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Welcome to Evolution of Networking Prepared By : VINAY ALEXANDER KV JHAGRAKHAND What is a Computer Network? Two or more computers or communications devices connected by transmission media and channels and guided by a set of rules for communication purposes that allow users to communicate with each other and share applications and data. Hardware: Computer Network card Routers Modem … Media: Cable Wire Microwave … Components of a Computer Network Software: Network OS Utilities … 2 Network Design: Logical layout Physical layout … Advantages of NETWORK • Share Resource • Can Share Software • Share storage • Improve Communications Disadvantages of NETWORK • The system are more sophisticated and complex to run. This can add to costs and you may need specialist staff to run the network. • If s/w and files are held centrally, it may be impossible to carry out any work if the central server fails. • If networks are badly managed services can becomes unusable and productivity falls. • File security is more important especially if connected to WAN. Application of NETWORK • Sharing : • Access to remote database • Communication facilities Evolution of NETWORK Evolution of networking started way back 1969 by the development of Internet. ARPANET, NSFnet, Internet ARPANET (Advanced Research Projects Agency NETwork): In 1969, ARPANET was started to connect computers at US defense & different universities. NSFnet (National Science Foundation Network) : In 1980 NSFnet was started to make a highcapacity network to be used strictly for academic and engineering research. Internet : In 1990 the internetworking of ARPANET , NSFnet and other private networks resulted into Internet. Gateway & Backbone Network A Gateway is a device that connects dissimilar networks. A Backbone is central interconnecting structure that connects one or more networks just like the trunk of a tree or the spine of a human being Internet Functioning =>A protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints The communication protocol used by internet is TCP/IP. The TCP ( Transmission Control Protocol) part is responsible dividing the files/massage into packet on the source computer. It is also responsible for reassembling the received packet at the destination computer. The IP (Internet Protocol) part is responsible for handling the address of destination computer so that each packet is routed to its proper destination. Interspace The future of internet is said to be in Interspace. Interspace is a client/server software program that allows multiple users to communicate online with real-time audio, video and text chat in dynamic 3D environments. Elementary Terminology of Networks Nodes: the term nodes refers to the computers that are attached to a network and are seeking to share the resources of the network. A computer becomes a workstation of a network as soon as it is attached to a network. => A server is any combination of hardware or software designed to provide services to clients. =>A server is primarily a program that runs on a machine, providing a particular and specific service to other machines connected to the machine on which it is found => A computer, or a software package, that provides a specific kind of service to client software running on other computers. 12 Figure 15.1 Client/Server interaction • TYPES OF SERVER Non-Dedicated Server: A Non-dedicated server can be used as a workstation as well as a server. Using a server as a workstation has several disadvantages and is not advisable for larger networks Dedicated Server: Dedicated servers are used only as a server, not as a workstation. Dedicated servers cannot be used for ordinary work. In fact, access to the server is often limited to prevent any access by unauthorized users. Most of the high-end network packages assume you are using a dedicated server. If the network has a dedicated server, it is most likely a file server. Differences: Non-dedicated servers are used both as a server and a workstation. Networks with a dedicated server are known as server-based networks; those with non-dedicated servers are known as peer-to peer networks 13 Elementary Terminology of Networks NIU (Network Interface Unit) : A network interface unit is an interpreter that helps establish communication between the server and workstation. MAC address : The MAC address refers to the physical address assigned by NIC manufacturer. Switching Techniques Switching Techniques are used for transmitting data across networks. Circuit Switching : 1st the complete physical connection between two computers is established and then data are transmitted from source computer to the destination computer. Switching Techniques MMessageSwitching: The source computer sends data or the message to the switching office first, which stores the data in its buffers. It then looks for free link to another switching office and then send the data to this office. This process is continued until the data are delivered to the destination computers. It is also known as store and forward. Switching Techniques PPacket Switching: With message switching, there is no limit on block size, in contrast, packet switching places a tight upper limit on block size. A fixed size of packet which can be transmitted across the network is specified. Packets are stored in main memory whereas in massage switching the data are stored on the disk. This improves the performance as the access time is reduced, thus the throughput of the network is improved. Transmission Media Sending of data from one device to another is called transmission of data Medium used to transmit the data is called Media Transmission of data through Medium is called Transmission Media Transmission media or communication cannels meant that the ‘connecting cables’ or ‘connection media’. Topic Included Tranmission media Definition Types of Transmission Media Guided Media 1. Twisted Pair cable 2. Coaxial Cables 3. Optical Fiber Unguided media 1. Microwave 2. Infrared 3. Bluetooth 4. WI-FI (Wireless Fidelity) Applications Types Of Transmission Media • Guided (Wired) – Twisted Pair – Coaxial cable – Fiber Optics • Unguided (Wireless) – Wi-Fi – Bluetooth – Infrared – Microwave – Lasers Guided ( Wired ) • The medium itself is more important in determining the limitations of transmission. • The transmission capacity, in terms of either data rate or bandwidth, depends critically on the distance and on whether the medium is point-to-point or multipoint. Twisted Pair • A twisted pair consists of two insulated copper wires arranged in a regular spiral pattern. • The twisting tends to decrease the crosstalk interference between adjacent pairs in a cable. • Twisted pair may be used to transmit both analog and digital transmission. • Twisted pair is limited in distance, bandwidth, and data rate. • The attenuation for twisted pair is a very strong function of frequency Twisted-Pair Cables • If the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors CROSSTALK • The bleeding of a signal from one wire to another and which can corrupt signal and cause network errors. This form of signal interference is called CROSSTALK • Advantages: • It is Simple • It is Physically flexible • It can