Or thought about another way:
2^64 = 18446744073709551616 bytes/sec = 147573952589676412928 bits/sec.
Which means a 64 bit counter will roll over in 5 minutes at
491913175298921376 bits/sec, or 491Pbps (Petabits/sec).
Under the current naming scheme, this will be OC-9444732864. Better start
planning for 128 bit counters, we wouldn't want to be stuck in something
which doesn't scale.