This document describes the representation of identity information in POLICY_DATA object for supporting policy based admission control in the Resource ReSerVation Protocol (RSVP). The goal of identity representation is to allow a process on a system to securely identify the owner and the application of the communicating process (e.g., user id) and convey this information in RSVP messages (PATH or RESV) in a secure manner. We describe the encoding of identities as RSVP policy element. We describe the processing rules to generate identity policy elements for multicast merged flows. Subsequently, we describe representations of user identities for Kerberos and Public Key based user authentication mechanisms. In summary, we describe the use of this identity information in an operational setting. This document corrects an RSVP POLICY_DATA P-Type codepoint assignment error and a field size definition error in ErrorValue in RFC 2752.