be easily connected • It is easy to install and maintain • It has a low weight • It is very inexpensive. • Disadvantage: • 1.High Attenuation, it is incapable carrying a signal over long distances without the use of repeater. • 2. Its low bandwidth capabilities make it unsuitable for broadband application. • 3.It supports max data rates 1Mbps without conditioning and 10 Mbps with conditioning. • TYPES OF TWISTED PAIR CABLES Unshielded Twisted-Pair (UTP) • Typically wrapped inside a plastic cover (for mechanical protection) • A sample UTP cable with 5 unshielded twisted pairs of wires Insulator Metal Shielded Twisted-Pair (STP) • STP cables are similar to UTP cables, except there is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires Twisted Pair Types • Unshielded Twisted Pair (UTP) – ordinary telephone wire – cheapest – easiest to install – suffers from external EM interference • Shielded Twisted Pair (STP) – metal braid or sheathing that reduces interference – more expensive – easiest to install – harder to handle (thick, heavy) Coaxial cable Coaxial cable It consists of solid wire core surrounded by one or more foil or wire shield, each separated by some kind of plastic insulator. the inner core carries the signal , and outer shield provides the ground. the coaxial cable has high electrical properties and is suitable for high speed communication. it is used in television signal. In general, coaxial cables, or coax, carry signals of higher freq (100KHz–500MHz) than UTP cables. Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit. =>versatile transmission medium, used in a wide variety of applications, including: • Television distribution - aerial to TV systems. Advantages • Better than twisted pair cable. • Used as shared cable network • Used for broadband transmission. • Higher bandwidth upto 400 MBPS Disadvantages • Expensive compared to twisted pair cables • The coaxial cables are not compatible with twisted pair cables. BNC connectors • BNC Connectors are used for connecting to co-axial cables together at connecting points is when repeaters are required TYPES OF COAXIAL CABLES • There are two types . 1.Thicknet: It is a thicker than thinner. It is used upto 500 meters long. 2. Thinner: It is used upto 185 meters long. Optical-Fiber Cables • Light travels at 3108 ms-1 in free space and is the fastest possible speed in the Universe • Light slows down in denser media, e.g. glass • Refraction occurs at interface, with light bending away from the normal when it enters a less dense medium • Beyond the critical angle total internal reflection • An optical fiber consists of a core (denser material) and a cladding (less dense material) • Simplest one is a multimode step-index optical fiber • Multimode = multiple paths, whereas step-index = refractive index follows a step-function profile (i.e. an abrupt change of refractive index between the core and the cladding) • Light bounces back and forth along the core • Common light sources: LEDs and lasers Fiber Optics Optical Fiber - Transmission Characteristics uses total internal reflection to transmit light effectively acts as wave guide for 1014 to 1015 Hz can use several different light sources Light Emitting Diode (LED) cheaper, wider operating temp range, lasts longer Injection Laser Diode (ILD) more efficient, has greater data rate relation of wavelength, type & data rate • Fiber optic cable is known as most sophisticated cables used in long distance network connection. • Through this cable data transmission is done through Light ray signal transmission rather than electrical signal transmission. • It has inner core of glass that conducts light.This inner core is surrounded by cladding. • Cladding is nothing but layer of glass material that reflects light back into the core. • Each fiber is then surrounded by plastic sheath Advantages • Immune(प्रतिरक्षिि ) to electrical and magnetic interference. • Highly suitable for harsh industrial environments. • Secure transmission and very high transmission capacity. • Used for broadband transmission. Disadvantages • Installation problem. • Connecting two fibers together is a difficult process. • Because of noise immunity, they are virtually impossible to tap. • Light can reach the receiver out of phase. • Connection losses are common problem • Difficult to solder • Most expensive. Optical Fibre Transmission Mode Types of fibre optic cable 1.single node: It is used upto 2kms and band width of upto 100Mbps 2. Multinode: It is used upto 100kms and band width of 2Gbps. microwave • A microwave is an electromagnetic wave with a very short wavelength, between .039 inches (1 millimeter) and 1 foot (30 centimeters). Within the electromagnetic spectrum, microwaves can be found between radio waves and shorter infrared waves. Their short wavelengths make microwaves ideal for use in radio and television broadcasting. They can transmit along a vast range of frequencies without causing signal interference or overlap. • It consist of a transmitter, receiver and atmosphere. • Microwave technology was developed during World War II (1939–45) in connection with secret military radar research. Today, microwaves are used primarily in microwave ovens and communications. A microwave communications circuit can transmit any type of information as efficiently . • • • • • • • • • • • • • Advantages: No cables needed Multiple channels available Wide bandwidth It have the ability to communicate over oceans and difficult terrain. Cheaper Disadvantages: Line-of-sight will be disrupted if any obstacle, such as new buildings, are in the way Signal absorption by the atmosphere. Microwaves suffer from attenuation due to atmospheric conditions. Towers are expensive to build line of sight requirement expensive towers and repeaters subject to interference such as passing airplanes and rain It is insecure communication. Radio Transmission • Radio transmission works with or without line of sight. If line of sight is possible then transmission can take place between sending antenna and receiving antenna. The placement of antenna has to take into account the curvature of the Earth with antenna being built taller accordingly. This will also allow for greater transmission distances. If line of sight cannot be implemented then signals can be broadcast to the upper layers or the atmosphere or space and then transmitted back to Earth. • The electromagnetic spectrum used for radio communication consists of eight distinct ranges which are regulated by government authorities: • It consist of two parts 1. The Transmitter 2. The Receiver • Advantages • Disadvantages • It offers mobility • Cheaper • Offers freedom from land acquisition rights • Ease of communication over difficult terrain • Insecure communication • It effects from rain, thunder storms • Satellite Microwave Satellite communication is special case of microwave relay system. Satellite communication use the synchronous satellite to relay the radio signal transmitted from ground station. • A satellite is any object that revolves around a planet in a circular or elliptical path. The moon is Earth's natural satellite at 240,000 miles distant. Other satellites that fulfill this definition are man made and have been launched into orbit to