Class work 1 computer networks-cse-317

Class work 1 computer networks-cse-317

• 1.
  Class Work-1 Topic Name: Introduction To Computer Networks ( History Of Computer Networks, ARPANET, Goals Of Computer Networks, Application Of Computer Networks, Network Hardware & Software) Course Title:Computer Networks Theory Course Code: CSE-317 Submitted To Pranab Bandhu Nath Senior Lecturer Department Of CSE City University Submitted By Khondoker Sadia Id:1834902542 Semester:8th Batch:49th
• 2.
  History Of ComputerNetworks: ❖ A network is a group of connected communicating devices such as computers and printers. An internet is two or more networks that can communicate with each other. In 1967, at an Association for Computing Machinery (ACM) meeting, ARPA presented its ideas for ARPANET, a small network of connected computers. By 1969, ARPANET was a reality. In 1972, Vint Cerf and Bob Kahn, both of whom were part of the core ARPANET group, collaborated on what they called the Internetting Projec1. Cerf and Kahn's landmark 1973 paper outlined the protocols to achieve end-to-end delivery of packets. This paper on Transmission Control Protocol (TCP) included concepts such as encapsulation, the datagram, and the functions of a gateway. Shortly thereafter, authorities made a decision to split TCP into two protocols: Transmission Control Protocol (TCP) and Internetworking Protocol (lP). ARPANET: ❖ ARPANET, in full Advanced Research Projects Agency Network. • ARPANET was the network that became the basis for the Internet. Based on a concept first published in 1967, ARPANET was developed under the direction of the U.S. Advanced Research Projects Agency (ARPA). In 1969, the idea became a modest reality with the interconnection of four university computers.The initial purpose was to communicate with and share computer resources among mainly scientific users at the connected institutions. ARPANET took advantage of the new idea of sending information in small units called packets that could be routed on different paths and reconstructed at their destination. • In the 1980s, ARPANET was handed over to a separate new military network, the Defense Data Network, and NSFNet, a network of scientific and academic computers funded by the National Science Foundation. In 1995, NSFNet in turn began a phased withdrawal to turn the backbone of the Internet (called vBNS) over to a consortium of commercial backbone providers (PSINet, UUNET,ANS/AOL, Sprint, MCI, and AGIS-Net99). • Because ARPA's name was changed to Defense Advanced Research Projects Agency (DARPA) in 1971, ARPANET is sometimes referred to as DARPANET. (DARPA was changed back to ARPA in 1993 and back to DARPA again in 1996.) The history of ARPANET and developments leading up to today's Internet can be found in Where Wizards Stay Up Late, by Katie Hafner and Matthew Lyon.
• 3.
  Computer Networks : ❖Networking is referred as connecting computers electronically for the purpose of sharing information. Resources such as files, applications, printers and software are common information shared in a networking.WAN is a network that covers wider area than LAN and usually covers cities, countries and the whole world. Goals Of Computer Networks: ❖ The following are some important goals of computer networks: 1. 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. 2. 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. 3. Inter-process Communication – Network users, located geographically apart, may converse in an interactive session through the network. In order to permit this, the network must provide almost error-free communications. 4. 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, Saving money, Access to remote information, Person to person communication etc. 5. Security – It means protecting data from unauthorized access.
• 4.
  Application of ComputerNetworks: • Business Applications . • Communication Medium. • e-commerce. • Home Applications. • Electronic commerce. • Mobile Users. • Social Issue. Network Hardware & Software: ❖ There are three components of Computer Networks. 1. Hardware Equipment. 2. Software. 3. Cables and 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, Coaxial cable,Fiber-optic cable. Hardware: 1. NIC: A network interface card (NIC) is a hardware component without which a computer cannot be connected over a network. It is a circuit board installed in a computer that provides a dedicated
• 5.
  network connection tothe computer. It is also called network interface controller, network adapter or LAN adapter. Purpose • NIC allows both wired and wireless communications. • NIC allows communications between computers connected via local area network (LAN) as well as communications over large-scale network through Internet Protocol (IP). • NIC is both a physical layer and a data link layer device, i.e. it provides the necessary hardware circuitry so that the physical layer processes and some data link layer processes can run on it. Types of NIC Cards NIC cards are of two types – Internal Network Cards: In internal networks cards, motherboard has a slot for the network card where it can be inserted. It requires network cables to provide network access. Internal network cards are of two types. The first type uses Peripheral Component Interconnect (PCI) connection, while the second type uses Industry Standard Architecture (ISA).
• 6.
  External Network Cards: Indesktops and laptops that do not have an internal NIC, external NICs are used. External network cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the motherboard, however no network cable is required to connect to the network. They are useful while traveling or accessing a wireless signal. 2. Server: A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network. In theory, whenever computers share resources with client machines they are considered servers. There are many types of servers, including web servers, mail servers, and virtual servers. Types of servers There are many types of servers that all perform different functions. Many networks contain one or more of the common server types:
• 7.
  i File servers. iiPrint server. iii Application servers. iv DNS servers. v Mail servers. vi Web servers. vii Database servers. viii Computer hardware servers. ix Virtual servers. x Cloud servers etc. 3. Client: A client is a piece of computer hardware or software that accesses a service made available by a server as part of the client- server model of computer networks. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network.It is a computer that connects to and uses the resources of a remote computer, or server. Many corporate networks comprise a client computer for each employee, each of which connects to the corporate server. 4. Peers: In networking, a peer is a node that provides the same functionality as another. For example, two desktop PCs in a network are peers. A desktop PC and a server are not peers as they perform different operations. The desktop PC may query the server for business data, but the server does not query the PC for the same data. 5. Transmission: Transmission media is a communication channel that carries the information from the sender to the receiver. Data is transmitted through the electromagnetic signals. The main functionality of the transmission media is to carry the information in the form of bits through LAN(Local AreaNetwork). 6. Medium: Communication medium refers to the physical channel through which data is sent and received. Data is sent in the form of voltage levels which make up the digital signal. ... The speed of data
• 8.
