1. Thank you!!!

    1. I'm happy to hear routing is not a solved problem. :)
      But for the rest, I'm not sure I agree with Mark.

      > There will never be perfect information

      This touches a core principle of routing.
      We gain scalability because of 2 things: hierarchy and summarization.
      But as soon as you summarize something, you lose some information.
      This is indeed a choice that the operator must make (to summarize or not).
      But you can't have both: reduction of information and perfect information.

      > There will always be an area of futzing to find optimization points
      > across multiple competing objectives

      When this is configurable, each customer can tweak his network.
      I don't see this as a reason why networking is not a solved problem.

      > just beginning .... much discovery yet to happen

      What problems are you thinking about?

      All the problems that I see as reasons why routing is not a solved
      problem, were already known problems 25-30 years ago.
      We aren't done yet, not because of new incoming problems.
      We are not done yet, because so little real progress has been made.

      Physics, timing, ordering, I don't see those as limitations.
      We know how to deal with those things.
      Different requirements for different networks:
      just implement everything, and then make stuff configurable.

      The problems I see with routing are:
      *) site multi-homing
      *) host multi-homing
      *) easy renumbering (with persistent connections during the renumbering)
      *) mobility

      To solve some of those, we should have true identifier/locator separation.
      Not an after-thought like LISP.
      But something built into the layer-3 addressing architecture.
      IPv6 was a chance, but we messed that chance up.

      You could add a few more practical issue:
      Like trustworthiness of BGP global routes.

      As I said earlier, how can we do hierarchy (in IGPs, with areas),
      and still have all our features work across ABRs? In a scalable way.
      From my perspective we don't really have that yet.

      Another issue is configuration and troubleshooting.
      I think we can make improvements there (and make running a network easier).

    2. Thank you for the feedback Henk.

      While I feel the observation that the laws of physics are invariant may lead to different sense of what a "solved problem is", one specific clarification I would ask is whether the following is an agreement or a disagreement:

      "But you can't have both: reduction of information and perfect information"

      It reads a little like an agreement.

    3. > "But you can't have both: reduction of information and perfect information"

      Yes, we agree there.
      I'm not sure we're thinking about the same details. :) But your statement was certainly correct. But not because of physics or timing or ordering. For me the main reason is: you want to summarize for scaling, but you do not want to summarize if you want to find optimal routes.

      Many networks don't need summarization. Because scalability is not a real issue for them. But for the biggest networks (e.g. 10k+ routers in one IGP domain), we do need summarization. So those networks lose optimal routes. This is a fundamental issue that I don't see an easy solution for.

      One aspect of a solution would if operators would design their networks with a few more constraints. But it seems the stubborn bastards don't like that. :)

    4. Well resources are not infinite, but that is another issue. Some people claim route processor scaling etc is a solved problem, others disagree.

      I'll right a little more to see if I can strike some different language. Some things can be mitigated, but that does not mean they are remediated. It is in this sense I am saying somethings will never be solved.

      Best Mark

Add comment