On Sep 8, 2010, at 1:02 PM, Christopher Morrow wrote:
> this all gets 'crazy', I suppose if we wanted to route on flow-label
> not destination-ip-address this might happen, but ... that seems
> 'crazy' as I said before :) since not everyone would be using the
> flow-label (maybe) and inconsistent routing would suddenly make the
> internet look a lot like a PSTN network (to me).
well, we could talk about MPLS... that has always seemed to me a might PSTN-ish.
My presumption here is that flow label routing would be within a single
administration or a set of consenting administrations, and as such would not be
affected by whether neighboring administrations chose to use it r chose how to
use it.
One example of a use case for it is in the IAB-TE.pdf deck (google that, it's
under iab.org somewhere) that Jason Schiller used in the IAB Routing Workshop a
few years back. One of the questions was how to simplify this case: We have N+1
ISPs, one that is in a bad way and N others trying to get data to it. They are
interconnected by some number of undersea cables (and therefore lambdas), which
are in turn operated by multiple administrations.
,-------. ,-------.
,-' `-. ,-' `-.
/ ISP #1 \ / ISP #2 \
( ) ( )
\ / \ /
`-. ,-' `-. ,-'
`-------' || || `-------'
|| ||
Undersea|| ||Undersea
Cable|| ||Cable
Network|| ||Network
|| ||
,-------.
,-' `-.
/ \
( ISP #3 )
\ /
`-. ,-'
`-------'
ISP #3 has a problem; due to the issues of laying undersea cable, "just add
bandwidth" is a lot more easily said than done. The total amount of traffic
destined to it approximates the capacity of the cables/lambdas in use, but of
course varies in composition over time. As a result, ISP #3 is forever
gerrymandering /24s to bias traffic towards one link or another. ISPs #1 and #2
go slightly mad with route flaps as a result.
What I am about to describe doesn't solve load spreading across ISPs #1 and #2.
But, for the traffic that arrives at let's say ISP #1, if its ingress nodes
were each given permission to route traffic for ISP #3 to one of the relevant
cables/lambdas up to some rate, and then to a second cable/lambda up to some
rate, and so on. The sum of the rates granted to the ingress points is less
than or equal to the rate of the cable/lambda in question. What this means is
that ISP #1 is in control of its own routing without being micromanaged by the
ISP downstream, and can sell a service to ISP #3 of delivering the indicated
data in a manner that is reasonably load balanced across the cables/lambdas
connecting them.
One could just as easily imagine doing that with MPLS; the point is to have an
appropriate set of tags. I just happen to not be fond of circuit or virtual
circuit networks, and I think this doesn't require the explicit N^2 problem
implied by a mesh of LSPs.
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