carry out specific functions. These satellites are typically between 100 and 24,000 miles away. Satellite Microwave Satellite is relay station Receives on one frequency, amplifies or repeats signal and transmits on another frequency Typically requires geo-stationary orbit Eg. Uplink 5.925-6.425 ghz & downlink 3.7-4.2 ghz Height of 35,784km Spaced at least 3-4° apart Typical uses Television Long distance telephone Private business networks Global positioning • Advantages: • High bandwidth • Develop stronger relationships with classmates • Area coverage through satellite is quire large. • The laying and maintenance is easy and inexpensive. • Heavy usage of intercontinental traffic makes it commercial attractive. • Disadvantages: • Huge initial cost • Technological limitation preventing the deployment of large, high gain antennas on the satellite platform. • Over-crowding • High investment and insurance cost associated with significant probability of failure. • High atmospheric losses. Satellite Point to Point Link Satellite Broadcast Link Continue…. Comparisiom of Major Wireless Transmission Media Medium Description and Advantages Limitations and Drawbacks Microwave Point-to-point communication in lineof-sight path. Must have visual contact between antennas. Antennas are used (30 miles apart). Susceptible to environmental interferences THANK YOU Provide large capacity. Can be done quickly at lower cost Satellites Can be at high, medium, or low orbit; used in GPSs. Expensive to build and maintain. Complete global coverage is available with three satellites. Radio/electromagnetic Effective for short ranges; used in LANs Limited range; difficult to secure. Inexpensive and easy to install. Can create interference with communication devices. Applications Wireless Transmission Frequencies • • • 2GHz to 40GHz – microwave – highly directional – point to point – Satellite 30MHz to 1GHz – Omni directional – broadcast radio 3 x 1011 to 2 x 1014 – infrared – local Continue…. Infrared “Infrared technology allows computing devices to communicate via short-range wireless signals. With infrared, computers can transfer files and other digital data bidirectionally. The infrared transmission technology used in computers is similar to that used in consumer product remote control units.” Modulate noncoherent infrared light End line of sight (or reflection) Are blocked by walls No licenses required Typical uses TV remote control Infrared Installation and Usage - Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. Infrared light has a range of wavelengths, just like visible light has wavelengths that range from red light to violet. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum. The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are the size of cells, or are microscopic . Infrared adapters are installed in many laptops and handheld personal devices. • Range - Infrared communications span very short distances. Place two infrared devices within a few feet (no more than 5 meters) of each other when networking them. Unlike Wi-Fi and Bluetooth technologies, infrared network signal cannot penetrate walls or other obstructions and work only in the direct "line of sight.“ • Performance - Infrared technology used in local networks exists in three different forms: • IrDA-SIR (slow speed) infrared supporting data rates up to 115 Kbps • IrDA-MIR (medium speed) infrared supporting data rates up to 1.15 Mbps • IrDA-FIR (fast speed) infrared supporting data rates up to 4 Mbps • Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns. (A micron is the term commonly used in astronomy for a micrometer or one millionth of a meter.) This image ( which is courtesy of the Infrared Processing and Analysis Center at CalTech), shows a man holding up a lighted match! Which parts of this image do you think have the warmest temperature? How does the temperature of this man's glasses compare to the temperature of his hand? IR Advantages: • Low power requirements: therefore ideal for laptops, telephones, personal digital assistants • Low circuitry costs: $2-$5 for the entire coding/decoding circuitry • Simple circuitry: no special or proprietary hardware is required, can be incorporated into the integrated circuit of a product • Higher security: directionality of the beam helps ensure that data isn't leaked or spilled to nearby devices as it's transmitted • Portable IR Disadvantages: • Line of sight: transmitters and receivers must be almost directly aligned (i.e. able to see each other) to communicate • Blocked by common materials: people, walls, plants, etc. can block transmission • Short range: performance drops off with longer distances • Light, weather sensitive: direct sunlight, rain, fog, dust, pollution can affect transmission • Speed: data rate transmission is lower than typical wired transmission Laser wave • It Requires direct line of sight. it is unidirectional like microwave, but has higher speed than microwaves. It requires the use of laser transmitter and a photo-sensitive receiver at each end • Disadvantages • It effected by weather. Data communication technologies 1. Data Channel: is the medium to carry information from one point to another. 2. Baud: is the unit of measurement for the information carrying capacity. 3. Bits per second: it refers to a thousand bit transmitted per second. 4. Bandwidth: it refers to the difference between the highest and lowest frequencies of transmission channels. 5. Data transfer Rate: Amount of data transfer per second. • Local area network: A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. Each computer or device on the network is a node. Current wired LANs are most likely to be based on Ethernet technology • Metropolitan area network :A metropolitan area network (MAN) 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. • Wide area network :A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN 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. Personal Area Network (PAN) • A personal area network is the interconnection of information technology deice within the range of an individual person, within a range of 10 meters. • Laptop connect to a portable printer using wifi technologies The pattern of interconnection of nodes in a network is called the Topology. The selection of a topology for a network cannot be done in isolation as it affects the choice of media and the access method used. There are a number of factors to consider in making this choice, the most important of which are set out below: 1. Cost. For a network to be cost effective, one would try to minimize installation cost. This may be achieved by using well understood media and also, to a lesser extent, by minimizing the distances involved. 