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Re: About the address allocation convention between ISPs
From: Teng Fei <tfei () ipanema ecs umass edu>
Date: Wed, 4 Jun 2003 13:02:08 +0000 (UTC)

Dear Mr. Fort,

Thank you very much for your help!  But there are cases the ISPs are
providing connectivity, albeit the address block of the customer was not
obtained from the provider.  For example, my university use Cable and
Wireless as the commercial provider but our address was not assigned by
C&W.  In such as case, is the interface addresses at both ends of the
interdomain link also assigned by the larger ISP?



On Tue, 3 Jun 2003, Andrew Fort wrote:

Hi Teng,
Every ISP I've worked at (3), and every ISP I've purchased service from (4), allocates link addressing (/30s) from 
its own pools, rather than making the customer provide the link addressing. (These parties are all in Australia, if 
that matters).

As I understand it, this is 'the convention' (you purchase a service, the provider definately has addresses, so it 
has them to provide).

The matter is less clear with private peering agreements, as both parties are generally ISPs and have address space 
of their own which could be used.

In the cases I've been involved in, one party has decided to use its own space (maybe due to their IGP design, but 
either way it'll work), which happens
to have been the larger party in every case (don't know if that's by design or logic of the method of agreement).

Subject: About the address allocation convention between ISPs
  From: Teng Fei <tfei () ipanema ecs umass edu>
  Date: Tue, 3 Jun 2003 01:10:33 +0000 (UTC)
    To: <nanog () merit edu>

Hello everyone,

I have a question about the convention of address allocation between ISPs.
If a smaller ISP tries to establish connection with its provider, does
this small ISP configure one of the interface on its boarder router using
an IP address obtained from the provider, or it is the other way around,
that is, the provider uses one of the IP address belongs to the customer
to configure the provider's boarder router?

I have this question because I am trying to identify the link between two
organizations from traceroute measurements.   How the addresses are
allocated will affect the identification of the inter-domain link by
exactly one hop.

I am not sure if there is such a convention at all, or the address
assignment is randomly decided according to the agreement between the
customer and the provider?

Since I know there are many seasoned network professionals on this mailing
list, I think it might be a proper question to ask here.  Would anyone
kindly be willing to share your experience?  Thank you very much!



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