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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: December 15, 2011 K. Chan 5 Huawei Technologies 6 M. Menth 7 University of Tuebingen 8 P. Eardley 9 BT 10 June 15, 2011 12 Requirements for Signaling of (Pre-) Congestion Information in a 13 DiffServ Domain 14 draft-ietf-pcn-signaling-requirements-05 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- 25 traffic between that PCN-ingress-node and PCN-egress-node. The 26 decision point may be either collocated with the PCN-ingress-node or 27 a centralized node (in the latter case, (2) is not required). The 28 signaling requirements pertain in particular to two edge behaviours, 29 "controlled load (CL)" and "single marking (SM)" 30 [draft-ietf-pcn-cl-edge- behaviour-08], 31 [draft-ietf-pcn-sm-edge-behaviour-05]. 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on December 15, 2011. 50 Copyright Notice 52 Copyright (c) 2010 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 Copyright (c) 2011 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Requirements Language 70 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 71 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 72 document are to be interpreted as described in RFC 2119 [RFC2119]. 74 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 76 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 77 Decision Point(s) . . . . . . . . . . . . . . . . . . . . . . . . 3 78 2.1. Specification of PCN-Flow Identifiers . . . . . . . . . . . 4 79 3. Signaling Requirements for Messages between Decision Point(s) and 80 PCN-Ingress-Nodes . . . . . . . . . . . . . . . . . . . . . . . . 5 81 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 5 82 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 6 83 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 84 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 85 7.1. Normative References . . . . . . . . . . . . . . . . . . . . 6 86 7.2. Informative References . . . . . . . . . . . . . . . . . . . 6 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 89 1. Introduction 91 The main objective of Pre-Congestion Notification (PCN) is to support 92 the quality of service (QoS) of inelastic flows within a Diffserv 93 domain in a simple, scalable, and robust fashion. Two mechanisms 94 are used: admission control and flow termination. Admission control 95 is used to decide whether to admit or block a new flow request while 96 flow termination is used in abnormal circumstances to decide 97 whether to terminate some of the existing flows. To support these 98 two features, the overall rate of PCN-traffic is metered on every 99 link in the domain, and PCN-packets are appropriately marked when 100 certain configured rates are exceeded. These configured rates are 101 below the rate of the link thus providing notification to boundary 102 nodes about overloads before any congestion occurs (hence "pre- 103 congestion" notification). The PCN-egress-nodes measure the rates of 104 differently marked PCN traffic in periodic intervals and report these 105 rates to the decision points for admission control and flow 106 termination, based on which they take their decisions. The decision 107 points may be collocated with the PCN-ingress-nodes or their function 108 may be implemented in a centralized node. 109 For more details see [RFC5559], 110 [draft-ietf-pcn-cl-edge-behaviour-08], 111 [draft-ietf-pcn-sm-edge-behaviour-05]. 113 This memo specifies the requirements on signaling protocols: 114 o to carry reports from a PCN-egress-node to the decision point, 115 o to carry requests, from the decision point to a PCN-ingress-node, 116 that trigger the PCN-ingress-node to measure the PCN-sent-rate, 117 o to carry reports, from a PCN-ingress-node to the decision 118 point. 120 The latter two messages are only needed if the decision point and 121 PCN-ingress-node are not collocated. 