Re: [p2pi] ALTO Information Export Service

John Leslie <> Wed, 29 October 2008 15:47 UTC

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Date: Wed, 29 Oct 2008 11:47:44 -0400
From: John Leslie <>
To: Laird Popkin <>
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Subject: Re: [p2pi] ALTO Information Export Service
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Laird Popkin <> wrote:
> Keep in mind that ASNs are just an option in ALTO (as we're discussing
> it so far), so even if the P2P network uses a public IP to ASN mapping
> database, the ISP can provide their own IP prefix guidance without
> referencing ASNs if they care to.

   Indeed they can -- (by omitting any ASN guidance at all).

   But then, why include the option?

   The advantage of including an ASN option, IMHO, is that a policy can
be stated in a reasonably static manner using ASNs -- provided that the
meaning of those ASNs is clearly "where my routers will forward packets".

   This avoids having to frequently update policy as routing tables change
and having to state policy for hundreds of thousands of CIDR blocks.

   A downside is that ALTO clients may lack up-to-the-minute routing
information when mapping IPs to ASNs. That, IMHO, is something to work
on when the ALTO WG is formed. Several "good-enough" approaches suggest

   But if clients are encouraged to use mapping quite unrelated to the
actual routing, then policy stated in ASNs is actively misleading. I
would much prefer not to _design_ misleading policy into ALTO.

John Leslie <>
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