Last Call Review of draft-ietf-dhc-mac-assign-06
review-ietf-dhc-mac-assign-06-iotdir-lc-jimenez-2020-06-03-00

Jaime Jimenez review input:

draft-ietf-dhc-mac-assign-06 iodir review
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In general, I am not convinced about the concept presented in the draft of
assigning MAC addresses to IoT devices using DHCP. IoT devices normally already
arrive with that information from the factory. An IoT device thus would not use
a temporary MAC address but the one assigned by the manufacturer instead. On
top of my head, I cannot envision a scenario in which the device would need to
change its MAC address to the one provided by the DHCP server, maybe other
"IoT-people" can pitch in more info on this.

Abstract: It's unclear what "devices" refers to. Might be better to say virtual
machines, virtualized processes, network endpoints, etc.

Section 1: Would be useful to add a reference to the "birthday paradox" or a
short paragraph describing the problem. I am not qualified to judge but I would
think that the sheer number of potential identifiers guarantees that there
won't be collisions. Moreover if collisions would occur and are detected, the
recovery situation is a simple as assigning a new address.

Section 1: "The huge number of such devices would likely exhaust a vendor's OUI
global address space". Pardon the question but aren't OUI's identifying
vendors? Is it due to a huge number of IoT vendors then that the address space
may be exhausted?

Section 3: The definition of address indicates it is of 6 bytes of length (3
bytes OUI + 3 bytes NIC). It also says that "some network architectures may use
different lengths", would it not be better to be precise here as to which are
the address formats this document allows? Which is the structure and length of
the address block? Is it 6 bytes for the address + 4 bytes for the number? How
is it serialized in the DHCP communication?

Section 4.2: It is a bit odd to have an informative reference which is a short
bullet point Power Point presentation. Aren't there other references to
[IEEE-802.11-02-109r0]? It is good that there is a description within the
paragraph. typo: "assigns a address" / an notes: "(e.g. medical) / could be a
more exhaustive list; medical, environmental, presence...

Section 5: what does "IA container" stand for?

Section 6: This section could provide one or two examples, also an example of a
serialized address block.

Section 13: I think there are probably new security threads when using this
mechanism for IoT. I'd guess the mechanism can be abused by, for example,
requesting multiple address blocks to the DHCP server.

Ciao!
-- Jaime
(jaime@iki.fi)

Review is partially done. Another assignment may be needed to complete it.

Reviewer: Samita Chakrabarti
Review result: Almost Ready

 I took a quick glance at the draft from IoT point of view (only partial review
 ).

Section 4.2 talks about the IoT usecase as Direct Client Mode -- where they
talk about cheap devices which may not have unique UUID associated with it.

Note that a client that operates as above that does not have a
   globally unique link-layer address on any of its interfaces MUST NOT
   use a link-layer based DUID (DHCP Unique Identifier), i.e., DUID-LLT
   or DUID-LL.  For more details, refer to Section 11 of [RFC8415].

1. However,  it is not clear what  source initial link-layer address should be
used by these devices. should it point to section 6? will that suffice?

2. Moreover,  how safe the mechanism would be if the Security section says that
mechanism defined in this draft may be used by a bad actor ?

3. It appears to me the mechanisms are designed for VMs behind an hypervisor
and then IoT usages are added. My concerns are two fold for challenged low
capability IoT devices -- 1) will they be able to handle the complicated option
processing described here? 2) How to mitigate the security vulnerability for
IoT devices as direct clients?  (The security section does not talk about
mitigation)

Should there be a simpler option processing structure without TLV option
processing ( i,e a fixed structure part + then TLV part for optional
information]?