Re: [6lowpan] Mesh under routing and Neighbor Discovery

Samita Chakrabarti <samita.chakrabarti@ericsson.com> Tue, 05 June 2012 00:10 UTC

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From: Samita Chakrabarti <samita.chakrabarti@ericsson.com>
To: Damien Roth <d42roth@gmail.com>, "6lowpan@ietf.org" <6lowpan@ietf.org>
Date: Mon, 4 Jun 2012 20:10:17 -0400
Thread-Topic: [6lowpan] Mesh under routing and Neighbor Discovery
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Subject: Re: [6lowpan] Mesh under routing and Neighbor Discovery
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Hi Damien,

Please find responses in-line.


________________________________
From: 6lowpan-bounces@ietf.org [mailto:6lowpan-bounces@ietf.org] On Behalf Of Damien Roth
Sent: Monday, June 04, 2012 5:03 AM
To: 6lowpan@ietf.org
Subject: [6lowpan] Mesh under routing and Neighbor Discovery

Hello,

I continue my investigations the neighbor discovery protocol for 6LoWPAN (draft-ietf-6lowpan-nd-18), and there is one point that remains unclear to me.

With 6LoWPAN, two routing mechanisms can be used : route over and mesh under. Everything is OK with the route over mechanism but I'm locked with mesh-under. In mesh-under routing, there is only two entities, the 6LBR (border router) and the hosts. Multiple hops may be needed to for hosts to reach the 6LBR.

====> In mesh under case, the assumption is that all hosts are directly IP-reachable from 6LBR. How the packets are flown from a host to the 6LBR ( using a L2-mechanism) is out of scope of the document. Currently I don't know of  L2-routing protocols for mesh-under network - however, there might be some proprietary ones.

My problem is in multihop configuration : how the multicast Router Solicitation messages, used by the neighbor discovery protocol, can reach the 6LBR ?
Does it depends on the routing protocol used ?


====>  Please check the section 10 (Examples) to get an understanding how the routers and hosts bootstrap in the multi-hop 6lowpan networks.  Initial multicast RS is sent only to the local subnet  and taken care by the local 6LR router in case of route-over scenario.



-Samita