Internet Engineering Task Force G. Karagiannis Internet-Draft University of Twente Intended status: Informational T. Taylor Expires: September 8, 2010 K. Chan Huawei Technologies M. Menth University of Wurzburg March 8, 2010 Requirements for Signaling of (Pre-) Congestion Information in a DiffServ Domain draft-karagiannis-pcn-signaling-requirements-01 Abstract Precongestion notification (PCN) is a means for protecting quality of service for inelastic traffic admitted to a Diffserv domain. The overall PCN architecture is described in RFC 5559. This memo describes the requirements for the signaling applied within the PCN domain: PCN feedback is carried from the PCN-egress-node to the decision point and the decision point may demand for the measurement and delivery of the PCN rate sent at the PCN-ingress-node. The decision point may be either collocated with the PCN-ingress-node or a centralized node. 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." 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 September 8, 2010. Karagiannis, et al. Expires September 8, 2010 [Page 1] Internet-Draft PCN Signaling requirements March 2010 Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Requirements Language 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 RFC 2119 [RFC2119]. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Signaling requirements between PCN-egress-nodes and Decision Point . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 PCN Reporting Frequency . . . . . . . . .. . . . . . . . . . . 4 2.2 Signaled PCN egress Feedback . . . . . . .. . . . . . . . . . .4 2.3 Signaling requirements . . . . . . . . . .. . . . . . . . . . .5 2.3.1 Priority of signaling messages . . . . . . . . . . . . . . 5 2.3.2 Local information exchange. . . . . . . . . . . . . . . . .5 2.3.3 Carry identification of PCN edge nodes . . . . . . . . . .5 2.3.4 Carry identification of ingress-egress-aggregates . . . . 5 2.3.5 Signaling load. . . . . . .. . . . . . . . . . . . . . . . 6 2.3.6 Reliability. . . . . . .. . . . . . . . . . . . . . . . . 6 2.4. Filter specifications . . . . . . . . . . . . . . . . . . . . 6 3. Signaling Requirements between Decision Point and PCN-ingress-nodes . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Signaled PCN ingress Feedback. . . . . . . . . . . . . . . . . 7 3.2 Signaled decision point trigger. . . . . . . . . . . . . . . . 7 3.3 Signaling requirements . . . . . . . . . .. . . . . . . . . . .7 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 8 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Karagiannis, et al. Expires September 8, 2010 [Page 2] Internet-Draft PCN Signaling requirements March 2010 1. Introduction The main objective of Pre-Congestion Notification (PCN) is to support the quality of service (QoS) of inelastic flows within a Diffserv domain in a simple, scalable, and robust fashion. Two mechanisms are used: admission control and flow termination. Admission control is used to decide whether to admit or block a new flow request while flow termination is used in abnormal circumstances to decide whether to terminate some of the existing flows. To support these two features, the overall rate of PCN-traffic is metered on every link in the domain, and PCN-packets are appropriately marked when certain configured rates are exceeded. These configured rates are below the rate of the link thus providing notification to boundary nodes about overloads before any congestion occurs (hence "pre- congestion" notification). The PCN-egress-nodes measure the rates of differently marked PCN traffic in periodic intervals and report these rates as so-called PCN feedback to the decision points for admission control and flow termination based on which they take their decisions.The decision points may be collocated with the PCN-ingress- nodes or their function may be implemented in a centralized node. For more details see[RFC5559, [draft-ietf-pcn-cl-edge-behaviour-02], [draft-ietf-pcn-sm-edge-behaviour-02]. Thus, signaling is needed to transport PCN feedback from PCN-egress- nodes towards the decision point. Moreover, signaling is needed that the decision point can trigger the PCN-ingress-node to measure the PCN traffic rate and send these measurement results to the decision point. This memo briefly describes the signaled content and specifies the requirements that have to be satisfied by the signaling protocols. 