http://www.rfc-editor.org/rfc/rfc2836.txt
RFC 2836: Per Hop Behavior Identification Codes, S. Brim, B. Carpenter, F. Le Faucheur2000-05-01T23:00:00-00:00This document defines a binary encoding to uniquely identify PHBs (Per Hop Behaviors) and/or sets of PHBs in protocol messages. [STANDARDS-TRACK]