DCCN part 2 Data Communication and computer Networks
- 1. Data Communication & Computer Networks Instructor: Attia Irum
- 2. Types of Network • Computer networks are divided into the following types based on the size and physical area or distance covered by the network • Local Area Network (LAN) • Wide Area Network (WAN) • Metropolitan Area Network (MAN)
- 3. Local Area Network (LAN) • Covers a small area. (limited to building or group of adjacent buildings) • Consists of limited number of computers. • Designed to share different resources (such as printers, scanners, storage devices, and application programs) • Examples: • Computer network in laboratory of a college • Network of computers in an office building • Connected using cables or wireless transmission medium and Network Interface Card (NIC). • Fast data transmission rate: from 10 Mbps to 1000 Mbps.
- 4. Local Area Network (LAN)
- 5. Wide Area Network (WAN) • Covers a large area such as different cities of the country or different countries of the world. • Typically, consists of many LANs connected across a wide geographical area. • Example: • An organization has a LAN at each site. • LANs of all sites are connected to WAN. • World’s largest WAN is Internet • Computers and other devices are connected through telephone lines. • Can also be connected through leased lines, microwave, or satellite systems. • Expensive and transmission rate slower.
- 6. WAN
- 7. Metropolitan Area Network (MAN) • Covers an area of a single city or town. • Usually, connects two or more LANs in a city or town. • Larger than LAN and smaller than WAN. • Fiber optic cables are used as communication media. • That’s why, very high speed network. • Examples • Cable TV network in a city. • Mobile phones (cellular) systems. • Internet Service Providers network in a city. • The network connecting different branches of a company in the same city.
- 8. MAN
- 9. Network Topologies • In networking, term topology is the way of connecting computers or nodes on a network • There are many ways in which computers can be connected together in a computer network • Way in which computers or other devices are connected in a network is called network topology • Shortly term network topology refers to the physical layout or shape of network
- 10. Network Topologies • Commonly used network topologies • Bus topology • Star topology • Ring topology • Tree topology • Mesh topology
- 11. Bus Topology • In a Bus topology, all nodes are connected to a common communication medium or central single cable • This central cable is the backbone cable. • This cable is called as Bus • The devices or nodes are connected to the Bus through an interface connector • Both ends of the cable are closed with terminators • A terminator is a special small device that absorbs data signals (or prevents data signals) • It is also known as terminating resistance • Bus topology is suitable for small networks
- 12. Bus Topology
- 13. Bus Topology - Working • When a sending computer wants to send a message, it has to determine whether the media is in use or free • If no other device is transmitting the data, it sends a message to the destination computer • Address of the destination computer is also attached to the message • This message moves from one computer to another through the bus • Each computer connected to the network receives the message, checks the attached address • If the attached message matches with the address of the computer, then it accepts the message • Otherwise, the message moves toward the next computer • When message reaches the destination computer, it accepts the message
- 14. Bus Topology Pros • Very simple network • Easy to install and to maintain • Less expensive because it requires a single cable to connect devices • When nodes are added and removed in the network, network is not affected • If one node fails in the network, other nodes are not affected Cons • Entire network fails if there is any problem with the bus (central cable) • It supports only a small number of nodes. So it is not suitable for a large • network
- 15. Star Topology • In a star network, all nodes are directly connected to a central device, called Hub or Switch • This central device controls all the traffic • Usually, nodes are connected to the Hub with unshielded twisted pair (UTP). • Shape of the Star network looks like a star. • Star topology is most commonly used in LAN • Many home networks use the star topology.
- 16. Star Topology-Working • Computers communicate with each other through a central device i.e. hub • Sending computer sends data to the central device • Central device sends data to the receiving computer • In this way, data is transferred from one computer to another in the Star network
- 17. Star Topology- Advantages • Easy to install and to maintain • Nodes can easily be added or removed without affecting the network • If any node or cable fails then the rest of the network is not affected • It is easy to detect and remove faults in the network • It is suitable for small and large networks
- 18. Star Topology- Disadvantages • This type of network depends upon the central device If this device fails, whole network breaks down • It requires more cables than any other networks. • So it becomes more costly.
- 19. Ring Topology • In a ring topology, each node is connected to next node and last node is connected to first • Thus, shape of the network is formed just like a ring
- 20. Ring Topology - Working • In Ring topology, a token is passed around the network • Computer that has control of the token can transmit data/message • When a computer sends a message to another computer on the network, message flows from one computer to the next computer • Every computer receives a message from previous computer and retransmits it to the next computer until the destination computer receives the message • Destination computer sends an acknowledgment of receiving a message to the sender computer • Sender computer then releases the token back to the network • This method of controlling access to shared network cable is called token passing
- 21. Ring Topology - Advantages • Less expensive to implement • Easy to install and to maintain • All computers have equal access to the network • Every computer regenerates/refreshes the data signal that’s why it can travel over a longer distance
- 22. Ring Topology - Disadvantages • If one node fails (or the ring is broken at any point), the entire network stops functioning • Adding or removing a computer in the network affects the whole network.
