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Date: Fri, 25 Jul 2003 10:20:43 -0700
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: Jeff Sipek <jeffpc@optonline.net>
Cc: vda@port.imtp.ilyichevsk.odessa.ua, ecki-lkm@lina.inka.de,
       linux-kernel@vger.kernel.org
Subject: Re: Net device byte statistics
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On Fri, 25 Jul 2003 12:23:37 -0400 Jeff Sipek <jeffpc@optonline.net> wrote:

| -----BEGIN PGP SIGNED MESSAGE-----
| Hash: SHA1
| 
| On Friday 25 July 2003 03:03, Denis Vlasenko wrote:
| > I sample the data every minute. Will need to do it much more often
| > on 10ge ifaces, when those will appear at my home ;)
| 
| Speed			Time for one overflow
| 
| 10Gbits/s	=> 3.436 seconds
| 1Gbit/s		=> 34.36 seconds
| 100Mbits/s	=> 343.6 seconds
| 
| > Or we will need 64bit counters then.
| 
| For anything up to (and including) 1GBit/s it is possible to do in easily in 
| userspace, but then were are getting into an area where a program would have 
| to check the files every 3 seconds (and a bit of load could delay it long 
| enough for an overflow to happen.)

Yes, a common solution for this is to use some SNMP agent that does
64-bit counter accumulation.

IETF expects that some high-speed interfaces will have 64-bit
counters.  From RFC 2233 (Interfaces Group MIB using SMIv2):

<quote>
For interfaces that operate at 20,000,000 (20 million) bits per
second or less, 32-bit byte and packet counters MUST be used.
For interfaces that operate faster than 20,000,000 bits/second,
and slower than 650,000,000 bits/second, 32-bit packet counters
MUST be used and 64-bit octet counters MUST be used. For
interfaces that operate at 650,000,000 bits/second or faster,
64-bit packet counters AND 64-bit octet counters MUST be used.
</quote>

However, this is a MIB spec.  It does not require a Linux
(/proc) interface to support 64-bit counters.

--
~Randy
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