speed of transfer

[=?x-user-defined?Q?toylet=2Elinux=5B=A4p=AA=B1=B7N=5D?=]

is there a generic tool that could log and report the input and output
speed of a selected netwoking interface (eth0/ppp0/...) for the past say
5 minutes? 

How about a breakdown per daemon if possible?

mainly for knowing the transfer speed of proftpd. Those M$ ftp server
program has this kind of gimmicks.

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