LECTURE 1 
Protocols • Internet Technologies & Services 
Connection Speed
Accessing the Internet requires a connection. Your connection to the Internet will be made through a service provider, who owns or leases the copper or fiber lines to your home or business.
The service provider charges you a fee for using its line. The speed at which you can download information from the Internet is dependant on the type of line and the type of access that the service provider offers you at your location. This connection speed is called bandwidth.
Bandwidth is used to describe how fast data flows on a given transmission path. Generally speaking, bandwidth is directly proportional to the amount of data transmitted or received per unit of time.
Large sound files, computer programs, and animated videos require more bandwidth than simple text. Consequently, it takes longer to download a photograph than a full page of text using the same bandwidth. This download time is a critical factor in developing useable web sites.
Bandwidth is expressed as data speed in bits per second (bps). A dial-up modem that works at 57,600 bps has twice the bandwidth of a dial-up modem that works at 28,800 bps.
Dial-up
The easiest, least expensive, and probably the slowest method to connect to the Internet is via a modem. The technology behind modems is actually quite old. Modems work by translating the computer's native binary language of zeros and ones from a serial port into a series of analog waves via a process called modulating.
These analog waves are then sent over the phone line. The modem on the other end of the connection takes these analog waves and demodulates them back into the computer's binary language through its own serial port. The word modem comes from the combination of the words modulating and demodulating.
Modems range in speed, with the highest current speed being 56Kbps. Even if you have a fast modem, it can only send information as fast as your phone line is equipped to handle. Many phone lines have poor bandwidth, slowing the amount of data that can be transmitted in a fixed amount of time. You will find that even with a 56Kbps modem, your transfer rates can be close to 28Kbps per second.
High-speed
High-speed Internet access, also called "broadband," relates generally to any method of connecting to the Internet that is faster than a traditional modem.
Broadband access comes in a variety of technologies:
ISDN (Integrated Services Digital Network)—ISDN makes use of terminal adapters over digital lines. This is a very different connection from a standard modem connection, with faster results of about 128Kbps.
DSL (Digital Subscriber Line)—DSL brings high bandwidth information to homes and businesses via standard telephone lines. You must be close enough to a central office that offers this service. Speeds are around 512Kbps.
Cable—Cable modems connect your PC to your local cable line for access to the Internet at broadband speed. Typical cable speeds are around 1.5Mbps, significantly faster than ISDN or DSL.
T-carrier Systems—T-carrier systems are digital and are also the framework of the Internet. T1 lines are capable of 1.544Mbps and are often available in business and industry. T3 lines are capable of 44.736Mbps but are not widely available.
Despite the fact that over half of the web users in the United State now have access to broadband, web designers still must bear in mind that many are using the much slower conventional modem connections. As such, even if you have the luxury of broadband, you will need to account for your website users who do not
Service Providers
An ISP (Internet Service Provider) is a company that provides access to the Internet for a monthly fee. Some ISPs are large commercial vendors offering Internet access and their own proprietary services, such as America Online. Other ISPs provide dial-up or broadband accounts so their customers can directly access the Internet.