RFC 5586 generalized the applicability of the pseudowire Associated
Channel Header (PW-ACH) into the Generic Associated Channel G-Ach.
However, registries and allocations of G-ACh parameters had been
distributed throughout different, sometimes unrelated, registries.
This document coalesces these into a new "Generic Associated Channel
(G-ACh)" registry under the "Multiprotocol Label Switching
Architecture (MPLS)" heading. This is an update to RFC 5586
This document also updates RFC 6374, RFC 6428, RFC 6378, RFC 6427,