Internet - Draft ECN Tunnelling March 2009

Tunnelling of Explicit Congestion Notification draft-ietf-tsvwg-ecn-tunnel-02 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Abstract This document redefines how the explicit congestion notification (ECN) field of the IP header should be constructed on entry to and exit from any IP in IP tunnel. On encapsulation it brings all IP in IP tunnels (v4 or v6) into line with the way RFC4301 IPsec tunnels now construct the ECN field. On decapsulation it redefines how the ECN field in the forwarded IP header should be calculated for two previously invalid combinations of incoming inner and outer headers, in order that these combinations may be usefully employed in future standards actions. It includes a thorough analysis of the reasoning for these changes and the implications.