Subject: RE: [Autoconf] The case for address uniqueness

From: "Templin, Fred L" <[email-masked]>
Date: Wed, 8 Feb 2006 13:21:34 -0800

> > -----Original Message-----
> > From: Green, David B RDECOM CERDEC STCD SRI 
> > If the lower 64bit address identifiers in MANET AS router 
> > neodes are made with a guaranteed Unique IDentification (UID) 
> > numbers do we need DAD for IPv6 Unique Local Addresses (ULAs) 
> > and global addresses?
> 
> IMHO, the answer is no, you do not need DAD if you can
> guarantee unique IDs in the lower 64bits of an IPv6
> address simply because there are enough bits available
> to ensure uniqueness to a high probability.

Exploring this just a bit further; suppose there existed an
IPv6 Internet for which some centralized authority was
responsible for assigning each node a guaranteed-unique
ID and it actually worked out that way in practice. The
Internet would also be such that the guaranteed-unique node
IDs were always used in constructing IPv6 addresses, and
mechanisms like privacy addressing were never used.

Then, an IPv6 address on that Internet could be thought of
as containing a locator component in the upper 64 bits and
an identifier component in the lower 64 bits, i.e., a clear
locator/identifier split. This would seemingly allow for DAD
avoidance in all cases, but would essentially restrict the
Internet to only having 2^64 unique addresses instead of 2^128.

What are the other benefits and drawbacks you could imagine
for such an Internet?

Fred
[email-masked]  

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---

From: Christophe Jelger <[email-masked]>
Date: Thu, 09 Feb 2006 14:44:50 +0100

Hello,

See some comments below.

Templin, Fred L wrote:
> (...)

Actually this is roughly what happens with IPv6 stateless address
autoconfiguration. The network prefix (usually 64 bits) is the locator
("where you are", or rather "the network link your are attached to"),
and the EUI-64 is one of your identifiers. That is it identifies one NIC
of your PC, IPAQ, Palm or whatever device is yours (or actually yours
via your company ;-). What you propose is essentialy to stick the 64-bit
identifier to the device (or the user itself but that would probably
raise so much privacy concern that it would be rejected).

> What are the other benefits and drawbacks you could imagine

Actually although I tend to find such a solution as being "elegant", I
think it suffers from many problems.

First there is the centralized authority (which could in fact be
decentralized as IANA decentralizes IPv6 address allocation via RIRs)
which would have to deal with the registration of millions of devices.
Quite complex and open concerns such as "Are you really who you tell us
you are".

Second, that doesn't help much to locate somebody. I mean you would look
for a given host and its associated HUI-64 (Host Unique Identifer) but
could not easily derive the locator ... unless there is somewhere a huge 
  database that keeps track of location (unless there is some home 
network associated to each HUI and a Mobile IP like home agent in each 
local network).

Finally I am not sure whether it's a good idea to embedd this numerical 
  identity into the IP address because even if there is a clear 
locator/identity split it's still after all an IPv6 address which is not 
supposed to have anything to do with identity. I think something like 
HIP (Host Identity Protocol) does the same thing but in a cleaner way.

Regards,
Christophe