Re: [Monami6] More comments on draft-bagnulo-shim6-mip-00

[marcelo bagnulo braun <[e-mail]>]

Hi Thierry,

thanks for reading and commenting the draft

El 27/07/2005, a las 12:28, Thierry Ernst escribió:

>
> I start a new thread since the other one "[Monami6] Fwd: I-D
> ACTION:draft-bagnulo-shim6-mip-00.txt" has diverged from the draft
> itself.
> I have some questions that may appear a little bit stupid, but it may
> help to clarify things:
>

questions are always welcomed and there ain't such things as stupid 
questions,

> - why do you consider the Shim6 layer over the Mip6 layer?

actually, in the initial discussions we cosnidered both SHIM over MIP 
and also MIP over SHIM configurations, but we finally thought that 
cosnidering all the possibilities would result in a major headache for 
anyone who read the draft. So we decided to keep the configurations 
that made a clear case and provide a clear benefit. In particular, 
layering the SHIM over MIP results in the possibility of supporting 
multiple Hoas

> Couldn't the shim6 layer be cotemplated as an extension of the MIP6
> layer, I mean both of them sitting together, not one above the other ?
>

i don't know...
I mean, i see them as modular items, and we played to see how the 
interact without integrating them
I am afraid that integrating them would result in major modifications 
in the SHIM and in the MIP modules.
So, the first approach was to see if layering one over the other would 
result in useful outcomes

> - for Shim, there is a need for a protocol to exchange the set of
> locators. Couldn't be MIP6 extensions used for such a task (I'm not
> contemplating MIP6 as the protocol for doing it, I'm rather thinking
> that given a node for a MIP6 protocol stack, it could be easier to
> deploy Shim6 for MIP6-enabled nodes than for non-MIP6 enabled nodes.
>

i think that this would be possible, i.e. allowing coas to be included 
in the locator set of SHIM. Actually this reminds me to the celp 
proposal by D. Crocker a while ago.

I guess that we should consider security implications, depending on how 
CoAs are validated...

This is one of the points where MIP SHIM interaction would need further 
exploration i guess

> - on 050714 you said "the SHIM work currently does not
> considers the mobility scenario, so adding/removing addresses is still
> somehow undefined": does Shim6 consider that all the set of locators is
> known in advance ; can't new locators be added dynamically, or you just
> mean the operation for doing is undefined ?
>

well, the charter explicetly says that dynamic locators sets must be 
supported, and imho there are security mechanisms that could deal with 
this requirement.

So i would go for the second option, that the operation for doing it is 
not yet completelly specified.

> - on 050714 you wrote "SHIM may be useful to  provide some of the
> features required to multihoming support in the MIP protocol": Could 
> you
> detail what features you are thinking about ?
>

I think the the SHIM work can be useful in several aspects:
- the support of multiple HoAs could be provided using the SHIM support 
in the CN without requiring additional mechanisms
- The failure detection mechanisms and the path exploration mechanisms 
defined by the shim could be used (for HoAs and perhaps for CoAs)
- The ingress filtering mechanisms could be useful both in the Home 
network and in the visited network
- The address selection mechanism (in particular retrial with 
alternative source address) could also be useful to initiate 
communications after outaages

IMHO all these mechanisms are worth to be explored and see if the match 
with the requirements imposed by mip multihoming


> Note, I also read  draft-ietf-shim6-l3shim-00.txt and:
>
> - Section 2: wouldn't be useful to define what a shim is ?
> - Section 4: [M6REFER]: reference not present in reference section. 
> Must
> be a typo
>

we will check these out, thanks, marcelo


> Thierry
>
>
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