Data communication and computer networking

1 CHAPTER-4 DATA COMMUNICATION AND COMPUTER NETWORKING By Kenbon.A

2 CONTENTS Definition Modes of Data Communication Transmission Media Computer Networking Types of Networks

3 Data Communication Communication is the process of sharing a message. Data communications refers to the sharing of a virtual message. Electronic communications, like emails and instant messages, as well as phone calls are examples of data communications.

4 For data communication to be effective, the following three fundamental characteristics should be considered. a. Delivery: The system must deliver data to the correct of the intended destination. b. Accuracy: The system must deliver data accurately (error free) c. Timeliness: The system must deliver data in a timely manner without enough time lags.

5 Elements of Data Communication There are five basic components in data communication system: A. Message: It is the information that is to be communicated. B. Sender: The sender is the device that sends the message C. Receiver: The receiver is device that receives the message D. Medium: The transmission medium is the physical path that communicates the message from sender to receiver.

6 E. Protocol: Protocol refers to a set of rules that coordinates or governs the exchange of information. • Both the sender and receiver should follow the same protocol to communicate data. • Without the protocol, the sender and receiver cannot communicate with each other.

7 Modes of Data Communication The manner in which data is transmitted from one location to another location is called data transmission mode. There are three ways or modes for transmitting data from one location to another. These are:- I. Simplex II. Half duplex III.Full duplex

8 I. Simplex Mode: - In this transmission signals (information) are transmitted in only one direction: One station is sender and the other is receiver. • Television Transmission can be considered as an example of simplex mode of transmission where the satellite only transmits the data to the television, vice versa is not possible.

9 II. Half Duplex: - In half duplex mode, data can be transmitted in both directions but only in one direction at a time. • During any transmission, one is the transmitter and the other is receiver. • The most common example of half-duplex transmission is the wireless handsets (generally used by military personnel) where one user talks at a time and another listens.

10 III.Full Duplex: - In this transmission signals transmitted in both direction, both stations may transmit simultaneously. The medium carries signals in both directions at the same time. It can be compared to a two way road with traffic flowing in both directions. A common example of full duplex transmitting mode is the Telephone network, where two people communicate over a telephone line; both can talk as well as listen at the same time.

11 Data transmission Data transmission refers to the movement of data in form of bits between two or more digital devices. When we enter data into the computer via keyboard, each keyed element is encoded by the electronics within the keyboard into an equivalent binary coded pattern, using one of the standard coding schemes that are used for the interchange of information.

12 Transmission Media The transmission media are media through which data is transferred. Transmission media can be defined as physical path between transmitter and receiver in a data transmission system.

Classes of transmission media 1. Guided Media Guided transmission Media use a cabling system that guide the data signals along a specific path. Cabling refers to transmission medium that consists of cable of various metals like Copper, Tin or Silver. Some of the guided transmission media are twisted pair cable, coaxial cable, and optical fiber cables. I. Twisted pair Cable: Pairs of wires are twisted together which are surrounded by an insulating material and an outer layer called jacket and they are available in two forms: Unshielded and Shielded. 13

14 Shielded Twisted Pair (STP) Cable Twisted pair network cables are often shielded in an attempt to prevent electromagnetic interference. This type of shielding protects cable from external electromagnetic interference (EMI) entering or exiting the cable and also protects neighboring pairs from crosstalk.

15 Advantages of Shielded Twisted Pair Cable ✓ Easy to install ✓ Performance is adequate ✓ Can be used for Analog or Digital transmission ✓ Higher capacity than unshielded twisted pair ✓ Eliminates crosstalk Disadvantages of Shielded Twisted Pair Cable ✓ Difficult to manufacture ✓ Heavy

16 Unshielded Twisted Pair (STP) Cable It is the most common type of telecommunication when compared with Shielded Twisted Pair Cable which consists of two conductors usually copper, each with its own color plastic insulator UTP cables consist of 2 or 4 pairs of twisted cable. Most UTP cable uses RJ45 connectors, which look like telephone connectors (RJ11) but have eight wires instead of four.

17 Advantages of Unshielded Twisted Pair Cable Installation is easy ✓ Flexible ✓ Cheap ✓ It has high speed capacity Disadvantages of Unshielded Twisted Pair Cable ✓ Bandwidth is low when compared with Coaxial Cable ✓ Provides less protection from interference

18 Coaxial Cable  Coaxial cable is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield. The inner conductor and the outer shield share a geometric axis. Many coaxial cables have an insulating outer sheath or jacket. Its applications include feedlines connecting radio transmitters and receivers with their antennas, computer network connections, digital audio, and distributing cable television signals.

19 Advantages of Coaxial Cable ✓ Bandwidth is high ✓ Used in long distance telephone lines. ✓ Transmits digital signals at a very high rate of 10Mbps. ✓ Much higher noise immunity Disadvantages of Coaxial Cable ✓ Single cable failure can fail the entire network. ✓ Difficult to install and expensive when compared with twisted pair.

20 Optical Fiber Cable Optical fiber cabling is an excellent transmission medium for its high data capacity and supported long distances. It has a fiber/glass core within a rubber outer coating and uses beams of light rather than electrical signals to relay data. Because light doesn't diminish over distance.

