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Transcript
Networking & Connectivity Mendelsohn A Computer Network • What is a network? – A system of two or more computing devices that are linked together. • Why are networks useful? – Share information (e.g. databases, software, other data) – Share peripherals (e.g. printers) – Share access (e.g. internet) – Allow people to work together Early Networks • Telegraph • Voice (telephone) What type of information does a computer network typically carry ? • Voice • Data • Both Copyright 2008 M J Davidson What type of signal does the network carry ? • Digital • Analog Copyright 2008 M J Davidson Terminology • Node: Any device on the network such as computers or peripherals (printers, routers, etc) is called a node. • Nodes are typically connected to hubs (or sometimes switches). – Think of how you get your electronics on the electrical “network” by plugging them into an outlet. – Similarly, to get devices onto a network, you need to plug them into the network. Frequently this is done by connecting the node to a hub. A Hub Ethernet cable A network can be as simple as two computers connected to each other • Most networks involve at least a few computers frequently with some peripherals (printer). • With multiple computers, the nodes need to be plugged into a hub. Home networks • Most people create a home network for the purpose of sharing an internet connection. • However it is also possible to share peripherals such as scanners and printers. A Home Network Sharing an Internet Connection wall outlet Connecting a device to the network • Wired – Various types of cabling are available • Wireless – Requires the use of a shared or agreed-upon standard such as WiFi Wired – Types of Cables • Twisted Pair (shielded, unshielded) • Coaxial • Fiber-Optic Modems • One wired method of connecting to a network – Increasingly obselete • Networks such as telephone systems use analog signals (as opposed to digital) • Before a computer can work with the data, it has to be “translated” into digital • The process of converting an analog signal to digital is called MO-dulation. • Converting digital to analog is called DEM-odulation. • These days, modems are becoming less common as most people are networked digitally. – They don’t have to “dial in” using a telephone line. Bandwidth • If your online experience seems slow and jerky— particularly when dealing with multimedia (audio, video), your problem is likely a question of bandwidth. • When talking about internet connections, bandwidth refers to the quantity of data that can be transferred from an ISP to your PC in a given period of time (e.g. each second). • These days, is typically measured in megabits per second (mps). Broadband • Broadband refers to a high-bandwidth connection. – Typically several mps – That said, there is typically a large difference between your theoretical bandwidth and the actual bandwidth you get at home. • Types of broadband: – – – – DSL: uses standard phone lines – therefore, widely available Cable: requires a cable line (same as TV cable) Wireless: such as WiFi, Satellite, Infrared, Bluetooth Fiber-Optic: far faster than any other technology. However, fiberoptic wiring is still only available in a small number of locations. • 1 FO cable can transmit the equivalent of 10,000 copper (e.g. cable) cables Broadband Penetration Worldwide Wireless Technologies/Standards • In terms of connectivity, wireless technologies include Satellite, Infrared, WiFi, Bluetooth, and others WiFi (IEEE 802.11) • More and more people every day are connecting to networks such as the internet using WiFi • Not surprisingly, WiFi is the fastest growing networking technology. • The IEEE standard is known as 802.11 – Versions: 802.11a, 802.b, 802.11g, 802.11n – These versions have varying ranges and speeds • Speed ranges from 10 mps to 100+ depending on the version (Version ‘n’ is the fastest, ‘b’ is the slowest) • Very limited range: about 30 meters. – Version ‘n’ has a greater range – but still measured in meters • Not as fast as Ethernet, but still quite fast and good enough for multimedia networking WiMax (802.16a) • A new wireless standard • WiMax towers have a range covering about a 25 square mile area Broadband Comparison Bluetooth (IEEE 802.15) • Another wireless standard • Very low range (about 10 m) • Low bandwidth (about 1-3 mps in practice) • Costs less – therefore popular with manufacturers • Given low range and bandwidth, not widely used for network connectivity • Much more popular for wirelessly connecting two devices together – provided they are in close proximity Read this!!! • There will be an exam question that comes from reading this article…. • http://dvice.com/archives/2006/08/shift_ver izons_fios_and_sprint.php Connecting a PC to a Network • Wired – Requires a network adapter or “network interface card” (NIC) • Wireless – Requires a wireless network adapter A typical home cable/DSL broadband connection 1. Pre-existing cable wires are extended to the interior of your home. • 2. 3. 4. This cabling may already be in place (e.g. if you have cable TV) Your internet service provider (ISP) provides a cable or DSL “modem” that establishes the connection between the cable wiring and the internet. The cable/DSL modem is typically connected either directly to a PC or sometimes to a wireless router. If a wireless router is in place, the internet signal to and from the wireless router is broadcast throughout the home. Classifying networks • By Distance (LAN, WAN), Relationship (e.g. client-server), Protocol (e.g. TCP/IP) Copyright 2008 M J Davidson Classify by Distance • PAN – personal – E.g. a home network: • sharing one internet connection • sharing a printer • LAN – local – Usually implies that the networked computers are in the same building – E.g. a small business • WAN – wide – A network spanning a wider area such as a city or even larger. – DePaul’s network on several campuses around the Chicagoland area – City-wide networks are sometimes referred to as ‘MAN’s (metropolitan area networks) Classify by Relationship • Client-server • Peer-to-peer Copyright 2008 M J Davidson Classify by Protocol • a set of rules for the exchange of data over a communications channel • Examples – SNA – TCP/IP • The internet is classified based on the type of protocol it uses (TCP/IP) – More on this in a later lecture Copyright 2008 M J Davidson Wired Communication Ports – – – – – – – Serial - single bit at a time Parallel – eight bits at a time FireWire (IEEE 1394 ) Universal Serial Bus (USB) Ethernet VGA Etc Parallel Port – Parallel – eight bits at a time • Before USB, was commonly used for printers. Many printers still come with cables to connect to a parallel port. • Before faster and more efficient ports were developed, was also used for CD ROMs, Zip drives, etc VGA Port • These days, pretty much exclusively limited to connecting a monitor to a PC. USB Port – USB Universal Serial Bus • 1.0 (11 Mbps) or • 2.0 (480Mbps) - the current standard – Developed to replace connections that previously were limited to serial or parallel ports. • • • • Printers Keyboard Mice You name it…. IEEE 1394 (Firewire, i.Link) – High-speed communications – Brand names: • Firewire (Apple) • i.Link (Sony) – Fast! – Popular uses: Devices that require speedy transfer • external hard drives • Camcorders (transfer of large data devices from camera to PC) Ethernet Port • Ethernet wiring is far and away the most popular (wired) method of connecting a computer to a network • Pros: – Faster than wireless – More reliable than wireless – Easier to set up • Cons – Wired!