1 Internet and LAN Technology 2 Network Building Blocks A communications network is a collection of computers and other devices that communicate to share data, hardware and software In 1948, Claude Shannon published an article that described a communication model 3 Network Building Blocks 4 Network Building Blocks In order to communicate, information must be transformed into the format the network uses 5 Network Building Blocks The number of units of information you can convey is simply the number of different combinations that you can make with a given number of bits 6 Network Building Blocks Computers use several coding schemes based on binary digits ASCII EBCDIC Unicode Binary numbers 7 Network Building Blocks When data is transmitted, it usually takes the form of an electromagnetic signal On a communication network, your data may be converted into several different types of waves 8 Network Building Blocks 9 Network Building Blocks Waves can have different shapes, referred to as waveforms or wave patterns 10 Network Building Blocks Data can travel from one network device to another over a cable or through the air A communications channel is a physical path or a frequency for a signal frequency Networks use different types of cables 11 Network Building Blocks Today s networks use twisted-pair cables UTP (unshielded twisted pair) STP (shielded twisted pair) looks similar to telephone cable
has square plastic RJ-45 connector 12 Network Building Blocks Another option is coaxial cable resembles cable-tv cable round, silver BNC connector 13 Network Building Blocks Fiber-optic cable is a bundle of extremely thin tubes of glass Each optical fiber (tube) is thinner than a human hair Consists of strong inner support wire, multiple strands of optical fiber and a tough outer cable Transmit pulses of light Data can also travel airways in form of RF signals sent and received by a transceiver 14 Network Building Blocks Microwaves provide another option for transporting data Radio and microwave transmissions are bent around the surface of the earth to reach towers Communications satellites play an important part in long-distance communications A transponder on the satellite receives the signal, amplifies it, and retransmits the signal back to a ground station 15 Network Building Blocks Infrared light can also carry data signals, but for short distances with a clear line of sight Best for transmitting between notebook computers and a printer, or between a PDA and a desktop computer Laser light can also carry data signals, for a longer distance, but requires a clear line of sight Experimental, but possibly may be useful for transmitting data between buildings 16 Network Building Blocks Bandwidth is the transmission capacity of a communications channel High-bandwidth communications systems, such as cable TV, are sometimes referred to as broadband Systems with less capacity, such as the telephone system, are referred to as narrowband The bandwidth of a digital channel is usually measured in bits per second (bps) 17 Network Building Blocks Each device that is connected to a network is referred to as a node The term workstation usually refers to a personal computer connected to a local area network (LAN), it is also called a client A modem is a device that converts signals from a computer into a signal that can travel over a wide area network 18 Network Building Blocks A network interface card (NIC) is the key hardware component for connecting a computer to a local area network.
small circuit board that sends data to and from workstation to network A server refers to any computer on a LAN or the Internet that contains the software to manage and process files for other network nodes 19 Network Building Blocks A host computer usually refers to any computer that provides services to network users A hub is a device that connects several nodes of a LAN A router is a device that is connected to at least two networks and makes decisions about the best route for data A gateway is a device that performs functions similar to a router A repeater amplifies and regenerates signals so they can retain the strength th to reach their destinations 20 Network Building Blocks Every node on a network has an address Every packet of data that travels over a network also has an address which helps to route a packet to its destination 21 Network Building Blocks An address is built into the circuitry of most network devices This is the device s physical address On a network, a device will be assigned a logical address A A protocol on the network keeps track of which physical address corresponds to each logical address 22 Network Building Blocks The layout of a network is referred to as its physical topology 23 Network Building Blocks A A real-world network can make use of more than one topology 24 Network Building Blocks Networks also have a logical topology which corresponds to the way that messages flow 25 Network Building Blocks When you transmit data, it is broken up into small pieces called packets A packet is a parcel of data that is sent across a network Has the address of its sender Has the address of the destination Has some data When they reach the destination, they are put back together into original form 26 Network Building Blocks Short answer: shorter packets are easier to handle Long answer: Telephone network uses circuit switching, which establishes a private link between telephones for duration of call This provides a direct pipeline
