Should i enable Quality of service on my ZTE adsl modem an1020-16t?

Assalam o alaikum brothers i want to know that is it important to enable quality of service in adsl modem and kindly tell me the whole procedure in brief. thanks in advance!

First of all its not a ZTE modem i guess, second its not important :D

Well thanks bro for ur kind reply but m using ZTE's modem and is it really not of any importance if we dont enable QOS in our modem's WAN settings what's the effect of not enabling this!