Subject: [RADIR] Section 4.3. End Site Renumbering

From: Thomas Narten <[email-masked]>
Date: Fri, 01 Jun 2007 12:12:31 -0400

Added to the definition section:

   Provider Aggregatable (PA) address space  Address space that an end
      site obtains from an ISP's address block.  The main benefit of PA
      address space is that reachability to all of a provider's
      customers can be achieved by advertising a single "provider
      aggregate" address prefix into the DFZ, rather than needing to
      announce individual prefixes for each customer.  An important
      disadvantages is a requirement that the customer return those
      addresses (and renumber) when changing providers.

   Provider Independent (PI) address space  Address space that an end
      site obtains directly from a Regional Internet Registry (RIR) for
      numbering its devices.  The main advantage (for the end site) is
      that it does not have to return those addresses (and renumber its
      site) upon changing providers.  However, PI address blocks are not
      aggregatable and thus each individual PI assignment results in an
      indvidual prefix being injected into the DFZ.

For Section 4.3.  End Site Renumbering

   It is generally considered painful and costly to renumber a site,
   with the cost proportional to the size and complexity of the
   network. When using PA space, however, a site must renumber when
   changing providers. Larger sites object to this cost and view the
   requirement to renumber akin to being held "hostage" to the
   provider from which PA space was obtained. Consequently, many sites
   desire PI space. Having PI space provides independence from any one
   provider and makes it easier to switch providers (for whatever
   reason). However, each individual PI prefix must be propagated
   throughout the DFZ and adds to the DFZ routing load.

   It should be noted that while larger sites may also want to
   multihome, the cost of renumbering drives some sites to seek PI
   space, even though they do not multihome.

Thomas

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From: Jason Schiller <[email-masked]>
Date: Mon, 04 Jun 2007 15:53:59 -0400 (EDT)

On Fri, 1 Jun 2007, Thomas Narten wrote:

>    network. 

I'm not sure the cost of renumbering is always "proportional to the size
and complexity of the network".  Take for example a fairly small network
with a fairly small address space that builds many VPN links to other
networks in their supply chain.  Imagine 300 IP-SEC tunnels that are are
built to a single IP address.  Changing that one address may be very
painful as the configuration on 300 routers each at a different compnay
may be required.

I think it is partly a function of the number of addresses that need to
change, partly a function of the number of other things also need to
change with the new address, how difficult it is to change those other
things, and partly a function of if you control those other things that
need to change.

Changing 1,000 workstations that used DHCP and have no DNS requirement is
one thing, changing a single server that has DNS, and appears in router
ACLs, and firewall policies is quite another.  Yet getting other prople to
change thier routers, firewalls and applications with hard coded addresses 
is yet another.

__Jason

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From: "John G. Scudder" <[email-masked]>
Date: Tue, 5 Jun 2007 13:48:48 -0400

> painful as the configuration on 300 routers each at a different  
...

To me, it seems like that gets captured by the "and complexity" part.

--John