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Re: [dns-wg] Global Vs local node data in www.root-servers.org
From: Joe Abley <jabley () hopcount ca>
Date: Mon, 17 Mar 2014 10:17:56 -0400


On 17 Mar 2014, at 7:39, John Bond <john.bond () icann org> wrote:

Global and Local nodes are very loosely defined terms.  However general
consensus of a local node is one that has a desired routing policy which
does not allow the service supernets to propagate globally.  As we impose
no policy we mark all nodes as global.

I think the taxonomy is probably my fault. At least, I thought I invented it when I wrote

  http://ftp.isc.org/isc/pubs/tn/isc-tn-2003-1.txt

the pertinent text of which is this:

   Two classes of node are described in this document:

   Global Nodes advertise their service supernets such that they are
      propagated globally through the routing system (i.e. they
      advertise them for transit), and hence potentially provide service
      for the entire Internet.

   Local Nodes advertise their service supernets such that the radius of
      propagation in the routing system is limited, and hence provide
      service for a contained local catchment area.

   Global Nodes provide a baseline degree of proximity to the entire
   Internet. Multiple global nodes are deployed to ensure that the
   general availability of the service does not rely on the availability
   or reachability of a single global node.

   Local Nodes provide contained regions of optimisation. Clients within
   the catchment area of a local node may have their queries serviced by
   a Local Node, rather than one of the Global Nodes.

The operational considerations that you mention would have been great for me to think about when I wrote that text 
(i.e. it's the intention of the originator of the route that's important, not the practical limit to propagation of the 
route due to the policies of other networks).

We did a slightly better job in RFC 4768 (e.g. "in such a way", "potentially"):

   Local-Scope Anycast:  reachability information for the anycast
      Service Address is propagated through a routing system in such a
      way that a particular anycast node is only visible to a subset of
      the whole routing system.

   Local Node:  an Anycast Node providing service using a Local-Scope
      Anycast Address.

   Global-Scope Anycast:  reachability information for the anycast
      Service Address is propagated through a routing system in such a
      way that a particular anycast node is potentially visible to the
      whole routing system.

   Global Node:  an Anycast Node providing service using a Global-Scope
      Anycast Address.


Joe

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