2. Flexibility. Because the arrangement of furniture, internal walls etc. in offices is often subject to change, the topology should allow for easy reconfiguration of the network. This involves moving existing nodes and adding new ones. 3. Reliability. Failure in a network can take two forms. Firstly, an individual node can malfunction. This is not nearly as serious as the second type of fault where the network itself fails to operate. The topology chosen for the network can help by allowing the location of the fault to be detected and to provide some means of isolating it. In networking, the term “topology” refers to the layout of connected devices on a network. One can think of a topology as a network’s virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find an actual ring topology there. Network topologies are categorized into the following basic types : bus, ring, star, tree, mesh. More complex networks can be built as hybrids of two or more of the above basic topologies. Point-to-Point Topology Transmit X • Point-to-point (PTP) topology connects two nodes directly together. The following examples are pure point to point links: • Two computers Receiver communicating via modems. Y In Star, all computers are connected to central device called hub, router or switches using Unshielded Twisted Pair (UTP) or Shielded Twisted Pair cables. In star topology, we require more connecting devices like routers, cables unlike in bus topology where entire network is supported by single backbone. The most practical point of Star topology success is that the entire network does not go down incase of failure of a computer or cable or device, it will only affect the computer whose wire failed rest of the network will be working fine.. Star topology is widely used in homes, offices and in buildings because of its commercial success. Star Topology • Advantages • Easy to add devices as the network expands • One cable failure does not bring down the entire network (resilience) • Hub provides centralised management • Easy to find device and cable problems • Can be upgraded to faster speeds • Lots of support as it is the most used • Disadvantages • A star network requires more cable than a ring or bus network • Failure of the central hub can bring down the entire network • Costs are higher (installation and equipment) than for most bus networks each node is daisy-chained (connected one right after the other) along the same backbone. Information sent from a node travels along the backbone until it reaches its destination node. Each end of a bus network must be terminated with a resistor. =>Network maintained by a single cable =>Uses thin coaxial cable (backbones will be thick coaxial cable) =>Extra stations can be added in a daisy chain manner =>Simple and low-cost =>A single cable called a trunk (backbone, segment) =>Only one computer can send messages at a time Passive topology - computer only listen for, not regenerate data • Thick Ethernet (10Base5) used for backbones • Limited to 500m • Max of 100 nodes per segment • Total of four repeaters , 2500m, with a total of 488 nodes Bus Topology • • • • • • • • Advantages Inexpensive to install Easy to add stations Use less cable than other topologies Works well for small networks A single node failure does not bring the network down Most widely implemented topology Network can be added to or changed without affecting other stations Disadvantages • No longer recommended • Backbone breaks, whole network down • Limited no of devices can be attached • Fault diagnosis is difficult • Fault isolate is Difficult • Sharing same cable slows response rates (Repeater Configuration) • Collisions can occur easily • Only one device can access the network media at a time. Each node is connected to two and only two neighboring nodes. data is accepted from one of the neighboring nodes and is transmitted onwards to another. thus data travels in one direction only, from node to node around the ring . After passing through each node, it returns to the sending node, which removes it =>USES A TOKEN TO PASS INFORMATION FROM 1 COMPUTER TO THE OTHER. A TOKEN IS ATTACHED TO THE MESSAGE BY THE SENDER TO IDENTIFY WHICH COMPUTER SHOULD RECEIVE THE MESSAGE. AS THE MESSAGE MOVES AROUND THE RING, EACH COMPUTER EXAMINES THE TOKEN. IF THE COMPUTER IDENTIFIES THE TOKEN AS ITS OWN, THEN IT WILL PROCESS THE INFORMATION. •Short cable length. •No wiring closet space required. •Suitable for optical fibers. •Node failure causes network failure. •Difficult to diagnose faults. •Network reconfiguration is difficult. =>Tree topology is a variation of bus topology =>A special node is designated as root =>The primary reason for this topology is to segment nodes so that not all nodes need to listen to packets broadcast on a segment =>This adds a layer of security in the form of unwanted nodes not listening to the network traffic. =>Looks like an upside-down tree where end nodes are linked to interior nodes that allow linking through to another end node. Tree topology diagram Root PC 7 PC 1 PC 6 PC 2 PC 3 PC 4 PC 5 In this topology, nodes are connected together in an arbitrary fashion. A link may or may not connect two or more nodes. There may be multiple links also. It is not necessary that all the nodes are connected. But if a path can be established in two-nodes via one or more links, it is called a connected graph. In this topology, each node is connected to more than one node to provide an alternative route in the case the host is either down or too busy. It is an extension to P-P network. =>The mesh topology is excellent for long distance networking because it provides extensive back-up, rerouting and pass-through capabilities. Communication is possible between any two nodes on the network either directly or by passing through. Mesh Topology FULL CONNECTED Each node is connected to every other node directly i.e. , there is a direct link between each host , then the network is called fully connected. • Allows communication to continue in the event of a break in any one connection FULL CONNECTED Topologies are essence of computer networks design. Efficient networks can only be built based on the complete knowledge and understanding of above mentioned topologies. Knowledge of every communication device is of equal importance to help you find the best option for your network requirements. Optimum networks can be built with complete knowledge and understanding of computer network devices and how they are designed, any mistake in choosing inappropriate techniques, device etc can only be the waste of time, resources and efforts. NETWORK DEVICES =>MODEM (modulator-demodulator): It is a device that allows you to connect and communicate with other computer via telephone lines. =>Modem changes the digital data from your computer into analog data, a format that can be carried over telephone lines. =>In the same the modem receiving the call then changes the analog signal back into digital data that the computer can understand. =>Modulation: • • • • It is process of sending data on a wave form Type of modulation 1.Amplitude modulation (AM), in which the voltage applied to the carrier is varied over time 2.Frequency modulation (FM), in which the frequency of the carrier waveform is varied in small but meaningful amounts 3.Phase modulation (PM), in which the natural flow of the alternating current waveform is delayed temporarily Internal Modem: The modem that are fixed within the computer External Modem: The modem that are connected externally to a computer RJ-45 :RJ-45 is short of registered jack45. RJ-45 is an eight-wire connecter, which is commonly used to connect computers on the LAN especially Ethernets.