Java Glossary : transmission speed

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transmission speed

How fast data can be tranmitted from place to place, sometimes called bandwidth. It is measureds in kilobits, kbps, 1000s of bits per second, or megabits, Mbps, millions of bits per second.

Transmission Speeds in Bits Per Second
Downstream Receive	Upstream Send	Service
56K	56K	ordinary 56K V.90 modem
64K	64K	slow ISDN 1-channel
128K	128K	fast ISDN 2-channel
700K	80K	satellite
256K to 1,500K	256K to 1,500K	DSL
500K	400K	slow ADSL
1.554M	1.554M	T1
2.5M	640K	fast ADSL
1.5M to 3M claimed	128K, 300K, 400K or 600K	cable modem shared with other subscribers. See table below.
6.312M	6.312M	T2
45M	45M	T3
44.730M	0	DS3, STS, OC-1
155.52M	0	OC-3
622.08M	0	OC-12
2,488M	0	OC-48
9,953M	0	OC-192

How do you decide between ADSL and cable modems for Internet access? Here in BC, these are the differences. In your area details may vary.

Benefits of ADSL vs Cable modems in BC Canada
ADSL	Cable Modem
$40.00 CAD /month including modem	$40.00 CAD /month including modem
consistent bandwidth availability	faster uploads
private line to phone company.	shared line to cable company, fairly easy for other subscribers to snoop on your traffic.
5 email addresses	5 email addresses
5 static IP addresses for the small business package, 5 dynamic IPs for home users.	2 static IPs
no special software required.	no special software required.
2 months wait for install.	3 weeks wait for install.
?MB for your personal website	5MB for your personal website
transparently shares your phone line.	transparently shares your cable TV connection. (If you don't have one, it is $10.00 CAD extra.)
Online database claims services is available, but you discover it is not when you talk to a human.	Online database claims services is available, but you discover it is not when you talk to a human.
May be leaving the business.	Heavily advertises the service.

Providers

Provider	Type	Downlink Speed KiloBytes per second thousands of bytes per second
Cablevision	cable	800kBps
Comcast	cable	794kBps
Cable Industry Average	cable	787kBps
Shaw	cable	700kBps, 290kBps upstream. Drops to as low as 183 and as high 874. Measured at 500 without the router firewall or Win2K software firewall. Drops to 200 with it. Claim 1400 typical. Recently it has dropped to 50.
AT&T WorldNet	DSL	762kBps
Cox	cable	688kBps
SBC	DSL	584kBps
Adelphia	cable	574kBps
DSL Industry Average	DSL	467kBps
Earthlink	DSL	369kBps
Telus Velocity Enhanced	ADSL	250kBps
Qwest	DSL	240kBps
Telus	ADSL	150kBps

Source: Ziff Davis. Beware any speed ratings from the vendors. Inflating by over a factor of 5 is common.

Download Times

A megabyte is one million bytes. A full floppy contains 1.44 Megabytes. A full CD-ROM contains 600 MB. A gigabyte is 1000 megbytes.

A 56K modem transmits 5.6k bytes a second. A DSL connection transmits about 467K bytes a second. A cable connection transmits about 787k bytes a second. A 100 Mbps Ethernet LAN connection transmits about 8 Megabytes a second.

Approximate Download Times
Capacity	56K Modem	DSL Modem	Cable Modem	Ethernet LAN
meg	3 min	2.2 secs	1.3 secs	0.13 secs
floppy	4 min	3.1 secs	1.8 secs	0.18 secs
cd	30 hours	21 mins	13 mins	1.3 mins
gig	50 hours	36 min	21 mins	2.1 mins

Measuring Speed

To fairly measure the speed of a your local link, you need to find a test server as close as possible. Here are sites to measure and tweak your transmission speed:

numion: very easy to use, with graphical results.
PCPitStop.com
BroadbandReports.com
toast.net
shaw.ca

The one that gives the fastest result is the most accurate, since it is the closest and least affected by net delays.

If you are not getting expected speed, check the following:

back out PC Booster settings. It is incompetent and will slow your machine by a factor of 4.
Try running without the router to see how much overhead it is adding.
Try running without your firewall software to see how much overhead it is adding.
Use TweakDUN to fine tune your TCP/IP settings.

Check carefully if you are measuring in bits per second or Bytes per second. To convert from bits per second to bytes per second download speed, divide by 10.

Comparing Costs

To compare costs, check if the modem is included and what the one time installation costs are. Often they suck you in with a low or even free introductory rate and won't tell you what the rate will eventually rise to. Your actual download and upload speed will be considerably less because the speed of the server you are talking to, net delays, delays in the ISP's computer you are directly connected to and contention for access to the coax cable connecting you to your ISP. Before you purchase, try measuring competing services in your area on someone else's machines at the time of day you do most of your work.

ADSL ¤ hub ¤ Rogers Wave ¤ router

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