common method to count traffic volume on IX

[bicknell at ufp.org (Leo Bicknell)]

On Sep 17, 2013, at 3:15 PM, Niels Bakker <niels=nanog at bakker.net> wrote:

> I don't know of any IXP that does this.  Industry standard is as you and others wrote before: the 5-minute counter difference on all customer-facing ports, publishing both input and output bps and pps.
> I guess MRTG is to 'blame' for these values more than anything.

Serious question, at an IXP shouldn't IN = OUT nearly perfectly?

Most exchanges do everything possible to eliminate broadcast packets, and they don't allow multicast on the unicast VLAN's.  So properly behaved you have a bunch of routers speaking unicast to each other.  The only way to get a difference is if there is packet loss, IN - loss = OUT.

-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/