On Mon, Apr 11, 2011 at 11:26 AM, Owen DeLong <owen@delong.com> wrote:
I'd agree with you if it weren't for the fact I keep thinking I just about understand LISP and then get told that my understanding is incorrect (repeatedly).
I agree it is not simple. At a conceptual level, we can think of existing multi-homing practices as falling into one of three broad categories: 1) more state in DFZ -- end-site injects a route into BGP 2) triangular routing -- tunnel/circuits/etc to one or more upstream routers while not injecting anything to DFZ 3) added work/complexity on end-host -- SCTP and friends LISP is a compromise of all these things, except #3 happens on a router which does tunneling, not the end-host. Whether you think it's "the best of both [three?] worlds," or the worst of them, is up to you. I personally believe LISP is a horrible idea that will have trouble scaling up, because a large table of LISP mappings is not any easier to store in FIB than a larger DFZ. The "solution" the LISP folks think works for this is a side-chain mapping service which the router can query to setup encapsulation next-hops on-demand, which means if your FIB isn't big enough to hold every mapping entry, you are essentially doing flow-based routing, but with "flows" defined as being toward a remotely-defined end-site rather than toward an individual IP address (so not quite as bad as "flow-based routing" of the past, but still bad.) Maybe I also don't understand LISP and need to RTFM more, but my current understanding is that it is a dead-end technology without the ability to dramatically scale up the number of multi-homed end-sites in a cheaper manner than what is done today with BGP. I think we would be better off with more work on things like SCTP. -- Jeff S Wheeler <jsw@inconcepts.biz> Sr Network Operator / Innovative Network Concepts