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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: January 03, 2012 K. Chan 5 Huawei Technologies 6 M. Menth 7 University of Tuebingen 8 P. Eardley 9 BT 10 July 03, 2011 12 Requirements for Signaling of (Pre-) Congestion Information in a 13 DiffServ Domain 14 draft-ietf-pcn-signaling-requirements-07 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-09], 31 [draft-ietf-pcn-sm-edge-behaviour-06]. 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 January 03, 2012. 50 Copyright Notice 52 Copyright (c) 2011 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Requirements Language 67 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 68 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 69 document are to be interpreted as described in RFC 2119 [RFC2119]. 71 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 73 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 74 Decision Point(s) . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2.1. Specification of PCN-Flow Identifiers . . . . . . . . . . . 4 76 3. Signaling Requirements for Messages between Decision Point(s) and 77 PCN-Ingress-Nodes . . . . . . . . . . . . . . . . . . . . . . . . 5 78 4. Security Considerations . . . . . . . . . . . . . . . . . . . . . 5 79 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 6 80 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 81 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 82 7.1. Normative References . . . . . . . . . . . . . . . . . . . . 6 83 7.2. Informative References . . . . . . . . . . . . . . . . . . . 6 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 86 1. Introduction 88 The main objective of Pre-Congestion Notification (PCN) is to support 89 the quality of service (QoS) of inelastic flows within a Diffserv 90 domain in a simple, scalable, and robust fashion. Two mechanisms 91 are used: admission control and flow termination. Admission control 92 is used to decide whether to admit or block a new flow request while 93 flow termination is used in abnormal circumstances to decide 94 whether to terminate some of the existing flows. To support these 95 two features, the overall rate of PCN-traffic is metered on every 96 link in the domain, and PCN-packets are appropriately marked when 97 certain configured rates are exceeded. These configured rates are 98 below the rate of the link thus providing notification to boundary 99 nodes about overloads before any congestion occurs (hence "pre- 100 congestion" notification). The PCN-egress-nodes measure the rates of 101 differently marked PCN traffic in periodic intervals and report these 102 rates to the decision points for admission control and flow 103 termination, based on which they take their decisions. The decision 104 points may be collocated with the PCN-ingress-nodes or their function 105 may be implemented in a centralized node. 106 For more details see [RFC5559], 107 [draft-ietf-pcn-cl-edge-behaviour-09], 108 [draft-ietf-pcn-sm-edge-behaviour-06]. 110 This memo specifies the requirements on signaling protocols: 111 o to carry reports from a PCN-egress-node to the decision point, 112 o to carry requests, from the decision point to a PCN-ingress-node, 113 that trigger the PCN-ingress-node to measure the PCN-sent-rate, 114 o to carry reports, from a PCN-ingress-node to the decision 115 point. 117 The latter two messages are only needed if the decision point and 118 PCN-ingress-node are not collocated. 120 2. Signaling Requirements for Messages from the PCN-Egress-Nodes to 121 Decision Point(s) 123 The PCN-egress-node measures- per ingress-egress-aggregate the rates 124 of differently marked PCN-traffic in regular intervals. The 125 measurement intervals are recommended to take a fixed value between 126 100 ms and 500 ms, see [draft-ietf-pcn-cl-edge-behaviour-09], 127 [draft-ietf-pcn-sm-edge-behaviour-06]. At the end of each measurement 128 interval, the PCN-egress-node calculates the congestion-level- 129 estimate (CLE) based on these quantities. The PCN-egress-node MAY be 130 configured to record a set of identifiers of PCN-flows for which it 131 received excess-traffic-marked packets during the last measurement 132 interval. The latter may be useful to perform flow termination in 133 networks with multipath routing. 135 At the end of each measurement interval, or less frequently if 136 "optional report suppression" is activated, see 138 [draft-ietf-pcn-cl-edge-behaviour-09], [draft-ietf-pcn-sm-edge- 139 behaviour-06], the PCN-egress-node sends a report to the decision 140 point. 142 For the SM edge behaviour, the report MUST contain: 143 o 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 rate of not-marked PCN-traffic (NM-rate) in octets/second, 147 o rate of PCN-marked traffic (PM-rate) in octets/second, 148 o congestion-level-estimate, which is a number between zero and 149 one. 151 For the CL edge behaviour, the report MUST contain: 152 o 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 rate of not-marked PCN-traffic (NM-rate) in octets/second, 156 o rate of threshold-marked PCN traffic (ThM-rate) in 157 octets/second, 158 o rate of excess-traffic-marked traffic (ETM-rate) in octets/second, 159 o congestion-level-estimate, which is a number between zero and 160 one. 162 The number format and the rate units used by the signalling protocol 163 will limit the maximum rate that PCN can use. If signalling space is 164 tight it might be reasonable to impose a limit, but any such limit 165 may impose unnecessary constraints in future. 167 For both CL and SM edge behaviours, the report MAY also contain: 168 o a set of PCN-flow identifiers (see Section 2.1). 170 The signaling report can either be sent directly to the decision 171 point or it can "piggy-back", i.e., be included within some other 172 message that passes through the PCN-egress-node and then reaches the 173 decision point. 175 Signaling messages SHOULD have a higher priority than data packets to 176 deliver them quickly and to avoid that they are dropped in case of 177 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 -09], [draft-ietf-pcn-sm-edge-behaviour-06]. 194 2.1 Specification of PCN-Flow Identifiers 196 The representation of a PCN-flow identifier depends on the 197 surrounding 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 225 PCN-ingress-node, the decision point requests and in response the 226 PCN-ingress-node measures and reports the PCN-sent-rate for a 227 specific ingress-egress-aggregate. Signaling is needed only if the 228 decision 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-09] 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)", June 2011. 279 [draft-ietf-pcn-sm-edge-behaviour-06] 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)", June 2011. 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. 290 [RFC3175] Baker, F., Iturralde, C. Le Faucher, F., Davie, B., 291 "Aggregation of RSVP for IPv4 and IPv6 Reservations", 292 RFC 3175, 2001. 294 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., 295 and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 296 Tunnels", RFC 3209, December 2001. 298 [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching 299 (GMPLS) Signaling Resource ReserVation Protocol-Traffic 300 Engineering (RSVP-TE) Extensions", RFC 3473, 301 January 2003. 303 [RFC4804] F. Le Faucheur, "Aggregation of Resource ReSerVation 304 Protocol (RSVP) Reservations over MPLS TE/DS-TE Tunnels", 305 RFC 4804, February 2007. 307 Authors' Addresses 309 Georgios Karagiannis 310 University of Twente 311 P.O. Box 217 312 7500 AE Enschede, 313 The Netherlands 314 EMail: g.karagiannis@ewi.utwente.nl 316 Tom Taylor 317 Huawei Technologies 318 1852 Lorraine Ave. 319 Ottawa, Ontario K1H 6Z8 320 Canada 321 Phone: +1 613 680 2675 322 Email: tom111.taylor@bell.net 324 Kwok Ho Chan 325 Huawei Technologies 326 125 Nagog Park 327 Acton, MA 01720 328 USA 329 Email: khchan@huawei.com 331 Michael Menth 332 University of Tuebingen 333 Department of Computer Science 334 Chair of Communication Networks 335 Sand 13 336 72076 Tuebingen 337 Germany 338 Phone: +49 7071 29 70505 339 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