1. Deaggregation to help spread out traffic flow. As someone who used to send a lot of traffic toward some big providers, it can be hard to balance traffic efficiently when all you get is one short prefix at multiple peering points. Having more-specifics, and possibly
A slight exaggeration, large providers have more than one assignment of IPs and according to the RIR info they are used regionally anyway
Yes, but as the prefix length gets shorter, you lose visibility into how traffic might efficiently be divided up among the points at which a prefix is offered (whether you listen to MEDs or manipulate metrics yourself). Treating North America as a region, a provider might announce a /8 at five different places in that region. For any given point, you might be trying to reach a more-specific that's in the same city, or across the continent. To the extent that providers announce longer prefixes because that's what the RIRs gave them, and practice allocation policies that concentrate use of that space topologically within their network, yes, your comment is a sensible refinement of mine. The practice of announcing more-specifics to help peers with traffic engineering is certainly in use today (just as the practice of not doing so is in use today); the extent to which that puts AS701 where it is on Tony's list is something I don't know. I'm assuming, though, that application of that practice by AS701 would cause them to be higher on Tony's list than if they did not engage in that practice. Whether AS701 thinks that way or not is up to AS701 folks to say (or not).
2. Cut-outs for those pesky dot-coms; you know, the ones with the most compelling content on the Internet jumping up and down in your face with a need to multi-home their /24 to satisfy the crushing global demand for such essentials as "the hamster dance."
Overlap the more specific with the main block? (I assume) Tony's report shows originating AS, in which case the sub-assignments wont show towards UUs count.
I was making the assumption that longer prefixes within a shorter one did contribute to what Tony is counting.
Let's consider the converse, though - what if AS701 were to suddenly become a paragon of routing table efficiency, and collapse all their announcements into one (not possible, I know, but indulge me, please)?
First, some decrease in revenue because all the more-specifics for multi-homed customers would be preferred over the one big AS701 announcement.
They will still announce the customer's BGP more specifics tho?
You're applying reality to the example. This is a contrived example to illustrate the end of the spectrum where AS701 emits one very short prefix - kind of like some IPv6 people seem to think that inter-provider routing should work (to use a current analogy).
Second, a traffic balancing nightmare as everyone who touches AS701 in multiple places tries to figure out how to deliver traffic to AS701 efficiently.
As above, it is at least as far as I can tell assigned per country.
What do countries have to do with this? AS701 is UUNET's North American (for the most part) AS number. It is possible to have a handful of attachments to it within the United States alone. As noted above, if AS701 were to announce a short prefix with no more-specifics at several points, your options to efficiently balance traffic among those points are less than if you were supplied with more-specific prefixes that give you clues as to how the short prefix is partitioned internally (say, east-coast US vs. west-coast US). Stephen