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Networking I Chapter II The Internet How does one Connect? • • • • • • • • Dial-Up Connection – Modem ISDN – Integrated Services Digital Network DSL – Digital Subscriber Line Cable Modem Satellite Radio Waves T1 T3 Telephone Modem • Speed up to – 56K bits/second (download) – 32K bits/second (upload) • Available everywhere • Service Cost up to $25 monthly • Modem cost “free” to $50 or so ISDN • Integrated Services Digital network • Over Ordinary phone line but not always available • Can share a phone line with voice • Speeds up to 128k bps. • Service Cost up to $100 per month or so. • No longer as popular as it was about 4 years ago. DSL • • • • • Digital Subscriber Line Service cost from 30 to 50 pre month Not available in many places Shares a line with voice. Speed up to 7 or 8 megabits/second Cable Modem • • • • (What I have at home) Service about $40 per month Always on Requires a NIC for your computer and an RJ45 cable between modem and NIC. • Modem costs about 150 to 200 (but is “free” with most packages. • NIC costs from $10 to $150 or more. • Speed depends on the number of users but ranges from standard modem speed up to about 10 megabits/second. Satellite • Primarily for downloads. • Typically use phone lines for uploads • Speed is slow – 400k bits/second download; 56k bits/second upload • Expensive – up to about $125 per month. • Wireless and available everywhere, much like satellite TV. Radio Waves • Available on some more advanced cell phone plans. • Cost typically $40 per month plus cost of phone plan. • Extremely fast (in the 100mb per second range) T1 and T3 • Expensive – T1 in the $500 to $2000 per month depending on the distance from the station; T3 in the $10,000 per month range. • Fast – T1 is 1.5 megabits/second; and T3 is 45 megabits/second. • [The campus network at the UofS is hooked to the internet by a “partial” T3 line, which we share with others. Our bandwidth is 25 mbps.] ISPs – Intenet Service Providers • Free – Typically heavily sponsored. Most of the free services are no longer available because of technology which kills ad windows. • Basic – Few Features: dialup number, software (which is free with windows anyway), limited tech support, simple e-mail and perhaps USENet -- $10 to 16 monthly • Full– ISPs such as AOL, MSN, Compuserve, 24/7 tech support, multiple e-mail accounts, web pages -$20 to $20 per month. Choosing an ISP • In your case if you are a resident student then you have an account through the U for “free” with purchase of a NIC • Find what’s locally avaliable and what it costs. • You can normally get a free trial for a month from most major providers. IP Addressing • All machines on the Internet have an IP address (internet protocol address) • This address is 4 numbers from 0 through 255, so for example the machine in my office is 134.198.169.33 • Some addresses are static and some are dynamic. Dynamic vs. Static Addressing • Dynamic addressing gives you a possibly different address each time you connect to the Internet. • Static addressing gives you the same address all the time. • My office machine is static. • My laptop is dynamic because it has different IP addresses in my office and in the classroom. • In my office it can also have different addresses on different days. Domain Name Addressing • IP addresses are hard to remember. • Domain name addressing uses several “words” separated by dots. • My office machine has a domain address of peculier.cs.scranton.edu • Domain addresses are normally used for email and web pages although you can use IP addresses if you want to. E-mail • You already understand this. • Addresses consist of a username followed by an at sign @ followed by a domain for mail. • I have several local e-mail addresses: – [email protected] – [email protected] – [email protected] • Typically e-mail user names ARE case sensitive but domain names are NOT. E-mail software • Included in other software – e.g. Outlook Express is part of Windows; AOL has e-mail built in; Outlook is part of MS Office • Web based e-mail. You don’t have software for reading e-mail. It is read through a browser and e-mail accounts are “free” from a variety of sources. • Separate e-mail programs – e.g. Eudora. E-mail attachments • MIME – Multipurpose Internet Mail Extensions • Types of attachments to mail messages typically denoted by file name EXTENSION. • A source of viruses but can also be used to send files containing, voice, pictures, animation, etc. Instant Messaging • The ability to “talk” via keyboard with other individuals in real time. • AOL/Netscape IM is currently the most popular but the service is offered by MSN, ICQ, Yahoo and others. • Powerful features such as private chat room for several people and file sharing are available in many of these programs. Mailing Lists • E-mail that is sent to a list-serv for distribution to a list of people • Open mailing lists can be subscribed to by many, while closed lists can only be subscribed to by invited guests. • Moderated lists have all their messages examined by the moderator for appropriate content. • Lists can either be a digest or separate message form. The World Wide Web • Typically the content is multimedia – containing text, graphics, sound, and “animation”. • Hyperlinks enable convenient navigation. • HyperText Markup Language (HTML) is used to write web pages. • Some pages contain special code to implement features. This code is typically written in a programming language called JavaScript.