Storage and Bandwidth

Storage and Bandwidth

Introduction

Any discussion of "storage" and "bandwidth" must start with an understanding of basic terms. Even beginning computer users quickly come to understand that a computer can only hold so much information. A hard disk on a personal computer may store anywhere from as little as 10 or 20 Megabytes up to several gigabytes.

The Shorthand...

K = kilo = 1 thousand
M = mega = 1 million
G = giga = 1 billion
T = tera = 1 trillion
P = peta = 1 quadrillion
E = exa = 1 quintillion

Multimedia materials can take up an enormous amount of computer storage space. Individual files (text, pictures, audio or video) vary greatly as to how much of a computer's storage space they take up. The information below gives you some idea of how much:
(These can actually vary much more than indicated. The figures below are what I consider to be ranges for files used on the Internet).

Text Files: From a few bytes up to 100 Kilobytes

Still Image Files: From 5 Kilobytes up to 200 Kilobytes

Audio Files: From 20 Kilobytes up to 2 Megabytes

Moving Video Files: From 50 Kilobytes up to 20 Megabytes

The information above illustrates that Moving Video files tend to be the biggest, followed by audio, images and then text.

But, storing these files on a computer's hard disk isn't the only thing that comes into play. Now, imagine having to send these individual files over the Internet. The Internet is essentially a Distributed Network. Information moves from one computer to the next via phone lines, coaxial cable, fiber optic lines, microwave relay and even via satellite. The larger a file, the greater amount of "bandwidth" the file takes up when pumped down this network.

NOTE:
Whereas computer storage is usually talked about in terms of bytes, the tranmission of data is usually talked about in terms of bits. Be careful not to confuse bytes and bits.

Definitions of "Bandwidth"

The definitions below come from a variety of sources. The source is listed in parantheses at the end of each definition:

The capacity of a network to transmit data is called Bandwidth, and it is expressed in bits per second. (Dr. Internet)

Sending data through a phone wire is like sending water down a pipe. The wider the pipe-the more information you can send, faster. In telecommunications, transport capacity (the size of the pipe) is called bandwidth. The narrower the bandwidth, the less amount of information that can be "squeezed" through it at any one time, and the longer it takes. (Source Unknown)

Bandwidth is a term used to describe how much information can be sent with a particular method. In typing classes this is words per minute and on the highway it is miles per hour, etc. If you have two people typing, or two cars going down the highway, you double the bandwidth, if they are going the same speed. (Dr. Internet)

The measure of how much information can be processed, stored, transmitted by an information system. The need for compression is a result of bandwidth limitations in computing power, storage space and data transmission channels. (Dr. Internet)

Bandwidth is the capacity of the network, usually expressed in storage divided by time. . .i.e. megabytes per second.(Dr. Internet)

If they talk about megabits per second, they are usually trying for an impressive figure which should be divided by 10, as it usually takes a whole ten bits to send one byte |8 bits| due to start and stop bits.(Dr. Internet)

NOTE

Low-end video (low quality MPEG-1 compression) requires at least 1 megabit/sec
Full-motion, full-screen, "VHS quality" video requires between 4 and 6 megabits/sec.
(The more movement there is in video, the more bandwidth it requires).

Internet Connection Types

Multimedia files over the Internet may arrive at your home in any number of ways. The material may get to your home through a 14.4 Kilobit modem or perhaps you may someday benefit from an even higher speed type of connection. The information below will give you some idea of how fast the various connection types may be.

Type Kilobits or Megabits per second Description Cost
14,400 bits/sec. Modem 14.4 Kilobits/sec. Low speed modem Phone Line

28,800 bits/sec. Modem 28.8 Kilobits/sec. High speed modem Phone Line

56 Kilobits/sec. Dedicated Line 56 Kilobits/sec. 56 "K" Line $250 per mo.

ISDN 64-128 Kilobits/sec. Normal copper twisted pair line, changed to digital from analog. Allows simultaneous voice and data $30-$200 per mo. (depending on service options) U.S. West says it will try to keep the cost down to around $35.00 a month and expects full availability in its service area late in 1996.

ADSL (asymmetrical digital subscriber line) 1.5 Megabits/sec. Requires an ADSL modem. Uses existing twisted-pair, copper phone lines. Meant to compete with "cable modems." While cable modems could be slowed greatly when many people are logged on, 1.5 Megabits/sec. for ADSL is pretty much guaranteed. Technical performance is greater over phone lines than coaxial cable lines which are susceptible to a range of service problems (i.e. outages and RF interference problems). Also, Telcos don't have to make the major upgrades that cable companies would need to undergo to get into the cable modem business. To be tested in No. VA for $30 per mo.

T1 Line 1.544 Megabits/sec. or faster Fancy Phone Line-more twists/Lower limit of low-quality MPEG-1 compressed video $300-$800 per mo.

Ethernet 10 Megabits/sec. ? ?

