Internet Engineering Task Force M. Menth Internet-Draft University of Wuerzburg Expires: January 8, 2009 J. Babiarz Nortel T. Moncaster BT July 7, 2008 End-to-end Extension for PCN Encoding draft-menth-pcn-e2e-encoding-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 8, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). Menth, et al. Expires January 8, 2009 [Page 1] Internet-Draft End-to-end Extension for PCN Encoding July 2008 Abstract This document proposes an encoding of PCN marks based on the ECN field of the Voice-Admit DSCP. It has global meaning and ECN semantics are not applied to that field. The PCN codepoints are the same as those for packet-specific dual marking (PSDM) within a single PCN domain, but the general concept can also be applied to other encodings requiring only a single PCN-enabled DSCP. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Encoding Support for End-to-End PCN . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . . . 11 Menth, et al. Expires January 8, 2009 [Page 2] Internet-Draft End-to-end Extension for PCN Encoding July 2008 1. Introduction Pre-congestion notification provides information to support admission control and flow termination at the boundary nodes of a Diffserv region in order to protect the quality of service (QoS) of inelastic flows [PCN-arch]. This is achieved by marking packets on interior nodes according to some metering function implemented at each node. Excess traffic marking marks PCN packets that exceed a certain reference rate on a link while exhaustive marking marks all PCN packets on a link when the PCN traffic rate exceeds a reference rate [PCN-marking-behaviour]. These marks are monitored by the egress nodes of the PCN domain. This idea that the use of PCN marks is limited to a single domain is called edge-to-edge PCN. Packet-specific dual marking (PSDM) [PCN-pcn-encoding-PSDM] proposes an encoding of PCN marks that reuse the ECN field of PCN-enabled DSCP to record the marks in IP packets. However, these codepoints can be used only within PCN domains and packets with such PCN codepoints must not leave the PCN domain. With end-to-end PCN the entities monitoring and evaluating the PCN marks reside in the end systems such that the notion of PCN domains no longer exists [Menth08-PCN-Comparison]. Here, an encoding is required that has a global scope. In this document, we propose to use the ECN field of the Voice-Admit DSCP for that use. As a consequence, ECN cannot be used with Voice-Admit anymore. Note that Voice-Admit DSCP with this modified meaning can be used both for edge-to-edge and for end-to-end PCN. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Menth, et al. Expires January 8, 2009 [Page 3] Internet-Draft End-to-end Extension for PCN Encoding July 2008 2. Terminology The terminology used in this document is defined either in [PCN-arch] or in [PCN-pcn-encoding-PSDM]. o Edge-to-edge PCN - Admission for a PCN domain is requested explicitly for flows. When their packets enter the PCN domain, the ingress node sets a PCN-enabled DSCP and a PCN-capable codepoint (ECN field). The packets are metered and possibly re- marked by the traversed node in the PCN domain. The markings are evaluated by the egress node of that domain, and the DSCP and ECN field of the packet is reset before packets leave the PCN domain. o End-to-end PCN - The source node or a proxy thereof issues PCN packets with a PCN-enabled DSCP and PCN-capable codepoint (ECN field). Packets are metered and possibly marked by PCN nodes on their way. They pass ingress and egress nodes without special treatment of their DSCP or ECN field. The destination node or a proxy thereof evaluate the PCN markings. Menth, et al. Expires January 8, 2009 [Page 4] Internet-Draft End-to-end Extension for PCN Encoding July 2008 3. Encoding Support for End-to-End PCN In this section describes the changes to [PCN-pcn-encoding-PSDM] to support end-to-end PCN. In [PCN-pcn-encoding-PSDM] the Voice-Admit DSCP is proposed as the preferred