> > Pascal> [Pascal] The FL based proposal for RPL uses 12 mutable bits. > > Pascal> They are used as an in-band control plane that checks the > Pascal> consistency of routing states along a path. Those states can > Pascal> easily get out of sync due to the nature of the links, but > Pascal> the maintenance can be costly. We want to accelerate the > Pascal> repairs on those links that are actually used when an > Pascal> inconsistency is detected that will impact the delivery. > > I don't understand how the FL helps us on this! Probably I missed something > important. What you write below was my entire understanding of our need for > an in-band tag.
[Pascal] This point is not about the flow label specifically but about the RPL strategy, and it works whether we use the flow label or the hop by hop techniques to transport the info. In short, the mere fact that there is a packet on the broken path causes us to 1) detect and 2) fix the issue. If there's no packet on a broken path then it can stay broken for a while. There will probably be many broken paths at any point of time in the network, due to transient link interference, movement, and all sorts of routing desyncs. Considering the cost of proactive rapid resolution, we have chosen not to fix the routing issues as soon as they appear but 1) lazily and 2) on-demand. The lazy piece is a global reconstruction of the DAG that happens periodically. The on-demand piece is a data path validation that allows us to fix a path as it is being used, either using a mutable flow label field or the Hop by Hop header. Pascal -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
