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comments on draft-moore-ipv6-optimistic-dad-04.txt
Here are comments on draft-moore-ipv6-optimistic-dad-04.txt. I have
one relatively-substantial comment and several editorial ones.
The relatively-substantial comment is:
I don't see the strong need for the unsolicited neighbor
advertisements described in Section 3.1:
* (adds to 7.2.6) The Optimistic node MAY send an unsolicited
Neighbour Advertisement to All Nodes when it first configures an
address. The Override flag on this advertisement MUST be set to
* (adds to 7.2.6) The Optimistic node SHOULD send an unsolicited NA
to All Nodes when it completes DAD. The Override flag on this
advertisement SHOULD be set to 1.
In particular, I don't understand why we SHOULD send the unsolicited
NA in the latter case.
Other (mostly) editorial comments.
1. the draft contain many acronyms without or before (clearly) showing
the original term. those include: DAD, ND, SAA, SLLAO, RS, RA, ON,
NC, NS, NA, MN, and LLAO.
2. The second paragraph of Introduction contains an incomplete
... Disruption is minimized by limiting nodes' participation in
Neighbour Discovery while their addresses are still Tentative,
(or perhaps the comma should actually be a period)
3. One definition in Section 1.3 is not well defined (IMO):
Well-Distributed Address - Address suffixes used for Optimistic DAD
should be well distributed, eg: there should be an equal
probability of any given suffix occuring. This minimizes the
probability of an address collision.
I would say this is a requirement, not a definition. I'd also like
to point out "well distributed" is not really clear in a
definition, but this is probably a minor issue (I can live with the
3. In section 2,
* Never using a Tentative address ...
.... Another address, or the unspecified
address, may be used, or the RS may be send without an SLLAO.
s/may be send/may be sent/
4. In section 2.
When the MN wants to contact another neighbour, but it cannot because
I guess MN stands for "mobile node" (see my first comment BTW), but I
don't see why we need to use this word here. As far as I can see,
there is nothing specific to a mobile node in this context.
5. In the same paragraph,
router should then provide the MN with a ICMP redirect, which may
s/a ICMP/an ICMP/
6. In Section 3.2
* (modifies 5.5) If an initial suffix is not supplied, a new suffix
SHOULD be generated as per "Address Generation" below.
What does "initial suffix" mean? RFC2462 (or its bis) doesn't use
7. In Section 3.2
* (modifies 5.4.5) ... If the address is a
link-local address formed from a fixed interface identifier, the
interface SHOULD be disabled. Otherwise, if the address was
What does "a fixed interface identifier" mean? (e.g.) An interface
identifier derived from a hardware address like EUI-64? FYI,
the latest rfc2462bis draft contains the following sentence in Section
If the address is a link-local address
formed from an interface identifier based on the hardware address
(e.g., EUI-64), the interface SHOULD be disabled.
8. In Section 3.3
* If the interface offers a method to create a supposedly globally
unique IPv6 address, this address MAY be used for the initial
This is not very clear to me. What exactly does "a supposedly
globally unique" mean? For instance, is an EUI-64 based IPv6 address
supposedly globally unique?
9. In Section 3.3
* In order to minimize the effect of DoS attacks, a delay of at least
RETRANS_TIMER (as used in [RFC2461]) milliseconds MUST be
introduced between attempts if DAD has already failed more than
once. An exponential backoff SHOULD be used.
Does more than once mean "two times or more" (the answer should be yes
in the literal sense)? If so, why don't we need a delay after the
10. In Section 3.4
... In order to minimize the probability of an undetected
address collision, it would seem prudent to always configure and
check the link-local address for any given suffix as well as checking
the actual address being configured.
I'm not really sure what "the actual address" means. Do you mean "non
11. In Section 4.2
... An NA with O=0,S=0 and no LLAO may [Note 1],
however cause the NC entry to be set to STALE, causing NUD to be
performed on the address.
Shouldn't the "no LLAO" really be "with LLAO"? If not, what is the
purpose of this NA (O=0,S=0, no LLAO)?
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
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