|
Satellite connections suffer from high latency, which is the time it takes for a signal to get from its point of origin to its destination. The problem is that each packet has to go all the way to the satellite and back, and it can't go any faster than the speed of light. It takes about half a second for a packet to go to the satellite and back, which is far slower than typical dialup connections. (traceroute on my dialup is about 200 milliseconds, which translates to a latency of 100 milliseconds.) You can get an idea of the latency of a connection using the traceroute command. (It's "tracert" on Windows and "traceroute" on UNIX. I haven't used a Mac for a long time, but I assume that some form of traceroute should be available, as OS/X is a UNIX variant.) In theory, high latency should not affect file transfer performance. HOWEVER, that is only true if the TCP buffer at the transmitting site is large enough to keep the "pipe" full. If the transmitting site's buffer is too small, then it will run out of data to send before it receives an acknowledgement from the receiving site. When this happens, the file transfer is interrupted and you don't get the full bandwidth. I suggest that you try downloading files from different sites and see if the performance is consistently much worse than whatever bandwidth your friend is paying for. If it is, he needs to complain to his service provider.
|