( Ethernet is a LAN architecture developed by Xerox Corp along with DEC and Intel. Ethernet uses either a bus or star topology and supports data transfer rates of upto 10Mbps) Ethernet Card :Ethernet is a LAN architecture developed by Xerox Corp along with DEC and Intel. Ethernet uses either a bus or star topology and supports data transfer rates of upto 10Mbps The computers that are part of Ethernet, have to install a special card called Ethernet card. HUB :A hub is a hardware device used to connect several computers together. Active Hub: An electrically amplify the signal as it moves from one connected device to another. Active Hubs used like a repeater. Passive Hub : It allow the signal to pass from one computer to another without any change. Concentrator : A concentrator is a device that provides a central connection point for cables from workstations, servers, and peripherals. •Function of HUB: •A hub is a common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets. •The functions of a hub within a network is so they produce packets to the location of the service required to load or view a webpage or document Switch :A switch is a device that is used to segment networks into different sub-networks called subnets or LAN segments. A switch is responsible for filtering that is transforming data in a specific way and for forwarding packets between LAN segments. Network switches are capable of inspecting data packets as they are received, determining the source and destination device of that packet, and forwarding it appropriately Repeater : A repeater is a network device that amplifies and restores signals for longdistance transmission. There are two types of repeator. 1. Amplifier: It amplifies both the sinal and concurrent noise. 2. Signal Repeater: It collect the inbound packet and then retransmits the packet as if were starting from the source station. Repeater REPEATER Bridge : A bridge is a network device that establishes an intelligent connection between two local networks with the same standard(protocol) but with different types of cables. => Bridges are smart enough to know which computers are on which side of the bridge , so they only allow those messages that need to get the other side to cross the bridge. This improves performance on both sides of the bridge. As a packet at the bride , the bridge examines the physical address of the packet. The packet then decides whether or not to let the packet cross. Router : A Router is a network device that is used to separate different segments in a network to improve performance and reliability. A router works like a bridge but can handle different protocols. How a router Functions: => A router forwards data packets from one connected network to another depending upon their IP address and not their MAC addresses. =>A router is a device that determines the next network point to which a packet should be forwarded toward its destination. =>A router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet. =>A packet will travel through a number of network points with routers before arriving at its destination. Gateway :A Gateway is a network device that connects dissimilar networks. It establishes an intelligent connection between a local networks and external networks with completely different structure e.g. to connect a LAN with Novell Netware with another LAN with Microsoft NT. =>In enterprises, the gateway is the computer that routes the traffic from the workstation to the outside world. =>In homes, the gateway is the ISP that connects the user to the Internet. =>In enterprises, the gateway node acts as a proxy server( a machine that is not actually a server but appear as a server) and a FIREWALL (a system designed to prevent unauthorized access to or from a private network Network Design Access Need and costs Select topologies and technologies to satisfy needs Model network workload Simulate behavior under expected load Perform sensitivity tests Rework design as needed Connecting Networks • Repeater: physical layer • Bridge: data link layer • Router: network layer • Gateway: network layer and above. Communication Protocols A protocols means the rules that are applicable for a network. Protocol defines standardized formats for data packets, techniques for detecting and correcting errors and so on. It is a formal description of massage formats and the rules that two or more machines must follow to exchange those message. HTTP (Hypertext Transfer Protocol) : IT is the set of rules for transferring hypertext( text, graphic , image , sound , video etc ) on W W W =>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources, called hypertext documents, led to the establishment of the World Wide Web in 1990 by English physicist Tim Berners-Lee. There are two major versions, HTTP/1.0 that uses a separate connection for every document and HTTP/1.1 that can reuse the same connection to download, for instance, images for the just served page. Hence HTTP/1.1 may be faster as it takes time to set up such connections FTP (File Transfer Protocol) : File Transfer Protocol (FTP) is a standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications. Client applications were originally interactive command-line tools with a standardized command syntax, but graphical user interfaces have been developed for all desktop operating systems in use today. Objectives of FTP are: 1. To promote sharing of files. 2. To encourage indirect or implicit use of remote computer. 3. To shield a user from variations in file storage systems among hosts. 4. To transfer data reliably and efficiently. FTP, through usable directly by a user at a terminal , is designed mainly for use by program. TCP/IP (Transmission Control Protocol / Internet Protocol) TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet. As with all other communications protocol, TCP/IP is composed of layers: On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time. TCP/IP (Transmission Control Protocol / Internet Protocol) : As with all other communications protocol, TCP/IP is composed of layers: IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world. TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received. Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems. Datagram: It is a collection of the data is send as a single message SLIP/PPP (Serial line internet Protocol / Point to Point Protocol) : SLIP is for delivering IP packets over dialup lines. PPP is for transmitting Ip packets over serial lines. Lets you connect your computer system to the Internet itself, rather than logging on through an Internet access provider's host computer and issuing commands through a shell. SLIP/PPP connections lets you communicate directly with other computers on the network using TCP/IP connections. Wireless/Mobile Computing =>Wireless communication is simply data communication without the use of landlines. =>Mobile computing means that the computing device is not continuously connected to the base or central network. Wireless Mobil e No No No yes yes No yes yes yes yes examples Stationary Computer Notebook in a hotel Wireless LAN in HS Personal digital assistant Smart phones, pagers =>GSM (Global System for Mobile communications: It is the most popular standard for mobile phones in the world. Its promoter, the GSM Association, estimates