On 08/11/2011 17:20, András Császár wrote:
I think we should first see if there is a solution which provides full coverage
and practical (=reasonable complexity).
One problem with non-full-coverage solutions is bidirectional coverage. I.e.
even if a flow is covered for a failure in one direction it may not be covered
in the reverse direction which is, for most applications, equal to not being
covered at all. This property is often neglected in coverage estimates. As an
example consider the LFA unfirendly sub-topologies like longer-than-triangle
rings. In those rings it might seem that the failures on the opposing side to
the exit point are covered by the LFA. But they are not covered in the reverse
direction. Might be a factor to consider for PQ and co too.
Can you give me an example here?
I would expect a ring to have symmetric properties except when there are
asymmetric costs, but normally assymetric costs are a configuration
accident.
Stewart
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