Re: [Roll] Way forward for draft-clausen-lln-rpl-experiences

Martin Heusse <Martin.Heusse@imag.fr> Tue, 22 May 2012 14:38 UTC

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From: Martin Heusse <Martin.Heusse@imag.fr>
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References: <258D7E2F-F0C7-49EA-B831-81070C86EDB3@thomasclausen.org> <2257A578-B2DF-4145-8393-9BB5D7E1CFBD@cisco.com> <2225986E-992E-43C7-B0CA-9CDA91CE1F3A@thomasclausen.org> <B1B81482-0F7E-4BCE-BBA7-B21949E3C16C@cisco.com> <0958556A-7D9A-4E8B-8091-1D6EC0B813B4@thomasclausen.org> <ACBA7834-F4A1-4D9C-80D6-E76C793A6770@cisco.com> <91E71E23-8797-4C70-A1F8-1CE64BD4ED39@thomasclausen.org> <1D6FEB49-CB62-4FFA-9E34-3FEF82DB644C@cisco.com> <BE51553F-67BE-4652-A8E8-9654BF953A96@thomasclausen.org> <78FB3B50-3150-4729-A089-D9EAF0B02BB6@cs.stanford.edu> <2AF45E51-6C3B-48D9-908F-117ECF0CABAA@imag.fr> <B665C776-CF85-4EF6-8637-77D8F717D229@cisco.com>
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Subject: Re: [Roll] Way forward for draft-clausen-lln-rpl-experiences
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Jean-Philippe,

you wrote:

> How often do you think that ISIS LSA should be refreshed ?
> Or OSPF opaque LSA for TE extensions be flooded ?
--> "It depends"?
I am not saying that we would need to mention in the (general) RFC when, or at which rate,
- global repairs should take place or;
- DAO should be sent out on a regular basis…
(Although this could perfectly appear in applicability, isn't it?)

My point was that the DAO mechanisms are not so clearly defined... Which may be fine: then Mukul is right and if you really need to reach everyone, then P2P RPL is there...
Right now, there can be a problem with DAOs
- if they are lost along the way (not unlikely if not using DAO-ACKs **even with L2 ACKs**, still possible otherwise) 
- if a sub-dodag moves... all routes are broken, and we don't really know how to re-establish them (although DTSN could help here, although it's a little vague)
- if an inconsistency is detected on a downward route, you'd have to ask everyone to re-send DAOs (Pascal's DAO requests would have helped of course -- this shows up on the list every now and then).

--> for opaque LSA, the information in the packet does not matter, but the flooding mechanism is robust and well defined. For DAOs, we know how the packet must look like...

> Or BFD packets ? 
> Or PCEP Keepalive when turned on ?
> 
> Very seriously … these questions apply to all protocols … and you cannot expect the specifications to give you
> hard coded values (but default whenever possible); these are topology and application specific, don't you think ?
Yes, I agree! 

Martin