Last Call Review of draft-ietf-6man-stable-privacy-addresses-16
review-ietf-6man-stable-privacy-addresses-16-opsdir-lc-chown-2014-01-23-00

Hi,

First, I would note that I have already contributed comments/text to this
draft, as acknowledged by Fernando.  It’s been a few versions since I last read
it.

The goal of the draft has considerable merit, and I believe the document is
worthy of publication, subject to comments belwo being considered.

I would classify the document as ‘Ready with issues’.

Issues:

1. In the discussion in section 5 on the algorithm, it may be desirable to
suggest that implementations allow a choice of IID generation based on
‘classic’ SLAAC with EUI-64 or via this new proposed method, with a default of
the new method.

2. In the algorithm section, there is a comment that interface names MUST
remain the same across boots or down/up events for the stable privacy address
to remain stable. I have (admittedly some time ago, and in rare cases) seen
Linux installations where network interface names can ‘swap’, thus changing the
address in use on the interface under the proposed algorithm, whereas with
existing EUI64 SLAAC the IIDs would remain the same even if the interface name
for a physical interface changed. This is probably rather more likely if
replacing a network card on motherboard with on-board NIC(s).  Perhaps Fernando
can comment on whether this is a realistic concern with modern OSes.

3. I assume the IID may/will vary for a different OS run on the same host, e.g.
where the host is dual-boot, or where a new OS installed (or the same OS
re-installed). A different OS may well use a different F(), given that’s not
specified.  With EUI-64, a dual-boot host would likely have the same address
under either OS (well, not Windows any more…).  This may be worth making
explicit.

4. The draft talks (in one place in Section 3) about stable privacy addresses
being allocated by DHCPv6; some further discussion of how this might be
achieved may be useful given the secret key is presumed to be generated on and
reside on the host, not the DHCPv6 server.  Or would this be described in a
separate future draft?  This may be a case where the administrator being able
to display or change the secret key needs to be more than a MAY as currently
satted in the text.

5. Design goal 1 might add “and same interface” for scenarios where a host has
two interfaces in the same subnet (with the same prefix).  This scenario is one
that may cause ‘interesting’ effects with addresses if interface names swap and
no Network_ID is used.

6. I’d suggest not mentioning MD5.

Nits:

1. Some references are included multiple times, e.g. [RFC4941], rather than
only at the first instance.

2. Design goal 2, perhaps say “must” rather than “do”?

3. In section 4 the author states the goal of stable IIDs within a given
subnet. It may be better to say for a given prefix, given a renumbering process
will change the prefix and with it the IID, though by loose language you might
refer to it as the same subnet.

In response to recent discussion on 6man, I don’t believe it’s practical or
desirable for a node to store addresses related to locations (networks)
visited.  I agree with the author that the static address per network should be
generated statelessly.

Tim