123 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 124 Decision Point(s) 126 The PCN-egress-node measures- per ingress-egress-aggregate the rates 127 of differently marked PCN-traffic in regular intervals. The 128 measurement intervals are recommended to take a fixed value between 129 100 ms and 500 ms, see [draft-ietf-pcn-cl-edge-behaviour-08], 130 [draft-ietf-pcn-sm-edge-behaviour-05]. At the end of each measurement 131 interval, the PCN-egress-node calculates the congestion-level- 132 estimate (CLE) based on these quantities. The PCN-egress-node MAY be 133 configured to record a set of identifiers of PCN-flows for which it 134 received excess-traffic-marked packets during the last measurement 135 interval. The latter may be useful to perform flow termination in 136 networks with multipath routing. 138 At the end of each measurement interval, or less frequently if 139 "optional report suppression" is activated, see 141 [draft-ietf-pcn-cl-edge-behaviour-08], [draft-ietf-pcn-sm-edge- 142 behaviour-05], the PCN-egress-node sends a report to the decision 143 point. 145 For the SM edge behaviour, the report MUST contain: 146 o the identifier of the PCN-ingress-node and the identifier of the 147 PCN-egress-node (typically their IP addresses); together they 148 specify the ingress-egress-aggregate to which the report refers, 149 o the rate of not-marked PCN-traffic (NM-rate) in octets/second, 150 o rate of PCN-marked traffic in octets/second, 151 o the congestion-level-estimate, which is a number between zero and 152 one. 154 For the CL edge behaviour, the report MUST contain: 155 o the identifier of the PCN-ingress-node and the identifier of the 156 PCN-egress-node (typically their IP addresses); together they 157 specify the ingress-egress-aggregate to which the report refers, 158 o the rate of threshold-marked PCN traffic (ThM-rate) in 159 octets/second, 160 o rate of excess-traffic-marked traffic (ETM-rate) in octets/second, 161 o the congestion-level-estimate, which is a number between zero and 162 one. 164 The number format and the rate units used by the signalling protocol 165 will limit the maximum rate that PCN can use. If signalling space is 166 tight it might be reasonable to impose a limit, but any such limit 167 may impose unnecessary constraints in future. 169 For both CL and SM edge behaviours, the report MAY also contain: 170 o a set of PCN-flow identifiers (see Section 2.1). 172 The signaling report can either be sent directly to the decision 173 point or it can "piggy-back", i.e., be included within some other 174 message that passes through the PCN-egress-node and then reaches the 175 decision point. 177 Signaling messages SHOULD have a higher priority than data packets to 178 deliver them quickly and to avoid that they are dropped in case of 179 overload. 181 The load generated by the signaling protocol SHOULD be minimized. We 182 give three examples that may help to achieve that goal: 183 o piggy-backing the reports by the PCN-egress-nodes to the decision 184 point(s) onto other signaling messages that are already in place, 185 o reducing the amount of reports to be sent by optional report 186 suppression, 187 o combining reports for different ingress-egress-aggregates in a 188 single message (if they are for the same decision point). 190 As PCN reports are sent regularly, additional reliability mechanisms 191 are not needed. This also holds in the presence of optional report 192 suppression as reports are sent periodically if actions by the 193 decision point(s) are needed, see [draft-ietf-pcn-cl-edge-behaviour- 194 -08], [draft-ietf-pcn-sm-edge-behaviour-05]. 196 2.1 Specification of PCN-Flow Identifiers 198 The representation of a PCN-flow identifier depends on the 199 surrounding environment, e.g., pure IP, MPLS, GMPLS, etc. 200 Examples of such PCN-flow identifier representations can be found in 201 [RFC2205], [RFC3175] [RFC3209], [RFC3473], [RFC4804]. 203 In pure IP networks, the identifier may consist of a subset of the 204 following information: 206 o source IP address; 208 o destination IP address 210 o protocol identifier and higher layer (port) addressing 212 o flow label (typical for IPv6) 214 o SPI field for IPsec encapsulated data 216 o DSCP/TOS field 218 Note, where a PCN-flow consists of a collection of microflows, then 219 the PCN-flow is identified by the PCN-ingress-node's and PCN-egress- 220 node's identifiers (typically their IP addresses), which are already 221 part of the report. 