Computer network
- 1. Introduction to Computer Networks
- 2. Basic concept of Computer networks and Goals of networking ❖Computer network history: 18th Centuries • watt's Steam Engine. • Optical Telegraph. • The Lightning Rod. 19th Centuries • Telephone - 1876 • Electric Battery – 1800 • .Camera – 1888 • Typewriter – 1867 • Telegraph – 1837 20th Centuries • Radio • Television • The Personal Computer • Information Gathering • Processing and Distribution 21st Centuries • Satellites • Fiber Optics
- 3. • Internet ARPANET ARPANET - Advanced Research projects Agency Network ARPANET was first network which consisted of distributed control. It was first to implement TCP/IP protocols. It was basically beginning of Internet with use of these technologies. It was designed with a basic idea in mind that was to communicate with scientific users among an institute or university. History of ARPANET : ARPANET was introduced in the year 1969 by Advanced Research Projects Agency (ARPA) of US Department of Defense. It was established using a bunch of PCs at various colleges and sharing of information and messages was done. It was for playing as long separation diversions and individuals were
- 4. asked to share their perspectives. In the year 1980, ARPANET was handed over to different military network, Defense Data Network. Characteristics of ARPANET : ✓ It is basically a type of WAN. ✓ It used concept of Packet Switching Network. ✓ It used Interface Message Processors(IMPs) for sub-netting. ✓ ARPANETs software was split into two parts- a host and a subnet. Advantages of ARPANET : ❖ ARPANET was designed to service even in a Nuclear Attack. ❖ It was used for collaborations through E-mails. ❖ It created an advancement in transfer of important files and data of defense. Limitations of ARPANET : ❖ Increased number of LAN connections resulted in difficulty handling. ❖ It was unable to cope-up with advancement in technology. Computer Network: A computer network is defined as the interconnection of two or more computers. It is done to enable the computers to communicate and share available resources. Goals of Computer Network The following are some important goals of computer networks:
- 5. Resource Sharing – Many organization has a substantial number of computers in operations, which are located apart. Ex. A group of office workers can share a common printer, fax, modem, scanner, etc. High Reliability – If there are alternate sources of supply, all files could be replicated on two or more machines. If one of them is not available, due to hardware failure, the other copies could be used. Inter-process Communication – Network through the network. In order to permit this, the network must provide almost error-free communications. Flexible access – Files can be accessed from any computer in the network. The project can be begun on one computer and finished on another. Other goals include Distribution of processing functions, Centralized management, and allocation of network resources, Compatibility of dissimilar equipment and software, Good network performance, Scalability,
- 6. Saving money, Access to remote information, Person to person communication, etc. users, located geographically apart, may converse in an interactive session Application of Computer network ✓Business Application ✓Communication Medium ✓E-Commerce ✓Home application ✓Electronic commerce ✓Mobile users Network hardware & software There are three component of computer network 1. Hardware equipment 2. Software 3. Cables & connectors Hardware: NIC, Server, Client, Peers, Transmission, Medium, Router, Bridge, Hub, Switches, Gateway, Repeaters Software: Network Operating System, Protocols Switches (TCP/IP, OSI Cables and Connectors: twisted pair cable, coxial cable, fiber- optic cable
- 7. Classification of Computer Network COMPUTER NETWORK TYPES: • PAN (personal area network) – up to 10 meter distance • LAN (local area network) – upto 1 kilometer distance • MAN (metropolitan area network) • WAN ( wide area network) Personal Area Network (PAN) It is an interconnection of personal technology devices to communicate over a short distance, which is less than 33 feet or 10 meters or within the range of an individual person, typically using some form of wireless technologies. Thomas Zimmerman was the first research scientist to bring the idea of the personal area network Pan includes mobile devices,tablet,and laptop Some of these technologies are: Bluetooth technology: The idea behind Bluetooth is to embed a low cost transceiver chip in each device, making it possible for wireless devices to be totally synchronized without the user having to initiate any operation. The chips would communicate over a previously unused radio frequency at up to 2 Mbps. The overall goal of Bluetooth might be stated as enabling ubiquitous connectivity between personal technology devices without the use of cabling as written in Mckeown (2003a).
- 8. High rate W-PANs: As per standard IEEE 802.15 TG3, launched in 2003, these technologies use higher power devices (8 dBm) than regular Bluetooth equipment (0 dBm) to transmit data at a rate of up to 55 Mbps and over a range of up to 55 m Ailisto et al (2003). Low power W-PANs: As per standard IEEE 802.15 TG4, these technologies are particularly useful for handheld devices since energy consumption for data transmission purposes, and costs, are extremely low. The range of operation of up to 75 m is higher than current Bluetooth applications, but the data transfer rate is low (250 Kbps) Ailisto et al (2003).
