transmission speed : Java Glossary

by Roedy Green ©1996-2008 Canadian Mind Products
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transmission speed

How fast data can be transmitted from place to place, sometimes called bandwidth. It is measured in kilobits, kBps, 1000s of bits per second, or megabits, Mbps, millions of bits per second. Actual transfers are considerably lower because of software and protocol overhead. To get the equivalent kilo Bytes per second divide by 8.

Using a simple tool like TCP Optimizer, TweakMaster or TweakDUN to tune your TCP/IP connection can make an incredible difference in speed, sometimes a 100x improvement.

Service Types

Transmission Speeds in Bits Per Second For Various Types of Service
Downstream Receive	Upstream Send	Service
56K	56K	ordinary 56K V.90 modem
56K	56K	Netzero 3G — same as ordinary dialup. With software they do some premptive caching, but the actual transmission speed is no faster.
64K	64K	slow ISDN 1-channel
114K	114K	GSM cell phone
128K	128K	fast ISDN 2-channel
721K	721K	Bluetooth (wireless radio range 30 feet) What is the data throughput speed of a Bluetooth connection? Bluetooth transfers data at a rate of 721 Kbps, which is from three to eight times the average speed of parallel and serial ports, respectively. This bandwidth is capable of transmitting voice, data, video and still images.
700K	80K	satellite
256K to 1,500K	256K to 1,500K	DSL
400K	?K	Verizon Wireless Broadband
500K	400K	slow ADSL
500K	?	EV-DO cell phone, 2.4M theoretical
1.5M	128K?	Wi-Fi cell phone
1.554M	1.554M	T1
2M	?M	UMTS cell phone
2.5M	640K	fast ADSL
1.5M to 3M claimed	128K, 300K, 400K or 600K	cable modem shared with other subscribers. See table below.
4M	4M	FIR fast infrared, typical in laptops and digital cameras
6.312M	6.312M	T2
45M	45M	T3
10M	10M	old style Ethernet LAN
12M	12M	USB-1
44.730M	0	DS3, STS, OC-1
54M	54M	Wi-Fi wireless Internet Access via IEEE 802.11
100M	100M	Ethernet LAN
155.52M	0	OC-3
480M	480M	USB-2
622.08M	0	OC-12
2,488M	0	OC-48
9,953M	0	OC-192

Providers

Provider	Type	Downlink Speed KiloBits per second thousands of bits 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 SMC router firewall or Win2K software firewall. Drops to 200 with it. Claim 1400 typical. Recently it has dropped to 50. With D-Link DI-604 router speed is 864 downstream 389 kBps upstream.
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 megabytes.

A 56K modem transmits 5.6k bytes a second. A DSL connection transmits about 46K bytes a second. A cable connection transmits about 78k 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	100M Ethernet LAN
meg	3 min	22 secs	13 secs	0.13 secs
floppy	4 min	31 secs	18 secs	0.18 secs
cd	30 hours	3.6 hours	2.2 hours	1.3 mins
gig	50 hours	6 hours	3.5 hours	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. Just use several tests and take the fastest.

numion: very easy to use, with graphical results.
PCPitStop.com: has tool that boosted my download speed fourfold by upping the receive buffer size.
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. If it is a a problem, check the firewall settings or try a different router. It should be set on 100 mbps not 10 mbps for the LAN side.
Try running without your firewall software to see how much overhead it is adding. If it is a problem, check your firewall settings or try a different firewall.
Use TweakDUN to fine tune your TCP/IP settings.
Fine tune your registry setting with TCP Optimizer.

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 8.

If you have poor quality lines, you will get scrambled or lost packets that have to be retransmitted, slowing down the flow. To estimate the quality of your lines see ping.

On 2007-11-24 CBC Newsworld tested various Canadian providers.

Performance of Canadian ISPs
% of advertised bandwidth actually provided	ISP
92	Rogers
77	Shaw
67	Telus
16	Bell

The bigger the percentage the better. A truly honest company would provide 100% of bandwidth advertised. They pointed out that older computers, routers, network cards and wiring can all slow you down. Most of the time, when you buy premium service, your bandwidth is no better. The companies justify scamming their customers this way because the entire industry does it and because they can’t guarantee an absolute minimum under all conditions.

Personal

I use Telus DSL. In the middle of the night I get better than advertised:

	Actual Speed KBits/Sec	Actual Speed KBytes/Sec	Advertised Speed KBits/Sec	Advertised Speed KBytes/Sec
Download	1,562	195	1500	188
Upload	555	69	512	64

ADSL
ADSL vs cable
bandwidth chart
Canadian IAPs
DSL
hub
IAP
ping
registry cleaner
Rogers Wave
router
TCP Optimizer
TCP/IP
TweakDUN
TweakMaster

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