that 70% of the global mobile market uses the standard. GSM uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. TDMA (Time Division Multiple Access) works by dividing a radio frequency into time slots and then allocating slots to multiple calls. In this way , a single frequency can support multiple, simultaneous data channels. SIM (Subscriber identification Module): Sim cards are small removable disks that slip in and out of GSM cell phones. =>CDMA (Code Division Multiple Access) :It is a channel access method utilized by various radio communication technologies. This allows several users to share a bandwidth of different frequencies. This concept is called multiplexing. =>CDMA uses spread-spectrum technique where data is sent in small pieces over a number of discrete frequencies. Each user’s signal is spread over the entire bandwidth by unique spreading code. At the receiver . The same unique code is used to recover the signal. WILL (Wireless in Local Loop) or Wireless local loop (WLL), is a term for the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service (POTS) and/or broadband Internet to telecommunications customers. Various types of WLL systems and technologies exist. => WLL is a system that connects subscribers to the public switched telephone network (PSTN) using radio signals as a substitute for other connecting media =>GPRS (General packet radio service) :It is technology for radio transmission of small packets of data between mobile device and internet. => HOW does GPRS work: The information is split into smaller units or packets and sent through the network and is reassembled at the receiving end =>1G, 2G AND 3G NETWOKS: “G” Means Generation. 1G: First analog cellular systems , which stated early 1980s. It is designed purely for voice calls. 2G(GSM , CDMA) : It is a first digital cellular system launched early 1990.it improve sound quality, better security and higher total capacity it allow users to place dial-up data call digitally. 2.5G(GPRS CDMA2000): It is enhance version of 2G network with theoretical data t\rates up to about 144 kbit/s. 3G(UMTS, FDD,CDMA2000): broadband, packet-based transmission of text, digitized voice, video and multimedia at data rates up to 2 megabits per second (Mbps), offering a consistent set of services to mobile computer and phone users 3G (Third Generation) • 3G and EDGE (Enhanced Data Rates for GSM Evolution) : 3G Mobile communication technology is a broadband, packet-based transmission of text, digitized voice, video and multimedia at data rates up to and possibly higher then 2Mbps, offers a consistent set of service to mobile computer and phone users no matter where they are located in the world. Enhanced Data rates for GSM Evolution (EDGE) (also known as Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC), or Enhanced Data rates for Global Evolution) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE is standardized by 3GPP as part of the GSM family, and it is an upgrade that provides more than three-fold increase in both the capacity and performance of GSM/GPRS networks. It does this by introducing sophisticated methods of coding and transmitting data, delivering higher bit-rates per radio channel. EDGE can be used for any packet switched application, such as an Internet connection. EDGE-delivered data services create a broadband internet-like experience for the mobile phone user. High bandwidth data applications such as video services and other multimedia benefit from EGPRS' increased data capacity. Chat • Online textual talk in real time is called chatting. =>SMS (Short Massage Service ) : It is a communication service standardized in the GSM mobile communication system, using standardized communications protocols allowing the interchange of short text messages between mobile telephone devices. SMS text messaging is the most widely used data application on the planet. Chatting: Online textual talk, in real time, is called chatting. you type a message on your screen , which is immediately received by the recipient . The the recipient can type a message in response to your message , which is received by you instantly. Video Conferencing: A two way videophone conversation among multiple participants is called video conferencing. Video Conferencing • It is a two-way videophone conversation among multiple participants. Email (Electronic Mail) • Electronic Mail is sending and receiving messages by computer. E-Mail (Electronic Mail ) :Electronic mail, often abbreviated as email, or e-mail, is a method of exchanging digital messages. E-mail systems are based on a store-and-forward model in which e-mail computer server systems accept, forward, deliver and store messages on behalf of users, who only need to connect to the e-mail infrastructure, typically an e-mail server, with a network-enabled device (e.g., a personal computer) for the duration of message submission or retrieval. Originally, e-mail was always transmitted directly from one user's device to another's; nowadays this is rarely the case. Voice Mail • It refers to e-mail systems that support audio. Voice Mail: Voicemail (or voice mail, voice-mail, vmail or VMS, sometimes called message bank) is a centralized system of managing telephone messages for a large group of people. The term is also used more broadly, to denote any system of conveying voice message, including the answering machine. Protocols for Chat and video conferencing: IRC (Internet relay chat) H.323 and SIP(Session Initiation protocol) For video conferencing. Voice over Internet protocol, VoIP. “WiFi or Wireless Fidelity refers to the technology surrounding the radio transmission of internet protocol data from an internet connection wirelessly to a host computer. Most often the internet connection is a higher speed one such as satellite, DSL or cable rather than slower dial-up connections.” i-Fi •Basic concept is same as Walkie talkies. How Wi-Fiis Network Works •A Wi-Fiahotspot created by installing an access point to an internet connection. •An access point acts as a base station. •When Wi-Fi enabled device encounters a hotspot the device can then connect to that network wirelessly. •A single access point can support up to 30 users and can function within a range of 100 – 150 feet indoors and up to 300 feet outdoors. •Many access points can be connected to each other via Ethernet cables to create a single large network. Wi-Fi Applications •Home •Small Businesses or SOHO •Large Corporations & Campuses •Health Care •Wirelests ISP (WISP) •Travellers Wi-Fi Gadgets WiMAX (Worldwide Interoperability for Microwave Access) is a wireless communications standard designed to provide 30 to 40 megabit-per-second data rates with the 2011 update providing up to 1 Gbit/s for fixed stations. The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. • Uses • The bandwidth and range of WiMAX make it suitable for the following potential applications: • Providing portable mobile broadband connectivity across cities and countries through a variety of devices. • Providing a wireless alternative to cable and digital subscriber line (DSL) for "last mile" broadband access. • Providing data, telecommunications (VoIP) and IPTV services (triple play). • Providing a source of