wet-behind-the-ears whippersnapper seeking advice on building a nationwide network

Dorn Hetzel dorn at hetzel.org
Tue Sep 20 17:50:30 CDT 2011


On Tue, Sep 20, 2011 at 5:19 PM, Brett Frankenberger <rbf+nanog at panix.com>wrote:

> On Tue, Sep 20, 2011 at 04:13:57PM -0400, Dorn Hetzel wrote:
> >
> > "full time connection to two or more providers" should be satisfied when
> the
> > network involved has (or has contracted for and will have) two or more
> > connections that are diverse from each other at ANY point in their path
> > between the end network location or locations and the far end BGP peers,
> > whether or not the two or more connections are exposed to one or more
> common
> > points of failure, as long as their are any failure modes for which one
> > connection can provide protection against that failure mode somewhere in
> the
> > other connection.
>
> The GRE tunnel configuration being discussed in this thread passes this
> test.
> Consider the following:
>   ISP #1 has transit connections to upstream A and B.
>   ISP #2 has transit connections to upstream C and D
>   ISP 1 and ISP 2 peer.
>
> Customer gets a connection to ISP #1 and runs BGP, and, over that
> connection, establishes a GRE tunnel to ISP #2, and runs BGP over that
> also.
>
> I assume your last clause requires that each connection provide
> protection against a failure more in the other connection (not just
> that one of the two provide protection against a failure mode on the
> other).  This is satisfied.  In my example:
>
> ISP #1 provides protection against ISP #2 having a complete meltdown.
>
> ISP #2 provides protection against ISP #1 losing both its upstream
> connections.
>
>     -- Brett
>

Yes, that is what I was trying to say, that there are at least k providers,
k>=2, and that at least 2 of those k
providers offer at least some redundancy for some possible failure modes in
the other provider.

Your example is especially plausible if it happens that the router from
which ISP #1 provides me service
is the same router, or at least close in the same POP, to the router from
which they peer with ISP#2.

ISP#1 might then have a complete backbone meltdown, but retain their local
peering session with ISP#2,
which would allow me to still reach my tunnel endpoint in ISP#2 and the BGP
session resulting.

-Dorn


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