  transmission or datarate depends upon the type of medium being used in the network. 7. Router:A router receives and sends data on computer networks. Routers are sometimes confused with network hubs, modems, or network switches. However, routers can combine the functions of these components, and connect with these devices, to improve Internet access or help create business networks. 8. Bridge:A bridge in a computer network is one kind of network device, used to separate a network into sections. Every section in the network represents a collision domain that has separate bandwidth. So that network performance can be improved using a bridge. In the OSI model, a bridge works at layer-2 namely the data link layer. The main function of this is to examine the incoming traffic and examine whether to filter it or forward it. bridge-modem Working principle of a bridge: The working principle of a bridge is, it blocks or forwards the data depending on the destination MAC address and this address is written into every data frame.
• 9.
  Bridge-in- computer-network In acomputer network, a bridge separates a LAN into different segments like segment1 & segment2, etc and the MAC address of all the PCs can be stored into the table. For instance, PC1 transmits the data to PC2, where the data will transmit to the bridge first. So the bridge reads the MAC address & decides whether to transmit the data to segment1 or segment2. Therefore, the PC2 is accessible in segment1, which means the bridge transmits the data in segment1 only & eliminates all the connected PCs in segment2. In this way, the bridge reduces traffic in a computer network. 9. Hub:Hubs are those devices that are used to link several computers together. Hubs repeat one signal that comes in on one port and then copies it to other ports. • A network hub is basically a centralized distribution point for all the data transmission in a network. • Hub is a passive device. • The hub receives the data and then rebroadcasts the data to other computers that are connected to it. Hub mainly does not know the destination of a received data packet. Thus it is required to send copies of data packets to all the hub connections. • Also, Hubs consumes more bandwidth on the network and thus limits the amount of communication. • One disadvantage of using hubs is that they do not have the intelligence to find out the best path for the data packets which then leads to inefficiencies and wastage.
• 10.
  10. Switch:Switch mainlyresembles a Hub. It is a layer-2 device and it is used for the intelligent forwarding of messages. By intelligent we mean the decision-making ability of the switch. As hub works in the way by sending data to all ports on the device, whereas the switch sends the data to only that port that is connected with the destination device. • The switch is a network component and is mainly used to connect the segments of the network. • The switch is more intelligent than the network hub. • Mainly Switches are capable of inspecting the data packets as soon as they are received, then determine the source and destination of that packet, and then forward it appropriately. • Switch differs from the hub as it also contains ports of different speeds. • Before forwarding the data to the ports switch performs the error checking and this feature makes the switch efficient. • As the switch delivers the message to the connected device it was intended for, thus it conserves the bandwidth of the network and offers better performance than the hub. • The most important feature of the switch is that it supports unicast(one to one), multicast(one to many), and broadcast(one to all) communications. • The switch makes use of MAC address in order to send data packets to the selected destination ports. 11. Gateway: A gateway is a network node that forms a passage between two networks operating with different transmission protocols. The most common type of gateways, the network gateway operates at layer 3, i.e. network layer of the OSI (open systems interconnection) model. However, depending upon the functionality, a gateway can operate at any of the seven layers of OSI model. It acts as the entry – exit point for a network since all traffic that flows across the networks should pass through the gateway. Only the internal traffic between the nodes of a LAN does not pass through the gateway.
• 11.
  12. Repeaters:The repeateris a Physical layer device. As the name suggests, the repeater is mainly used to regenerate the signal over the same network and it mainly regenerates before the signal gets corrupted or weak. They are incorporated into the networks in order to extend the coverage area. Repeaters can connect signals by making the use of diffrent types of cables. • Repeaters are cost-effective. • Repeaters are very easy o install, and after their installation, they can easily extend the coverage area of the network. • But there is a problem with repeaters and it is they cannot those networks that are not of the same type. • Repeaters do not help to reduce the traffic in the network. Software: i. Network Operating System: Network Operating System is a computer operating system that facilitates to connect and communicate various autonomous computers over a network. An Autonomous computer is an independent computer that has its own local memory, hardware, and O.S. It is self capable to perform operations and processing for a single user.
• 12.
  ii. Protocols switches:Protocolswitching can be used to upgrade network protocols or fix minor bugs at run-time without having to restart applications Security. • Communication protocols include basic data communication tools like TCP/IP and HTTP. • A network switch is a device that operates at the Data Link layer of the OSI model—Layer 2. Cables and Connectors: i. Twisted pair cable: One of the earliest guided transmission media is twisted pair cables. A twisted pair cable comprises of two separate insulated copper wires, which are twisted together and run in parallel. The copper wires are typically 1mm in diameter. One of the wires is used totransmit data and the other is the ground reference. ii. Coaxial cable : Coaxial cable, or coax is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric; many coaxial cables also have a protective outer sheath or jacket.
• 13.
  Types of CoaxialCables There are two types of coaxial cables: iii. Fiber-optic cable: Fiber optic cable is a high-speed data transmission medium. It contains tiny glass or plastic filaments that carry light beams. ... The receiving end of a fiber optic transmission translates the light pulses into binary values, which can be read by a computer.