DefaultExponential is an exponential backoff implementation using the default values for all the configurable knobs defined in https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.

Exponential implements exponential backoff algorithm as defined in https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.

Strategy defines the methodology for backing off after a grpc connection failure.