1.1. Terminology In addition to the terms defined in [RFC5559], this document uses the following terms: Decision Point: The node that makes the decision about which flows to admit and to terminate. In a given network deployment, this may be the ingress node or a centralized control node. Of course, regardless of the location of the decision point, the ingress node is the point where the decisions are enforced. Karagiannis, et al. Expires September 8, 2010 [Page 3] Internet-Draft PCN Signaling requirements March 2010 PCN egress feedback: Content used by the PCN-egress-node to report and inform the decision point about measurements required during flow admission and flow termination decisions. PCN ingress feedback: Content used by the PCN-ingress-node to report and inform the decision point about measurements required during flow termination decisions. ingress rate request: A message sent by the decision point towards the PCN-ingress-node to request the PCN-ingress-node to measure and report the value of the rate of admitted PCN traffic for a given ingress-egress-aggregate. 2. Signaling requirements between PCN-egress-nodes and Decision Point The PCN-egress-node measures the rates of differently marked PCN traffic in regular intervals and signals them as PCN egress feedback to the decision point. This section describes the PCN egress feedback and the requirements that apply to signaling protocols used for the transport of PCN feedback from PCN-egress-nodes to decision points. Note that if the decision point and the PCN-ingress-node are collocated, then the signaling requirements described in this section apply to the signaling between PCN-egress-nodes and PCN-ingress- nodes. 2.1 PCN Reporting Frequency The specification of PCN-based admission control and flow termination in [draft-ietf-pcn-cl-edge-behaviour-02], [draft-ietf-pcn-sm-edge- behaviour-02] suggest measurement and reporting intervals at the PCN- egress-nodes of 100 to 500 ms. 2.2 Signaled PCN egress Feedback The PCN-egress-node measures per ingress-egress-aggregate the following rates o rate of not-marked PCN traffic; o rate of threshold-marked PCN traffic, which applies to CL edge behaviour only; o rate of excess-traffic-marked PCN traffic. Karagiannis, et al. Expires September 8, 2010 [Page 4] Internet-Draft PCN Signaling requirements March 2010 These values are reported in octets/second to the decision point at the end of each measurement interval. If multipath routing is enabled, the PCN-egress-node tracks a list of flows for which it has recently received excess-traffic-marked packets. The list of these flow IDs is included in the PCN feedback because these flows are candidates for termination. The representation of a flow ID depends on the surrounding environment, e.g., "pure IP", MPLS, GMPLS, etc. For the representation of a flow ID in a "pure IP" surrounding environment, see Section 2.4. 2.3 Signaling requirements This section describes the requirements for signaling protocols that are used to carry the PCN egress feedback from PCN-egress-nodes to the decision point. 2.3.1 Priority of signaling messages Signaling messages SHOULD have a higher priority than data packets. This is needed to avoid as much as possible the situations that during severe overload cases the signaling messages are dropped within the PCN domain. 2.3.2 Local information exchange Signaling messages MUST be able to carry the PCN egress feedback from the PCN-egress-node to the decision point. 2.3.3 Carry identification of PCN edge nodes The signaling protocol MUST be able to carry identification (address information) of the PCN edge nodes. However, the identification of the PCN edge nodes MUST NOT be visible outside the PCN domain. 2.3.4 Carry identification of ingress-egress-aggregates The signaling protocol MUST be able to carry identification (address information) of the ingress-egress-aggregates. It is proposed to identify them using the addresses of the PCN-ingress-node and PCN-egress-node between which they pass. If each of the edge nodes do not have unique addresses, then other identifiers could be used. Karagiannis, et al. Expires September 8, 2010 [Page 5] Internet-Draft PCN Signaling requirements March 2010 2.3.5 Signaling load The load generated by the signaling protocol to carry the PCN egress Feedback from the PCN-egress-nodes to the decision point SHOULD be minimized as much as possible. 2.3.6 Reliability There are situations that messages need to be sent in a reliable way, meaning that the PCN-egress-node MUST be acknowledged that the sent message is successfully received by the decision point. It is considered that the PCN egress feedback that is sent in a regular fashion SHOULD NOT be sent reliably. 