Ran, On 2011-06-22 01:03, RJ Atkinson wrote: > Earlier, Brian Carpenter wrote: >> I'd have to trawl the archive to find all the arguments, >> but the main issue was that any attempt to include semantics >> in the bits of the flow label leads to complexity that >> probably can't be handled at line speed in a scaleable way. > > That claim presumes that a typical IPv6 router is using CPU-based > packet forwarding. I believe that assumption to be incorrect. > (By the way, this assumption underlies a lot of the discussion > on the IPv6 list. Those of us who build ("have built", in my own > case) real routers try to speak up about this from time to time, > apparently without having much impact on WG thinking. > > I believe that most deployed IPv6 routers are using ASIC-based > or FPGA-based forwarding of IPv6 packets. NP-based forwarding > is not uncommon, but is probably less common. An advantage > of NP-based forwarding engines or FPGA-based forwarding engines > is that new capabilities can be added on the fly. While some > deployed ASIC-based forwarding engines are programmable, most > IPv6-capable ASIC forwarding engines are not programmable. > > Even the really low-cost consumer electronics routers that > support IPv6 generally do so via commodity silicon packet > processors offered by a range of different merchant silicon > firms based in various countries (example: Broadcom). > > Since the majority of the lifespan of IPv6 is well into the > future, and deployment today remains pretty small today, > compared with say 3 years from now, re-allocating those 4 bits > seems entirely possible to me.
Anything's possible. I was trying to summarise what I recall from the discussions that led to the WG consensus. > >> Also 16 bits might make it too easy for a malicious party >> to predict flow label values. > > That makes no mathematical sense to me. > > To the extent 16 bits is problematic, 20 bits also would be > problematic. So that argument also does not make sense to me. > Even if someone has formal maths behind that claim, which so far > I haven't seen claimed on the IPv6 WG list, Moore's Law would > defeat any claim that 20 bits is adequate within ~5 years. Sure, we are talking about the difference between a brute force attack with a million choices vs 65k choices; not a strong argument, of course. Brian -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------