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packet dropsWhat 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.
UDPUDP packets are used where delivery is not guaranteed. That sounds a bit odd, doesn't it? Of course delivery of most packets is highly likely, its just that some of it may not get there. What use is that? well, for some information like video and audio, some loss of data can be tolerated. The advantage of UDP is that the sender and recipient agree on a constant data rate. This means that you don't have to run the link as fast as you can, which is the natural design of tcp/ip. UDP based protocols are going to become increasingly common in future, as the convenience of being able to set a fixed data rate between two points is worth the hassle of coping with missed bits of the message.
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