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RE: What is the limit? (was RE: multi-homing fixes)
--On Wednesday, 29 August, 2001 11:29 AM -0700 Roeland Meyer <[email protected]> wrote:
The point remains that it is nonsensical, given a finite universe. The curve doesn't fit observable reality.
...in that it is assumed (for instance) that network nodes will not grow exponentially for ever. And recent prefix growth (the poster made clear they were talking about histotic growth) has been far less than exponential. See the slides at IETF/Ptomaine for example. However, if you accept the analysis in that very same presentation, you will believe that the a big chunk of growth comes in 'Traffic Engineered' /24s (interesting use of the term TE here which includes some leaks and cluelessness, but I guess that's just traffic misengineering, and we'll put that aside), and another chunk comes from 'small' multihoming, especially announcing more specifics. In general, these prefixes can be dropped, without loss of reachability. And they cost to support. So we are back to the 'who pays', and 'is this an appropriate technology' questions. Oh yes, there has two other conflations: One is that for 'the internet' to support P prefixes in a 'full table' (terms in quotes lack good definition), the cost is O(P), for an ISP with a fixed number of customers. In a single ISIS autonomous system, this might be true. I suspect even in terms of a single router, in practical terms it's at least O(P log P), if not worse. The second is that the expensive part of a router is the main CPU running the routing process, and its RAM. This is not true (I'm sure you could run Zebra on a palm pilot and take a full table over IR these days). The expensive part is the forwarding hardware, and the glue that gets the forwarding decisions out the main processor onto the line cards. [I'm sure router gurus will add detail/corrections to this simplification]. This has to grow not only with number of prefixes, but also with amount of traffic (forwarding decisions per second). So comparing just one of the growth items to Moore's law does not tell the full picture. I believe most traffic forecasts still show growth ahead of Moore's law. Therefore even linear prefix growth is going to increase further an already increasing hardware bill. -- Alex Bligh Personal Capacity