common method to count traffic volume on IX

Leo Bicknell bicknell at
Wed Sep 18 17:23:12 UTC 2013

On Sep 17, 2013, at 3:15 PM, Niels Bakker <niels=nanog at> 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 - CCIE 3440
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