>Another way of saying this is that mesh under is more often than not >akin to NBMA. Fully mesh might exist and multicast emulation might exist >though I've seen neither so far.
FYI 802.15.5 does have multicast support (15.5 being the mesh standard). If you have IEEE Xplore you can get 15.5 from there, otherwise it should be out around Dec 8th at http://standards.ieee.org/getieee802/802.15.html by my count if they keep up with the '6 months after publication in PDF it's free'. Multicast is done with a combination of broadcast & unicasting messages. It has systems to avoid a forwarding loop and some considerations to low-power. Despite the addition of the multicasting support, it does remain wasteful of network air time & node power. So even when we do have support for Multicasting at the mesh layer, there are significant advantages to avoiding it. Regards, -Colin O'Flynn -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pascal Thubert (pthubert) Sent: November 16, 2009 7:08 AM To: Carsten Bormann; Ralph Droms (rdroms) Cc: 6lowpan Subject: Re: [6lowpan] Thoughts on draft-ietf-6lowpan-nd-07 Hi Ralph >> 1. In a mesh-under network, the L2 characteristics of the lowpan are >> close to those usually assumed for implementation of IPv6; in >> particular, there are no "lowpan routers" at L3 and L3 messages *can* >> be delivered (perhaps with lower probability of success) directly >> between lowpan nodes. Why is ND not sufficient in this model? > >RFC 4861 ND works in a pure RFC 4944 mesh-under network if: >1) the mesh-under (L2) routing protocol provides subnet-wide multicast, >2) that is efficient enough to be used for routine ND messages, >3) nodes are awake often enough to detect and reply to NS messages. > >Such networks do exist, but these assumptions are not necessarily compatible with many application >scenarios we have in mind; this is the reason we started with ND optimizations. _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
