
no matter how rudimentary. The crudest form of restoration is typically
accomplished by reprovisioning connec tions through their connection setup
control mechanisms in response to network failure.
(4) It is important to understand how the behavior of a link, X, at a given layer
depends on lower-layer restoration. If X is provided as a restorable connection
by the lower layer and a failure originates at the lower layer that causes X to
go into an unavailable state (go down), then it is down for the (usually very
short) period until the connection is restored at the lower layer by rerouting its
connection to a nonfailed path, assuming that sufficient ...