Wireless Cable Modems 10 Megabits/sec.
(27mbps is in the works) The system operates in the 2-gigahertz range reserved for MMDS (multichannel-multipoint distribution system...essetially small microwave receiving dishes on a rooftop used to receive only). The rooftop receiver is connected to a cable modem. The system sends Ethernet-like packets over the air to homes. However, phone lines must be used to send user-originated requests "upstream." Because these are "connection based," a phone line is tied up the entire time of the connection. In contrast, cable's bi-directional systems offer connection-less, session-based transmissions, meaning that headend demodulators can juggle multiple incoming requests in a way that's transparent to the user. Wireless cable modems, dubbed RLA 161, are priced at about $800. Those prices, like the prices of cable modems, are expected to decline over time.

Cable Modems 10-30 Megabits/sec.
(Effective rate could be 200-300 Kilobits/sec.)
Your standard cable TV coaxial cable. Will utilize a switching technology called ATM (asnychronous transfer mode). Data speeds up to 155 mbps from national internet sites to regional data centers, 45 mbps from regional data centers to cable head ends, and 27 mbps from head ends to the home (128 kbps from home to head end). Phone technology such as ISDN & ADSL are dedicated while cable modems could be slowed markedly if many others are also online. If many users are logged on, the effective speed may be much lower than 10 Megabits/sec. At peak times you may get no more than 200-300 Kilobits/sec. This means that telephone based technology such as ADSL could result in an effective higher data rate than cable modems. Also, cable modems have signal quality problems. In engineering parlance, it must be "locked down tight." In essence, RF (radio frequency) interference could disrupt service. Also, cable companies don't have much experience with the delivery of data, lack supporting personnel and will have to undergo expense plant upgrades to get into the business. $30-$40 per mo.

T3 Line 45 Megabits/sec. Fiber Optics $3,000 per mo. (approx.)

FDDI 100 Megabits/sec. Fiber Optics ?

Type	Kilobits or Megabits per second	Description	Cost
14,400 bits/sec. Modem	14.4 Kilobits/sec.	Low speed modem	Phone Line
28,800 bits/sec. Modem	28.8 Kilobits/sec.	High speed modem	Phone Line
56 Kilobits/sec. Dedicated Line	56 Kilobits/sec.	56 "K" Line	$250 per mo.
ISDN	64-128 Kilobits/sec.	Normal copper twisted pair line, changed to digital from analog. Allows simultaneous voice and data	$30-$200 per mo. (depending on service options) U.S. West says it will try to keep the cost down to around $35.00 a month and expects full availability in its service area late in 1996.
ADSL (asymmetrical digital subscriber line)	1.5 Megabits/sec.	Requires an ADSL modem. Uses existing twisted-pair, copper phone lines. Meant to compete with "cable modems." While cable modems could be slowed greatly when many people are logged on, 1.5 Megabits/sec. for ADSL is pretty much guaranteed. Technical performance is greater over phone lines than coaxial cable lines which are susceptible to a range of service problems (i.e. outages and RF interference problems). Also, Telcos don't have to make the major upgrades that cable companies would need to undergo to get into the cable modem business.	To be tested in No. VA for $30 per mo.
T1 Line	1.544 Megabits/sec. or faster	Fancy Phone Line-more twists/Lower limit of low-quality MPEG-1 compressed video	$300-$800 per mo.
Ethernet	10 Megabits/sec.	?	?
Wireless Cable Modems	10 Megabits/sec. (27mbps is in the works)	The system operates in the 2-gigahertz range reserved for MMDS (multichannel-multipoint distribution system...essetially small microwave receiving dishes on a rooftop used to receive only). The rooftop receiver is connected to a cable modem. The system sends Ethernet-like packets over the air to homes. However, phone lines must be used to send user-originated requests "upstream." Because these are "connection based," a phone line is tied up the entire time of the connection. In contrast, cable's bi-directional systems offer connection-less, session-based transmissions, meaning that headend demodulators can juggle multiple incoming requests in a way that's transparent to the user.	Wireless cable modems, dubbed RLA 161, are priced at about $800. Those prices, like the prices of cable modems, are expected to decline over time.
Cable Modems	10-30 Megabits/sec. (Effective rate could be 200-300 Kilobits/sec.)	Your standard cable TV coaxial cable. Will utilize a switching technology called ATM (asnychronous transfer mode). Data speeds up to 155 mbps from national internet sites to regional data centers, 45 mbps from regional data centers to cable head ends, and 27 mbps from head ends to the home (128 kbps from home to head end). Phone technology such as ISDN & ADSL are dedicated while cable modems could be slowed markedly if many others are also online. If many users are logged on, the effective speed may be much lower than 10 Megabits/sec. At peak times you may get no more than 200-300 Kilobits/sec. This means that telephone based technology such as ADSL could result in an effective higher data rate than cable modems. Also, cable modems have signal quality problems. In engineering parlance, it must be "locked down tight." In essence, RF (radio frequency) interference could disrupt service. Also, cable companies don't have much experience with the delivery of data, lack supporting personnel and will have to undergo expense plant upgrades to get into the business.	$30-$40 per mo.
T3 Line	45 Megabits/sec.	Fiber Optics	$3,000 per mo. (approx.)
FDDI	100 Megabits/sec.	Fiber Optics	?

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(Dr. Steve Anderson at Utah State University).