ARP request retransmitting

[Gleb Smirnoff]

On Fri, Nov 11, 2005 at 02:09:26PM +0000, Bruce M Simpson wrote:
B> On Mon, Nov 07, 2005 at 05:04:51PM +0300, Gleb Smirnoff wrote:
B> >   I suggest to keep sending ARP requests while there is a demand for
B> > this (we are trying to transmit packets to this particular IP),
B> > ratelimiting these requests to one per second. This will help in a
B> > quite common case, when some host on net is rebooting, and we are
B> > waiting for him to come up, and notice this only after 1 - 20 seconds
B> > since the time it is reachable.
B> >   Any objections?
B> 
B> In response to the other replies to this thread citing broadcast
B> pollution on Ethernet-based networks:
B> Please add this functionality under a sysctl where it is turned off by default.
B> 
B> It is desirable in situations where ARP entries cached further upstream are
B> stale, but it may cause flooding in an environment where the layer 2 backbone
B> hasn't been split or has not been segregated well.
B> 
B> Other people cited examples where vendor switch implementations were
B> retransmitting across VLANs -- this week I've been offering moral support
B> to a friend who is dealing with similar VLAN brokenness at his $DAYJOB
B> (there was an extension to 802.1d to support multiple spanning tree instances
B> across VLANs which I think not everyone supports correctly).

I'd like to see a proven evidence that this functionality leads to a measurable
increase in broadcast traffic. Many modern operating systems behave in such way
and no-one complains. The increase of broadcast traffic is very theoretical,
it happens only when there are downed hosts.

-- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE