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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force G. Karagiannis 2 Internet-Draft University of Twente 3 Intended status: Informational T. Taylor 4 Expires: August 08, 2012 Huawei 5 K. Chan 6 Consultant 7 M. Menth 8 University of Tuebingen 9 P. Eardley 10 BT 11 February 08, 2012 13 Requirements for Signaling of (Pre-) Congestion Information in a 14 DiffServ Domain 15 draft-ietf-pcn-signaling-requirements-08 17 Abstract 19 Precongestion notification (PCN) is a means for protecting quality of 20 service for inelastic traffic admitted to a Diffserv domain. The 21 overall PCN architecture is described in RFC 5559. This memo 22 describes the requirements for the signaling applied within the PCN 23 domain: (1) PCN-feedback-information is carried from the PCN-egress- 24 node to the decision point;(2) the decision point may ask the PCN- 25 ingress-node to measure, and report back, the rate of sent PCN- 26 traffic between that PCN-ingress-node and PCN-egress-node. The 27 decision point may be either collocated with the PCN-ingress-node or 28 a centralized node (in the first case, (2) is not required). The 29 signaling requirements pertain in particular to two edge behaviors, 30 "controlled load (CL)" and "single marking (SM)". 32 Status of this Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at http://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on August 08, 2012. 49 Copyright Notice 51 Copyright (c) 2012 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Requirements Language 66 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 67 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 68 document are to be interpreted as described in RFC 2119 [RFC2119]. 70 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 73 Decision Point(s) . . . . . . . . . . . . . . . . . . . . . . . . 3 74 3. Signaling Requirements for Messages between Decision Point(s) and 75 PCN-Ingress-Nodes . . . . . . . . . . . . . . . . . . . . . . . . 5 76 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 5 77 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 6 78 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6 79 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 80 7.1. Normative References . . . . . . . . . . . . . . . . . . . . 6 81 7.2. Informative References . . . . . . . . . . . . . . . . . . . 6 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 84 1. Introduction 86 The main objective of Pre-Congestion Notification (PCN) is to support 87 the quality of service (QoS) of inelastic flows within a Diffserv 88 domain in a simple, scalable, and robust fashion. Two mechanisms 89 are used: admission control and flow termination. Admission control 90 is used to decide whether to admit or block a new flow request while 91 flow termination is used in abnormal circumstances to decide 92 whether to terminate some of the existing flows. To support these 93 two features, the overall rate of PCN-traffic is metered on every 94 link in the domain, and PCN-packets are appropriately marked when 95 certain configured rates are exceeded. These configured rates are 96 below the rate of the link thus providing notification to boundary 97 nodes about overloads before any congestion occurs (hence "pre- 98 congestion" notification). The PCN-egress-nodes measure the rates of 99 differently marked PCN traffic in periodic intervals and report these 100 rates to the decision points for admission control and flow 101 termination, based on which they take their decisions. The decision 102 points may be collocated with the PCN-ingress-nodes or their function 103 may be implemented in a centralized node. 104 For more details see [RFC5559], 105 [draft-ietf-pcn-cl-edge-behaviour-11], 106 [draft-ietf-pcn-sm-edge-behaviour-08]. 108 This memo specifies the requirements on signaling protocols: 109 o to carry reports from a PCN-egress-node to the decision point, 110 o to carry requests, from the decision point to a PCN-ingress-node, 111 that trigger the PCN-ingress-node to measure the PCN-sent-rate, 112 o to carry reports, from a PCN-ingress-node to the decision 113 point. 115 The latter two messages are only needed if the decision point and 116 PCN-ingress-node are not collocated. 118 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 119 Decision Point(s) 121 The PCN-egress-node measures per ingress-egress-aggregate the rates 122 of differently marked PCN-traffic in regular intervals. The 123 measurement intervals are recommended to take a fixed value between 124 100 ms and 500 ms, see [draft-ietf-pcn-cl-edge-behaviour-11], 125 [draft-ietf-pcn-sm-edge-behaviour-08]. At the end of each measurement 126 interval, the PCN-egress-node calculates the congestion-level- 127 estimate (CLE) based on these quantities. 129 The PCN-egress-node MAY be configured to record a set of identifiers 130 of PCN-flows for which it received excess-traffic-marked packets 131 during the last measurement interval. The latter may be useful to 132 perform flow termination in networks with multipath routing. 134 At the end of each measurement interval, or less frequently if 135 "optional report suppression" is activated, see 137 [draft-ietf-pcn-cl-edge-behaviour-11], [draft-ietf-pcn-sm-edge- 138 behaviour-08], the PCN-egress-node sends a report to the decision 139 point. 141 For the SM edge behavior, the report MUST contain: 142 o identifier of the PCN-ingress-node and the identifier of the 143 PCN-egress-node (typically their IP addresses); together they 144 specify the ingress-egress-aggregate to which the report refers, 145 o rate of not-marked PCN-traffic (NM-rate) in octets/second, 146 o rate of PCN-marked traffic (PM-rate) in octets/second, 148 For the CL edge behavior, the report MUST contain: 149 o identifier of the PCN-ingress-node and the identifier of the 150 PCN-egress-node (typically their IP addresses); together they 151 specify the ingress-egress-aggregate to which the report refers, 152 o rate of not-marked PCN-traffic (NM-rate) in octets/second, 153 o rate of threshold-marked PCN traffic (ThM-rate) in 154 octets/second, 155 o rate of excess-traffic-marked traffic (ETM-rate) in octets/second, 157 The number format and the rate units used by the signaling protocol 158 will limit the maximum rate that PCN can use. If signaling space is 159 tight it might be reasonable to impose a limit, but any such limit 160 may impose unnecessary constraints in future. 162 The signaling report can either be sent directly to the decision 163 point or it can "piggy-back", i.e., be included within some other 164 message that passes through the PCN-egress-node and then reaches the 165 decision point. 167 As described in [draft-ietf-pcn-cl-edge-behaviour-11], PCN reports 168 from the PCN-egress-node to the decision point may contain flow 169 identifiers for individual flows within an ingress-egress- 170 aggregate that have recently experienced excess-marking. Hence, 171 the PCN report messages used by the PCN CL edge behavior MUST be 172 capable of carrying sequences of octet strings constituting such 173 identifiers." 175 Signaling messages SHOULD have a higher priority and a lower drop 176 precedence than PCN-packets, see [RFC5559], to deliver them quickly 177 and to avoid that they are dropped in case of overload. 179 The load generated by the signaling protocol SHOULD be minimized. We 180 give three examples that may help to achieve that goal: 181 o piggy-backing the reports by the PCN-egress-nodes to the decision 182 point(s) onto other signaling messages that are already in place, 183 o reducing the amount of reports to be sent by optional report 184 suppression, 185 o combining reports for different ingress-egress-aggregates in a 186 single message (if they are for the same decision point). 188 As PCN reports are sent regularly, additional reliability mechanisms 189 are not needed. This also holds in the presence of optional report 190 suppression as reports are sent periodically if actions by the 191 decision point(s) are needed, see [draft-ietf-pcn-cl-edge-behaviour- 192 -11], [draft-ietf-pcn-sm-edge-behaviour-08]. 194 3. Signaling Requirements for Messages between Decision Point(s) and 195 PCN-Ingress-Nodes 197 Through request-response signaling between the decision point and 198 PCN-ingress-node, the decision point requests and in response the 199 PCN-ingress-node measures and reports the PCN-sent-rate for a 200 specific ingress-egress-aggregate. Signaling is needed only if the 201 decision point and PCN-ingress-node are not collocated. 203 The request MUST contain: 204 o the identifier of the PCN-ingress-node and the identifier of the 205 PCN-egress-node; together they determine the ingress-egress- 206 aggregate for which the PCN-sent-rate is requested, 207 o the identifier of the decision point that requests the PCN-sent- 208 rate. 210 The report MUST contain: 211 o the PCN-sent-rate in octets/second, 212 o the identifier of the PCN-ingress-node and the identifier of the 213 PCN-egress-node. 215 The request MUST be addressed to the PCN-ingress-node, and the report 216 MUST be addressed to the decision point that requested it. 218 The request and the report SHOULD be sent with high priority, a lower 219 drop precedence than PCN-packets, and reliably, because they are sent 220 only when flow termination is needed, which is an urgent action. 222 Note that a complete system description for a PCN domain with 223 centralized Decision Point includes the signaling from Decision Point 224 to the PCN-ingress-nodes to control flow admission and termination. 225 However, this is a known problem whose solutions were given by, 226 for example, [RFC3084] or [RFC5431], and it lies outside the scope of 227 the present document. 229 4. Security Considerations 231 [RFC5559] provides a general description of the security 232 considerations for PCN. This memo relies on the security related 233 requirements on the PCN signaling, provided in [RFC5559]. In 234 particular, the signaling between the PCN-boundary-nodes must be 235 protected from attacks. For example, the recipient needs to 236 validate that the message is indeed from the node that claims to have 237 sent it. Possible measures include digest authentication and 238 protection against replay and man-in-the-middle attacks. 240 For the generic aggregate RSVP protocol, specifically, additional 241 protection methods against security attacks are described in 242 [RFC4860]. 244 5. IANA Considerations 246 This memo includes no request to IANA. 248 6. Acknowledgments 250 We would like to acknowledge the members of the PCN working group for 251 the discussions that produced the contents of this memo. 253 7. References 255 7.1. Normative References 257 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 258 Requirement Levels", BCP 14, RFC 2119, March 1997. 260 [RFC5559] P., Eardley, "Pre-Congestion Notification (PCN) 261 Architecture", RFC 5559, June 2009. 263 [draft-ietf-pcn-cl-edge-behaviour-11] T. Taylor, A, Charny, 264 F. Huang, G. Karagiannis, M. Menth, "PCN Boundary Node 265 Behaviour for the Controlled Load (CL) Mode of Operation 266 (Work in progress)", December 2011. 268 [draft-ietf-pcn-sm-edge-behaviour-08] A. Charny, J. Zhang, 269 G. Karagiannis, M. Menth, T. Taylor, "PCN Boundary Node 270 Behaviour for the Single Marking (SM) Mode of Operation 271 (Work in progress)", December 2011. 273 7.2. Informative References 275 [RFC3084] K. Chan, J. Seligson, D. Durham, S. Gai, K. McCloghrie, S. 276 Herzog, F. Reichmeyer, R. Yavatkar, A. Smith, "COPS Usage 277 for Policy Provisioning (COPS-PR)", RFC 3084, March 2001. 279 [RFC4860] F. Le Faucheur, B. Davie, P. Bose, C. Christou, M. 280 Davenport, "Generic Aggregate Resource ReSerVation 281 Protocol (RSVP) Reservations", RFC 4860, May 2007. 283 [RFC5431] D. Sun, "Diameter ITU-T Rw Policy Enforcement Interface 284 Application", RFC 5431, March 2009. 286 Authors' Addresses 288 Georgios Karagiannis 289 University of Twente 290 P.O. Box 217 291 7500 AE Enschede, 292 The Netherlands 293 EMail: g.karagiannis@utwente.nl 295 Tom Taylor 296 Huawei Technologies 297 1852 Lorraine Ave. 298 Ottawa, Ontario K1H 6Z8 299 Canada 300 Phone: +1 613 680 2675 301 Email: tom.taylor.stds@gmail.com 303 Kwok Ho Chan 304 Consultant 306 Email: khchan.work@gmail.com 308 Michael Menth 309 University of Tuebingen 310 Department of Computer Science 311 Chair of Communication Networks 312 Sand 13 313 72076 Tuebingen 314 Germany 315 Phone: +49 7071 29 70505 316 Email: menth@informatik.uni-tuebingen.de 318 Philip Eardley 319 BT 320 B54/77, Sirius House Adastral Park Martlesham Heath 321 Ipswich, Suffolk IP5 3RE 322 United Kingdom 323 EMail: philip.eardley@bt.com