Internet Engineering Task Force (IETF) S. Perreault, Ed. Request for Comments: 6888 Viagenie BCP: 127 I. Yamagata Updates: 4787 S. Miyakawa Category: Best Current Practice NTT Communications ISSN: 2070-1721 A. Nakagawa Japan Internet Exchange (JPIX) H. Ashida Cisco Systems April 2013 Common Requirements for Carrier-Grade NATs (CGNs) Abstract This document defines common requirements for Carrier-Gr