connections at 10 Km.

(i) Coaxial (ii0 STP (iii) STP (iv) Fiber optic

10. Cell phone/mobile phone uses ------- transmission technology.

(i) Radio (ii) Microwave (iii) Satellite

11. ------only splits and transmits signals received and it can not amplify/regenerate it.

(i) Active hub (ii) Passive hub (iii) Switching hub

12. -------- cable is difficult to install but provides high quality transmission.

(i) Coaxial (ii) UTP (iii) STP (iv) Fiber optic

13. In ------- topology all devices are connected to common line.

(i) Bus (ii) Star (iii) Ring (iv) Mesh

14. In ------ topology, every device is connected to every other device

(i) Bus (ii) Star (iii) Ring (iv) Mesh

2. Match the following.

1. A B

(a) Coaxial cable (i)  Wireless signal

(b) Twisted pair cable (ii) Single stand of copper

(c) Fiber optic cable (iii) Many pairs of copper conductors

(d) Microwave (iv) Light signal

2. A B

(a) WAN (i) Small size network

(b) MAN (ii) Large size network/telephone system

(a) LAN (iii) Medium size network/cable TV

3 A B

(a) BUS topology (i) Every device is connected to every other device

(b) STAR topology (ii) Common cable/line

(c) RING topology (iii) Central hub

(d) MESH topology (iv) Every device is connected to its neighbor

4. A B

(a) MODEM (i) Internetwork connectivity

(b) HUB (ii) Extension of cable network

(c) Repeater (iii) Modulation/demodulation

(d) Router (iv) LAN

3. Answer the following.

1. What is transmission media? List the characteristics of transmission media.

2. Explain cost and installation requirement of transmission media.

3. Explain band width and band usage of transmission media.

4. Explain attenuation and electromagnetic interference of transmission media.

5. Explain coaxial cable in detail.

6. Write a note on twisted pair cable.

7. What are the types of twisted pair cable?

8. Write a note on shielded twisted pair cable and unshielded twisted pair cable.

9. Differentiate between shielded twisted pair cable and unshielded twisted pair cable.

10. Differentiate between twisted pair cable and coaxial cable.

11. Explain fiber optic cable. Write its construction with diagram.

12. Write characteristics of fiber optic cable.

13. Compare fiber optic cable with coaxial cable.

14. What are different wireless media? Explain each. 

15. What is computer network? State its advantages.

16. Name the different computer networks. Explain in detail.

17. What is topology? Differentiate between physical and logical topology.

18. Explain BUS topology with diagram. 

19. Explain RING topology with diagram. 

20. Explain STAR topology with diagram. 

21. Explain RING topology with diagram. 

22. What is protocol? List its types.

23. What is modem? Explain it.

24. Explain hubs with diagram.

25. What is use of repeater in networking? Explain with diagram.

26. Write a short note on router.