Subject: RE: [rohc] Do we need a special profile for Mobile IPv6 packets?

From: "Lars-Erik Jonsson (EAB)" <[email-masked]>
Date: Sun, 8 Dec 2002 18:27:39 +0100

>  In your previous mail you wrote:
> 
> > According to your draft, the extension headers that would 
> > have to be handled for MIPv6 can basically be considered
> > as static.
> 
> => the extensions headers are the most static part in a Mobile IPv6
> communication. For instance, the home address option is same in all
> packets when the source address in the IPv6 header changes at each
> handoff... So I fully agree with Wang.

Fine, then there should be no problem handling these efficiently with
the list compression scheme.

> > I am therefore not sure what explicit compression mechanisms
> > would be needed to compress these, since the list compression
> > scheme should already be capable of compressing these headers,
> > i.e. to initialize them as list items, which can thereafter be
> > omitted as long as they do not change (and if they do, that can
> > also be handled).
>    
> => IPv6 option extensions are not like the TCP options: even if the
> list compression can handle them this can become highly suboptimal.

Then you will have to explain why. What you have stated about these
headers seem to indicate the opposite, i.e. that list compression
as it is currently defined should handle this optimally.

> PS: in my real world IPv6 experience, I never found a dynamic option.
> You can transmit the question to the IPv6 WG if you don't believe me
> but if the ROHC WG has still some interests in a reasonable support
> of IPv6, ideas like presented in draft-hwang-rohc-mipv6-00.txt
> should be taken into account.

I am sorry if I miss something here, but I see a contradiction in
these statements. If options are *always* static, to me this is just
very good news for the list compression scheme, because then options
can be efficiently compressed already with the current mechanisms.

BR
/L-E
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---

From: Francis Dupont <[email-masked]>
Date: Mon, 09 Dec 2002 14:35:08 +0100

=> no, the list compression scheme is not the right mechanism
and some new profiles are really needed.

   
=> the optimum is static (static-def in fact) for the real addresses
which are in an extension header or the IPv6 header. For other fields
the trade-off is between being static or in list compression, within
specific profiles the more efficient should be used.

=> it seems you suggest that the list compression scheme is as efficient
as the "static" compression scheme? Don't forget we talk about cases
where options are builtin (mobile IPv6, multicast listener discovery, ...)
so the fact they are static is part of specific profiles.

Regards

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