On 2011-04-13 21:13, Jeff Wheeler wrote:
Plain and simple, it does not scale up any better than injecting more routes into the DFZ, unless you 1) accept macro-flow-based routing; or 2) scale up the size of your FIB along with the much larger number of prefixes which would be introduced by lowering the barrier-to-entry for multi-homing and provider-independent addressing.
LISP scales better, because with introduction of *location* prefix, you're at the same time (or ideally you would) withdraw the original aggregate prefix. And as no matter how you count it, the number of *locations* will be somewhat limited vs number of *PI* address spaces that everyone wants do drag around the world and advertise in a number of places, specially with IPv6. And that's exactly what LISP had in mind - to prevent massive explosion of FIB for IPv6. For IPv4 the battle was lost somewhat already - and even for that, with LISP you can actually reverse the trend, by moving back with the allocations. As the control plane of the whole system is moved off the edge routers into potentially very capable servers, you also have the extra potential of actually shaping the policies for traffic engineering dynamically without affecting routing nodes. We may of course argue that the current routers are pretty capable in terms of processing power for control-plane, but the convergence times for exchanging and calculating prefixes for VPNs in a large (1-2-3-5M+) L3VPN deployments are counted in tens of minutes, not in seconds. Calculating them offsite and just dumping per-router-calculated table would be more efficient and faster.
However, LISP does have non-Internet applications which are interesting. You can potentially have multi-homed connectivity between your own branch offices.
If the LISP is deployed by commercial entities, just as Google and Facebook are experimenting right now, LISP would also mean multihoming, load-balancing and trafic engineering options that are today not available with BGP or highly limited in the accuracy.
Beyond non-Internet applications such as this, I think LISP is useful largely as a case study for what happens when a bunch of engineers get together and "solve" some problems they do not understand -- DFZ size/growth being chief among them.
Can't comment on that. I personally find Vince Fuller, Dino Farinacci, Dave Meyer and Darrel Lewis quite knowledgeable in routing and proficient in explaining why the LISP was created in the first place, but you of course may know better. -- "There's no sense in being precise when | Łukasz Bromirski you don't know what you're talking | jid:lbromirski@jabber.org about." John von Neumann | http://lukasz.bromirski.net