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Bachelor of Computer Applications (Part-III) Introduction: Network Definition, Basic components of a network, network types and topologies, Uses of computer networks, network architecture. Transmission Media: Coaxial cable, twisted pair cable, fibre optics & satellites. OSI referable model, TCP/IP references model, comparison of OSI and TCP reference model. Introduction to Analog and Digital Transmission: Telephone system, Modems, Types of modems, pulse code modulation. Transmission & Switching: Multiplexing, circuit switching packet switching, hybrid switching, ISDN service transmission. Local Area Network Protocols: CSMA Protocols, BRAP, MLMA, IEEE standards 602, Token Bus, Token Ring, FDDI. Data Link Layer Design Issues: Services provided to Network layer framing, error control, flow control, link management. Error detection & correction, Elementary Datalink Protocols. Design Issues of Network Layer: Services provided to transport layer, routing, connection, internet & world wide web. Network Security and Privacy: Brief Introduction to Cryptography. Network Services: File transfer, Access & Management, Electronic Mail, Remote logic

Unit 1 Introduction: Network Definition, Basic components of a network, network types and topologies, Uses of computer networks, network architecture. Transmission Media: Coaxial cable, twisted pair cable, fibre optics & satellites. OSI referable model, TCP/IP references model, comparison of OSI and TCP reference model.

Networking A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. In the world of computers, networking is the practice of linking two or more computing devices together for the purpose of sharing data. Networks are built with a mix of computer hardware and computer software.

Network Classification The following list presents major categories used for classifying networks. Local Area Network (LAN), Wide Area Network (WAN), Metropolitan Area Network (MAN).

Connection method/ Transmission MediaComputer networks can also be classified according to the hardware technology that is used to connect the individual devices in the network such as: Coaxial cable Twisted pair cable Fibre optics satellites Ethernet, Wireless LAN.

Optical Fiber An optical fiber (or fibre) is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher data rates ("bandwidth"), than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications.

Coaxial cableCoaxial cable is a cable consisting of an inner conductor, surrounded by a tubular insulating layer typically made from a flexible material with a high dielectric constant, all of which is then surrounded by another conductive layer (typically of fine woven wire for flexibility, or of a thin metallic foil), and then finally covered again with a thin insulating layer on the outside. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis. Coaxial cables are often used as a transmission line for radio frequency signals.

Coaxial cable

Twisted pair cable

Twisted pair cableTwisted pair cabling is a form of wiring in which two conductors (two halves of a single circuit) are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources; for instance, electromagnetic radiation from unshielded twisted pair (UTP) cables, and crosstalk between neighboring pairs. Twisting wires decreases interference because the loop area between the wires (which determines the magnetic coupling into the signal) is reduced. In

Fibre optics

Fibre optics An optical fiber (or fibre) is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers. Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher data rates (a.k.a "bandwidth"), than other forms of communications. Fibers are used instead of metal wires because signals travel along them with less loss, and they are immune to electromagnetic interference. Optical fibers are also used to form sensors, and in a variety of other applications.

satellites In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.

Ethernet :Ethernet uses physical wiring to connect devices. Often deployed devices are hubs, switches, bridges, and/or routers. Wireless LAN: Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves as transmission medium.

Network topology Network Topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network. Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a Bus Topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout.

Network topologyComputer networks may be classified according to the network topology upon which the network is based, such as: Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network.

Bus Topology A bus topology connects computers along a single or more cable to connect linearly as figure 1. A network that uses a bus topology is referred to as a "bus network" which was the original form of Ethernet networks

Ring Topology

Ring Topology Each computer in the ring examines all messages, passes them on if they are not the destination node. If no computer accepts a message, it returns to the sender, which removes it from the ring. All clients have equal access to data. This gives even performance under heavy demand conditions.Difficult to add another host to the ring.

Start Topology

Star Topology All signals are directed through the central hub. Reduces risk of failure. Expanding the network is simple. Managing the network is centralised. If the hub breaks down, the system fails.

Hybrid Topology

Hybrid Topology A series of star topologies with the hubs connected by a bus trunk (the backbone of the network). Network expansion is simple. If one client fails, the entire network does not fail. If one hub fails, all connections to that hub fail, although other hubs continue to function.

Mesh Topology Mesh topologies are networks in which many paths connect computers. This redundancy allows the system to continue if some connections fail. However, multiple connections are expensive.

Types of networksBelow is a list of the most common types of computer networks in order of scale: Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN)

Local Area Network (LAN) A network covering a small geographic area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library may have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) and to connect to the internet.

Wide Area Network (WAN)A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer

Metropolitan Area Network (MAN) A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a Metropolitan Area Network.

Internetwork Two or more networks or network segments connected using devices, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork. In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them: Intranet Extranet Internet Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.

Intranet An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is th