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Re: Setting DSCP for IPv6 Neighbor Discovery packets

    Date:        Tue, 06 Jul 2010 20:37:22 -0400
    From:        Patrik Lahti <>
    Message-ID:  <>

  | I'm of the opinion that IPv6 Neighbor Discovery packets are network 
  | control packets

I disagree.    With the possible exception of RA's (I'm not sure if your
use of the "IPv6 Neighbor Discovery" term includes everything, or just NS/NA
the elements of the part of ND that is ARP like), and just perhaps unsolicited
NA's after an address change, there's nothing about ND that is network control.

Network control is about keeping the network working - which could include
stuff needed for loop detection (were anything of the kind needed), and
certainly, I think, RA's that advertise prefixes.

On the other hand, NS/NA just allow hosts to use the network - how important
that is depends entirely upon how important the communications are, which
will vary from host to host, and with each of its peers, and even from time
to time depending upon why it is sending packets.

The traffic class of an NS should be the same as the highest traffic class
of the packets that are to be communicated - which in practice, means the same
as the packet that triggered the NS, unless ND was already in progress with
a higher traffic class.   A reply NA should have the same class as the ND
that requested it.   "Refresh ND's" (if we generate such things) can be any
random (fairly low) class.  NS used for DAD should be nothing at all.
RS should also be 0.   RA (and perhaps an unsolicited NA, that one would
take more thought) might be worthy of being considered network control.


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