RE: about Wedgelayer 3.5 / Fat IP approaches

["Henderson, Thomas R" <thomas.r.henderson@boeing.com>]

> -----Original Message-----
> From: marcelo bagnulo braun [mailto:marcelo@it.uc3m.es] 
> Sent: Wednesday, June 30, 2004 7:42 AM
> To: Jukka Ylitalo
> Cc: Henderson, Thomas R; Multi6 List; Erik Nordmark
> Subject: Re: about Wedgelayer 3.5 / Fat IP approaches
> 
> 
> 
> El 30/06/2004, a las 16:15, Jukka Ylitalo escribió:
> 
> > Hi,
> >
> > Henderson, Thomas R wrote:
> >
> >>
> >> Rather than NOID kind of split, maybe CB64-like split is 
> preferable?
> >> (where lower bits of AID match the HIT and upper bits the prefix,
> >> rather than having the AID be unrelated to the HIT)?  It wouldn't
> >> have to be a /64 split necessarily-- just reverse mappable with
> >> DNSSEC.  I agree that HIP opportunistic mode should be 
> able to deal 
> >> with it.
> >>
> > CB64 -like split sounds good.  Right, there arises some AID
> > ownership problems if it is not bound to the HIT.
> > It would be nice to have a new version of Multi6 HIP draft that
> > describes how HIP could be used with CB64 -like AIDs.
> >
> 
> how this would differ from the cb64 draft by Erik?
> 

So, assuming that HIP hosts started to use low order bits of the
HIT in their locators, and then used such a locator as an AID,
the main differences I see are in the use of/reliance on PK crypto
in the context establishment handshakes, as well as IPsec reliance 
(HIP relies on PK signings for handshakes, and relies on IPsec, 
while CB64 relies on neither), and some of the basic protocol 
mechanisms of the two proposals (which one might argue are just
details):
- CB64 handshake occurs in parallel with start of data transfer
(actually, after first data packet has been sent), while HIP holds
the first packet waiting for HIP handshake to complete (or
possibly piggybacks it on the HIP exchange). 
- CB64 uses flow IDs and locators as keys to find context state
for the session, while HIP uses IPsec SPIs
- CB64 adds new locator for peer upon discovering it as a source
address in a packet (and issuing PK-signed challenge/response), 
while HIP explicitly signals the new locator in a signed HIP 
exchange.

Another difference is length of the hash of the key, which may
cause some subtle differences.  With 64 bit IDs (or, strictly
speaking, ID tags, since the public keys are the actual
identifiers), we can provide an embedded stack name in the AID, 
whereas with HITs, we can only provide a mapping between 
(truncated) stack name and AIDs.  When we have discussed 
shortening HITs to accommodate some structure to aid reverse 
lookups, there have been concerns raised that 64 bit IDs might 
not be strong enough to withstand server farm attacks in the 
future (generating different key that hashes to same ID).  
If a larger hash is used as the identifier, then the AID with 
truncated HIT can be viewed as a slightly less secure 
identifier used for support of referrals for non-multi6/HIP 
aware apps, which keeps the door open for future HIP-aware 
apps to directly use the full IDs.

Tom