As the Diffserv work has evolved, there have been several cases where terminology has needed to be created or the definitions in Diffserv standards track RFCs have needed to be refined. Some minor technical clarifications were also found to be needed. This memo was created to capture group agreements, rather than attempting to revise the base RFCs and recycle them at proposed standard. It updates in part RFC 2474, RFC 2475 and RFC 2597. RFC 2598 has been obsoleted by RFC 3246, and clarifications agreed by the group were incorporated in that revision.