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 RJ- 45 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 and perhaps USENet -- $10 to 16 monthly Full– ISPs such as AOL, MSN, Compuserve, 24/7 tech support, multiple 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 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 e- mail and web pages although you can use IP addresses if you want to.

You already understand this. Addresses consist of a username followed by an at followed by a domain for mail. I have several local addresses: Typically user names ARE case sensitive but domain names are NOT.

software Included in other software – e.g. Outlook Express is part of Windows; AOL has built in; Outlook is part of MS Office Web based . You don’t have software for reading . It is read through a browser and accounts are “free” from a variety of sources. Separate programs – e.g. Eudora.

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 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.