Internet connectivity as part of a business continuity plan. • Smart grids and metering WWW (World Wide Web) • It is a set of protocols that allows you to access any document on the net through a naming system based on URL’s. • It is a small part of internet. • WWW Attributes:1. User-friendly 2. Hypertext and Hyperlink 3. Interactive 4. Frames Internetworking Terms And Concepts TelNet : Telnet (teletype network) is a network protocol used on the Internet or local area networks to provide a bidirectional interactive communications facility. Typically, telnet provides access to a command-line interface on a remote host via a virtual terminal connection which consists of an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP). User data is interspersed in-band with TELNET control information. Telnet Web Browser and Web Server : a Web Browser is a www client that navigates through the world wide web and display web page. A web server is a www server that responds to the requests made by web browsers. Web Site, Web Address and Web Pages : A location on a net server is called a web server. Each web site has a unique address called URL (uniform resource locator) . URL and Domain : The internet structure of the www is built on a set of rules called Hypertext Transfer Protocol (HTTP) and a page description language called Hypertext Markup Language (HTML). HTTP uses Internet addresses in a special format called a URL. A URL(Uniform Resources Locator) specifies the distinct address for each resource on the internet Type://address/path An internet address which is character based is called a Domain Name. the character based naming system by which servers are identified is also known as domain name system (DNS). Web Hosting : Web Hosting is a means of hosting web-server application on a computer system through which electric content on the internet is readily available to any web-browser. (i) Free hosting, (ii) virtual or shared hosting, (iii) dedicated hosting, (iv) co-llocation hosting HTML(Hyper Text Markup Language):It is a document layout and hyperlink-specification language. It tells the browser how to display the contents of a hypertext document. It also tells how to make a document interactive through special hyperlinks. It provides many layout commands, called tags that let us control the presentation of information on a web page. It is written in the form of HTML elements consisting of "tags" surrounded by angle brackets within the web page content. It can include or can load scripts in languages such as JavaScript which affect the behavior of HTML processors like Web browsers; and Cascading Style Sheets (CSS) to define the appearance and layout of text and other material. The W3C, maintainer of both HTML and CSS standards, encourages the use of CSS over explicit presentational markup Internetworking Terms And Concepts XML : XML (Extensible Markup Language) is a set of rules for encoding documents electronically. It is defined in the XML 1.0 Specification produced by the W3C and several other related specifications; all are fee-free open standards DHTML : Dynamic HTML, or DHTML, is a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (such as CSS), and the Document Object Model. DHTML allows scripting languages to change variables in a web page's definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load. Web Scripting : The process of creating and embedding scripts in a web page is known as webscripting. Script are interpreted and executed by a certain program of scripting-engine. Client-side scripting generally refers to the class of computer programs on the web that are executed clientside, by the user's web browser, instead of server-side (on the web server). This type of computer programming is an important part of the Dynamic HTML (DHTML) concept, enabling web pages to be scripted; that is, to have different and changing content depending on user input, environmental conditions (such as the time of day), or other variables. Web authors write client-side scripts in languages such as JavaScript (Client-side JavaScript) • Server-side scripting is a web server technology in which a user's request is fulfilled by running a script directly on the web server to generate dynamic web pages. It is usually used to provide interactive web sites that interface to databases or other data stores. This is different from client-side scripting where scripts are run by the viewing web browser, usually in JavaScript. The primary advantage to server-side scripting is the ability to highly customize the response based on the user's requirements, access rights, or queries into data stores. Welcome to Open Source Terminologies Free software: The software is freely accessible and can be freely used, changed, improved, copied and distribute by all who wish to do it. No payments are needed to be made for free software. There are four kinds of freedom for the users of the software. 1.The freedom to run the program , for any purpose 2. The freedom to study how the program work, and adapt it to your needs. Access to the source code is a precondition for this. 5 May 2017 165 3.The freedom to redistribute copies so you can help your neighbor. 4.The freedom to improved the program, and release your improvements to the public, so that the whole community benefits. Access to the code is a precondition for this. 5 May 2017 166 =>Open Source Software: The software/programs whose licenses do not impose much conditions. =>Software give users freedom to run/use the software for any purpose, to study and modify the program, and to redistribute copies of either the original or modified program (without having to pay royalties to previous developers). => Open Source Software can be freely used but it not have to be free of charge. =>Open Source doesn’t just access to the source code. the distribution terms of Open Source Software must comply with the following criteria. 1.Free Redistribution: The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different source. The license shall not require a royalty or other fee for such safe. 5 May 2017 168 2. Source Code: The program must include source code and must allow distribution in source code as well as compiled form. 3. Derived works: The license must allow modifications and derived works and allow them to be distributed under the same terms as the license of the original software. 5 May 2017 169 4. Integrity of the Author’s Source Code: The license may restrict source-code from being distributed in modified from only if the license allows the distribution of “patch files” with the source code for the purpose of modifying the program at build time. 5.No Discrimination Against persons or groups: The license must not discriminate against any person or group of persons. 6.No Discrimination Against Fields or Groups: The license must not restrict anyone from making use of the program in a specific field of endeavor. 7.Distribution of License: The Right attached to the program must apply to all to whom the program is redistributed without the need for execution of an additional license by those parties. 8.License Must Not be Specific to a Product: The rights attached to the program must not depend on the program’s being part of a particular software distribution. 