Decide speed of information transfer is capped by terminals of data server (9)
I believe the answer is:
arbitrate
'decide speed of information transfer' is the definition.
'arbitrate' can be an answer for 'decide' (I've seen this before). I'm not certain of the 'speed of information transfer' bit.
'capped by terminals of data server' is the wordplay.
'capped' becomes 'bitrate' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'by' is a charade indicator (letters next to each other).
'terminals of' says to take the final letters (I've seen 'terminal' mean this (terminal refers to the end)).
The last letters of 'data server' are 'ar'.
'bitrate' after 'ar' is 'ARBITRATE'.
'is' is the link.
Can you help me to learn more?
(Other definitions for arbitrate that I've seen before include "Act between disputing parties" , "judge" , "Decide" , "Help settle a dispute" , "Mediate" .)