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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 27, 2011) is 4748 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 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: October 27, 2011 K. Chan 5 Huawei Technologies 6 M. Menth 7 University of Tuebingen 8 P. Eardley 9 BT 10 April 27, 2011 12 Requirements for Signaling of (Pre-) Congestion Information in a 13 DiffServ Domain 14 draft-ietf-pcn-signaling-requirements-04 16 Abstract 18 Precongestion notification (PCN) is a means for protecting quality of 19 service for inelastic traffic admitted to a Diffserv domain. The 20 overall PCN architecture is described in RFC 5559. This memo 21 describes the requirements for the signaling applied within the PCN 22 domain: (1) PCN-feedback-information is carried from the PCN-egress- 23 node to the decision point;(2) the decision point may ask the PCN- 24 ingress-node to measure, and report back, the rate of sent PCN-traffic 25 between that PCN-ingress-node and PCN-egress-node. The decision point 26 may be either collocated with the PCN-ingress-node or a centralized 27 node (in the latter case, (2) is not required). The signaling 28 requirements pertain in particular to two edge behaviours, "controlled 29 load (CL)" and "single marking (SM)" [draft-ietf-pcn-cl-edge- 30 behaviour-08], [draft-ietf-pcn-sm-edge-behaviour-05]. 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 October 27, 2011. 49 Copyright Notice 51 Copyright (c) 2010 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 Copyright (c) 2011 IETF Trust and the persons identified as the 55 document authors. All rights reserved. 57 This document is subject to BCP 78 and the IETF Trust's Legal 58 Provisions Relating to IETF Documents 59 (http://trustee.ietf.org/license-info) in effect on the date of 60 publication of this document. Please review these documents 61 carefully, as they describe your rights and restrictions with respect 62 to this document. Code Components extracted from this document must 63 include Simplified BSD License text as described in Section 4.e of 64 the Trust Legal Provisions and are provided without warranty as 65 described in the Simplified BSD License. 67 Requirements Language 69 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 70 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 71 document are to be interpreted as described in RFC 2119 [RFC2119]. 73 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 76 Decision Point(s) . . . . . . . . . . . . . . . . . . . . . . . . 3 77 2.1. Specification of PCN-Flow Identifiers . . . . . . . . . . . 4 78 3. Signaling Requirements for Messages between Decision Point(s) and 79 PCN-Ingress-Nodes . . . . . . . . . . . . . . . . . . . . . . . . 5 80 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 5 81 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 6 82 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 83 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 84 7.1. Normative References . . . . . . . . . . . . . . . . . . . . 6 85 7.2. Informative References . . . . . . . . . . . . . . . . . . . 6 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 88 1. Introduction 90 The main objective of Pre-Congestion Notification (PCN) is to support 91 the quality of service (QoS) of inelastic flows within a Diffserv 92 domain in a simple, scalable, and robust fashion. Two mechanisms 93 are used: admission control and flow termination. Admission control 94 is used to decide whether to admit or block a new flow request while 95 flow termination is used in abnormal circumstances to decide 96 whether to terminate some of the existing flows. To support these 97 two features, the overall rate of PCN-traffic is metered on every 98 link in the domain, and PCN-packets are appropriately marked when 99 certain configured rates are exceeded. These configured rates are 100 below the rate of the link thus providing notification to boundary 101 nodes about overloads before any congestion occurs (hence "pre- 102 congestion" notification). The PCN-egress-nodes measure the rates of 103 differently marked PCN traffic in periodic intervals and report these 104 rates to the decision points for admission control and flow 105 termination, based on which they take their decisions. The decision 106 points may be collocated with the PCN-ingress-nodes or their function 107 may be implemented in a centralized node. 108 For more details see [RFC5559], [draft-ietf-pcn-cl-edge-behaviour-08], 109 [draft-ietf-pcn-sm-edge-behaviour-05]. 