Re: WG last call: draft-ietf-zeroconf-ipv4-linklocal-08.txt

<wg chair hat on>
Folks:

Please read the final document and send comments.

<wg chair hat off>

These are responses to Stuart's mails during the first week in June.

LL32

   > 'will not advertise scoped address information'

   This paraphrases the essential MUST NOT from LL23.  It could
   be reworded slightly for clarity.

   >must be reached by forwarding to the destination
   >"...must be reached by sending directly to the destination..."

   Agreed we should replace forwarding to sent.  This is a slight
   rewording.

   > The phrase "run the algorithm independently on each interface" may
   > seem a simple thing to say, but when you have Ethernet and wireless,
   > and (unknown to you) the wireless base station you're talking to is
   > bridged onto the same Ethernet, the interfaces aren't independent
   > any more, even if you wish they were.

   We disagree.  If each interface runs the algorithm independently then
   the hosts wireless and wired interface will select and defend
   properly.  Only if they attempt to select and defend the same address
   will they fail.  In that case they need to choose different addreses.
   Using the algorithm, they are very likely to choose a different
   address that the other interface did not choose, and therefore will
   succeed.

LL11

   > As it stands, the paragraph reads like something saying, "This
   > standard says you should pick a new address if you detect a
   > conflict; here are some reasons why making your implementation
   > actually do that would be a terrible mistake."

   We disagree.  It says something like 'doing this exposes you to
   vulnerabilities.'  Its like driving - you should know that you
   could be smooshed every time you go on the freeway.  You don't
   have to go on the freeway, but it would be extremely negligent
   of your driving instructor to not let you know what you are facing.
   You should not neglect what precautions you have like seat belts
   insurance, etc (higher layer security protocols, no assumptions
   that no one would ever perform an active attack as described).

LL18

   This issue was never codified, but we discussed it on the list
   and there was broad agreement for it.  If you notice, this is
   addressed in the new section 3 and section 2.6.2, both of which
   have gone through WG last calls.  Your text changes the MAY to
   a MUST, i.e. from

    If the host does not have a routable source
    address, then it MAY choose to ARP for the destination address and
    then send its packet, with a Link-Local IPv4 source address and a
    routable destination IPv4 address, directly to its destination on the
    same physical link.

   to

    If the host has no appropriate
    routable source address, then it MUST ARP for the destination address
    and then send its packet, with a link-local source IP address and a
    routable destination IP address, directly to the destination on the
    same physical link.

  I support this change.

LL11

<wg chair hat on>

  This text has been reopened twice.  I do not think it should be
  opened again.

<wg chair hat off>

  >   When ready to begin probing, the host should then wait
  >   for a random time interval selected uniformly in the range
  >   zero to one seconds, and should then send three probe
  >   packets, spaced randomly, zero to one seconds apart.
  >
  > This means that, technically, if a device waits zero seconds, sends
  > three ARP Probes spaced zero seconds apart, and then immediately
  > begins using the address, that's legal.

  While it is technically legal, there is an effective zero probability
  that four random numbers selected uniformly will all occur at the
  same 'zero' value.

Best regards,

Erik