- 23. Tree Topology • Tree topology has combined features of both bus and star topologies • Whole network is divided into segments • Each segment represents a Star topology • All segments (i e Star topologies) are combined through central cable or bus • Thus, Bus topology works as the backbone of the Tree network • Tree network looks like a tree structure
- 24. Tree Topology
- 25. Tree Topology - Working • In Tree topology network, usually, multiple hubs are used • Each hub controls the nodes directly connected to it and exchanges data among them • It also exchanges data to other devices connected to the other hubs • Advantages • Can be expanded very easily. • Segments easily managed and maintained. • One segment fails, other segments are not affected. • Easy errors detection and correction.
- 26. Tree Topology • Disadvantages • More expensive (more hubs are required) • Relies on the central cable or bus.
- 27. Mesh Topology • Each node is directly connected to every other node • Involves the concept of routes. • Rarely used in LAN. Mostly used in WANs like Internet. • Working • In Mesh topology, each node can send a message to the destination through multiple paths • It means that each node of the Mesh network has several possible paths to send or to receive a message, but in Bus, Star, and Ring topologies each node has only one path • Data always travels through the best suited path
- 28. Mesh Topology
- 29. Mesh Topology - Advantages • It provides multiple routes If one route is blocked, then another suitable route can be used for data communication • Its performance is not affected by the heavy load of data transmission • It ensures data privacy or security • Troubleshooting of this topology is easy as compared with other networks Disadvantages • It becomes very expensive because a large number of cabling and I/O ports are required • It is difficult to install and configure. • Its maintenance is also difficult.
- 30. Hybrid Topology • A hybrid topology is a type of network topology that uses two or more differing network topologies. • These topologies can include a mix of bus topology, mesh topology, ring topology, star topology, and tree topology. • For Example • A department uses a Bus network, second department uses the ring network, third department uses the Mesh network and fourth department uses the star network. • All networks of different departments can be connected through a central hub.
- 31. Hybrid Topology
- 32. Hybrid Topology Advantages • Flexibility in design • Potentially easier to manage • Potentially easier to add or remove nodes • Suitable for larger networks Disadvantages • Difficult to design and maintain • Costly
- 33. Communication Devices • An electronic device that is used for sending and receiving data between the sending device and receiving device is called a communication device • Most of the communication devices have the ability to convert the digital signal of the computer into an analog signal so that the signals can be transmitted on the communication line to another end • The reverse is also true
- 34. NIC • NIC stands for Network Interface Card • NIC is a communication device that is used to connect a computer to a LAN • It is also called a LAN card • NIC is a circuit board which is installed on the motherboard • A computer must have a network card ( to connect to the LAN • Nowadays, most computer systems have built in network card into the motherboard
- 35. HUB & Switch • Hub and Switch are communication devices • Both provide a central connection point for connecting computers/nodes together in a computer network • Typically, Hub does not manage any of the traffic that comes through it • It broadcast data packets to every computer/node • Only the receiver computer/node accepts the message and other computers/nodes ignore the message • A switch is like a Hub but it is more intelligent than the Hub • It records the addresses of the computers connected to it in a table • It sends a message to the receiver computer/node only
- 36. Modem • Modem stands for modulator & demodulator • It is a commonly used communication device that converts digital signals into analog signals and vice versa • It is used to send and receive data between two computers through the telephone line • Both sending and receiving computers must have modems • Data is stored inside the digital computers in digital form • However, data is transmitted over the telephone line in the form of analog signals
- 37. Modem • The sender computer sends data to the receiving computer as follows • Modulator • Dialup modem of sending a computer converts digital signals into analog signals and sends it to the receiving computer through a telephone line • The process of converting digital signals into analog signals is called modulation • Demodulator • Modem of receiving computer receives data from the telephone line in the form of analog signals. • It converts these signals into digital signals and enters in the computer. • The process of converting the analog signals into digital form is called demodulation
- 39. Router • A router is a communication device that connects multiple computers/devices or other routers together and transmits data to its correct destination on a network • Typically, routers are used to connect two or more different or similar networks and transfers data packets from one network to another • Networks can be LANs or WANs • Router stores addressing information (routing information) of each computer on the connected networks • When a router receives a packet of data, it looks at the address attached with the data packet where the packet of data is to be sent • It determines the best route (path) to forward the data packet at its destination and then sends it accordingly
- 40. Router
- 41. Gateway • A gateway is a communication device (or networking device) • It is used to connect two different types of networks (i e networks that use different protocols) • It is an intelligent device • It translates data from one format to the other • Different networks may have different types of data and of different formats • Gateway receives a data packet from one type of network • It reads the address of the computer on the networks where the data packet is to be sent • It converts the data packet into a format that the destination computer can understand • For example, computers connected to a LAN require a gateway to access the Internet
- 42. Bridge • A bridge is a communication electronic device that is used to connect two similar network segments • A segment is a part of a network • It also controls the data flow between them • When a bridge receives a message, it reads the addresses of both the sender and receiver • If the sender and receiver are in the same network segment, the bridge does not pass the message to the other network segment • The message is directly sent to the receiver • The bridge, therefore, reduces network traffic • So the performance of the network is increased
- 43. Lecture End