111 This memo specifies the requirements on signaling protocols: 112 o to carry reports from a PCN-egress-node to the decision point, 113 o to carry requests, from the decision point to a PCN-ingress-node, 114 that trigger the PCN-ingress-node to measure the PCN-sent-rate, 115 o to carry reports, from a PCN-ingress-node to the decision 116 point. 118 The latter two messages are only needed if the decision point and PCN- 119 ingress-node are not collocated. 121 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 122 Decision Point(s) 124 The PCN-egress-node measures- per ingress-egress-aggregate the rates 125 of differently marked PCN-traffic in regular intervals. The 126 measurement intervals are recommended to take a fixed value between 127 100 ms and 500 ms, see [draft-ietf-pcn-cl-edge-behaviour-08], 128 [draft-ietf-pcn-sm-edge-behaviour-05]. At the end of each measurement 129 interval, the PCN-egress-node calculates the congestion-level-estimate 130 (CLE) based on these quantities. The PCN-egress-node MAY be configured 131 to record a set of identifiers of PCN-flows for which it received 132 excess-traffic-marked packets during the last measurement interval. 133 The latter may be useful to perform flow termination in networks with 134 multipath routing. 136 At the end of each measurement interval, or less frequently if 137 "optional report suppression" is activated, see 138 [draft-ietf-pcn-cl-edge-behaviour-08], [draft-ietf-pcn-sm-edge- 139 behaviour-05], the PCN-egress-node sends a report to the decision 140 point. 142 For the SM edge behaviour, the report MUST contain: 143 o the identifier of the PCN-ingress-node and the identifier of the 144 PCN-egress-node (typically their IP addresses); together they 145 specify the ingress-egress-aggregate to which the report refers, 146 o the rate of not-marked PCN-traffic (NM-rate) in octets/second, 147 o rate of PCN-marked traffic in octets/second, 148 o the congestion-level-estimate, which is a number between zero and 149 one. 151 For the CL edge behaviour, the report MUST contain: 152 o the identifier of the PCN-ingress-node and the identifier of the 153 PCN-egress-node (typically their IP addresses); together they 154 specify the ingress-egress-aggregate to which the report refers, 155 o the rate of threshold-marked PCN traffic (ThM-rate) in 156 octets/second, 157 o rate of excess-traffic-marked traffic (ETM-rate) in octets/second, 158 o the congestion-level-estimate, which is a number between zero and 159 one. 161 The number format and the rate units used by the signalling protocol 162 will limit the maximum rate that PCN can use. 163 If signalling space is tight it might be reasonable to impose a limit, 164 but any such limit may impose unnecessary constraints in future. 166 For both CL and SM edge behaviours, the report MAY also contain: 167 o a set of PCN-flow identifiers (see Section 2.1). 169 The signaling report can either be sent directly to the decision 170 point or it can "piggy-back", i.e., be included within some other 171 message that passes through the PCN-egress-node and then reaches the 172 decision point. 174 Signaling messages SHOULD have a higher priority than data packets to 175 deliver them quickly and to avoid that they are dropped in case of 176 overload. 178 The load generated by the signaling protocol SHOULD be minimized. We 179 give three examples that may help to achieve that goal: 180 o piggy-backing the reports by the PCN-egress-nodes to the decision 181 point(s) onto other signaling messages that are already in place, 182 o reducing the amount of reports to be sent by optional report 183 suppression, 184 o combining reports for different ingress-egress-aggregates in a 185 single message (if they are for the same decision point). 187 As PCN reports are sent regularly, additional reliability mechanisms 188 are not needed. This also holds in the presence of optional report 189 suppression as reports are sent periodically if actions by the 190 decision point(s) are needed, see [draft-ietf-pcn-cl-edge-behaviour- 191 -08], [draft-ietf-pcn-sm-edge-behaviour-05]. 193 2.1 Specification of PCN-Flow Identifiers 195 The representation of a PCN-flow identifier depends on the surrounding 196 environment, e.g., pure IP, MPLS, GMPLS, etc. 198 Examples of such PCN-flow identifier representations can be found in 199 [RFC2205], [RFC3175] [RFC3209], [RFC3473], [RFC4804]. 