[dhcwg] Robert Wilton's Discuss on draft-ietf-dhc-mac-assign-07: (with DISCUSS and COMMENT)

Robert Wilton via Datatracker <noreply@ietf.org> Mon, 08 June 2020 11:08 UTC

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Subject: [dhcwg] Robert Wilton's Discuss on draft-ietf-dhc-mac-assign-07: (with DISCUSS and COMMENT)
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Robert Wilton has entered the following ballot position for
draft-ietf-dhc-mac-assign-07: Discuss

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DISCUSS:
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Hi,

Thank you for this document.  Mostly I found this document to be straight
forward to read, but there are a few areas that were unclear to me, that could
probably help being clarified.

Hopefully none of these are too difficult to address, or they may turn out not
to be issues at all ...

Client SHOULD, server MUST ignore.  In a couple of places in the document
(sections 6, 10.1, 10.2), it states that the client SHOULD set 0.  To allow the
protocol to evolve in future, I believe that it would be better if the SHOULD
is changed to a MUST.

There doesn't appear to be any specification of how an OPTION_IA_LL should be
handled if there are no IA_LL-options, or it contains an IA_LL-option that is
not understood by the server.  The text does also not specify if IA_LL-options
can contain multiple options, and if so how those are encoded (presumably as an
array/list of option values), perhaps this is already covered by the DHCPv6
spec?  Similar comments also apply to the LLaddr-options field.

9. Releasing Addresses

Once a block of addresses have been released, can they immediately be allocated
to a different client?  Or should they avoid being reused straight away if
possible?  Perhaps this consideration is already covered by DHCPv6, but it
probably makes sense to say something about this, either in section 9, and/or
maybe in the security considerations.


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COMMENT:
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1. Introduction

   Typically the new VM instances are assigned a random link-layer (MAC)
   address, but that does not scale well due to the birthday paradox.

Perhaps either have a reference to birthday paradox, or briefly describe (in a
sentence) what the paradox is.

4.3. Mechanism Overview

Contains both:

   This mechanism can be administratively disabled by the server sending
   "infinity" as the T1 and T2 values (see Section 7.7 of [RFC8415]).

And

   An administrator may make the address assignment permanent by
   specifying use of infinite lifetimes, as defined in Section 7.7 of
   [RFC8415].

Perhaps these sentences could be amalgamated?

7.  Requesting Addresses

    The client MUST be able to handle a Reply message containing a smaller
    number of addresses, or an address or addresses different from those
    requested.

Perhaps clarify whether the "smaller number of addresses" relates to the
initial request from the client, or the value received by the client from the
server in teh advertise message.  E.g. could a server "advertise" a block of
100 addresses, but then only "reply" with a block of 50 addresses?

8. Renewing Addresses

IAID is used before it defined.  Perhaps either add it to the terminology, or
reference where it is defined when it is first used?

10.1
I found the subtle distinction between "IA_LL option" vs "IA_LL-options" to
probably be a bit more confusing than necessary.  Possibly always refering to
the "IA_LL_OPTION option" vs "IA_LL-options field" would add clarify, or
perhaps rename "IA_LL-options" to "IA_LL-suboptions".  The same comment
obviously applies to the LLADDR option definition as well.