UCLA Microsoft Cisco Microsoft ISI Cisco Sun Microsystems Microsoft Differentiated Services (diff-serv) and RSVP/Integrated Services (RSVP/int-serv) provide complementary approaches to the problem of providing QoS for Internet end systems. These approachs must be able to coexist and effectively interoperate. This document outlines one important model for such interoperation, in which diff-serv is used by transit networks in the core of the Internet while hosts and edge networks use RSVP/int-serv. It also contains a brief discussion of some alternative models for interoperation.