27 Network Building Blocks 28 Network Building Blocks Engineers wanted a more robust communications link for computer networks They devised packet switching in which a message was divided into several packets that can be routed independently to their destination to avoid out-of-service or congested links Packet switching makes very efficient use of available bandwidth and provides a steady stream of data 29 Network Building Blocks Communications protocolrefers refers to set of rules for transmitting data from one node to another Protocols allow two devices to negotiate and agree on how data will be transmitted 30 Network Building Blocks Protocols establish communications through handshaking The devices decide on how to coordinate its transmission Synchronous protocols are synchronized by a signal called a clock when sending and receiving data Asynchronous protocols require the transmitting computer to send a start bit, then data is sent, and a stop bit to mark the end of the data 31 Network Building Blocks Simplex signal travels in only one direction Half duplex signal travels in both directions, but only one direction at a time Full duplex signal travels in both directions at the same time 32 Network Building Blocks Computers use error-checking protocols to make ensure accurate delivery of data (such as over the Internet) Parity bit added to keep track of the number of 1s and 0s Even parity protocol requires number of 1s to be an even number 33 Network Building Blocks Even parity protocol example 34 Network Building Blocks Internet work a network composed of many smaller networks Intranet uses TCP/IP protocols but owned by a private business and does not typically allow remote access Extranet similar to intranet except that it allows remote password-protected protected access WAN (wide area network) covers a large geographical area and may consist of smaller networks 35 Network Building Blocks LAN (local area network) typically covers a very limited geographical area Wireless network uses radio frequencies
HomeRF network low-power wireless network for home use HomePLC uses building s existing power line cables HomePNA uses existing telephone cables Novell LAN that uses Novell Netware 36 Network Building Blocks Ethernet one of most popular technologies Uses CSMA/CD (carrier sense multiple access with collision detection) tion) 37 Network Building Blocks 10Base networks refer to two of the most popular cabling options for Ethernet networks 10BaseT uses twisted-pair cable called 10BaseT and transmits 10 Mbps 100BaseT Fast Ethernet transmits at rates up to 100 Mbps 38 Network Building Blocks Token Ring connects nodes in a physical star configuration, but passes data around a logical ring using a technology called a token 39 Network Building Blocks FDDI (Fiber Distributed Data interconnect) high speed network that uses fiber-optic cables ATM (asynchronous transfer mode) transmits packets over same channel Client/server contains servers and clients Peer-to-peer (P2P) every computer is considered an equal 40 Network Building Blocks 41 Internet and LAN Technology 42 Internet Building Blocks The United States created ARPA (Advanced Research Projects Agency). to help scientists communicate and share valuable computer resourcesrces in response to the Soviet Union s launch of Sputnik in 1957, the first artificial satellite The ARPANET, created in 1969, connected computers at four universities 43 Internet Building Blocks In early 1990s, software developers created new user-friendly Internet access tools Today, the Internet connects computers all over the globe and supplies information to people of all ages and interests 44 Internet Building Blocks Difficult to diagram due to over 100 million nodes and 350 million users 45 Internet Building Blocks An ISP operates network devices that handle the physical aspects of
transmitting and receiving data from your computer Modems Domain name server Router 46 Internet Building Blocks 47 Internet Building Blocks An ISP links to other ISPs in a sort of ISP network Network service Providers (NSPs) supply ISPs with access to high-speed transmission lines that form the backbone of the Internet NSPs also provide routers at network connection points 48 Internet Building Blocks The Internet calls into play just about every modern communications ons technology Telephone cable TV cable Fiber-optic cable Satellite 49 Internet Building Blocks Ping (Packet Internet Groper) sends a signal to a specific address and waits for a reply If it gets a response, Ping Reports computer is online Displays the elapsed time (latency) for the round-trip message Trace route records a packet s path from your computer to its destination 50 Internet Building Blocks 51 Internet Building Blocks Using Ping or Trace route, you can discover how long data is in transit On average, data within the US usually arrives at its destination n 110-120120 ms (milliseconds) after it is sent Overseas transmission require a little more time 52 Internet Building Blocks Exact figures cannot be determined due to the immeasurable size of the Internet Estimates state that Internet traffic exceeds 100 terabytes each week Terabyte is 2 to the 40 th power (1,099,511,627,776) bytes 53 Internet Building Blocks TCP/IP provides a standard that is fairly easy to implement, public, free, and extensible The Internet is not owned, operated, or controlled by any single entity TCP/IP is glue that holds the Internet together 54 Internet Building Blocks It is a suite of protocols