2.4. Filter specifications In PCN the ingress and egress nodes should be able to identify the ingress-egress-aggregate to which each flow belongs. Moreover, the egress node also needs to associate an aggregate with the address of the ingress node for receiving reports, if the ingress node is the decision point. The filter specification at the PCN-egress-nodes depends on the surrounding environment, e.g., pure IP, MPLS, GMPLS. In this document, only the pure IP filter spec is given as an example. In this case the filter spec should be able to identify a flow using (all or a subset of the) following information: o source IP address; o destination IP address; o protocol identifier and higher layer (port) addressing; o flow label (typical for IPv6); o SPI field for IPsec encapsulated data; o DSCP/TOS field. o IP address of PCN-ingress-node o IP address of PCN-egress-node o IP address of decision point Karagiannis, et al. Expires September 8, 2010 [Page 6] Internet-Draft PCN Signaling requirements March 2010 3. Signaling Requirements between Decision Point and PCN-ingress-nodes The decision point monitors and uses the PCN egress feedback sent by the PCN-egress-node. There are situations that the decision point must obtain an estimate of the rate at which PCN-traffic is being admitted to the aggregate from the PCN-ingress-node. In order to receive this information the decision point has to request from the PCN-ingress-node to send the value of the PCN traffic admitted to a certain aggregate. Note that if the decision point and the PCN-ingress-node are collocated, then the signaling required between the decision point and PCN-ingress-node are internal operations. 3.1 Signaled PCN ingress Feedback The PCN-ingress-node measures per ingress-egress-aggregate the following rate o rate of admitted PCN traffic This value is reported in octets/second to the decision point as soon as possible after receiving the request from the decision point. . 3.2 Signaled decision point trigger The decision point uses the "ingress rate request" to request from the PCN-ingress-node to send for a certain ingress-egress-aggregate, the value of the admitted PCN traffic rate. The "ingress rate request" message identifies the ingress-egress-aggregate for which the admitted PCN traffic rate is required. 3.3 Signaling requirements The same signaling requirements described in Section 2.3 apply for this situation. The only difference is the fact that these signaling requirements apply for the signaling messages that have to be sent between the decision point and PCN-ingress-nodes. Moreover, since the "ingress rate request" message sent by the decision point towards the PCN-ingress-node and the admitted PCN traffic rate sent by the PCN-ingress-node towards the decision point are not sent regularly, they SHOULD be delivered reliably. Karagiannis, et al. Expires September 8, 2010 [Page 7] Internet-Draft PCN Signaling requirements March 2010 4. Security Considerations [RFC5559] provides a general description of the security considerations for PCN. This memo introduces no new considerations. 5. IANA Considerations This memo includes no request to IANA. 6. Acknowledgements We would like to acknowledge the members of the PCN working group for the discussions that generated the contents of this memo. 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. [RFC5559] Eardley, P., "Pre-Congestion Notification (PCN) Architecture", RFC 5559, June 2009. [draft-ietf-pcn-cl-edge-behaviour-02] T. Taylor, A, Charny, F. Huang, G. Karagiannis, M. Menth, "PCN Boundary Node Behaviour for the Controlled Load (CL) Mode of Operation (Work in progress)", March 2010. [draft-ietf-pcn-sm-edge-behaviour-02] A. Charny, J. Zhang, G. Karagiannis, M. Menth, T. Taylor, "PCN Boundary Node Behaviour for the Single Marking (SM) Mode of Operation (Work in progress)", March 2010. 7.2. Informative References Karagiannis, et al. Expires September 8, 2010 [Page 8] Internet-Draft PCN Signaling requirements March 2010 Authors' Addresses Georgios Karagiannis University of Twente P.O. Box 217 7500 AE Enschede, The Netherlands EMail: g.karagiannis@ewi.utwente.nl Tom Taylor Huawei Technologies 1852 Lorraine Ave. Ottawa, Ontario K1H 6Z8 Canada Phone: +1 613 680 2675 Email: tom111.taylor@bell.net Kwok Ho Chan Huawei Technologies 125 Nagog Park Acton, MA 01720 USA Email: khchan@huawei.com Michael Menth University of Wurzburg Institute of Computer Science Room B206 Am Hubland, Wuerzburg D-97074 Germany Email: menth@informatik.uni-wuerzburg.de Karagiannis, et al. Expires September 8, 2010 [Page 9]