On Tue, Sep 20, 2011 at 5:19 PM, Brett Frankenberger <rbf+na...@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
