Internet Engineering Task Force G. Karagiannis Internet-Draft University of Twente Intended status: Informational T. Taylor Expires: September 02, 2011 K. Chan Huawei Technologies M. Menth University of Tuebingen March 02, 2011 Requirements for Signaling of (Pre-) Congestion Information in a DiffServ Domain draft-ietf-pcn-signaling-requirements-02 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: (1) PCN feedback is carried from the PCN-egress-node to the decision point;(2) 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 in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 02, 2011. Karagiannis, et al. Expires September 02, 2011 [Page 1] Internet-Draft PCN Signaling requirements March 2011 Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Copyright (c) 2011 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 Simplified 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 . . . . . . . . . . . . . . . . . . . . . . . 4 2. Signaling Requirements between PCN-egress-nodes and Decision Point . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Reporting Frequency . . . . . . . . .. . . . . . . . . . . . . 4 2.2 Reporting Information. . . . . . .. . . . . . . . . . . . . . 5 2.2.1 PCN egress Feedback . . . . . . .. . . . . . . . . . . . . .5 2.3 Signaling Requirements . . . . . . . . . .. . . . . . . . . . .5 2.3.1 Priority of Signaling Messages . . . . . . . . . . . . . . 6 2.3.2 Local Information Exchange. . . . . . . . . . . . . . . . .6 2.3.3 Carry Identification of PCN edge Nodes . . . . . . . . . .6 2.3.4 Carry Identification of ingress-egress-aggregates . . . . 6 2.3.5 Signaling Load. . . . . . .. . . . . . . . . . . . . . . . 6 2.3.6 Reliability. . . . . . .. . . . . . . . . . . . . . . . . 6 2.3.7 Security. . . . . . .. . . . . . . . . . . . . . . . . . 6 2.4. Filter Specifications . . . . . . . . . . . . . . . . . . . . 7 3. Signaling Requirements between Decision Point and PCN-ingress-nodes . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Reporting Frequency . . . . . . . . .. . . . . . . . . . . . . 7 3.2 Reporting Information . . . . . . . . . . . . . . . . . . . . .8 3.2.1 PCN ingress Feedback. . . . . . . . . . . . . . . . . . . . .8 3.2.2 Decision Point Trigger. . . . . . . . . . . . . . . . . . . .8 3.3 Signaling Requirements . . . . . . . . . .. . . . . . . . . . .8 3.3.1 Priority of Signaling Messages . . . . . . . . . . . . . . 8 3.3.2 Local Information Exchange. . . . . . . . . . . . . . . . .8 Karagiannis, et al. Expires September 02, 2011 [Page 2] Internet-Draft PCN Signaling requirements March 2011 3.3.3 Carry Identification of PCN edge Nodes and Decision Point .8 3.3.4 Carry Identification of ingress-egress-aggregates . . . . 8 3.3.5 Signaling Load. . . . . . .. . . . . . . . . . . . . . . . 9 3.3.6 Reliability. . . . . . .. . . . . . . . . . . . . . . . . 9 3.3.7 Security. . . . . . .. . . . . . . . . . . . . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 7.1. Normative References . . . . . . . . . . . . . . . . . . . .10 7.2. Informative References . . . . . . . . . . . . . . . . . . .10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 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-08], [draft-ietf-pcn-sm-edge-behaviour-05]. This memo specifies the requirements that have to be satisfied by the signaling protocols needed to transport: o PCN egress feedback, from a PCN-egress-node to the decision point; o a request, from the decision point to a PCN-ingress-node, that triggers the PCN-ingress-node to measure the PCN-sent-rate; o PCN ingress feedback, from a PCN-ingress-node to the decision point. Karagiannis, et al. Expires September 02, 2011 [Page 3] Internet-Draft PCN Signaling requirements March 2011 A signaling message may either be sent directly, or may piggy-backed on some other message that is being sent via the relevant node. 1.1. Terminology In addition to the terms defined in [RFC5559], [draft-ietf-pcn-cl- edge-behaviour-08] and [draft-ietf-pcn-sm-edge-behaviour-05], this document uses the following terms: PCN egress feedback: A report sent by the PCN-egress-node to the decision point. It reports measurements made by the PCN-egress-node that inform decisions about flow admission and flow termination. PCN ingress feedback: A report sent by the PCN-ingress-node to the decision point. It reports: o measurements made by the PCN-ingress-node that inform decisions about flow termination; o measurements of the PCN-sent-rate. 