I have reviewed this document on behalf of the Operations and Management Directorate. I believe this document is well written. One clarification question I want to ask here is why not consolidate this document into I-D.ietf-idr-rfc5575bis since rc5575bis has just begun. Regarding Type 13 - Flow Label , I am wondering why Type 13 component values can not be be encoded as 8-byte quantities? why len=11 is not supported for IPv6 case? Regarding "the Sub-Type always TBD" in section 6.1, I want to suggest to add reference to IANA section, i.e., section 8.2.