MAKING THE CONNECTION

1. chapter3 MAKING THE CONNECTION The Basics of Networking (c) 2004 Addison Wesley

2. Digital Vs Analog • Analog Signals • Continuous • Digital Signals • Discrete • Carrying information in the signal (c) 2004 Addison Wesley

3. Speeds • Early Modems: • 300 bits per second • 56 k bits per second • K =thousand = 1024 • M = million • Today • Speeds in the million and billions of bits per second very common (c) 2004 Addison Wesley

4. Channels • Different types of materials • Twisted Pair : Copper • Coaxial Cable • Cable TV • Faster than copper • Fiber Optic • TV and Internet • Harder to snoop • Faster • Air • Affected by weather (c) 2004 Addison Wesley

5. Pics of types of medium (c) 2004 Addison Wesley

6. Wireless • Radio • Distribute to large audience • Cellular • Short distances uses towers and cells • Switch over from tower to tower • Problems with blind spots and density (c) 2004 Addison Wesley

7. Wireless • Microwave • Short distances • Weather related problems Speeds of different medium Twisted pair ~10 Mbps to 1 Bbps Coaxial – 10Mbps Fiber – 100 Mbps Cellular – 9.6 kbps – 14.4 kbps (c) 2004 Addison Wesley

8. Types of Networks • LAN • Local Area Networks • Fast • Small – building or couple of buildings • Ethernet • Metropolitan Networks • Size of a city • Wide Area Networks • World • Uses packet switched technologies or circuit switched (c) 2004 Addison Wesley

9. LAN (c) 2004 Addison Wesley

10. WAN (c) 2004 Addison Wesley

11. Net work Topologies (c) 2004 Addison Wesley

12. Network Architecture • Mainframe Based • Peer to Peer – computers can access each other • Client Server – xampp Apache Mysql (c) 2004 Addison Wesley

13. Public Switched Telephone Network PSTN • Dial Up • Slow uses analog connection – up to 56k • ISDN • Integrated Services Digital network • Used more for video conferencing • DSL • Digital Subscriber Line – uses high frequencies and leaves low frequencies for voice – options can be confusing – affected by distance away from central office 128k – 3 mpbs • T1 at 1.544Mbps – T3 at 44.376 Mbps -dedicated lines – reliable but expensive • FIOS – fiber optic – limited to single provider – not available in all areas – 10mbps+ (c) 2004 Addison Wesley

14. Wireless Oh Gee (c) 2004 Addison Wesley

15. Key communication concepts • Synchronous- Sender and receiver communicate ‘instantaneously’ (ex: telephone) • Asynchronous- Sender and receiver communicate at different times (ex: walkie-talkie) (c) 2004 Glenn L. Ray

16. Key communication concepts • Broadcast- Single sender & many receivers (ex: radio) • Multicast- Single sender & a subset of receivers (ex: videoconference) • Point-to-point- One sender & one receiver (ex: telephone) (c) 2004 Glenn L. Ray

17. Networking Terminology • LAN – Local Area Network • A discrete network linked by a single cable or pair of wires • Typically serves a single building (home or office) • WAN – Wide Area Network • Networks that communicate over greater distances where the computers are not directly connected • Internet is a collection of networked WANS • Intranet – A LAN that enables communication within the network and that allows connection to the internet via a gateway (c) 2004 Glenn L. Ray

18. Internet Capabilities • Internet is asynchronous but so fast it appears synchronous • Internet is an all-purpose communication network • Synchronous -> phone service • Multicasting -> chatrooms • Broadcasting -> web pages (c) 2004 Glenn L. Ray

19. Figure 3.1. A diagram of the Internet. (c) 2004 Addison Wesley

20. World Wide Web • Web Servers – Internet computers that send files to browsers • WWW = web servers + files • Lots of useful information that can be easily found and retrieved • Internet – the physical infrastructure (wires & routers) that connects computers • WWW is a subset of the internet (c) 2004 Glenn L. Ray