- 9. Local Area Network(LAN) LAN or Local Area Network connects network devices in such a way that personal computer and workstations can share data, tools and programs. The group of computers and devices are connected together by a switch, or stack of switches, using a private addressing scheme as defined by the TCP/IP protocol. Private addresses are unique in relation to other computers on the local network. Routers are found at the boundary of a LAN, connecting them to the larger WAN. Data transmits at a very fast rate as the number of computers linked are limited. By definition, the connections must be high speed and relatively inexpensive hardware (Such as hubs, network adapters and Ethernet cables). LANs cover smaller geographical area (Size is limited to a few kilometers) and are privately owned. One can use it for an office building, home, hospital, schools, etc. LAN is easy to design and maintain. A Communication medium used for LAN has twisted pair cables and coaxial cables. It covers a short distance, and so the error and noise are minimized Early LAN’s had data rates in the 4 to 16 Mbps range. Today, speeds are normally 100 or 1000 Mbps. Propagation delay is very short in a LAN. The smallest LAN may only use two computers, while larger LANs can accommodate thousands of computers. A LAN typically relies mostly on wired
- 10. connections for increased speed and security, but wireless connections can also be part of a LAN. The fault tolerance of a LAN is more and there is less congestion in this network. For example : A bunch of students playing Counter Strike in the same room (without internet) Metropolition Area Network(MAN) MAN or Metropolitan area Network covers a larger area than that of a LAN and smaller area as compared to WAN. It connects two or more computers that are apart but resides in the same or different cities. It covers a large geographical area and may serve as an ISP (Internet Service Provider). MAN is designed for customers who need a high-speed connectivity. Speeds of MAN ranges in terms of Mbps. It’s hard to design and maintain a Metropolitan Area Network. The fault tolerance of a MAN is less and also there is more congestion in the network. It is costly and may or may not be owned by a single organization. The data transfer rate and the propagation delay of MAN is moderate. Devices
- 11. used for transmission of data through MAN are: Modem and Wire/Cable. Examples of a MAN are the part of the telephone company network that can provide a high-speed DSL line to the customer or the cable TV network in a city WIDE AREA NETWORK(WAN) WAN or Wide Area Network is a computer network that extends over a large geographical area, although it might be confined within the bounds of a state or country. A WAN could be a connection of LAN connecting to other LAN’s via telephone lines and radio waves and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive.
- 12. There are two types of WAN: 1. Switched WAN 2. Point-to-Point WAN. WAN is difficult to design and maintain. Similar to a MAN, the fault tolerance of a WAN is less and there is more congestion in the network. A Communication medium used for WAN is PSTN or Satellite Link. Due to long distance transmission, the noise and error tend to be more in WAN. WAN’s data rate is slow about a 10th LAN’s speed, since it involves increased distance and increased number of servers and terminals etc. Speeds of WAN ranges from few kilobits per second (Kbps) to megabits per second (Mbps). Propagation delay is one of the biggest problems faced here. Devices used for transmission of data through WAN are: Optic wires, Microwaves and Satellites. Example of a Switched WAN is the asynchronous transfer mode (ATM) network and Point-to-Point WAN is dial-up line that connects a home computer to the Internet. NETWORK DEVICES Repeater – A repeater operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do not amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength. It is a 2 port device. Hub – A hub is basically a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices. In other words, collision domain of all hosts
- 13. connected through Hub remains one. Also, they do not have the intelligence to find out best path for data packets which leads to inefficiencies and wastage. Types of Hub ❖ Active Hub:- These are the hubs which have their own power supply and can clean, boost, and relay the signal along with the network. It serves both as a repeater as well as wiring centre. These are used to extend the maximum distance between nodes. ❖ Passive Hub :- These are the hubs which collect wiring from nodes and power supply from active hub. These hubs relay signals onto the network without cleaning and boosting them and can’t be used to extend the distance between nodes. ❖ Intelligent Hub :- It work like active hubs and include remote management capabilities. They also provide flexible data rates to network devices. It also enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Bridge – A bridge operates at data link layer. A bridge is a repeater, with add on the functionality of filtering content by reading the MAC addresses of source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device. Types of Bridges ❖ Transparent Bridges:- These are the bridge in which the stations are completely unaware of the bridge’s existence i.e. whether or not a bridge is added or deleted from the network, reconfiguration of the stations is unnecessary. These bridges make use of two processes i.e. bridge forwarding and bridge learning.
- 14. ❖ Source Routing Bridges:- In these bridges, routing operation is performed by source station and the frame specifies which route to follow. The host can discover frame by sending a special frame called discovery frame, which spreads through the entire network using all possible paths to destination. Switch – A switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports imply less traffic) and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, that makes it very efficient as it does not forward packets that have errors and forward good packets selectively to correct port only. In other words, switch divides collision domain of hosts, but broadcast domain remains same. Routers – A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.
- 15. Gateway – A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models. They basically work as the messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router. Brouter – It is also known as bridging router is a device which combines features of both bridge and router. It can work either at data link layer or at network layer. Working as router, it is capable of routing packets across networks and working as bridge, it is capable of filtering local area network traffic.