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Re: multi-homing fixes

  • From: Leo Bicknell
  • Date: Fri Aug 24 20:59:24 2001

On Fri, Aug 24, 2001 at 05:22:03PM -0700, Randy Bush wrote:
> haven't thought about it for a while, but ...  probably rethink my
> requirements a bit.  

Let me give you the first two requirements:

1) Your investors won't give you money unless you have 'redundant'
   connectivity for your e-whatever.

2) Your insurance auditors won't give you insurance for your
   e-whatever unless  you have 'redundant' connectivity.

> so i might seriously consider dual homing to separate pops of a
> single very reliable isp, and concentrating my energy on physical
> diversity of the local loop.

I believe you just limited yourself to an amazingly small number
of providers, if any at all.  Even in the large metro areas where
providers _might_ have two POPs, they are often fairly dependant
on a third location (ie 60 Hudson, 1 Wilshire) which in many cases
could just be an aggregation POP for that provider in the region.

How many cities does Verio have two POP's in set up in such a way
that the loss of all or part of one POP would result in almost no
effect on the other POP?

> if i really felt the need for multiple providers, i might do a double
> nat, but with full 1:1 mapping, i.e. pure address aliasing, not space
> compression.  of course, some persistent connections would be lost in
> the case of a link failure.  but insurance against very rare cases is
> ok if the expense is incurred on the rare case.

You want to explain that in a bit more detail.  Start with 'client
looks up www.example.com' and go to 'client establishes tcp connection
with the web server that services the content'.

Having DNS point at 2 IP's and having one "not be there" is not a
valid answer, it doesn't work in the real world.

-- 
Leo Bicknell - bicknell@ufp.org
Systems Engineer - Internetworking Engineer - CCIE 3440
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