Re: ARP request retransmitting

From: Gleb Smirnoff (glebius_at_FreeBSD.org)
Date: 11/07/05

  • Next message: Bill Vermillion: "Re: ARP request retransmitting" 
    Date: Mon, 7 Nov 2005 17:52:53 +0300
To: Robert Watson <rwatson@FreeBSD.org>

    On Mon, Nov 07, 2005 at 02:40:43PM +0000, Robert Watson wrote:
    R> > I have a proposition on changing the behavior of ARP retransmitting.
    R> >Currently we after sending several ARP requests, sending ARP requests
    R> >for given IP is suppressed for some interval (by default 20 seconds).
    R> >Probably this feature was designed in early 90th, when sending one
    R> >additional broadcast packet was an expensive thing.
    R> >
    R> > I suggest to keep sending ARP requests while there is a demand for this
    R> >(we are trying to transmit packets to this particular IP), ratelimiting
    R> >these requests to one per second. This will help in a quite common case,
    R> >when some host on net is rebooting, and we are waiting for him to come
    R> >up, and notice this only after 1 - 20 seconds since the time it is
    R> >reachable.
    R>
    R> While networks have gotten a lot faster in the last few years, I've
    R> noticed that many of the ones I deal with have also gotten a lot larger in
    R> terms of number of hosts. This has been possible both because of the
    R> absolute increase in bandwidth, and also because of the widespread use of
    R> switches to suppress unnecessary unicast traffic to segments. I worry
    R> that significantly increasing the amount of broadcast traffic will be a
    R> problem for sites with large bridged network configurations. On the other
    R> hand, they already have to deal with things like windows network
    R> neighborhoods, various service discovery protocols, and so on.
    R>
    R> Do you have any information on what other operating systems may have done
    R> in terms of tweaking ARP for improved responsiveness? I imagine we can't
    R> be the first to discuss such changes, and if there is already a widely
    R> deployed system with ARP adaptations of this sort, it would be interesting
    R> to know if they've seen any problems or have recommendations.

    Frankly speaking, I have written my email after looking at Linux behavior.
    It sends one ARP request per second while there is demand for this ARP entry.
    After demand has disapparead, it sends a few retransmits driven by timer. If
    again there is a demand, it starts to retransmit again. Under "demand" here
    I mean a traffic to this particular IP, either locally generated or routed. 

    -- 
Totus tuus, Glebius.
GLEBIUS-RIPN GLEB-RIPE
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  • Next message: Bill Vermillion: "Re: ARP request retransmitting"

    Relevant Pages

    • Re: ARP request retransmitting
      ... > Currently we after sending several ARP requests, ... > I suggest to keep sending ARP requests while there is a demand for this ... problem for sites with large bridged network configurations. ... Do you have any information on what other operating systems may have done ...
      (freebsd-arch)
    • ARP request retransmitting
      ... I have a proposition on changing the behavior of ARP retransmitting. ... Currently we after sending several ARP requests, sending ARP requests ... additional broadcast packet was an expensive thing. ...
      (freebsd-arch)
    • ARP request retransmitting
      ... I have a proposition on changing the behavior of ARP retransmitting. ... Currently we after sending several ARP requests, sending ARP requests ... additional broadcast packet was an expensive thing. ...
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