21 Advantages of Fibre Optic Cable ✓ Higher bandwidth ✓ Less signal attenuation ✓ Immunity to electromagnetic interference ✓ Resistance to corrosive materials ✓ Light weight ✓ Greater immunity to tapping  Disadvantages of Fibre Optic ✓ Installation and maintenance ✓ Unidirectional light propagation ✓ High Cost

22 2. Unguided Media Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Unguided media include radio, microwaves, infrared and lasers through the air.

23 COMPUTER NETWORKING Computer networking is defined as the interconnection of computers and other communication equipment’s connected by a communication channel. The communication channel (medium) will be either wired communication channel or wireless communication channel. Wired communication channel includes the different cable types like twisted pair cable, co-axial cable or fiber optic cable and Wireless communication channel includes microwave or satellite communication system.

24 Importance of Computer Networking The two major benefits of computer networking include: Computer networks are used for resource sharing and Computer networks are used as a communication medium  Resource sharing • A computer network is a collection of computers and other devices that communicate to share data, hardware, and software. • the importance of computer networking as a resource sharing includes:

25 Data /Information Sharing: - This involves access to remote or distributed database and files containing data, text, image or video. Program/software Sharing: - Programs stored on a central server can simultaneously be accessed and loaded for execution on several local computers. Device / hardware Sharing:- Computer networks enable us to share expensive hard wares (or peripheral devices). This includes access to computing resources such as other computers, printers, scanners etc.

26  Communication medium •Uses of computers as a communication medium includes: Electronic mail (e-mail) Video conferencing

27 Types of Networks Networks are commonly classified by ownership as: 1. Private Networks 2. Public Networks • Private Network: Private network is the type of network which is built by an organization for its exclusive use. Example the network in BHU campus is a private network. • Public Network: is established and operated by a network service provider (NSP)for the specific purpose of providing services to customer organizations and individuals.

28 Example: ETC (Ethiopian Telecommunications Corporation) Safaricom According to their geographical range networks are classified in to three i.e. Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN)

29 A. Local Area Network (LAN) LAN is the interconnection of computers and other peripheral devices with in a limited geographical area. For example, the network of computers with in the University campus, a school, a factory or an office. The connection is usually made through a cable. B. Metropolitan Area Network (MAN)  MAN is the interconnection of LANs within a city wide geographical area.

30 C. Wide Area Network (WAN) • WAN can cover large geographical area by using one or more communication channels such as: Telephone lines Fiber optic cables Microwave and satellite communication systems • WANs span large areas such as countries or the entire world

31 Network Topologies A Network topology is the layout or arrangement of computers in a network. The most common network topologies are: Bus topology Ring topology Star topology Mesh topology Tree topology

32 Bus Topology Bus topology is a network type in which every computer and network device is connected to single cable. It transmits the data from one end to another in single direction. No bi-directional feature is in bus topology.

33 Advantages of the Bus Network Easy to install and maintain. It is cheaper because it requires less wiring. It is comfortable for a small and temporary network. Easy to add a computer to the network. Internet and electricity cables can go together. Disadvantages of the Bus Network It is known as passive topology because computers do not regenerate the signal. Lose signal over distance (you can use repeaters). Its main drawback is that if the cable breaks at some point, the network is entirely inoperative. The speed in this network connection is deficient. Equipment limit depending on the signal quality. Performance decreases as the network grows.

34 Star Topology In star topology, all the devices are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node. The hub can be passive in nature i.e. not intelligent hub such as broadcasting devices, at the same time the hub can be intelligent known as active hubs. Active hubs have repeaters in them.

36 Advantages of Star Topology It is very reliable – if one cable or device fails then all the others will still work It is high-performing as no data collisions can occur Less expensive because each device only need one I/O port and wishes to be connected with hub with one link. Easier to put in Robust in nature Easy fault detection because the link are often easily identified. No disruptions to the network when connecting or removing devices. Each device requires just one port i.e. to attach to the hub. If N devices are connected to every other in star, then the amount of cables required to attach them is N. So, it’s easy to line up.

37 Disadvantages of Star Topology Requires more cable than a linear bus . If the connecting network device (network switch) fails, nodes attached are disabled and can’t participate in network communication. More expensive than linear bus topology due to the value of the connecting devices (network switches) If hub goes down everything goes down, none of the devices can work without hub. Hub requires more resources and regular maintenance because it’s the central system of star . Extra hardware is required (hubs or switches) which adds to cost Performance is predicated on the one concentrator i.e. hub.

38 Ring Topology In this topology, it forms a ring connecting a device with its exactly two neighboring devices. The following operations takes place in ring topology are:  One station is known as monitor station which takes all the responsibility to perform the operations.  To transmit the data, station has to hold the token. After the transmission is done, the token is to be released for other stations to use.  When no station is transmitting the data, then the token will circulate in the ring.

40 Advantages of ring topology It provides alternative round Cheap to install and extend Easy to reconfigure Each computer has equal access to resources Additional components do not affect the performance of a network There is no need for a network server to control the connectivity between workstations Performance is better than that of bus topology It is less costly than a star topology Data transmission is high speed Traffic is unidirectional In comparison with bus, ring, a tree is better than handling load Adding or removing of a network node is easy, as the process requires changing only two connections Good communication over long distance Handle high volume traffic Fault identification is easy No data collision

41 Disadvantages of ring topology A ring is not very scalable Troubleshooting is difficult Adding or deleting the computer disturb the network activity Failure of one computer the whole network Unique wiring require More complex networking and operational protocol A network is highly dependent on the wire which connects different component This topology is ordered for all computer to communicate with each other, all computers must be turned on Total dependence upon the one cable Data packets must pass through every computer between the sender and also a recipient side, therefore, this makes it slower If any of the nodes is fail then the ring is broken or fail and data cannot be transmitted successfully

42 Tree Topology Tree topology is the combination of the bus and the star topology. Tree topology allows users to have many servers on the network. Tree topology follows a hierarchical pattern whereby each level is connected to the next higher level in a symmetrical pattern. It connects multiple star topologies to another star topology network. Tree topology is the best when the network is large and not for a small network because it is a waste of cables to use it.

44 Advantages of Tree Topology : This topology is the combination of bus and star topology. This topology provides a hierarchical as well as central data arrangement of the nodes. As the leaf nodes can add one or more nodes in the hierarchical chain, this topology provides high scalability. The other nodes in a network are not affected if one of their nodes gets damaged or does not work. Tree topology provides easy maintenance and easy fault identification can be done. A callable topology. Leaf nodes can hold more nodes. Supported by several hardware and software vendors. Point-to-point wiring for individual segments. Tree Topology is highly secure. It is used in WAN. Tree Topology is reliable.

45 Disadvantages of Tree Topology This network is very difficult to configure as compared to the other network topologies. The length of a segment is limited & the limit of the segment depends on the type of cabling used. Due to the presence of a large number of nodes, the network performance of tree topology becomes a bit slow. Requires a large number of cables compared to star and ring topology. As the data needs to travel from the central cable this creates dense network traffic. The Backbone appears as the failure point of the entire segment of the network. Treatment of the topology is pretty complex. The establishment cost increases as well. If the bulk of nodes is added to this network, then the maintenance will become complicated.

46 Mesh Topology In mesh topology, every device is connected to another device via particular channel. Every device is connected with another via dedicated channels. These channels are known as links:  If suppose, N number of devices are connected with each other in mesh topology, then total number of ports that is required by each device is N-1.  If suppose, N number of devices are connected with each other in mesh topology, then total number of dedicated links required to connect them is N(N-1)/2.

48 Advantages of Mesh Topology Failure during a single device won’t break the network. There is no traffic problem as there is a dedicated point to point links for every computer. Fault identification is straightforward. This topology provides multiple paths to succeed in the destination and tons of redundancy. It provides high privacy and security. Data transmission is more consistent because failure doesn’t disrupt its processes. Adding new devices won’t disrupt data transmissions. This topology has robust features to beat any situation. A mesh doesn’t have a centralized authority.

49 Disadvantages of Mesh Topology It’s costly as compared to the other network topologies. Installation is extremely difficult in the mesh. Power requirement is higher as all the nodes will need to remain active all the time and share the load. Complex process. The cost to implement mesh is above other selections. There is a high risk of redundant connections. Each node requires a further utility cost to think about. Maintenance needs are challenging with a mesh.

50 Hybrid Topology • A network structure whose design contains more than one topology is said to be hybrid topology. • Hybrid topology inherits merits and demerits of all the incorporating topologies.

52 What is HTTP? HTTP stands for HyperText Transfer Protocol and is the foundation of the World Wide Web. HTTP is used when browsers want to get connected to websites. They communicate by sending HTTP requests and receiving HTTP responses.

53 World Wide Web (WWW) WWW can be defined as the collection of different websites around the world, containing different information shared via local servers(or computers). The World Wide Web is based on several different technologies: Web browsers, Hypertext Markup Language (HTML) and Hypertext Transfer Protocol (HTTP).

54 URL Also known as an internet address or web address, a URL (Uniform Resource Locator) is a URI and standardized naming convention for addressing documents accessible over the Internet and Intranet. The URL makes it possible for a computer to locate and open a web page on a different computer on the Internet. An example of a URL is https://www.computerhope.com.

55 Internet The Internet is a network built by the cooperative connectivity of millions of computers that are linked together. The Internet is made up of: People: The network is used and developed by people. Resources: A group of resources that can be accessed through those networks. A setup for collaboration: It is a collaborative arrangement that comprises members of the research and education committees from all around the world.

56 Intranet An intranet is a private network that only employees of a company may access. It's the most restrictive of the three networks. Intranets differ from the Internet in that private servers are not accessible to the general public.

57 Extranet An extranet is a type of network that allows external users to access an organization's intranet. An extranet is similar to an intranet, except that it is accessed through a Web portal. An intranet is a private network that is only available to members of the same group, corporation, or organization. Extranets are quickly becoming a popular way for business partners to securely communicate information.

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