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 Reporting Frequency The specification of PCN-based admission control and flow termination in [draft-ietf-pcn-cl-edge-behaviour-08], [draft-ietf-pcn-sm-edge- behaviour-04] suggest measurement and reporting intervals at the PCN- egress-nodes of 100 to 500 ms. The PCN reporting frequency can provide some level of reliability. Therefore, it is considered that for regularly reported information, additional reliability mechanisms are not needed, see Section 2.3.6. Karagiannis, et al. Expires September 02, 2011 [Page 4] Internet-Draft PCN Signaling requirements March 2011 The following PCN contents are sent regularly: rate of not-marked PCN traffic, rate of threshold- marked PCN traffic, rate of excess-traffic-marked PCN traffic, CLE. 2.2 Reporting Information This section briefly describes the information that is reported by the PCN-egress-node. 2.2.1 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 behavior only; o rate of excess-traffic-marked PCN traffic; o Congestion level estimate (CLE) The rate values are reported in octets/second to the decision point each time that the PCN-egress-node calculates them and when this is supported via configuration. A report may either be sent periodically, every time the PCN-egress- node measures the various rates, or else may be sent occasionally, see "optional report suppression", for instance in [draft-ietf-pcn-cl-edge-behaviour-08], [draft-ietf-pcn-sm-edge-behaviour-05]. If so configured (e.g., because multipath routing is being used), the PCN-egress-node MUST also include in the PCN feedback and report the set of flow identifiers of PCN-flows for which excess-traffic-marking was observed in the most recent measurement interval. The representation of a flow ID depends on the surrounding environment, e.g., "pure IP", MPLS, GMPLS, etc. Examples of such flow ID representations can be found in [RFC2205], [RFC3175] [RFC3209], [RFC3473]. For more details see [draft-ietf-pcn-cl-edge-behaviour-08], [draft- ietf-pcn-sm-edge-behaviour-04]. 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. Karagiannis, et al. Expires September 02, 2011 [Page 5] Internet-Draft PCN Signaling requirements March 2011 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 carry the identity of the PCN-egress-node that sends the message. 2.3.4 Carry Identification of ingress-egress-aggregates The signaling protocol MUST carry the identity (address information) of the ingress-egress-aggregates. 2.3.5 Signaling Load The load generated by the signaling protocol SHOULD be minimized. 2.3.6 Reliability There are situations that messages need to be received in a reliable way. There are different ways of achieving reliability. The specification of a mandatory solution of achieving this reliability is out of the scope of this document. It can be however considered, that when information is received on a regular fashion, additional reliability measures Should Not be required. 2.3.7 Security The PCN architecture [RFC5559] considers that all PCN-nodes are PCN- enabled and trusted to operate correctly. In the context of this document: o PCN-signaling messages MUST NOT leak out of the PCN-domain. This can be easily accomplished, since messages are sent to the PCN- boundary-node's address; o PCN-boundary-nodes MUST validate the signaling messages, to avoid that they come from an attacker. Considering that all PCN- nodes are trusted, see [RFC5559], this requirement could be easily fulfilled by verifying whether a message arrives on an interface internal to the PCN-domain. Karagiannis, et al. Expires September 02, 2011 [Page 6] Internet-Draft PCN Signaling requirements March 2011 2.4. Filter Specifications In PCN the PCN-ingress-node and PCN-egress-nodes should be able to identify the ingress-egress-aggregate to which each flow belongs. Moreover, the PCN-egress-node also needs to associate an aggregate with the address of the PCN-ingress-node for receiving reports, if the PCN-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, a possible IP filter spec for pure IP 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 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 report the value of the PCN traffic admitted to a certain ingress-egress-aggregate. Note that if the decision point and the PCN-ingress-node are collocated, then the information exchanges between the decision point and PCN-ingress-node are internal operations. 