Daniel When talking about SIP and IMS Registered has a specific connotation means SIP registered. The is no SIP Registration between the mobile device and the CS domain so using registered might be misleading. You are right that in the single radio case the mobile device is not simultaneously attached to both the IMS and CS domain. It would be in the dual radio case. Maybe change that last sentence to To achieve this the mobile device needs to communicate via both the IP/SIP/IMS domain and the circuit switched domain. Andrew -----Original Message----- From: Daniel Migault [mailto:daniel.migault@xxxxxxxxxxxx] Sent: Thursday, December 7, 2017 9:33 PM To: secdir@xxxxxxxx Cc: draft-atarius-dispatch-meid-urn-as-instanceid.all@xxxxxxxx; ietf@xxxxxxxx Subject: Secdir last call review of draft-atarius-dispatch-meid-urn-as-instanceid-05 Reviewer: Daniel Migault Review result: Ready Hi, I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments. The summary of the review is Ready Some comments / questions: 1. Introduction This specification specifies how the URN namespace reserved for 3GPP2 identities and its NSS for the MEID as specified in draft-atarius- dispatch-meid-urn [8] can be used as an instance-id as specified in RFC 5626 [2] and also as used by RFC 5627 [3]. <mglt> I think it would be good to have the acronyms (URN, 3GPP2, NSS, MEID) expanded in the introduction section as it is being done in the abstract.</mglt> 3GPP2 defines High Rate Packet Data (HRPD) with high data rates and it dispenses with the 1x Circuit Switched (1xCS) infrastructure. This means that with HRPD networks, voice calls will need to be conducted using IP and IMS. However, the transition to all IP, SIP based IMS networks worldwide will take a great many years from the time of this writing and mobile devices will need to operate in both IP/SIP/IMS mode and circuit switched mode. This means that calls and sessions will need to be handed over between IP/SIP/IMS mode and circuit switched mode mid-call or mid-session. To achieve this the mobile device needs to be simultaneously attached via both the IP/SIP/IMS domain and the circuit switched domain. <mglt> I am questioning whether "registered" would not be better appropriated than "attached". My reading of attached is a dual radio case while "register" seems to include the single radio. I might be wrong as well.</mglt>