when & how could policy be changed
Stephen Sprunk
spsprunk at paranet.com
Tue Jul 1 22:47:34 EDT 1997
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At 17:38 01-07-97 -0500, you wrote: >>I personally would like to see some PI space opened up with longer prefixes >>than /19. This could be a new /8 like 210/8 that we all agree to allocate >>in /20 blocks. Or we could use reclaimed space from the swamp and allocate >>it in /20 and/or /21 sizes. In the case of 210/8 we need providers to agree >>to adjust their filters. But before we can decide just how this should be >>done we need some hard numbers, especially on how many additional routes >>the new PI space would add. And we also need some more thorough analysis of >>the prefixes that appear to be eligible for aggregation in the weekly CIDR >>reports. > >The only problem is that going from /19 to /20 doubles the total >table size, assuming lack of greater aggregation, worst case. The proposal was to allocate a fixed number of PI /20 blocks which would be specifically for use by multihomed providers that didn't qualify for a /19 (or shorter) under RFC 2050. This will not double the total table size, only increase it by 4k routes in the short term; hopefully, in the long term it would reduce the number of more-specifics advertised out of the large ISPs' PA blocks, having a net REDUCTION in the routing table size. >There are issues with flap, and dampening helps but does not solve >the problem. The problem seens to growth with order N^M, >where N is the number of prefixes and M is the number of peering sessions >or views. N will remain roughly constant, since we are merely switching PA route(s) for an equal or slightly shorter PI route. M will remain constant, since the AS's in question are already advertising routes on the net. > Also for fun the cost of upgrading networks grows at N^R, in this >case R is the number of routers. We have some data to suggest >that todays hardware could handle the load generated by /19 aggregation, >but also seems to indicate that we cannot as a general rule freely >allocate /20s, without severly imparing network perfomance in the near >term. Again, N is not intended to grow significantly (and may in fact shrink). >Having renumbered several /20s and a /19, I don't see they need to >create PI /20 space. There is this ideal out there that the playing >field should be completely flat, however, in the real world, this >isn't the case. I'm not after a separate-but-equal net; there are technical problems that creating said PI space would solve. If done correctly, it would: . Reduce routing table entries . Reduce the effects of flap . Reduce the "holes" in the large ISPs' PA blocks . Reduce the number of unqualified AS's requesting RFC 2050 /19 blocks . Make it easier for small ISPs to grow, fostering competition >All modern hardware >and software can support dynamic assignment for networks. With a small >bit of planning and intergration, one change can renumber DNS A and PTR >records, and change the assigneds when the DHCP leases expire. You're ignoring the important minority here: servers. >If there is enough intereste I will work up this proposal to put >before the ARIN membership at the first suitable time. As I'm sure hundreds of others will as well. Stephen
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