21. Figure 3.3a. Two diagrams of domain hierarchy. (c) 2004 Addison Wesley

22. Figure 3.3b. Two diagrams of domain hierarchy. (c) 2004 Addison Wesley

23. Figure 3.2. Computers connected to the Internet are given IP addresses. (c) 2004 Addison Wesley

24. Internet Protocol Addresses • Every computer must have a destination address (IP address) • Currently, IP address is a series of 4 numbers • Ex: 128.95.1.207 • Each number ranges from 0-255 • Can handle 2564 computers (4.3 billion) -> not enough! • IPv6 will handle 25616 (340 trillion trillion trillion) • Domain is a related set of networked computers w/ hierarchical structure • Each computer has a name that corresponds to an IP address • Domain Name Servers translate names into IP addresses (c) 2004 Glenn L. Ray

25. Figure 3.4. Hosts like Spiff make requests to a local DNS server. (c) 2004 Addison Wesley

26. World Wide Web • URL – Uniform Resource Locator uniquely identifies each resource on the WWW, it has 3 parts • Protocol (http://) specifies how browser and web server communicate • Web server’s name (www.pitt.edu, for example) • Pathname for file requested from the server • WWW is based on client-server model • Browser is the client who requests resource from server • Server sends resource to client, then serves next request (c) 2004 Glenn L. Ray

27. Internet TCP/IP Protocol • Protocol- An agreed upon format for exchanging information between parties • Specifies data structure, error checking, when sender is finished, confirmation of receipt, etc. • All parties must know the protocol and follow it • Example protocols • TCP/IP (Transmission Control Protocol/Internet Protocol) • HTTP (Hypertext Transfer Protocol) • FTP (File Transfer Protocol) • A common protocol is required for communication via the internet • TCP/IP is the fundamental internet protocol (c) 2004 Glenn L. Ray

28. Figure 3.5. The TCP/IP postcard analogy. (c) 2004 Addison Wesley

29. Figure 3.6. The Internet makes use of whatever routes are available to deliver packets. (c) 2004 Addison Wesley

30. Internet TCP/IP Protocol • Transmission Control Protocol/Internet Protocol • TCP/IP breaks a message into a numbered series of IP packets. • Packet contains message, destination IP address, sequence number • Each packet may travel a different route • Reassembled in order at destination • Packets hop from WAN to WAN via various physical media (wire, fiber optic, satellite, etc.) (c) 2004 Glenn L. Ray

31. Figure 3.7. A ping from the author’s machine to eth.ch. (c) 2004 Addison Wesley

32. World Wide Web • Web pages usually stored in HTML format • Hypertext Markup Language – describes document layout • Browser displays document based on the HTML tags embedded in document • HTML is the next topic in the course (c) 2004 Glenn L. Ray

33. Figure 3.9. A Web page and the HTML source that produced it. Notice that an additional image file, alto.jpg, is also required to display the page. (c) 2004 Addison Wesley

34. Figure 3.9 (continued). A Web page and the HTML source that produced it. Notice that an additional image file, alto.jpg, is also required to display the page. (c) 2004 Addison Wesley

35. Figure 3.10. A hierarchy diagram showing the path between xerox-alto.jpg and the desktop. (c) 2004 Addison Wesley

36. Figure 3.11. The pathname hierarchy ending in pioneer.html. (c) 2004 Addison Wesley

37. Ethernet • Dominant network technology for LANs • Uses broadcast to achieve point-to-point communication • Only 1 communication at a time on the network • OK since LAN carries local traffic • If you want to talk, follow these rules… • If no one is talking, then talk • If someone is talking, listen until they stop, then start talking • If someone else starts talking at the same time, stop talking • Wait a random amount of time, then try to start talking (c) 2004 Glenn L. Ray

38. Ethernet • Sends bits by varying the voltage in the wire • A voltage increase = 1, voltage decrease = 0 • We’ll talk about bits later in the course • Bits are combined into data bundles called Frames • A protocol defines the data structure of each Frame • Frames are transmitted through the network (c) 2004 Glenn L. Ray

39. Figure 3.8. Robert Metalfe’s original drawing of the Ethernet design; the unlabeled boxes, computers, “tap” onto the wire that Metcalfe has labeled “The Ether.” (c) 2004 Addison Wesley