Internet: a network of network

Transcription

1 Internet: a network of network The internet consists of thousands of smaller networks They may be educational, commercial, nonprofit, military organizations, etc. 2-1

2 Internet History Began with 1969 s ARPANET for US Dept. of Defense 62 computers in computers in ,000 computers in 1987 Early 1990s, multimedia (www) became available on internet 2-2

3 2-3 PC-a IP:B.1.a Amazon.com Server IP: A.AS.0 NAP-A IP: A.0.0 ISP2/POP-1 IP:B.1.0 MAC-a IP:B.6.a ISP2/POP-6 IP:B.6.0 MAC-b IP:B.6.b MAC-c IP:B.6.c MAC-d IP:B.6.d NAP-B IP: B.0.0 NAP-C IP:C.0.0 IP: A.0.0 IP:C.0.0 Udel-4 IP:C.4.0 ISP1/POP-2 IP:E.2.0 PC-d IP:E.2.d NAP-E IP:E.0.0 PC-a IP:E.2.a PC-c IP:E.2.c PC-b IP:E.2.b NAP-D IP:D.0.0 Comcast/POP-5 IP:D.5.0 PC-a IP:D.5.a Comcast/POP-3 IP:D.3.0 PC-b IP:D.5.b MAC-a IP:C.4.a PC-b IP:C.4.b PC-b IP:D.3.b MAC-a IP:D.3.a

4 NAP (Network Access Point):A routing computerat a point on the internet where several connections come together Connects to the Internet Backbone(fast, expensive connection) Router: A device that forwards data from one network to another based on internal routing tables Routers read each packet s destination IP address and decide how to forward it. IP Address: Internet Protocol Address a unique address that identifies every computer and device connected to the internet POP Point of Presence A local access point to the internet ISP:Internet Service Provider A local, regional, or national organization/company that provides access to the internet LAN Local Area Network a computer network that spans a relatively small area 2-4

5 Protocols set of rules and encoding specifications for sending data Internet uses TCP/IP (Transfer Control Protocol/Internet Protocol Used for all internet transactions TCP Deals with Transfer of Data how it is broken up and reassembled to be sent across the internet Packets Fixed-length blocks of data for transmission Data transmissions (files) are broken up into packets Not all packets from the same file will follow the same pathway Data must be reassembled at the other end 2-5

6 IP Deals with the addressing and pathways the data travels over the internet IP Addresses Every device connected to the internet has an address Each IP address uniquely identifies that device The address is four sets of 3-digit numbers separated by periods Example:

7 The Internet is Distributed No centralized control of the internet If any one computer goes down, the internet can continue to function Allows for expansion of the internet as well Can easily add new computers and networks to the internet. Must assign unique IP addresses to computers connecting to the internet and Must update Router Tables 2-7

8 Client/Server Model Client: a computer requesting data or services Server: a host computer, a central computer supplying data or services requested of it Services can be requested over the internet E.g., Check your bank account A client program on your computer forwards your request to a server program at your bank. The bank server sends the info back to your client program Often multiple clients share the services of one server Or Services can be local requests Maybe one computer on a local network has extra disk space and can hold a large database Clients on the network make requests from the local server and the server sends only the data the client requests Peer to Peer (P2P) Model Computers that both provide services to and receive services from each other Services execute on a temporary basis E.g., Instant Messaging, 2-8

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10 The World Wide Web: Browsers Software for web-surfing Examples: Internet Explorer, Netscape Navigator, Mozilla FireFox, Opera, Apple Macintosh browser, Safari Browsers do 2 key things: Locate web sites via unique addresses Read web pages and display them 2-10

11 Website A location on the web that has a unique address and a set of interconnected web pages, usually on the same server Example: The website could be anywhere not necessarily at company headquarters 2-11

12 Web Pages The documents and files on a website Can include text, pictures, sound, and video Home page The main entry point for the website Contains links to other pages on the website 2-12

13 (URL) A string of that points to a specific (unique) on the web URL = It consists of The web protocol- The of the web server The directory or on that server The file within the directory, including optional extension protocol domain name directory file name. extension 2-13

14 Must be unique Identify the, and the type of it is is NOT the same as etc. 2-14

15 The used to access the World Wide Web Stands for The version of The version of The language used in writing and publishing The set of tags used to specify document structure, formatting, and links to other documents on the web NOT a programming language (but it can contain programming code) connect one web document to another 2-15

16 Organizations that maintain accessible through websites to help you find on the internet Users can ask questions or use to locate information Examples: Google, Ask Jeeves, and Gigablast are compiled using software programs called crawl through the World Wide Web Follow links from one page to another the words on that site 2-16

17 There is no that verifies all internet sites Should you information you find online? Guidelines to evaluate Web Resources Does the information appear on a maintained by a? Does the website appear to be legitimate? Is the website,, and? 2-17

18 Program Examples: Microsoft s Outlook Express, Mozilla s Thunderbird, Apple s Apple Mail Enables you to send by running software on your computer that interacts with an (usually at your ) mail is stored on the in an electronic mailbox Upon, mail is sent to your 2-18

19 Using 1. Get an, following the format User Name Domain name 2. Type addresses carefully, including capitalization, underscores, and periods 3. Use the to avoid addressing mistakes 4. Use the to store addresses 5. Sort your into or use 2-19

20 2 for transferring mail from the to the : I 1 for transferring mail from 2-20

21 (NOT to be confused with Point of Presence!) How this works: 1. holds your mail 2. logs on and requests mail 3. downloads all mail to the client (your computer) 4. removes your mail 5. can disconnect you ve got all your mail now! Advantages: Don t need to stay to the for long are used minimally More software is currently available for 2-21

22 How this works: 1. holds your mail 2. logs on 3. downloads headings (subject) only reads mail on the chooses which mail to and Mail remains on 2-22

23 Advantages: You can your anywhere, from any computer Faster time (not all your files) Good for Ability to handle (e.g., MIME messages) can act like functionally is a superset of 2-23

24 : Your limits your You use and only to read your You can only stay to the for a limited amount of time Your server has : You travel or check your from more than one You get a lot of and don t want to it all to your computer You want to your messages You can maintain a to your You have a lot of on your 2-24

25 used to transfer data from one to another Uses Think of it this way: When you send an message out, it uses to travel to. When you want to read an , you use or to get the message from the. 2-25

26 Any user on a given system can send a message and have it pop up instantly on the screen of anyone logged into that system Participants have a typed discussion while online at the same time is one-on-one, but has a list of participants 2-26

27 A software standard for transferring between computers with different Operating Systems A giant electronic discussion board Usenet is the of servers on the internet To participate you need a An -based Uses an automatic that sends to subscribers on selected topics 2-27

28 Internet Telephony Uses the internet to make Long-distance calls are either very inexpensive or free Currently to normal phone connections Programs that scour the web and pull together from several to one place Short for, a diary-style web page Have become popular, both privately and in politics Recording internet radio or similar internet audio programs Some radio stations their audio programs over the internet 2-28

29 Conducting business activities online is business-to-business e- commerce now involves online banking, stock trading online, and e-money such as PayPal Online link buyers with sellers is the most well-known example of personto-person 2-29