201 In pure IP networks, the identifier may consist of a subset of the 202 following information: 204 o source IP address; 206 o destination IP address 208 o protocol identifier and higher layer (port) addressing 210 o flow label (typical for IPv6) 212 o SPI field for IPsec encapsulated data 214 o DSCP/TOS field 216 Note, where a PCN-flow consists of a collection of microflows, then 217 the PCN-flow is identified by the PCN-ingress-node's and PCN-egress- 218 node's identifiers (typically their IP addresses), which are already 219 part of the report. 221 3. Signaling Requirements for Messages between Decision Point(s) and 222 PCN-Ingress-Nodes 224 Through request-response signaling between the decision point and PCN- 225 ingress-node, the decision point requests and in response the PCN- 226 ingress-node measures and reports the PCN-sent-rate for a specific 227 ingress-egress-aggregate. Signaling is needed only if the decision 228 point and PCN-ingress-node are not collocated. 230 The request MUST contain: 231 o the identifier of the PCN-ingress-node and the identifier of the 232 PCN-egress-node; together they determine the ingress-egress- 233 aggregate for which the PCN-sent-rate is requested, 234 o the identifier of the decision point that requests the PCN-sent- 235 rate. 237 The report MUST contain: 238 o the PCN-sent-rate in octets/second, 239 o the identifier of the PCN-ingress-node and the identifier of the 240 PCN-egress-node. 242 The request MUST be addressed to the PCN-ingress-node, and the report 243 MUST be addressed to the decision point that requested it. 245 The request and the report SHOULD be sent with high priority and 246 reliably, because they are sent only when flow termination is needed, 247 which is an urgent action. 249 4. Security Considerations 251 [RFC5559] provides a general description of the security 252 considerations for PCN. This memo does not introduce additional 253 security considerations. 255 5. IANA Considerations 257 This memo includes no request to IANA. 259 6. Acknowledgements 261 We would like to acknowledge the members of the PCN working group for 262 the discussions that generated the contents of this memo. 264 7. References 266 7.1. Normative References 268 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 269 Requirement Levels", BCP 14, RFC 2119, March 1997. 271 [RFC5559] Eardley, P., "Pre-Congestion Notification (PCN) 272 Architecture", RFC 5559, June 2009. 274 [draft-ietf-pcn-cl-edge-behaviour-08] T. Taylor, A, Charny, 275 F. Huang, G. Karagiannis, M. Menth, "PCN Boundary Node 276 Behaviour for the Controlled Load (CL) Mode of Operation 277 (Work in progress)", December 2010. 279 [draft-ietf-pcn-sm-edge-behaviour-05] A. Charny, J. Zhang, 280 G. Karagiannis, M. Menth, T. Taylor, "PCN Boundary Node 281 Behaviour for the Single Marking (SM) Mode of Operation 282 (Work in progress)", December 2010. 284 7.2. Informative References 286 [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. 287 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 288 Functional Specification", RFC 2205, September 1997. 289 [RFC3175] Baker, F., Iturralde, C. Le Faucher, F., Davie, B., 290 "Aggregation of RSVP for IPv4 and IPv6 Reservations", 291 RFC 3175, 2001. 293 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 294 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 295 Tunnels", RFC 3209, December 2001. 297 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 298 (GMPLS) Signaling Resource ReserVation Protocol-Traffic 299 Engineering (RSVP-TE) Extensions", RFC 3473, 300 January 2003. 302 [RFC4804] F. Le Faucheur, "Aggregation of Resource ReSerVation 303 Protocol (RSVP) Reservations over MPLS TE/DS-TE Tunnels", 304 RFC 4804, February 2007. 306 Authors' Addresses 308 Georgios Karagiannis 309 University of Twente 310 P.O. Box 217 311 7500 AE Enschede, 312 The Netherlands 313 EMail: g.karagiannis@ewi.utwente.nl 315 Tom Taylor 316 Huawei Technologies 317 1852 Lorraine Ave. 318 Ottawa, Ontario K1H 6Z8 319 Canada 320 Phone: +1 613 680 2675 321 Email: tom111.taylor@bell.net 323 Kwok Ho Chan 324 Huawei Technologies 325 125 Nagog Park 326 Acton, MA 01720 327 USA 328 Email: khchan@huawei.com 330 Michael Menth 331 University of Tuebingen 332 Department of Computer Science 333 Chair of Communication Networks 334 Sand 13 335 72076 Tuebingen 336 Germany 337 Phone: +49 7071 29 70505 338 Email: menth@informatik.uni-tuebingen.de 340 Philip Eardley 341 BT 342 B54/77, Sirius House Adastral Park Martlesham Heath 343 Ipswich, Suffolk IP5 3RE 344 United Kingdom 345 EMail: philip.eardley@bt.com