223 3. Signaling Requirements for Messages between Decision Point(s) and 224 PCN-Ingress-Nodes 226 Through request-response signaling between the decision point and 227 PCN-ingress-node, the decision point requests and in response the 228 PCN-ingress-node measures and reports the PCN-sent-rate for a 229 specific ingress-egress-aggregate. Signaling is needed only if the 230 decision point and PCN-ingress-node are not collocated. 232 The request MUST contain: 233 o the identifier of the PCN-ingress-node and the identifier of the 234 PCN-egress-node; together they determine the ingress-egress- 235 aggregate for which the PCN-sent-rate is requested, 236 o the identifier of the decision point that requests the PCN-sent- 237 rate. 239 The report MUST contain: 240 o the PCN-sent-rate in octets/second, 241 o the identifier of the PCN-ingress-node and the identifier of the 242 PCN-egress-node. 244 The request MUST be addressed to the PCN-ingress-node, and the report 245 MUST be addressed to the decision point that requested it. 247 The request and the report SHOULD be sent with high priority and 248 reliably, because they are sent only when flow termination is needed, 249 which is an urgent action. 251 4. Security Considerations 253 [RFC5559] provides a general description of the security 254 considerations for PCN. This memo does not introduce additional 255 security considerations. 257 5. IANA Considerations 259 This memo includes no request to IANA. 261 6. Acknowledgements 263 We would like to acknowledge the members of the PCN working group for 264 the discussions that generated the contents of this memo. 266 7. References 268 7.1. Normative References 270 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 271 Requirement Levels", BCP 14, RFC 2119, March 1997. 273 [RFC5559] Eardley, P., "Pre-Congestion Notification (PCN) 274 Architecture", RFC 5559, June 2009. 276 [draft-ietf-pcn-cl-edge-behaviour-08] T. Taylor, A, Charny, 277 F. Huang, G. Karagiannis, M. Menth, "PCN Boundary Node 278 Behaviour for the Controlled Load (CL) Mode of Operation 279 (Work in progress)", December 2010. 281 [draft-ietf-pcn-sm-edge-behaviour-05] A. Charny, J. Zhang, 282 G. Karagiannis, M. Menth, T. Taylor, "PCN Boundary Node 283 Behaviour for the Single Marking (SM) Mode of Operation 284 (Work in progress)", December 2010. 286 7.2. Informative References 288 [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. 289 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 290 Functional Specification", RFC 2205, September 1997. 292 [RFC3175] Baker, F., Iturralde, C. Le Faucher, F., Davie, B., 293 "Aggregation of RSVP for IPv4 and IPv6 Reservations", 294 RFC 3175, 2001. 296 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 297 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 298 Tunnels", RFC 3209, December 2001. 300 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 301 (GMPLS) Signaling Resource ReserVation Protocol-Traffic 302 Engineering (RSVP-TE) Extensions", RFC 3473, 303 January 2003. 305 [RFC4804] F. Le Faucheur, "Aggregation of Resource ReSerVation 306 Protocol (RSVP) Reservations over MPLS TE/DS-TE Tunnels", 307 RFC 4804, February 2007. 309 Authors' Addresses 311 Georgios Karagiannis 312 University of Twente 313 P.O. Box 217 314 7500 AE Enschede, 315 The Netherlands 316 EMail: g.karagiannis@ewi.utwente.nl 318 Tom Taylor 319 Huawei Technologies 320 1852 Lorraine Ave. 321 Ottawa, Ontario K1H 6Z8 322 Canada 323 Phone: +1 613 680 2675 324 Email: tom111.taylor@bell.net 326 Kwok Ho Chan 327 Huawei Technologies 328 125 Nagog Park 329 Acton, MA 01720 330 USA 331 Email: khchan@huawei.com 333 Michael Menth 334 University of Tuebingen 335 Department of Computer Science 336 Chair of Communication Networks 337 Sand 13 338 72076 Tuebingen 339 Germany 340 Phone: +49 7071 29 70505 341 Email: menth@informatik.uni-tuebingen.de 342 Philip Eardley 343 BT 344 B54/77, Sirius House Adastral Park Martlesham Heath 345 Ipswich, Suffolk IP5 3RE 346 United Kingdom 347 EMail: philip.eardley@bt.com