Re: ARP request retransmitting

From: Chuck Swiger (cswiger_at_mac.com)
Date: 11/07/05

  • Next message: John Baldwin: "Re: FreeBSD/xbox: updated 7.0 patchset" 
    Date: Mon, 07 Nov 2005 11:16:27 -0500
To: Gleb Smirnoff <glebius@FreeBSD.org>

    Hi--

    Gleb Smirnoff wrote:
    > I have a proposition on changing the behavior of ARP retransmitting.
    > Currently we after sending several ARP requests, sending ARP requests
    > for given IP is suppressed for some interval (by default 20 seconds).
    > Probably this feature was designed in early 90th, when sending one
    > additional broadcast packet was an expensive thing.

    Well, we've got ten or a hundred times as much bandwidth, so sending more data
    is relatively cheap, but the per-packet overhead hasn't improved to the same
    extent. ARP requests still get sent to and are processed by all machines on
    the network, even if a switch is being used.

    > I suggest to keep sending ARP requests while there is a demand for
    > this (we are trying to transmit packets to this particular IP),
    > ratelimiting these requests to one per second. This will help in a
    > quite common case, when some host on net is rebooting, and we are
    > waiting for him to come up, and notice this only after 1 - 20 seconds
    > since the time it is reachable.
    >
    > Any objections?

    No, no objection. However, this type of situation could be handled by either
    an incremental or exponential timeout. Instead of waiting:

    1 1 1 1 1

    ...seconds between packets as you proposed, consider waiting either of:

    1 2 3 4 5
    1 2 4 8 16

    ...seconds, and cap the maximum wait between ARP requests to 16 or so. Backing
    off politely and gradually when the host is not getting any answers is more
    network-friendly. 

    -- 
-Chuck
_______________________________________________
freebsd-arch@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-arch
To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"
  • Next message: John Baldwin: "Re: FreeBSD/xbox: updated 7.0 patchset"

    Relevant Pages

    • Re: ARP question
      ... I suspect these ARP requests are caused by botnets, on the Internet, ... UDP port 1026, ... I got 1871 ARP requests, 1870 were from the Cable company, and one was ... I also got 31 regular IP packets, of which 5 were TCP and 26 were UDP. ...
      (Fedora)
    • Re: Responds to ARP requests for specified subnet
      ... > The linux box shall respond to ARP requests for a specified subnet and ... > accept an IP packets for that subnet though the box itself can reside ... interface it will respond to arp requests received by that interface for IP ...
      (comp.os.linux.networking)
    • kernel module acquiring virtual ips
      ... I have a kernel module which "acquires" virtual ips ... To get the arp stuff working I handle all the ARP requests for virtual IP and reply to ... I can now receive all the packets destined to virtual IP. ... Nat Destination 192.168.1.21-> 192.168.1.2 ...
      (Linux-Kernel)
    • [SLE] compaq / HP ProLiant DL580
      ... Arp requests for eg. the mac ... Some sniffing on the network shows that the server send ... the fw answers with reply packets but the server does not recognize these ... Even a static arp ...
      (SuSE)
    • Re: ARP request retransmitting
      ... >> I suggest to keep sending ARP requests while there is a demand for ... >>this (we are trying to transmit packets to this particular IP), ... >...seconds between packets as you proposed, consider waiting either of: ... with things like windows network neighborhoods, ...
      (freebsd-arch)