http://www.rfc-editor.org/rfc/rfc2473.txt
RFC 2473: Generic Packet Tunneling in IPv6 Specification, A. Conta, S. Deering1998-12-01T23:00:00-00:00This document defines the model and generic mechanisms for IPv6 encapsulation of Internet packets, such as IPv6 and IPv4. [STANDARDS-TRACK]