Re: [dna] Review of draft-ietf-dna-simple-11

"Bernard Aboba" <bernard_aboba@hotmail.com> Tue, 24 November 2009 18:18 UTC

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From: "Bernard Aboba" <bernard_aboba@hotmail.com>
To: "'Ted Lemon'" <mellon@fugue.com>, <dna@ietf.org>
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Subject: Re: [dna] Review of draft-ietf-dna-simple-11
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Ted Lemon said:

"More, from section 4.3:

  It SHOULD also set all Neighbor
  Cache entries for the routers on its Default Router List to STALE.
  This is done to speed up the acquisition of a new default router when
  link change has occurred.

It's my impression that by default, a stale routing table entry won't
be used, so if an application writes to an open tcp connection while
the routing table entry is stale, it will get an EHOSTUNREACH, and the
connection will be dropped.  I have had this exact experience with
IPv4 DNA implementations when my WiFi router signal is flaky.  This is
much worse than taking a long time (500ms isn't really that long) to
identify a new link.

This would also be a problem in the case where you are on a WiFi
network with more than one device advertising the same SSID - when you
switch to a new beacon, arguably this is a DNA event, but it would clearly
be a mistake to break existing connections in this case.

[BA] I agree that the paragraph cited does not make sense.  RFC 4436 does
not contain equivalent advice.  In general, Simple DNAv6 should seek to 
minimize connectivity disruption.