[rbridge] Back to ND/ARP optimization

[Eastlake III Donald-LDE008]

Silvano,

I don't understand what these Rbridge CPUs will be doing. If an Rbridge
receives a native ARP broadcast frame for an unknown IP address it would
just learn the source IP->MAC mapping and then flood the ARP broadcast.

Donald

-----Original Message-----
From: rbridge-bounces at postel.org [mailto:rbridge-bounces at postel.org] On
Behalf Of Silvano Gai
Sent: Friday, May 04, 2007 3:01 PM
To: Arien Vijn
Cc: rbridge at postel.org; Radia.Perlman at sun.com
Subject: Re: [rbridge] Back to ND/ARP optimization

Arien

Thanks for the real world data, which proves that ARP/ND proxy must not
be implemented on RBridges.

In fact, since the queries toward unused addresses are dominant, the
ARP/ND cache will almost always miss and the RBridge CPU will be busy
trying to remotely resolve queries that will never complete.

-- Silvano

> -----Original Message-----
> From: Arien Vijn [mailto:arien.vijn at ams-ix.net]
> Sent: Friday, May 04, 2007 10:04 AM
> To: Silvano Gai
> Cc: Arien Vijn; Radia.Perlman at sun.com; rbridge at postel.org
> Subject: Re: [rbridge] Back to ND/ARP optimization
> 
> Hi,
> 
> On May 3, 2007, at 10:55 PM, Silvano Gai wrote:
> 
> [...]
> 
> >> Does anyone have a handle on how much traffic is caused by ARP/ND?
> >>
> >
> > With an ARP cache of 30 minutes, typical in hosts today, even with
> > a 100
> > K hosts in a VLAN we get at most 55 ARP seconds. Since not all the
> > hosts
> > talk with each other, it is more typically like 5 ARP/sec.
> >
> > BASICALLY NOTHING.
> 
> Well... that might be the case if all your hosts are actually
> answering. But query rates are pretty much determined by queries for
> unused addresses. In other words by the query rates hosts (routers)
> can achieve for addresses that are not in their caches.
> 
> For what its worth. I am involved in a real network with 400+ BGP
> routers in one broadcast domain (/23 IPv4 subnet). The average rate
> is little over 13 queries/second. That is with ARP mitigation and
> peak rates are much higher.
> 
> -- Arien


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