9.The license must Not Restrict other Software: The license must not place restrictions on other software that is distributed along with the licensed software 10. License Must Be technology Natural: No provision of the license may be predicted on any individual technology or style of interface. 5 May 2017 171 Free Software and Open Source Software FREE SOFTWARE freely accessible freely used, changed, improved, copied & distributed requires no payment emphasis on freedom OPEN SOURCE SOFTWARE freely used does not have to be free of charge source code is freely available to customer emphasis on technical progress OSS(open source Software): It refer to software whose source code is available to customers and it can be modified and redistributed without any limitation. FLOSS(Free Libre and Open Source Software or to Free Livre and Open Source Software): A software which is both free software as well as open source software. GNU: It refers to GNU’s Not Unix .GNU Project emphasizes on freedom and thus its logotype show a gnu, an animal living in freedom. 5 May 2017 173 GNU: GNU refer to GNU’s Not Unix. It emphasizes on freedom and its logotype shows a gnu, an anima living in freedom. objective to create a system compatible to Unix but not identical with it. FSF: Free Software foundation. it is a non-profit organization created for the purpose of supporting free software movement. OSI: Open Source Initiative. It is an organization dedicated to cause of promoting open software W3C(World wide Web consortium): W3C is responsible for producing the software standards for world wide web. 5 May 2017 174 Proprietory Software • • • • Neither open nor freely available Use is regulated Further distribution & modification forbidden Source code is normally not available. Freeware • • • • • Software available free of cost Allows copying and further distribution, not modification Source code not available Distributed in binary form without any licensing fee e.g. Microsoft Internet Explorer Shareware • • • • • Right to redistribute copies For use after trial period, a license fee to be paid Source code not available Modifications not allowed Distributed in binary form OSI (Open Source Initiative) • • Organization dedicated to cause of promoting OSS Specifies criteria for OSS and properly defines the terms & specifications of OSS. WELCOME TO Network Security Concepts Problems • Physical Security holes: When individuals gain unauthorized physical access to a computer and tamper with files. • Software Security holes: When badly written programs or privileged software are compromised into doing things that they shouldn’t be doing. • Inconsistent usage holes: When a system administrator assembles a combination of hardware and software such that the system is seriously flawed from a security point of view. Protection Methods • • • • • Authorization- e.g. username Authentication- e.g. password Encrypted smart card Biometric systems- e.g. fingerprint matching Firewall- e.g. Packet filter, Application gateway, Circuit-level gateway, Proxy server Network Security Measures • Firewall: A System designed to prevent unauthorized access to or from a private network. • It is a mechanism to prevent unauthorized internet users from accessing private networks connected to internet. Related terms • Cookies: Cookies are messages that a web server transmits to a web browser so that the web server can keep track of the user’s activity on a specific web site. • Hackers • Crackers • Cyber law • India’s IT Act • Cyber Crime Cookies Hackers & Crackers • Hackers: interested in gaining knowledge about computer systems & using this for playful pranks • Crackers: malicious programmers who break into secure systems for the purpose of stealing or corrupting data Ankit Fadia, famous hacker Cyber Law & India’s IT Act • Cyber law: Refers to all the legal and regulatory aspects of Internet & the World Wide Web • India’s IT Act: In India the cyber laws are contained in the IT Act 2000. Aims to provide legal infrastructure for e-commerce in India by governing transactions through internet and other electronic medium Cyber Crime An unlawful act where in a computer is either a tool or a target or both. classified as: – Tampering with computer source documents – Hacking – Publishing of obscene information in electronic form – Child Pornography – Accessing protected system – Breach of confidentiality & privacy IPR(Interllectual property reflect) Issues • Refers to a number of distinct types of creations of the mind for which property rights are recognized & corresponding fields of law. • Owners are granted certain exclusive rights to a variety of intangible assets, such as musical, literary, artistic works, discoveries, inventions, words, phrases, symbols & designs. • Common types of intellectual property are copyrights, trademarks, patents and industrial design rights VIRUS: A computer virus is a computer program that can replicate itself and spread from one computer to another. Depend on the nature of a virus, it may cause damage of your hard disk contents, and/or interfere normal operation of your computer. Characteristics of a computer virus: It is able to replicate. Reduced memory or disk space. Modification of data. Files overwritten or damaged. Hard drive erased. Types of Virus File Infectors: Attach themselves to a program file. Boot sector Virus: Install themselves on the beginning tracks of the hard drive Macro Virus : infect data file. How Computer Viruses Spread ? It moves from computer to computer by attaching themselves to files or boot records of disks. A virus travel from file to another on the same computer if the infected file executed, from computer memory to a file on the disk , on a disk that is carried from one computer to another. Damage Can destroy file allocation table(FAT) Can create bad sectors on the disk can decrease the space on the hard disks by duplicating file. can format specific tracks on the disk. Can destroy specific executable files can cause the system to hang. =>Trojan Horse: A Trojan Horses is code hidden in a program such as a game as spreadsheet that looks safe to run but has hidden side effects. SPREAD: It spread through e-mail and exchange of disks and information between computers. Damage: File, memory etc. Worm: A worm is a program designed to replicate. The program may perform any variety of additional tasks as well. Characteristics: It is able to replicate It is self-contained and does not required a host It is activated by creating process. if it is a network worm, it can replicate across communication links. SPAM: It is a electronic junk mail or junk newsgroup postings. Avoiding Spam: =>To create a filter that finds does something to e-mail that you suspect is spam. Not to register yourself with true id to sign up for things on the internet. Virus Prevention: =>VIRUS PROTECTION: The following guidelines to lead virus free computing life. Never use a CD without scanning it for viruses. Always scan files downloaded from the internet. Never boot your PC from floppy . Write protect your disks. Use licensed software. Password protect your PC. Make regular backup. Install and use antivirus software. Keep antivirus software up to date.