NANOG/IEPG/ISOC's current role

Michael Dillon michael at
Thu Apr 4 06:40:10 UTC 1996

On Wed, 3 Apr 1996, Paul Ferguson wrote:

> And honestly, I don't think a substantial percentage of end-networks
> will renumber if there are not substantial incentives. 

This is true. One incentive could be peer pressure created by industry 
magazines publishing how-to articles with tools being readily available 
and the stigma of toxic waste dumps attached to those who don't renumber.

Of course, use of RFC1918 addresses like 10/8 coupled with proxy 
firewalling solves the renumbering problem quite handily but ISP's who 
are trying to justify /16 allocations would be loathe to recommend 
use of RFC1918 to their customers. Negative incentives, eh?

> The scenario that was previously described by Michael Dillon, I believe,
> was one in which a singularly-homed [to provider 'a'] end-network [x]
> moved to another provider [provider 'b'] and wanted to take their
> provider [a] allocated address(es) with them. This is a case where, if
> a larger aggregate is being announced by [a], then a specific component
> announced from the [a] CIDR  block would be announced by [b].

One problem ISP's run into is that if they allocate addresses to customer 
networks and then move to another provider they either need to keep their 
IP allocation or force their customers to renumber. Many customers may 
choose to switch ISP's or other nasty things, therefore the ISP would 
like a way to keep the allocation. I'm not sure my idea was terribly 
great, the real solution is probably to keep the old T1 for the old 
customers and buy a new T1 for expansion with the new NSP and a new set 
of addresses. It's not neccessary to run BGP4 in order to have two T1's 
from two providers with two different CIDR blocks. 

Has anyone ever proposed this as a solution to an ISP?

> This just happens to be a Catch-22 with multihomed end-networks.

It really is about time that some of the larger ISP's started following 
the lead of folks like and become aggregate providers for 
local ISP's in their cities. This way the aggregator can be doubly and 
triply homed and deal with all the BGP4 nastiness. The ISP's gain the 
benefit of that multihoming to their city and in addition can get some of 
the redundancy-in-case-of-failure by buying a T1 and frame relay, or a T1 
and ISDN dialup to their aggregate provider.

Every ISP wants to have a backup connection and right now most assume 
that multi-homing is the only way to achieve this.

I believe that a middle-tier between the ISP and the NSP is the best way 
to achieve this and could very well decrease global routing table size.

Michael Dillon                                    Voice: +1-604-546-8022
Memra Software Inc.                                 Fax: +1-604-546-3049                             E-mail: michael at

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