TCP (Transmission Control Protocol) breaks a message or file into packets IP (Internet Protocol) responsible for addressing packets so that they can be routed to their destination 55 Internet Building Blocks 56 Internet Building Blocks The IP part of TCP/IP defines the format for the addresses that identify computers on the Internet These addresses are called IP addresses An IP address is a series of numbers, such as 204.127.129.001 It is separated into four sections by periods Each section s number cannot exceed 255 Each address requires 32 bits (8 bits per section) 57 Internet Building Blocks Static IP address permanently assigned IP address Dynamic IP address temporarily assigned ISPs need static IP addresses Clients typically use dynamic IP addresses as the IP addressing scheme provides approximately only 4.3 billion unique addresses 58 Internet Building Blocks Each ISP controls a unique pool of IP addresses, which can be assigned signed as needed to subscribers Mostly assigned by ISPs for dial-up connections, some DSL, ISDN, or cable modem connections Addresses change each time you connect to your ISP 59 Internet Building Blocks People find it difficult to remember long strings of numbers, so host computers also have names called domain names Domain name fully qualified domain name (FQDN), usually typed in all lowercase Key component of URLs and e-mail addresses www.thex-files.com/episode236 - www.thex-files is the domain name 60 Internet Building Blocks A domain name ends with an extension that indicates its top-level domain 61 Internet Building Blocks Each name corresponds to an IP address Domain name system huge database that houses the names and IP addresses Domain name servers computers that house the database 62 Internet Building Blocks Domain name system is based on a distributed database When you enter a domain name or URL, it is sent to your domain server It can send back the IP address If it doesn t have a record of the domain name, it contacts other domain name servers
It can send back the address for a domain server that is more likely to have the IP address of the name you requested 63 Internet Building Blocks Not for normal client-style Internet activities If you plan to operate your own Web server, you may want a name 64 Internet Building Blocks ICANN (Internet Corporation for Assigned Names and Numbers) global organization that coordinates the technical management of the Internet s domain name system, allocation of IP addresses, and the assignment of protocol parameters Organizations or individuals can select a domain name and register er it by using an online registration service 65 Internet Building Blocks 66 Internet Building Blocks You can register a domain name for a minimal annual fee ($25 - $50) Some Internet entrepreneurs have registered high-profile domain names and resell them Sell-videos.com - $35,000 Thelocallistings.com - $87,500 67 Internet and LAN Technology 68 Internet Access Uses POTS (plain old telephone service) to transport data between your computer and your ISP 69 Internet Access 70 Internet Access While connected to your ISP, your call is routed through the telephone ephone company s local switch to the ISP 71 Internet Access Modem derived from modulate and demodulate Modulation changing characteristics of a signal (digital to analog) Demodulation changing signal back to original state (analog to digital) 72 Internet Access 73 Internet Access Digital switches kick into action only after your call arrives at the local switching station The local loop is still analog 74 Internet Access Yes and No When connected to ISP, data is transmitted in same frequencies used for voice conversations
Voice over IP (VoIP) allows you to play games, and chat about your moves all while you are online 75 Internet Access Speed was measured as baud rate,, number of times per second that a signal in a communications channel varies speeds Today, measure in terms of bits per second V.90 theoretical maximum speed of 56 Kbps Even with perfect connection, a 56 Kbps modem tops out at about 44 Kbps Downstream vs. upstream 76 Internet Access Community antenna television CATV The satellite dish farm at which television broadcasts are received and retransmitted is referred to as the head-endend From the head-end, end, cabling system branches out and eventually reaches consumers s homes Topology is similar to computer network, and that is what is formed when you use cable TV as your ISP 77 Internet Access 78 Internet Access 79 Internet Access Lowest-capacity coaxial cable has far greater capacity than POTS lines Cable s bandwidth is divided among 3 activities 80 Internet Access Need an Ethernet NIC Need a cable modem,, which converts your computer s signal into one that can travel over CATV cable 81 Internet Access With CATV, your computer becomes part of a neighborhood data network More people on the network, means slower service Also, in early days your network neighborhood showed your neighbors 82 Internet Access 83 Internet Access Today, many use DOCSIS-compliant cable modems to block this crossover access DOCSIS (Data Over Cable Service Interface Specification) is a security technology that filters packets to certain ports Secures your computer from your neighbors, but does not close up all the security holes 84 Internet Access
An always-on connection is always connected A A hacker who discovers that your computer has a security weakness s can easily find it again, and its high-speed access makes it a very desirable target 85 Internet Access Disable file and print sharing 86 Internet Access Shut down your computer when you are not using it Install personal firewall software,, which is designed to analyze and control incoming and outgoing packets Customize to small detail Or pick level high, medium, or low 87 Internet Access Several services such as DSL, ISDN, T1, and T3 take advantage of full capacity of the telephone connections (normal dial-up services do not) Offers high-speed digital communications links for voice and data 88 Internet Access DSL (Digital Subscriber Line) is a high-speed, always-on, Internet access technology that runs over standard phone lines Several versions exist ADSL, SDSL, HDSL xdsl refers to entire group of DSL technologies DSLAM (DSL Access Multiplexor) interpret data signals 89 Internet Access 90 Internet Access Speed varies, but most are rated at 1.5 Mbps downstream 91 Internet Access Telephone line connected to DSL switch at your house Line connected to DSL modem which connects to your computer s Ethernet card 92 Internet Access ISDN (Integrated Services Digital Network) move data at speeds of 64 Kbps or 128 Kbps A device called an ISDN adapter connects a computer to a telephone wall jack and translates the computer s signal into signal that can travel over the ISDN connection 93 Internet Access T1 high-speed 1.544 Mbps digital network Consists of 24 individual channels (64 Kbps for each) Popular for businesses and ISPs Not as fast as DSL T3 672 channels Supports data rates of about 43 Mbps Sometimes referred to as DS3 (Digital Service-3) lines Provide many of the links on the Internet backbone
