What would be the best unix program to know which process is using the most bandwidth?

Zabbix is ""warning us that the eth0 interface is having outgoing traffic of more than 800Mbp / s (from 1Gb) every day at six in the morning. I want to crontab some program that monitors from 5:50 to 6:20 which or which programs are using so much bandwidth. Which would be best for this case? Nethogs? Iptraf? Remembering that I want to save the results to a file to see when I get to the service.

In log ** message ** you can see the following message at 06:05 "eth0 NIC link is Up 1000Mbps, flow control: none", in the syslog log there are the following messages around, if only around, 6am : "eht0 detected tx unit hang reset adapter".

The biggest suspicion is that it is some backup.