Forwarding without the mail attached (was bounced by the mailer) Pascal http://www.xtranormal.com/watch/7011357/
-----Original Message----- From: Pascal Thubert (pthubert) Sent: Friday, April 15, 2011 8:41 AM To: 'Erik Nordmark' Cc: [email protected] Subject: TID in ARO [was: "Advertize on Behalf" flag in ARO] Hi Erik: RPL can do what all classical IGPs can do WRT hosts. That is as long as the host address belongs to the router's prefix and stays attached to that router. When the topology becomes multilink subnet and mobility is required then it is a new problem entirely, and NO, 4861 is not a suitable interaction with the router to allow the router to redistribute a host route. Because the neighbor cache that 4861 builds is not a of the same nature as the binding table that 6LoWPAN ND builds. Another thing that 6LoWPAN ND fails to express correctly. I proposed text to explain that (attached) but it was not considered, contributing to the illusion that a cache is a table. The reality is also that those networks will need to scale to large subnets in plants, building, etc... (see the requirement drafts in ROLL). Registering to all LBRS is totally impractical. 6LoWPAN ND requires a coordination between LBRs but does not say how it happens. This problem was discussed in 6LoWPAN; the answer was in ND-01to07; and it requires a TID, for the same reason as RPL. Removing the backbone operation and the TID from the draft is ostrich policy. RPL already adapted to the new reality of large multilink subnet with inner mobility. Placing the blame on RPL is another illusionist trick. And this is not RPL last call. BTW 6LoWPAN ND needs a TID to correlate the NS and the NA as all other registrations do when strict ordering is not guaranteed (MIP being an example). Say that due to some config, a node registers a lifetime of X, then deregisters (lifetime 0), then reregisters (lifetime X) in a rapid sequence, but does not get an answer yet. Then it finally gets 2 AROs back, lifetime X and 0. What's the final state in the router? It seems we can never agree on any of this. I'd like to hear what others think. Pascal http://www.xtranormal.com/watch/7011357/ > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Erik Nordmark > Sent: Friday, April 15, 2011 1:30 AM > To: 6lo >> '6lowpan' > Subject: Re: [6lowpan] Fwd: Re: "Advertize on Behalf" flag in ARO > > > On 4/13/11 12:53 AM, Pascal Thubert (pthubert) wrote: > > Hi Erik: > > > > The RPL (DAO) sequence number allows the node to increment rapidly > > in case of rapid changes and then lazily when the situation is > > stable and DAO are scarce. The increase is strictly monotonous which > > is critical to us. > > > > A time stamp imposes a synchronization between the routers. We do > > not have such mechanism in RPL. A time unit (a granularity) must be > > agreed upon. Within that unit, movements go undetected so the time > > unit must be thin grained to cover rapid changes. Yet, depending on > > the medium, the time unit, and the size of the network, it is not > > necessarily easy/possible to guarantee a strictly monotonous value > > with a thin grained time unit. And we have limited space (2 octets) > > and have to deal with wrap around, which divides the space by at least 3. > > > > So RPL went for a sequence number. > > But the unstated assumption that RPL made is that all host-to-router > protocols have to now be RPL aware. That doesn't sound like good design. > A host isn't aware of whether the routers speak IS-IS or OSPF, so why > do the hosts need to be aware of RPL by passing some TID around? > > > I think ND has the same need as MIP for a TID == Sequence # . We > > know of MIP; We know of RPL. We know of the backbone router > > operation. We know we'll need the TID and we know exactly why. I > > think we should have it in the 6LowPAN ND spec right away to avoid > > interop issues when we add RPL and BR operations. > > I don't see a need in 6lowpan-nd for a TID; the protocol works fine without it. > I think RPL needs to be improved to deal with reality. Isn't there a > desire for RPL to handle 4861 hosts? Those would never know about a TID. > > Erik > > _______________________________________________ > 6lowpan mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/6lowpan _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
