[137675] in North American Network Operators' Group
Re: Internet Exchange Point(IXP) questions
daemon@ATHENA.MIT.EDU (Bill Woodcock)
Thu Feb 17 22:16:48 2011
From: Bill Woodcock <woody@pch.net>
In-Reply-To: <AANLkTi==qXjvwJf+WNBJNwOVBhF30bZOi+k75mmtqb1H@mail.gmail.com>
Date: Thu, 17 Feb 2011 19:16:31 -0800
To: "Yaoqing(Joey) Liu" <joey.liuyq@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Feb 17, 2011, at 6:03 PM, Yaoqing(Joey) Liu wrote:
> As I know, generally there are two types of IXPs
This is incorrect.
> type 1: use exchange routers, which works in layer 3
This is not an IXP. This is a router. That router would be owned by =
someone, who would have some sort of policy in the router, which would =
make it an Internet service provider, not an Internet exchange point.
> type 2: use switches and Ethernet topology, which works in layer 2.
This is an IXP. Routers belonging to Internet service providers, =
communicating with each other across a switch fabric, which is an =
Internet exchange point.
> 1. For type 1, the exchange routers may use several IP prefixes for =
routing,
> how often does the IP prefixes have their own AS?
Since this is not an IXP, I think the question is irrelevant to your =
research.
If an ISP wants to participate in BGP routing, and originate an IP =
prefix, that ISP must have an AS.
> 2. For type 2, all peers connected to the IXP must work in the same =
subnet
> required by Ethernet rules.
Generally, yes, though some IXPs are not that prescriptive, and would =
allow a subset of the ISPs to peer on a different subnet if they wished.
> Is possible that the subnet IP prefixes belong to some private IP =
address space, such as 192.168.x.x?
It is possible, but it does not follow best-practices, because it breaks =
traceroute and other diagnostic tools.
> How often does this happen?
Very very rarely.
Only two IXPs out of more than three hundred are using FRC1918 space at =
this point: Maputo and Santiago de Compostela.
This used to be a more common mistake, but as communications with the =
operators of new IXPs has improved over time, it's become very rare.
> If the subnet only contains public IP addresses, how are the addresses =
announced?
They are generally not announced. Occasionally they're announced by one =
or more participating ISPs at the IXP. Sometimes that's purposeful, =
other times it's accidental. Some IXPs have rules prohibiting the =
announcement of the exchange subnet, others actively seek out sources of =
transit for the exchange subnet.
-Bill Woodcock
Research Director
Packet Clearing House
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