Re: WG ACTION: 1 week to discuss [LL37] Aggressive Time-outs

Instead of trying to figure out how long it takes to send three probes,
I would like to step back a little and ask the question WHY exactly do
we have to send THREE PROBES? What exactly in v4LL necessitates sending
three DAD probes when IPv6 can get away with only one? Here's the
relevant bit from RFC2462:

...
5.1.  Node Configuration Variables

   A node MUST allow the following autoconfiguration-related variable to
   be configured by system management for each multicast interface:

      DupAddrDetectTransmits

                     The number of consecutive Neighbor Solicitation
                     messages sent while performing Duplicate Address
                     Detection on a tentative address. A value of zero
                     indicates that Duplicate Address Detection is not
                     performed on tentative addresses. A value of one
                     indicates a single transmission with no follow up
                     retransmissions.

                     Default: 1, but may be overridden by a link-type
                     specific value in the document that covers issues
                     related to the transmission of IP over a particular
                     link type (e.g., [IPv6-ETHER]).

                     Autoconfiguration also assumes the presence of the
                     variable RetransTimer as defined in [DISCOVERY].
                     For autoconfiguration purposes, RetransTimer
                     specifies the delay between consecutive Neighbor
                     Solicitation transmissions performed during
                     Duplicate Address Detection (if
                     DupAddrDetectTransmits is greater than 1), as well
                     as the time a node waits after sending the last
                     Neighbor Solicitation before ending the Duplicate
                     Address Detection process.
...

Here's my proposal (three fold):
     1. Let's specify DAD probe in the same way as in IPv6, defaulting
        to a single probe packet
     2. In the event of a conflict (slightly more probable with v4LL
        compared to IPv6), allow the node to select a new v4LL and retry
        up to, e.g., AddrSelectRetries times
     3. Let's get rid of the text describing shorter timeouts. If we
        default to a single probe, DAD only takes 1..2 seconds (with a
        high probability). That is good enough from the usability point
        of view.

Regards,

	MikaL

On Mon, 2003-12-15 at 15:08, Erik Guttman wrote:
> Please send your comments to the working group mailing list.  Unless
> there is an objection due to lack of time to work on this before the
> holidays, the discussion will conclude on December 23.
> 
> Please see: http://www.merit.edu/mail.archives/zeroconf/msg00001.html
> And: http://www.drizzle.org/~aboba/ZEROCONF/ll37.html
> 
> Regards,
> 
> Erik
>