Subject: RE: Need clarification on some of the IPv6 requirements

From: "Chang, Ellen" <[email-masked]>
Date: Wed, 3 Jul 2002 07:30:33 -1000

From: Robert Elz [mailto:[email-masked]]
Sent: Tuesday, July 02, 2002 5:49 PM
To: Chang, Ellen
Cc: [email-masked]'
Subject: Re: Need clarification on some of the IPv6 requirements 

  | 3.  If a IPv6 node A send an Echo Request with unrecognized options( and
  | their highest-order two bits set to 00)  to IPv6 node B, should the node
B
  | respond an Echo Reply without the unrecognized options from the Echo
  | Request, OR should the node B respond an Echo Reply with the
unrecognized
  | options? Or are both ways acceptable?

Without I'd say.

########  
4.2  Options
The Option Type identifiers are internally encoded such that their
   highest-order two bits specify the action that must be taken if the
   processing IPv6 node does not recognize the Option Type:

      00 - skip over this option and continue processing the header.

Does this requirement mean the node B should remove the option and respond
with an Echo Reply to node A? or should it not remove the option from its
response?. In my opinion, the term Skip means that node B should not process
or remove the option. So node B should really send back a response with the
option unchanged and intact. However, I have seen different responses from 2
different routers. one of them removes the option, while the other does not,
and I am not sure which one is behaving as it should as per this requirement
##########

  | 5. If a IPv6 node A sends an Router solicitation message to IPv6 node B,
  | should the node B respond to node A with an Router advertisement with
invoking router
  | solicitation message's source address as its destination address, OR
should the
  | node B  be allowed to respond back with Router advertisement with
multicast destination
  | address.

The multicast address.  And I think it isn't "allowed" but must.  That's
what prevents RS/R Astorms when a labfull of nodes all boot.   They all
delay their RS by a random interval.  One  of them (naturally) has the
shortest random interval.   That one sends its RS (assuming chance hasn't
caused a RA to appear in the meantime).   Routers that receive it all
send RA's to the multicast addr.   All the other nodes receive those RAs
and so never send an RS.

########
4.2.  Router Advertisement Message Format

   Routers send out Router Advertisement message periodically, or in
   response to a Router Solicitation.
      Source Address
                     MUST be the link-local address assigned to the
                     interface from which this message is sent.

      Destination Address
                     Typically the Source Address of an invoking Router
                     Solicitation or the all-nodes multicast address.

There are two possibilities for the destination address as indicated in the
spec, so if what you say is correct as stated in your email, then under what
circumstances would router B be using the Source Address of an invoking
Router Solicitation?
########

Ellen
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