On May 23, 2008, at 3:50 AM, Pascal Thubert (pthubert) wrote: > Hi JP: > > I see your concern. > > I'd argue that ECN is now pretty well defined now in RFC 3168, and > that > the basic operation is pretty simple: emulate a packet loss in RED but > save the packet. So the real problem is not ECN itself but what RED > becomes in a LowPAN forwarding node. And that is something that the > node > will have to define whether it does ECN or RED. > > If we do not have ECN then the LowPAN forwarding nodes will have to > destroy frames which might be fragments. Considering the cost of > energy > and bandwidth to getting the frame up to that forwarding node, the > latency introduced by transport layer time out, and the risk of > congestion collapse introduced by resending the whole segment, I'd > suggest that ECN is actually a good idea.
This gets back to the point I brought up December 14, 2006. In lossy networks, end-to-end fragmentation and assembly is a real problem. It makes much more sense to do per-hop fragmentation and assembly. In the former, the number of retransmitted fragments is exponential in the number of hops; in the latter, it is linear. Phil _______________________________________________ 6lowpan mailing list [email protected] https://www.ietf.org/mailman/listinfo/6lowpan
