- Nomaderwho
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- Exalted Mythic Member
No one likes a smart ass.....especially another smart ass!
1.5mbps is how much can be sent at one time (bandwidth), not how fast it is sent. Think of it like a highway. You didn't increase the speed limit, you just added more lanes.
Take from DSL Reports website
One of the most commonly misunderstood concepts in networking is speed and capacity. Most people believe that capacity and speed are the same thing. For example, it's common to hear "How fast is your connection?" Invariably, the answer will be "640K", "1.5M" or something similar. These answers are actually referring to the bandwidth or capacity of the service, not speed.
Speed (latency) and capacity (bandwidth) are two very separate things. The combination of latency and bandwidth gives users the perception of how quickly a webpage loads or a file is transferred. It doesn't help that broadband providers keep saying "get high speed access" when they probably should be saying "get high capacity access". Notice the term "Broadband" - it refers to how wide the pipe is, not how fast.
Latency:
Here's the most common example to compare latency and bandwidth:
Imagine water running through a pipe. The pressure is latency, the width of the pipe is bandwidth. If you have a wide pipe but low pressure, you can move more water through the pipe but at a slower rate. If you have a narrow pipe but high pressure, you can move less water but at a faster rate.
Another example that is sometimes given:
Imagine people in an aircraft. In this example, people are the data packets, the size of the aircraft is the bandwidth, and the speed of the aircraft is the latency. A 747 can carry about 400 people but a 707 can carry only 200 people. Both fly at about 500 knots. If both leave New York at the same time, they will arrive in Los Angeles at the same time. But notice that although the 747 has more capacity (or bandwidth) it is the same speed (latency) as the 707.
Latency is normally expressed in milliseconds. One of the most common methods to measure latency is the utility ping. A small packet of data, typically 32 bytes, is sent to a host and the RTT (round-trip time, time it takes for the packet to leave the source host, travel to the destination host and return back to the source host) is measured.
The following are typical latencies as reported by others of popular circuits type to the first hop. Please remember however that latency on the Internet is also effected by routing that an ISP may perform (ie, if your data packet has to travel further, latencies increase).
Ethernet--------.3ms
Analog Modem------100-200ms
ISDN-------15-30ms
DSL/Cable-------- 10-20ms
Stationary Satellite------- >500ms, mostly due to high orbital elevation
DS1/T1------ 2-5ms
Bandwidth:
Bandwidth is normally expressed in bits per second. It's the amount of data that can be transferred during a second.
Solving bandwidth is easier than solving latency. To solve bandwidth, more pipes are added. For example, in early analog modems it was possible to increase bandwidth by bonding two or more modems. In fact, ISDN achieves 128K of bandwidth by bonding two 64K channels using a datalink protocol called multilink-ppp.
Bandwidth and latency are connected. If the bandwidth is saturated then congestion occurs and latency is increased. However, if the bandwidth of a circuit is not at peak, the latency will not decrease. Bandwidth can always be increased but latency cannot be decreased. Latency is the function of the electrical characteristics of the circuit.
[Edited on 08.24.2007 4:41 AM PDT]