Fiber cut?

Steve Gibbard scg at
Tue Apr 22 04:42:39 UTC 2003

On Mon, 21 Apr 2003, McBurnett, Jim wrote:

> A small ISP at one of our small cities is claiming a fiber cut took
> them offline..

This is NANOG, and this is pretty basic, so this is probably the wrong
forum for this explanation.  That said, if a small ISP gets taken off line
by a fiber cut, it's far more likely to be somewhere between the major
backbone and the ISP (a circuit which from the ISP's perspective may be
controlled by the major backbone), than it is that the fiber cut will
actually isolate the major backbone's POP.  The major backbones at this
point have a fair amount of redundancy built in, while the circuit from
the major backbone to the ISP is likely to be a single circuit on a single

Still, even in that environment, most circuit outages are not fiber cuts.

> I can't buy it that it goes from ATlanta to San Fran in 1 hop....
> Trace to
> 10      0ms   10ms   10ms  TTL:  0  ( probable bogus rDNS: No DNS)
> 11   10ms   10ms    0ms  TTL:  0  ( probable bogus rDNS:
> 12 Request timed out

Not to mention that they'd have to have discovered faster light. ;)


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