linux/net/sched/sch_teql.c says:
1. Slave devices MUST be active devices, i.e., they must raise the tbusy
signal and generate EOI events. If you want to equalize virtual devices
like tunnels, use a normal eql device.
A normal ``eql'' device (linux/drivers/net/eql.c) simply does a simple form of round-robin scheduling among devices. It can round robin among devices of equal weight.
The teql scheduling device uses the scheduling system's back pressure (the dev->tbusy flag) to give each device as much as it wishes.