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) Parameters" registry under the "Multiprotocol Label
Switching Architecture (MPLS)" heading. This document updates RFC 5586.
This document also updates RFCs 6374, 6378, 6427, and 6428.