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Determining ownership of Internet routing problems

  • From: kenw
  • Date: Sat Dec 06 16:44:49 2003

I am a little hesitant to post this here, as it comes from the perspective
of a user (albeit not a lay user).  However, I believe the issue is very
much one for service providers. Although it has been previously discussed
on comp.protocols.tcp-ip, I have yet to determine whether there is a clear
answer, let alone what it is.

If I am posting inappropriately, feel free to tell me so.


I had an... "interesting" problem a little while ago.  I couldn't reach my
mail server, and I couldn't tell who was responsible.  

The problem appeared to be a routing loop somewhere between my connectivity
ISP and my hosting ISP.  I talked to the connectivity ISP, and they said
the router was outside of their network and run by someone they had no
contract with.  The hosting ISP said essentially the same thing.

Now, I realize that dynamic routing means that there's no real way to
predict the path a given packet will take.  But I had somehow thought that
the contractual arrangements between ISPs and their backbone providers
would mean that there must be service agreements between everyone on the
path between two points, and that if a link failed, there was a path of
contractual responsibility.  E.g.

              [backbone provider]
		/             \
     [intermediate A]     [intermediate B]
              /                 \
          [ISP A]             [ISP B]

where (say) ISP A is the connectivity provider, and ISP B is the hosting

So if I can't reach ISP B, either ISP A or B should be able to talk to his
upstream provider and get it fixed.

Now I'm wondering if that is even a valid assumption.  Maybe the truth is
more like this:

         [backbone provider A]     [backbone provider B]
            /             \          /            \
  [intermediate A]      [intermediate C]      [intermediate B]
          /                                         \
      [ISP A]                                     [ISP B]

and if the problems is with intermediate C, I'm probably SOL.  Clearly, I
would want my ISP to insist that his upstream providers not allow such
unreliable topologies to be used.

So, my questions are, am I asking too much?  Am I misunderstanding the real
world of the Internet?  And am I posting in the wrong forum?


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