sysV init
I've been using Linux ( RedHat, CentOS, Ubuntu), BSD (Solaris, SunOS, freeBSD) and Unix ( aix, sysv all of the way back to AT&T 3B2 servers) in farms of up to 400 servers since 1988 and I never, ever had issues with eth1 becoming eth0 after a reboot. I also never needed to run ifconfig before configuring an interface just to determine what the inteface was going to be named on a server at this time. Then they hired Poettering... now, if you replace a failed nic, 9 times out of 10, the interface is going to have a randomly different name.
/rant