Re: [6lowpan] 6lowpan-nd-15 node mobility and default router(s)

Zach Shelby <zach@sensinode.com> Mon, 13 June 2011 08:11 UTC

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From: Zach Shelby <zach@sensinode.com>
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Date: Mon, 13 Jun 2011 11:11:12 +0300
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To: "Dijk, Esko" <esko.dijk@philips.com>
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Subject: Re: [6lowpan] 6lowpan-nd-15 node mobility and default router(s)
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Esko,

On May 23, 2011, at 12:24 PM, Dijk, Esko wrote:

> Dear all,
>  
> A comment on Section 1.3 of 6lowpan-nd-15, last bullet:
>  
> When a node moves away from the registered default router, it SHOULD first de-register by
> sending a registration message with zero lifetime and then
> registers with a new default router that is reachable

This text was meant as an example of how to handle intra-domain mobility when registered with a single default router. You are correct that a host can be registered to multiple default routers (and this is recommended). This text in 1.3 shouldn't have been normative as you point out. The normative text for this was already in Section 5.5, so I will remove this from the assumptions. I added the bit about using a suitably short lifetime to Section 5.5 as that was missing there. 

Thanks,
Zach

> 
> - it should probably say “moves away from _a_ registered default router” here, because there may be more default routers? Or otherwise if there is only one that should be made explicit as a special case.
> - If a node has >1 default routers, it could also de-register from one without registering with a new router, or not?
> - why shouldn’t a node register first with a new default router before de-registering with the router it is moving away from? This ensures that the node remains reachable. This works only of course in those cases the new router is already available prior to the move.
> - finally, this text should probably not be under the “1.3 Assumptions” section because it describes normative node behaviour in case of mobility, not only an assumption.
>  
> best regards,
> Esko
>  
>  
> 
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Zach Shelby, Chief Nerd, Sensinode Ltd.
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