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Re: [RRG] yetAnotherProposal: AS-number forwarding




On Mar 10, 2008, at 5:34 AM, Xu Xiaohu wrote:

-----邮件原件-----
发件人: owner-rrg@psg.com [mailto:owner-rrg@psg.com] 代表 Lixia Zhang
发送时间: 2008年3月10日 12:22
收件人: Lars Westberg
抄送: rrg@psg.com
主题: Re: [RRG] yetAnotherProposal: AS-number forwarding


On Mar 9, 2008, at 11:40 PM, Lars Westberg wrote:

Hi,
I haven't had time to make a draft but I think it make sense for the
discussion. However, I don't know if it already have been discussed
so....

The proposal are simple: re-use AS-numbers into the forwarding of
packets such that prefixes could be aggregated per AS. One simple
implemetation is that the packets are tunneled and that the tunnel-
address is associated to a AS-number. The AS-numbers can be assigned
to the IP-addresses by DNS or by define a small address-prefix to AS-
numbers.

Comments?

in an ideal world, yes having AS number as part of address used for
routing has great benefit.  see the slide from a talk in 2006
(http://www.cs.ucla.edu/~lixia/0612Australia.pdf
, but ignoring the title), slide 17 & 18 is about this.
If we had a chance to influence address structure, you'd want to
include other info in addition to AS (as large ASes span large areas,
TE would want more info to do better job).
we have another paper (http://www.cs.ucla.edu/~rveloso/papers/
giro.pdf) showing the benefit for including location info (which
should be a subfield after AS number)

With support of routing aggregation at any desired level, I can't image that GIRO alone can do much help in routing scalability issue unless it brings in
some id/locator split idea, like GSE, SIX/ONE or HRA.

- as you can see from the talk slides, yes the basic idea IS to
  separate edge prefixes from transit routing space

- to the specific question of whether aggregation alone
  (by AS and then location) can help much with routing scalability:
  (a) it can indeed help a lot based on the analysis using today's
      routing table content
  (b) but if we want the global routing system to scale *independently*
      from the edge user site growth, then the separation becomes
      necessary.

The reason I referred to the 2nd paper is merely to show the benefit of including location info in address; not sure where you got the implication of no-split.

Lixia
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