3.1 Reporting Frequency The PCN content sent by the PCN-ingress-node and Decision Point are not sent regularly. Karagiannis, et al. Expires September 02, 2011 [Page 7] Internet-Draft PCN Signaling requirements March 2011 3.2 Reporting Information 3.2.1 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. This information is not sent regularly and SHOULD be delivered reliably. 3.2.2 Decision Point Trigger The decision point requests from the PCN-ingress-node to send for a certain ingress-egress-aggregate, the value of the admitted PCN traffic rate. This Decision Point Trigger message identifies the ingress-egress-aggregate for which the admitted PCN traffic rate is required. Moreover, since this Decision Point Trigger message sent by the decision point to the PCN-ingress-node is not sent regularly, it SHOULD be delivered reliably. 3.3 Signaling Requirements This section describes the requirements for signaling protocols that are used to carry the PCN ingress feedback and the Decision Point Trigger. 3.3.1 Priority of Signaling Messages Signaling messages SHOULD have a higher priority than data packets. 3.3.2 Local Information Exchange Signaling messages MUST be able to carry: o the PCN ingress feedback from the PCN-ingress-node to the decision point; o the Decision Point Trigger from the decision point to the PCN- ingress-node. 3.3.3 Carry Identification of PCN edge Nodes and Decision Point The signaling protocol MUST carry the identity: o of the PCN-ingress-node that sends the message, o of the decision point that sends the message. 3.3.4 Carry Identification of ingress-egress-aggregates The signaling protocol MUST carry the identity (address information) of the ingress-egress-aggregates. Karagiannis, et al. Expires September 02, 2011 [Page 8] Internet-Draft PCN Signaling requirements March 2011 3.3.5 Signaling Load The load generated by the signaling protocol SHOULD be minimized. 3.3.6 Reliability The PCN ingress feedback and the Decision Point Trigger are not sent regularly and SHOULD be delivered reliably. There are different ways of achieving reliability. The specification of a mandatory solution of achieving this reliability is out of the scope of this document. 3.3.7 Security The PCN architecture [RFC5559] considers that all PCN-nodes are PCN- enabled and trusted to operate correctly. The decision point is a PCN-node and therefore it is considered to be PCN-enabled and trusted to operate correctly. In the context of this document: o PCN-signaling messages MUST NOT leak out of the PCN-domain. This can be easily accomplished, since messages are sent to either the PCN-boundary-node's address or the decision point's address, o PCN-boundary-nodes MUST validate the signaling messages, to avoid that they come from an attacker. Considering that all PCN- nodes are trusted, see [RFC5559], this requirement could be easily fulfilled by verifying whether a message either arrives on an interface internal to the PCN-domain or that it is sent by a decision point. 4. Security Considerations [RFC5559] provides a general description of the security considerations for PCN. This memo introduces the additional security considerations described in Section 2.3.7 and Section 3.3.7. 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. Karagiannis, et al. Expires September 02, 2011 [Page 9] Internet-Draft PCN Signaling requirements March 2011 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-08] 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)", December 2010. [draft-ietf-pcn-sm-edge-behaviour-05] 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)", December 2010. 7.2. Informative References [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC3175] Baker, F., Iturralde, C. Le Faucher, F., Davie, B., "Aggregation of RSVP for IPv4 and IPv6 Reservations", RFC 3175, 2001. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. Karagiannis, et al. Expires September 02, 2011 [Page 10] Internet-Draft PCN Signaling requirements March 2011 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 Tuebingen Department of Computer Science Chair of Communication Networks Sand 13 Tuebingen 72076 Germany Phone: +49 7071 29 70505 Email: menth@informatik.uni-tuebingen.de Karagiannis, et al. Expires September 02, 2011 [Page 11]