[Hipsec] Feedback for 4423bis

[Sasu Tarkoma <[e-mail]>]

Hi all,

I read the latest HIP architecture draft (4423bis-05) and it looks
very good. Below you will find some observations that I made
when reading the draft.

Best regards,
- Sasu

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- Architecture and implementation details are partly
 intertwined here. Perhaps the generic model can
be summarised first and then the implementation
specific details. Theory of HI is mentioned in the 
beginning, but I think it is not clear for all readers what 
is meant by this. 

- It is stated that the model is general and it does not require 
public key crypto; however, this is not really elaborated. Also
it is stated that the model can be applied at any
layer, but this is not explained. The description assumes
that Host Identity decouples internetworking and
transport layers.

- The draft does not discuss architecture and protocol
deployment issues. This is one practical requirement given
the momentum of the current solutions.

- The description of the HIP protocol is quite light in this
draft. The introductory part to section 5 could briefly state the
key components of HIP including BEX, mobility/multihoming support,
and rendezvous that are covered by the following subsections.

- In section 5, it is stated that:
"Similarly, if it is possible to distribute the processing of a single
   Host Identity over several physical computers, HIP provides for
   cluster based services without any changes at the client end-point."

I think the base specification and implementation do not directly
support this, but additional management extensions are needed.

- Computational puzzle does not appear to be mentioned.

- Extensions (new hash functions) are not elaborated. This is
related to a general requirement that a protocol should be evolvable. 

- p. 17 section 10 needs a reference

- p. 21 the downgrade attack should be elaborated.

- Typo: p. 5 Identfier