[ppml] ppml 2002-7

Craig A. Huegen chuegen at cisco.com
Tue Feb 11 12:44:29 EST 2003

On Tue, 11 Feb 2003, CJ Wittbrodt wrote:

> Anyway, I have been doing some work with some students at UCLA.  The current
> results say that around 48% of allocated blocks are advertised identically
> to how they're allocated (same prefix length, not fragments).  Around
> 40% of the allocated blocks are advertised in one or modes of fragmentation
> (combinations of aggregates and fragments). This means that an ISP could
> get great benefit from being able to filter out the fragments of shorter
> provider blocks.   I am presenting this at NANOG so fee free to look at my
> slides.

There is a valid application for a difference between the prefix
allocation size and the actual announcements found on the Internet,
perhaps not at the scale that you're finding.  Large, multi-national
enterprises are depending more and more upon the Internet and connectivity
to it, and the distribution of Internet access points is increasing.
Where it was okay to have a single connection in 1995 for a large
organization, today's use of remote access VPN, branch office VPN, support
sites, etc. all demand that an organization's network be close to the

An enterprise is not a transit network, and it doesn't make sense for the
enterprise to pay a service provider to deliver Internet traffic to him in
a location far from his destination, then pay another service provider to
carry it on an internal WAN.

This should be considered when a discussion is made of allocation size
versus announced block size.  A large multi-national might have address
space needs of a /14, but may announce only portions of that block from
various regional hubs.

The alternative, of course, is to make more work for the registries in
forcing the enterprise to make individual block requests for each regional
hub to be deployed.  We could assure that allocation size was consistent
with announced size, for zero gain (same # of prefixes in the table) and
more work for the registry.


Craig A. Huegen, Chief Network Architect      C i s c o  S y s t e m s
IT Transport, Network Technology & Design           ||        ||
Cisco Systems, Inc., 400 East Tasman Drive          ||        ||
San Jose, CA  95134, (408) 526-8104                ||||      ||||
email: chuegen at cisco.com       CCIE #2100      ..:||||||:..:||||||:..

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