RE: [rohc] draft-ace-robust-hc-01.txt

[Mikael Degermark <micke@cs.arizona.edu>]

Hi Magnus, 

At 02:16 PM 3/30/00 +0200, Magnus Hartman wrote:
>Hi,
>
>Even though this discussion is somewhat old, I have a few comments/questions
>on IPsec and ACE and ACE as such. See below.
>
>-----Original Message-----
>From: zhigang.liu@nokia.com [mailto:zhigang.liu@nokia.com]
>Sent: Tuesday, March 14, 2000 3:38 AM
>To: L.Wood@eim.surrey.ac.uk
>Cc: rohc@cdt.luth.se
>Subject: RE: [rohc] draft-ace-robust-hc-01.txt
>
>>> I was wondering about compressing authentication overhead; some people
>>> believe authentication will be used on a hop-by-hop basis to give you
>>> IP header checksum functionality in IPv6...
>>> > L.
>> Hmm, that's interesting. Maybe we could do something here. But again,
>> it depends on the hop-by-hop assumption.
>>
>>Zhigang
>
>I am not an expert on IPsec, but as far as I've understood it, there are 4
>"modes": tunneling-ESP, transport-ESP, tunneling-AH and transport-AH?
>When it comes to header compression, the ESP is out of the question (except
>for compressing the "visible" IP header), since the whole idea is that no
>one should be able to manipulate your headers (and payload).

Yes, and the bits are cryptographically scrambled so there is no redundancy
to utilize for compression. 

>With the AH however, shouldn't it be possible to simply define profiles, in
>e.g. the ROCCO framework, for both tunneling and transport mode of AH, where
>the AH header have to be sent over the link? Regardless of the hop-by-hop
>assumption?
>Sure, there are probably more spectrum efficient solutions, but if AH will
>be used for different reasons, (e.g. to solve the lack of checksum in IPv6),
>then it is motivated?
>Have you ROCCO guys looked into this? Or somebody else?

rfc2507 defines how compress the AH. All fields of the AH except for the actual 
authentication data can be compressed away. 

>Finally, When browsing through the ACE draft, I realized that 'A' in ACE
>stands for 'Adaptive' (first time I heard about ACE the 'A' stood for
>'Acknowledged'.). So, what exactly does 'Adaptive' refer to? I suspect that
>it is related to the compression states (FH, FO, etc.) and that the
>algorithm as such adapts to the situation by means of changing compression
>states? Correct?
>In any case, could you please elaborate a little bit further on this, e.g.
>what exactly is adaptive in the algorithm and what does the algorithm adapt
>to, i.e. what kind of information is used for adaptation decisions,
>especially in the case of Unidirectional mode?
>
>Regards,
>
>Magnus Hartman
>---
>Magnus Hartman
>Northstream AB
>Phone: +46(0)70 6475551
>http://www.northstream.se
>
>
>
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