Hello Alex. I think this definition needs to be revised in order to accommodate not only the context of a 802.15.4 PAN but also the context of wireless subnets in general.
-----Original Message----- From: Alexandru Petrescu [mailto:[email protected]] Sent: Wednesday, April 22, 2009 11:13 AM To: Robert Assimiti Cc: [email protected] Subject: Re: [6loWPAN] 6loWPAN Design and Application Spaces for 6loWPANs - 02- Hi Robert, let me give my oppinion on this. Robert Assimiti a écrit : > Hello, > > I was going over the second spin of Draft-IETF-6lowpan-usercases. > > I am a bit unclear on the definition of the LoWPAN link. A LoWPAN Link > is coined as: > > /“//A low-power wireless link which is shared by a link-local scope in a > LoWPAN. In a LoWPAN, a link can be a very instable set of nodes, for > instance the set of nodes that can receive a packet/ > /that is broadcast over the air in a route over LoWPAN, or the set of > nodes currently reachable in an L2 mesh in a mesh under LoWPAN. Such a > set may vary from one packet to the next / > /as the nodes move or as the radio propagation conditions change.”/ > > It is clear that we are targeting point-to-point and point-to-multipoint > here, but there is nothing that indicates the directionality of the link. I am not sure what you mean being clear we're targetting ptp and pt-to-mpt links... I am aware ROLL WG targets the point-to-multipoint types of traffic (not the links). I think 802.15.4 link may be a point-to-point link, or a 'star' topology, which one may interpret as being a point-to-multipoint link. Whereas I understand very well running IP over a point-to-point link, I don't see how would it run over a point-to-multipoint link, never saw this before. As for the link-local scope mentioned in the paragraph above, I think it comes from what a "link-local scope" is for link like an Ethernet link. But, it is not clear at all what a link-local scope would be on a 802.15.4 star topology made of a point-to-multipoint link: would a packet sent by the center reach all edges? Or only one? Would a packet from an edge to another have a dst address the center or the edge? Two dst addresses? I prefer to think that a LoWPAN subnet is covered by an IP link-local scope, has at least one single IPv6 subnet prefix; and that IP packets addressed to a link-local IPv6 address reaches all nodes in the LoWPAN, without being 'IP-forwarded'. If such LoWPAN subnet sit on a 802.15.4 link then that 802.15.4 link should offer link-layer multicast support to the LoWPAN subnet, such that the words "link-local scope" to have a meaning for a 802.15.4-based LoWPAN. This is not the case today. > Is the definition here (since it is a wireless context) considered > unidirectional or bi-directional? This is a good question. I do suppose 6LoWPAN WG uses links which are bidirectional and symmetric. Alex > > > > Also, the definition given in RFC4861 does not really apply here. > > > > Thanks for anyone that could offer a clarification. > > > > > > > > *"The nice thing about standards is that there are so many to choose > from." - Andrew S. Tanenbaum * > > *Robert Assimiti* > > *Executive Staff Engineer* > > *Office: [678]-202-6859* > > *Mobile: [404]-578-0205* > > *[email protected]* > > > > > > > > > > > This e-mail (including any attachments to it) is confidential, > proprietary, legally privileged, subject to copyright and is sent for > the personal attention of the intended recipient only. If you have > received this e-mail in error, please reply to advise us immediately, > delete it and destroy any printed copies of it. You are notified that > reading, disclosing, copying, distributing or taking any action in > reliance on the contents of this information is strictly prohibited. No > employee is authorized to conclude any binding agreement on behalf of > NIVIS LLC with another party by e-mail without express written > confirmation by an officer of the company. Although we have taken > reasonable precautions to ensure no viruses are present in this e-mail, > we cannot accept responsibility for any loss or damage arising from the > viruses in this e-mail or attachments. > > > ------------------------------------------------------------------------ > > _______________________________________________ > 6lowpan mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6lowpan This e-mail (including any attachments to it) is confidential, proprietary, legally privileged, subject to copyright and is sent for the personal attention of the intended recipient only. If you have received this e-mail in error, please reply to advise us immediately, delete it and destroy any printed copies of it. You are notified that reading, disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited. No employee is authorized to conclude any binding agreement on behalf of NIVIS LLC with another party by e-mail without express written confirmation by an officer of the company. Although we have taken reasonable precautions to ensure no viruses are present in this e-mail, we cannot accept responsibility for any loss or damage arising from the viruses in this e-mail or attachments. _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
