1. Networking & Connectivity Mendelsohn

2. 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

3. Early Networks Telegraph Voice (telephone)

5. Copyright 2008 M J Davidson What type of information does a computer network typically carry ? Voice Data Both

6. Copyright 2008 M J Davidson What type of signal does the network carry ? Digital Analog

7. 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.

8. A Hub Ethernet cable

9. 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.

10. 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.

11. A Home Network Sharing an Internet Connection wall outlet

12. 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

13. Twisted Pair (shielded, unshielded) Coaxial Fiber-Optic Wired – Types of Cables

14. 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.

15. 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).

16. 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, fiber- optic 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

17. Broadband Penetration Worldwide

18. Wireless Technologies/Standards In terms of connectivity, wireless technologies include Satellite, Infrared, WiFi, Bluetooth, and others

19. 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

20. WiMax (802.16a) A new wireless standard WiMax towers have a range covering about a 25 square mile area

21. Broadband Comparison

22. 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

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24. Connecting a PC to a Network Wired –Requires a network adapter or “network interface card” (NIC) Wireless –Requires a wireless network adapter

25. A typical home cable/DSL broadband connection 1.Pre-existing cable wires are extended to the interior of your home. This cabling may already be in place (e.g. if you have cable TV) 2.Your internet service provider (ISP) provides a cable or DSL “modem” that establishes the connection between the cable wiring and the internet. 3.The cable/DSL modem is typically connected either directly to a PC or sometimes to a wireless router. 4.If a wireless router is in place, the internet signal to and from the wireless router is broadcast throughout the home.

27. Classifying networks By Distance (LAN, WAN), Relationship (e.g. client-server), Protocol (e.g. TCP/IP) Copyright 2008 M J Davidson

28. 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)

29. Copyright 2008 M J Davidson Classify by Relationship Client-server Peer-to-peer

30. 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

31. 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

32. 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

33. VGA Port These days, pretty much exclusively limited to connecting a monitor to a PC.

34. 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….

35. 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)

36. 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!