Hi folks, I would just like to add that our studies are ongoing, and this: > variety of Internet paths. It observes that on average, IP options > introduce between 7% and 26% (for different sets of paths at different > times) of additional delay. The article says that "In any case, the > additional delay is clearly an order of magnitude smaller than the > RTT." is only a part of our findings, which are only a part of all the things that *should* be looked at. As Simon suggests, processing overhead in routers may be an issue if they are flooded with packets carrying options. Moreover, we also saw that this: > 3.) Operators configure their routers to ignore IP Options. and this > 4.) Operators configure their routers to drop packets with IP Options. is already happening quite a bit nowadays. Our findings are also limited to NOP options vs. no option at all, and ICMP packets, not TCP. For different (even more disappointing) findings with TCP and a new option number, see pages 9/10 of: http://www.icir.org/mallman/papers/tcp-evo-submit.ps ... who knows what's happening to packets that carry RA. I believe that options are a very reasonable (and certainly the most flexible) means of communication between end systems and routers by design, and they could theoretically be used for lots of great things in the future. The point of my ongoing measurement effort is to show that they might not be absolutely useless in the current Internet, and give folks some concrete numbers - I don't believe that options are ALWAYS useless (but don't ask me for a counterexample :( ); depending on the envisioned usage scenario, the measured properties will make things look good or bad. Cheers, Michael _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf