[ppml] question on 2006-2 v6 internal microallocation

Howard, W. Lee Lee.Howard at stanleyassociates.com
Tue Aug 29 09:55:53 EDT 2006

> -----Original Message-----
> From: ppml-bounces at arin.net [mailto:ppml-bounces at arin.net] On 
> Behalf Of Michael.Dillon at btradianz.com
> Sent: Tuesday, August 29, 2006 8:49 AM
> To: ppml at arin.net
> Subject: Re: [ppml] question on 2006-2 v6 internal microallocation
> > > The Global Routing Table refers to the set of all 
> > > prefixes (address blocks) announced in the default-free
> > > zone of the public Internet via BGP4. Theoretically,
> > > the routing table in a peering router of any member
> > > of the default-free zone will consist of the "Global
> > > Routing Table" plus the more detailed local routes which
> > > are only found in that member's network.
> > > --------------
> > 
> > Pretty good.
> > What's the "default-free zone"?
> The set of BGP4 prefixes announced on the public Internet
> by network operators who do not make use of a "default route"
> in their interdomain routing.
> Some might argue that it is the set of AS numbers of the above
> operators and that may be a better definition.
> > Is it the case that the Global Routing Table as defined above
> > is the same for all members of this zone? 
> Yes. However, the actual routing tables in any given router
> belonging to any given network operator will not likely
> reflect the actual full Global Routing Table since most
> operators use filtering mechanisms. In other words, the
> Global Routing Table is an abstract concept that could
> be measured if there was demand to measure it, but which
> does not necessarily correspond to anything that is currently
> measured.

I see.  The Global Routing Table is not the list of all routes 
on a given router, but some superset of routing tables among
routers in a DFZ AS.

Your definition says, "the routing table in a peering 
router of any member of the default-free zone will consist 
of the "Global Routing Table" "
I took "member" to be "router," since I think of a routing
table as a router's routing table.
> > Connecting the dots, is it possible that some members of the
> > default-free zone will have and share certain prefixes among
> > themselves?
> I don't understand. The default free zone came about because
> a set of network operators DO share prefixes (announce prefixes)
> among themselves as their exclusive means of interdomain
> connectivity.

Yes.  But in our current context, discussing whether there should
be a rule or guideline that a prefix not be advertised in the DFZ, 
if a prefix is advertised between two DFZ ASes, is it in the Global
Routing Table?

> --Michael Dillon
> P.S. many of the larger network operators will also operate
> IP networks and IP internetworks that are not part of the 
> public Internet. They may not be default free in those 
> extra-networks but that is not relevant. The concept of 
> Default-Free Zone only applies to the public Internet.

How do you tell the difference?  

Thank you for using specific language; I think this is very


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