Networking Speeds

Topics this page:

Related:

Site Map  
About this site  

Connection	Wiring	Speed	KB/s	Wiring
DDS	telephone	56Kbps	7
ISDN 1 BRI (phone line)	-	65Kbps	8
ISDN 2 BRI (phone line)	-	128Kbps	16
“broadband”	--	> 128Kbps	> 16
Japanese I-mode, mLife	wireless	-	18
DSL	telephone	300Kbps	37.5
USB 1.0	"low-speed"	1.5 Mbps	187.5
USB 1.1	"full-speed"	12 Mbps	1,562.5
USB 2.0	"hi-speed"	480 Mbps	60,000
HDMI		10.2 Gbps	1,560,000	19 leads type A connectors
Frame Relay	--	64KB to 1.544 Mbps	8 - 194.375
Fractional T1	--	256 Mbps	256
DS1/T1 Carrier (24 channels)	dedicated	1.544 Mbps	1,544
DS3/T3 Carrier	dedicated	44.736 Mbps	44,736
ATM-25	twisted-pair copper	25 Mbps	25,000
ATM	twisted-pair copper	155 Mbps	155,000
OC-1 SONET	fiber	51 Mbps	51,000
OC-3 SONET	fiber	155 Mbps	155,000
OC-12 SONET	fiber	622 Mbps	622,000
OC-48 SONET	fiber	2.4 Gbps	2,400,000
OC-192 SONET	fiber	10 Gbps	10,400,000
OC-48 with WDM	fiber	40 Gbps	40,000,000
OC-768	fiber	40 Gbps	-
OC-3072	fiber	160 Gbps	-
OC-768 with DWDM	fiber	6.4 Tbps	-

This table normalizes.

Kbps = Kilo bits per second
Mbps = Mega bits per second
Gbps = Giga bits per second


WDM = Wave Division Multiplexing
DWDM = Dense Wave Division Multiplexing.

To calculate how long it would take to download a 100KB file, multiply your file's size by 8 to get the number of bits, then divide by the speed in kilobytes. Example: 100Kb file * 8 / 56Kbs = 14 seconds.

To avoid excessive Propagration delays on 802.3 networks, observe the 5-4-3 Rule: No more than 5 segments of cable, connected by 4 non-filtering repeaters, where only 3 of the segments have computers attached.

A network's physical characteristics are described using these values:

R = data rate (for example, 10 Mbps)

d = distance of network in meters (10 m, 100 m, 100 km)

V = propagation velocity of signal: (about 2 ´ 10m for copper wire)

L = length of frame in bits (for instance, 1000 b, 5000 b)

(R * d) / V defines the number of bits that can be on the wire at any time. For a 10 Mbps Ethernet segment that is 500 m long, the bit length is 25.

Since a sending device will want to put its entire frame on the wire, a useful way to think about the length of the network in bits is to put it in relation to the size of the frame that is being transmitted on the wire. The variable a represents the length of the medium in relation to the frame size:

a = length of wire (b) / length of frame (b) = (R * d) / (V * L)

If a = 1, then the length of the physical medium is equal to the length of one frame. Usually, a is much less than 1 for LANs, however. This means the frame is much longer than the length of the medium in bits. In the Ethernet example used above, the length of the wire was 25 bits, but frames are typically much larger than this on LANs-thousands of bits, thus a = 0.01 to 0.1.