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Re: [RRG] ALT's strong aggregation often leads to *very* long paths
Robin,
On Jan 30, 2008, at 5:27 PM, Robin Whittle wrote:
I doubt that there could be consensus in the RRG that such delays in
initial packet delivery and session establishment would be
acceptable unless there was also consensus that all other schemes
which do not delay packets (NERD, APT and Ivip) were completely
unworkable.
It seems we have a choice:
a) scalable to host granularity but imposing some delay at session
initiation
- or -
b) no additional latency but more limited scalability.
For me, it isn't a question of 'workability'. Both options can be
made to work. In case (a), people just learn to deal with the
additional delay and modify protocols appropriately. In case (b), you
limit the size/granularity of the PI Internet and people adjust
accordingly. The question is which is less likely to bite us before
we migrate to IPvN+1?
Even if ALT could be tweaked to improve its meshiness so as to
generally reduce the path length (but meshiness is unlikely to help
in every ITR-ETR case), it is still a global query server network -
meaning it is slow and unreliable.
A pull system would indeed be slower at session initiation. After
that, it isn't clear to me that there would be a latency difference.
However, I will admit some confusion about the lethality of this.
Session establishment invariably already needs to deal with
unreliability and various delays (DNS, ARP), yet the Internet
functions. Why do you feel the additional latency of a pull system is
fatal?
I think it would probably be
more expensive and harder to manage than the push systems it is
intended to avoid the need for.
I'm much more skeptical of this claim. Compare the cost of building
and maintaining a caching-only DNS server to a Netnews server with a
reasonable set of feeds...
Regards,
-drc
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