BGP Wedgies: Bad Routing Policy Interactions that Cannot be Debugged
It is now common knowledge that BGP routing policies can
interact to produce unexpected routing anomalies such as protocol oscillation.
We introduce a new class of anomalies, called BGP wedgies.
A BGP wedgie is defined as a policy interaction where
all policies make perfect sense locally,
local policies interact globally to allow multiple solutions (routings) at the AS level,
some solutions are intended, while others are not,
getting stuck in an unintended solution requires manual intervention to "kick the system back" to an intended solution,
no single AS has enough global knowledge to understand what is happening.
In such a situation the
routing is "wedged" into a local optimum that is very difficult to change.
Realistic examples are presented.