[173177] in North American Network Operators' Group
Re: Inevitable death, was Re: Verizon Public Policy on Netflix
daemon@ATHENA.MIT.EDU (Fred Baker (fred))
Fri Jul 18 20:34:21 2014
X-Original-To: nanog@nanog.org
From: "Fred Baker (fred)" <fred@cisco.com>
To: Scott Helms <khelms@zcorum.com>
Date: Sat, 19 Jul 2014 00:32:18 +0000
In-Reply-To: <CAMrdfRwzCj++ZrFL2ytBgW1SQVCCTxBqr3mGmh3ERUojR872NA@mail.gmail.com>
Cc: North American Network
Operators' Group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Jul 14, 2014, at 4:32 PM, Scott Helms <khelms@zcorum.com> wrote:
> I continue to vehemently disagree with the notion that ASN =3D ISP =
since
> many/most of the ASNs represent business networks that have nothing to =
do
> with Internet access.
And there are a number of ISPs with multiple ASNs.
If you look up the history of the term, "Autonomous System" is used =
without definition in most of its earlier RFCs, such as 820, 827, and =
1105. In short, though, it is a network that connects to other networks =
using a routing protocol such as EGP or eBGP. The best formal definition =
I have seen involves "a collection of physical networks under common =
administration which are reachable from the rest of the Internet by a =
common route." The quote is from RFC 1000 and refers to the domain of a =
prefix, but it's pretty close. An "Autonomous System Number" is a =
creature of EGP or BGP Routing, and identifies such a system.
If you look at http://bgp.potaroo.net/as6447/ and search for =93AS =
numbers=94, and you happen to be looking at exactly this instant (it =
changes), you=92ll find that AS 6447 sees 47879 individual AS numbers in =
the Internet, of which 40339 show up *only* as origins (and therefore =
have to do with the AS a source or destination of traffic), 236 *never* =
show up as end last AS in an AS Path (and therefore are *always* =
transit), and 7304 that are sometimes origin and sometimes transit. To =
my small mind, an AS that functions as an ISP if highly likely to show =
up as a transit network, and an AS that never shows up as transit is =
very likely to be multihomed or to have justified its AS number on the =
basis of plans to multihome. Of course, one will also find that 30134 =
AS=92s are origin AS=92s visible through exactly one AS path, which says =
that at this instant they=92re not actually multihomed.
No, AS !=3D ISP. An AS is a network that needs to be identifiable in =
global routing but would be entirely reachable even if it had exactly =
one link with some other network.
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