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HBA format (was Re: Comments on draft-bagnulo-multi6dt-hba-00.txt

Hi all,

With respect to the HBA format i guess that we can comment that:
- It is clear that it is valuable to support hybrid HBA/CGA format, in order to be able to do SeND and multi6 with the same address.
- In order to do this we need to define the HBA as a CGa extension, at least in this particular case
- This implies that the iids of the addresses of an HBA set will be different
- This is good because it provides enhanced privacy
- This may imply a more difficult management and would preclude
solutions based on source address rewriting by the site exit
router

Now w.r.t. HBA only addresses.
I guess we could define a different format for these, so that the same iid is maintained though the different addresses of an HBA, but this would imply an additional complexity. the cause of this complexity is that a node would need to support BOTH formats. This is so becuase it is difficutl to say that for instance fixed hosts won't need CGA features, since they are usefull to support renumbering events. Moreover, a given node may choose to use only HBA, but its peers may choose to use HBA/CGA addresses, so any node will have to understand both formats.
There have been concerns about the complexity of even implementing HBAs as an extension, i guess that these concerns would be greater if two different formats are proposed.

So sumarizing, the trade off as i see it is:

one common format provides less complexity, (only one format is required)
two formats provides same iids in the different asddreses in the HBA set. Soem people not even want this, so i guess that we would need to define privacy extensions for this format ( i have done this and it is just like CGA format)

i would prefer one format, becuase imho simplicity is important

regards, marcelo



El 17/11/2004, a las 2:34, Mohan Parthasarathy escribió:


Erik,

Mohan Parthasarathy wrote:

I don't have any problems with IIDs being
different :-) But i was more
trying to understand the compatibility problem.
Multi6 module anyway
has to do different processing if the address is a
HBA address or
if it is a CGA/HBA address. Now you can still use
the same format for
generating a single IID for all the prefixes e.g.
using all zeroes or all
ones for the subnet prefix field of the CGA
parameters data structure.
(but including the multi-prefix extension at the
end as specified now)
Assuming we can find such a thing, would it be 
considered simpler ?

But then the IID(s) needed for SeND would be
different than the IID(s)
needed for multi6, right?

Then which of the addresses (with which IDD) would a
host which wants to
take advantage of both SeND and multi6 at the same
time use?
Which addresses would it put in the DNS for itself?

If you want to have an address that can be used both
by SEND and Multi6, then you would generate an address
that includes both the public key and multi-prefix
extension as defined now. But my original question
was more specific to HBA addresses that can be
generated for all prefixes with the same identifier.
HBA only addresses anyway requires slightly
different processing. So, i don't know what
the issue is with generating the same identifier,
if needed or someone finds a use for it.

I realize that if a node wants to use SEND and multi6,
then the easy way to do is to generate a CGA/HBA
address. Otherwise the issues that you raise above
needs to be solved.

-mohan


     Erik



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