PCN-enabled DSCP to implement the PSDM encoding within single domains. PCN codepoints are interpreted as such only within PCN domains while they are interpreted as ECN codepoints outside PCN domains. Being conform with [RFC4774] requires special treatment of PCN packets by ingress and egress nodes of a PCN domain. We propose that the default ECN semantics [RFC3168] do not apply for the Voice-Admit DSCP [voice-admit] , but alternate PCN semantics are applied which are end-to-end PCN. This requires an update to [voice-admit]. Then, the ECN field can be used for PCN purposes in the general Internet. One of the benefits is that end-to-end PCN can be supported by such a codepoint. This extension of the scope of Voice-Admit DSCP for PCN has no impact on the treatment of the PCN encoding for edge-to-edge PCN wich is described in [PCN-pcn-encoding-PSDM]. o PCN packets have a PCN- capable codepoint only within a PCN domain. o Ingress and egress nodes need to perform special treatment of PCN packets of edge-to- edge controlled PCN flows. In contrast, packets from end-to-end PCN controlled flows are not dropped by the ingress node of a PCN domain and not re-marked by the egress node of a PCN domain. Special treatment of ECN-capable PCN flows is not needed because PCN flows are not ECN capable. PCN ingress and egress nodes can differentiate packets from end-to- end and edge-to-edge PCN flows because edge-to-edge PCN flows explicitly request admission for the PCN domain such that PCN ingress and egress nodes keep per-flow states and know whether an incoming packet is edge-to-edge or end-to-end PCN controlled. Menth, et al. Expires January 8, 2009 [Page 5] Internet-Draft End-to-end Extension for PCN Encoding July 2008 4. IANA Considerations This document makes no request to IANA. It does however request a change to [voice-admit], requesting that a statement to be added that the default behaviour for the ECN semantics [RFC3168] does not apply for the Voice-Admit [voice-admit] DSCP. Menth, et al. Expires January 8, 2009 [Page 6] Internet-Draft End-to-end Extension for PCN Encoding July 2008 5. Security Considerations TBD Menth, et al. Expires January 8, 2009 [Page 7] Internet-Draft End-to-end Extension for PCN Encoding July 2008 6. Conclusions The proposed encoding allows that PCN codepoint can be used in the general Internet. This opens the possibility for end-to-end PCN. Menth, et al. Expires January 8, 2009 [Page 8] Internet-Draft End-to-end Extension for PCN Encoding July 2008 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [RFC4774] Floyd, S., "Specifying Alternate Semantics for the Explicit Congestion Notification (ECN) Field", BCP 124, RFC 4774, November 2006. 7.2. Informative References [PCN-arch] Eardley, P., "Pre-Congestion Notification Architecture", draft-ietf-pcn-architecture-03 (work in progress), February 2008. [PCN-marking-behaviour] Eardley, P., "Marking behaviour of PCN-nodes", draft-eardley-pcn-marking-behaviour-01 (work in progress), June 2008. [PCN-pcn-encoding-PSDM] Menth, M., Babiarz, J., Moncaster, T., and B. Briscoe, "PCN Encoding for Packet-Specific Dual Marking (PSDM)", July 2008. [voice-admit] Baker, F., Polk, J., and M. Dolly, "DSCPs for Capacity- Admitted Traffic", draft-ietf-tsvwg-admitted-realtime-dscp-04 (work in progress), February 2008. Menth, et al. Expires January 8, 2009 [Page 9] Internet-Draft End-to-end Extension for PCN Encoding July 2008 Authors' Addresses Michael Menth University of Wuerzburg Am Hubland Wuerzburg D-97074 Germany Phone: +49-931-888-6644 Email: menth@informatik.uni-wuerzburg.de Jozef Z. Babiarz Nortel 3500 Carling Avenue Ottawa, Ont. K2H 8E9 Canada Phone: +1-613-763-6098 Email: babiarz@nortel.com Toby Moncaster BT B54/70, Adastral Park Ipswich IP5 3RE UK Phone: +44 1473 648734 Email: toby.moncaster@bt.com Menth, et al. Expires January 8, 2009 [Page 10] Internet-Draft End-to-end Extension for PCN Encoding July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Menth, et al. Expires January 8, 2009 [Page 11]