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high speed

High speed in terms of internet connectivity over long distances could be considered as anything better than ISDN. Speed is measured by bits per second, and when the numbers get big, using K or M to bring them down to size. Common speed inter-company data pipelines are T1, or T3 or faster, and these labels are also used as speed measures. A good 56k modem on a clean line will manage at most 48k bits per second. This is roughly 1/30th the speed of a T1. A smallish ISP may share a T1 amongst hundreds of simultaneous dialup sessions. An large office may share a T1 for internet and email traffic amongst 500 employees or more. On the other hand, DSL speeds are commercially available that range from 1/12th of a T1 to 5x a T1. This is truly high speed. Related topics to consider along with pure theoretical speed are also ping time/latency of the connection, sustainable transfer rates versus burst rates, as well as monthly traffic limits, and packet drops. In addition, for windows machines, registry settings can have a big effect on throughput.
Comparing DSL to 56k modems, it is obvious the jump in performance is huge.

packet drops

What good is a super fast connection if 20% of the packets transmitted get dropped on the floor? packet loss is the biggest enemy of getting good bandwidth.. when a packet drops, the receiver must tell the sender to re-send it, which adds even more congestion, and in addition, tcp/ip is designed to slow down in response to packet losses.. the assumption in the protocol is that the packet loss is because the network is loaded, therefore dynamic adjustments take place to reduce the rate at which the packets are sent. Where packet loss is because of a bad connection on a router somewhere, these assumptions make an otherwise fast link operate like a slow one.
Before eliminating packet loss as a problem when diagnosing a slow link, you really need to run a spray test to an echo port, which outputs UDP packets at the rate you expect the link to work, and check how many are dropped on the floor. Some implementations of ping have flags that you can use to adjust the size and rate of pings, which achieve the same effect.
Tools such as these are normally only provided on unix-based systems, although there are windows utilities you can find of variable quality that try to do the same thing.

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