Hi Alex, Thanks for sharing your definitions on LoWPAN terminology. I agree with you that the current definition of "LoWPAN Mesh Node" is incomplete. We must point out that it is a general term which includes both a LoWPAN Host or a LoWPAN Router.
The link definition of RFC4861 is indeed useful. For the Use Cases draft, we will follow the changes in the ND draft on what a "LoWPAN Link" is. It might be nit-picky, but didn't you mean "IP forwarding" when you defined "IP routing"? And I disagree with your statement that "it has two or more interfaces, each interface of the router has a different IP link-local scope." I think that LoWPAN nodes mostly likely won't have more than a single physical network interface... Greetings, Dominik On Thu, Apr 23, 2009 at 6:14 PM, Alexandru Petrescu <[email protected]> wrote: > As I said previously, I have difficulty understanding some terms in the > usecases draft. > > For example, it defines LoWPAN Host, LoWPAN Router and LoWPAN Node. However > it doesn't say a LoWPAN Node may be a LoWPAN Host or a LoWPAN Router. (I > think, commonly in IPv6, Nodes may be Host or Routers). > > It defines Mesh Under and Route Over; however I can't understand the > following: does a "Route-Over" LoWPAN contain the same IP link-local scope > or not? If yes then this is very difficult to udnerstand, next to > impossible. > > Also, another problem is that it defines the Route-Over and Mesh-Under in > apple-to-orange terms ("boundaries" vs "radio range"), whereas Route-Over > and Mesh-Under have often been easily compared, ie redapples-to-greenapples. > > Then on the use of 'single radio transmission' to define "Route Over" - what > is single radio transmission more precisely? One is tempted to believe all > nodes reachable by a single radio transmission from a certain node are all > within the same IP link-local scope... which is ok. > >> Route Over >> >> A LoWPAN configuration where the link-local scope is defined by >> those nodes reachable over a single radio transmission. [...] > > But because it doesn't say from _where_ are those nodes reachable (from > another single certain node) then one can easily also think this: B is > within a single radio transmission of both C and A, yet it is in two > different link-local scopes, which is of course not the intention. > > ----------------------- > |radiorange|radiorange| > A B C > > Knowing the above, I'm trying to offer my own definitions of terms in the > way I'd have written it. Of course it may not fit all the views, but I > thought I'd share: > > PHY repeating > > The act performed by a device repeating a packet at PHY level. It > doesn't inspect any field in any packet header. It has one or several > interfaces, they are all in the same IP link-local scope. > > MAC forwarding > > The act performed by a bridge - inspecting the dst MAC address of > incoming packet, exact-matching it to the first field in a table of > tuples [dst,nexthop] > MAC addresses and transmitting it to the identified nexthop. In the > process, the src and dst MAC address of the packet are potentially > modified. The device may have one or more interfaces but they are all > in the same IP link-local scope. > > IP routing > > The act performed by a router - inspecting the dst > IP address of an incoming packet, > longest-prefix matching it to the first field of each entry > in a table of triolets > [dst,prefixlength,nexthop] IP addresses and transmitting it to the > identified nexthop. In the process, neither the src nor the dst IP > addresses of the packet are ever modified. It has two ore more > interfaces, each interface of the router has a different IP link-local > scope. > > IP link-local scope > > The set of IP nodes reachable by an IP packet whose dst address starts > with 0xff02. All nodes on a link are within the same IP link-local > scope, and nodes outside the link are outside the scope. Transmitting > packets in the same link-local scope doesn't involve IP routing but > may involve MAC forwarding. > > Radio range of node > > The radio range of a node is the set of nodes reachable from it, at > PHY layer. For example, the radio range of a WiFi node is 50m in a > clear-sight atmospheric area, without physical obstacles and in good > weather. > > Obviously, all nodes in same radio range of a node could be understood > to be in the same IP link-local scope. > > However, a single-interface node can't be part of several IP > link-local scopes even if sits at the intersection of the radio ranges > of several other nodes. > > "Mesh-Under" LoWPAN > > A LoWPAN configuration where the IP link-local scope is extended to > more nodes (beyond the radio range of a node) by means of MAC > forwarding exclusively. All nodes in a "Mesh-Under" LoWPAN are within > the same IP link-local scope, despite the probable presence of several > PHY radio ranges - this alleviates the non-transitivity aspect. > > "Route-Over" LoWPAN > > A LoWPAN configuration where the IP link-local scope is extended to > more nodes (beyond the radio range of a node) by means of transmitting > IP packets, using a novel IP routing method. This novel method > runs on a LoWPAN Router (uses a single interface, instead of the > typical 2-interface router) and both interfaces are in the same IP > link-local scope (instead of the typical router having a different IP > link-local scope for each interface). > > "Routed" LoWPAN > > A LoWPAN configuration where the IP link-local scope is not extended > beyond the radio range. Certain nodes are manually designated as > special. The radio range of each special node contains the set of > nodes in the same IP link-local scope, and each such range forms a > unique link. Connecting two such links is performed by means of a > typical IP router (multiple interfaces, different link-local scope). > > Comments anyone? > > Alex > > > > _______________________________________________ > 6lowpan mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6lowpan > _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
