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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: NANOG 40 agenda posted
Thus spake "Randy Bush" <[email protected]> the average number of v4 prefixes per AS is ~10, and it's rising. In v6, the goal is that every PI site can use a single prefix**, meaning the v6 routing table will be at least one (and two or even three eventually) orders of magnitude smaller than the v4 one. A quick look at this week's CIDR Report says 35.9%, or 78,738 routes. [Update to earlier stats: The current v4 prefix/AS ratio is 8.7. However, there are ~11k ASes only announcing a single v4 route, so that means the other ~14k ASes are at a v4 ratio of 14.3. In contrast, the current v6 ratio is 1.1 and the deaggregate rate is 1.2%.] why won't they do this in v6? The simplistic answer is that nearly all assigned/allocated blocks will be minimum-sized, which means ISPs will be capable of filtering deaggregates if they wish. Some folks have proposed allowing a few extra bits for routes with short AS_PATHs to allow TE to extend a few ASes away without impacting the entire community. While many have derided the "classful" nature of IPv6 policies, the above was one of the reasons that it's being done. The other, obviously, is that IPv6 is big enough we can do it that way and skip all the administrative hassle of worrying about how much space people "need" and focus on whether they "need" a routing slot (as much as the RIRs pretend they don't care about routability). I said "simplistic" above because there will be a few extremely large orgs that will end up getting larger-than-minimum blocks, and they could deaggregate if they want to -- or deaggregate more bits than other folks get to. There's not much that can be done about that (without vendors inventing cool new knobs), and I already addressed why it shouldn't be that big a deal anyways in the ** footnote you snipped. However, this relies on RIRs rejecting "but we need to deaggregate" as justification for larger-than-minimum blocks. OTOH, the community may see how small the v6 table is and decide that N bits of deaggregation wouldn't hurt. After all, with ~25k ASes today, and router vendors claiming to be able to handle 1M+ routes, it seems we could tolerate up to 5 bits of deaggregation -- and 3 bits would leave us with a table smaller than v4 has today. S Stephen Sprunk "Those people who think they know everything CCIE #3723 are a great annoyance to those of us who do." K5SSS --Isaac Asimov
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