94 Internet Access Personal satellite connections expensive, but sometimes only option (particularly in remote rural areas) Cellular telephones slowest, but provides mobile Internet access 95 Internet Access Direct satellite service (DSS) uses a geosynchronous or low-earth satellite to send television, voice, or computer data directly to a satellite dish Two-way way satellite service ships both upstream and downstream data through the satellite offers 500 Kbps downstream 40-60 Kbps upstream 96 Internet Access 97 Internet Access You can use several devices Cellular-ready ready PC card modem Cellular telephone cable between telephone and computer Fastest speed 14.4 Kbps Static can terminate an Internet connection 98 Internet Access 99 Internet Access 100 Internet Access Some PDAs can use a wireless connection to access the Internet Limited viewing space Some special PDA web sites 101 Internet and LAN Technology 102 LAN Technology Main advantage of a LAN is that multiple users can share a limit ed number of resources Can share a high-speed connection 103 LAN Technology When you boot your computer, OS looks to see if it can access a LAN The OS keeps track of network resources you can access automaticallyally Some network resources become available as soon as your computer completes the boot process, and others after you use your networking utilities 104 LAN Technology LAN can connect as few as two computers or it may encompass hundreds of devices Each computer or peripheral device requires a NIC which provides a connection point for a cable A hub is used to connect more than two computers
Each network device requires one of the hub ports You can add hubs using an uplink port 105 LAN Technology 106 LAN Technology Most use Category 5 (cat 5) UTP (unshielded twisted pair) cables with plastic RJ-45 connections at both ends Transmit at speeds up to 100 Mbps Category 5e (Cat 5e) is suitable for 1 Gbps 107 LAN Technology HomePNA uses a special NIC and cable to connect each computer to a standard telephone wall jack Network frequency is usually different from voice, so can use network at same time you place a call You can not make a call when dial-up Internet connection is active however HomePLC uses special NIC to connect to standard electrical outlet, but power fluctuations can adversely affect signal 108 LAN Technology Wireless LANs are slower but eliminate unsightly wires Signals can be disrupted by large metal objects, cell phones, pagers, and other wireless devices Most popular s 802.11b 11 Mbps, spans 300 feet, and can be used with Ethernet networks Bluetooth 200-400 Kbps, range of 35 feet 109 LAN Technology 110 LAN Technology Several LAN standards exist Ethernet Token Ring ATM FDDI Local Talk Ethernet is the dominant standard 111 LAN Technology Most LANs use TCP/IP Alternate protocols include IPX/SPX and NetBios/NetBeui 112 LAN Technology When a NIC is manufactured, it is given a unique address called a MAC address (Media Access Control) 1 st 3 bytes identify the company 2 nd 3 bytes are the NIC s serial number TCP/IP, SPX/IPX, and other protocols will assign their own addresses 113 LAN Technology Special network operating systems (NOS) were quite popular and are still used on some
networks Need for a special NOS has declined due to today s OSs including the software necessary to establish communication with other computers and devices on a LAN 114 LAN Technology Most application software designed for stand-alone alone computers can be used on a network Some applications are stored primarily on a server A workstation installation copies some files to your local hard disk, and then updates system to include a listing for the new program which mainly resides on the server 115 LAN Technology Multiple-user user license allows more than one person to use a particular software package Concurrent-user user license allows a certain number of copies to be used at the same time Site license allows software to be used on any and all computers at a specif ic location 116 LAN Technology First make sure every PC contains an Ethernet NIC Next, attach each workstation to a hub With all workstations connected, turn them on Windows should automatically detect the NICs and establish a connection to the network 117 LAN Technology Each workstation can specify whether its files will be accessible e to other workstations on the network Drive mapping is Windows terminology for assigning a drive letter to a storage device that s located on a different workstation 118 LAN Technology 119 LAN Technology To add high-speed Internet access to a LAN, you need a cable modem or DSL modem and a corresponding ISP You also need a router or a hub with router capabilities 120 LAN Technology 121 LAN Technology LANs are susceptible to internal security breaches If it has an always-on Internet connection, it also becomes vulnerable to external attacks 122 LAN Technology Any home network with an always-on Internet connection is vulnerable to intrusions You should use password protection and perhaps firewall software as well You can also use network address translation (NAT) as a line of defense Within your LAN, use private Internet addresses that can t be routed over the Internet Router takes care of message passing