My husband, Frank, uses the computer to write database programs. He uses “middleware” tools like Cold Fusion to write internet ready computer code. As far as I know scientists are still working to make cold fusion feasible.
I use the computer to talk and shop, so let’s talk/shop.
Frank says that I can use my computer to send out a request or an email because I have a modem. I have an internal modem, a circuit board that plugs into the main board or motherboard inside my computer case. The modem (short for modulate/demodulate) modulates or changes the bits (binary digits) from my computer. The bits are transformed into an analog signal made up of sine waves of certain frequencies and amplitudes that can travel over the twisted and paired copper telephone lines.
My modem has to connect to my telephone line and dial a number to make a call. It can only “talk” to another modem on the other end of the phone line. The answering modem demodulates the signal from my modem to convert it back to the original bits and bytes.
This time of year I am shopping for garden seeds. How can I reach www.burpee.com to order zinnia seed?
My home computer modem calls and connects to an access server modem at my internet service provider (ISP). The ISP modem answers, but will negotiate the speed of data transfer and the rules for data transfer before the connection is complete. The ISP access server then connects to the authentication server, a special computer at the ISP that keeps track of all of the approved users. The ISP server will request a valid login and password to confirm that I am a valid customer and I am now online.
Once connected the ISP obtains my web browser request for online access to www.burpee.com. The ISP serves as a gateway to the internet for me by use of a “gateway” router. The router is a specialized computer that stores routing tables. The routing tables provide numerical addresses for all registered destinations on the internet.
My request will travel from my local ISP router to a “Peer” router on the backbone of the internet. The request then travels from router to router to eventually arrive at the gateway router and web server for the Warminster, PA Company of Burpee.
How can this happen so fast?
My modem may be a 56K modem capable of transmitting signals at 56,000 bits per second (in real life more like 48,000 bits per second). My ISP connects through dedicated digital fiber optic circuits to the “peer” router on the internet. These modems send and receive digital signals at much faster rates. In the case of T1 lines, 1.54 million bits per second, or for a T3, ~45 million bits per second. Many points along the internet backbone are connected by optical cable or “fiber” which can transmit the digital signal at gigabits per second (billions of bits per second).
With all of these signals zipping around, how do the routers keep it all straight?
My computer like every computer knows protocol. The PPP or Point to Point Protocol creates a standard way to send and receive messages. Each message will have TCP/IP standards. The TCP or Transmission Control Protocol breaks my message into small data packets.
My message will not travel in a long string of bits, but will be chopped into small parts that travel individually and probably along separate routes over the internet to arrive at the same destination. The fact that all internet messages are sent as small packets means that packets can quickly jump in and out of the online traffic without having to wait for long trains of data to go by.
The IP on Internet Protocol gives each packet an internet address, so that they all arrive at the same destination and can be reassembled into the original message and delivered to the machine on the other end of my request.
Or, as Dr. Seuss would say…
From there to here
From here to there
The internet
Is everywhere
Some are fast
None are slow
The router knows
Where bits should go
Modems talk
And verify
Access servers
Let data fly
Transmission control
Let’s data divide
Internet Protocol
Makes sure it arrives
From there to here
From here to there
The internet
Is everywhere.
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