On Sun, Jun 03, 2001 at 01:41:08PM -0400, Alex Rubenstein wrote:

...

No its not obvious. The SNMP byte counters are odometers - as long as you get two clean samples per counter wrap you can accurately count bytes. The trick is to ensure that you get a minimum of two clean samples of the odometer reading per counter wrap - for high speed interfaces that typically implies reading the MIB2 64 bit interface counters, or triggering an SNMP poll at relatively tight time intervals.

2^64 is 1.844 * 10^19

at 2.5 gb/s (OC48 line speed) (2,500,000,000 bits/sec), you transfer 312,500,000 bytes/sec, or 298 megabytes/sec.

2^64 / 312,500,000 = 6.189 * 10^16 seconds per rollover.

or, 1.719 * 10^13 hours or, 1,962,741,057 years.

My point: at least for the near future, 64 bit counters won't roll.

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. :P -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6)