[ppml] question on 2006-2 v6 internal microallocation

Michael.Dillon at btradianz.com Michael.Dillon at btradianz.com
Tue Aug 29 08:49:12 EDT 2006

> > 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

> 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

--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.

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