idnits 2.17.1 draft-ietf-pcn-sm-edge-behaviour-12.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 1 instance of lines with non-RFC6890-compliant IPv4 addresses in the document. If these are example addresses, they should be changed. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (April 6, 2012) is 4402 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Missing Reference: 'SM-Specific' is mentioned on line 328, but not defined == Missing Reference: 'SM-specific' is mentioned on line 1009, but not defined -- No information found for draft-tsvwg-rsvp-pcn - is the name correct? Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force A. Charny 3 Internet-Draft J. Zhang 4 Intended status: Experimental Cisco Systems 5 Expires: October 8, 2012 G. Karagiannis 6 U. Twente 7 M. Menth 8 University of Tuebingen 9 T. Taylor, Ed. 10 Huawei Technologies 11 April 6, 2012 13 PCN Boundary Node Behaviour for the Single Marking (SM) Mode of 14 Operation 15 draft-ietf-pcn-sm-edge-behaviour-12 17 Abstract 19 Pre-congestion notification (PCN) is a means for protecting the 20 quality of service for inelastic traffic admitted to a Diffserv 21 domain. The overall PCN architecture is described in RFC 5559. This 22 memo is one of a series describing possible boundary node behaviours 23 for a PCN-domain. The behaviour described here is that for a form of 24 measurement-based load control using two PCN marking states, not- 25 marked, and excess-traffic-marked. This behaviour is known 26 informally as the Single Marking (SM) PCN-boundary-node behaviour. 28 Status of this Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at http://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on October 8, 2012. 45 Copyright Notice 47 Copyright (c) 2012 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 64 2. [SM-Specific] Assumed Core Network Behaviour for SM . . . . . 9 65 3. Node Behaviours . . . . . . . . . . . . . . . . . . . . . . . 10 66 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10 67 3.2. Behaviour of the PCN-Egress-Node . . . . . . . . . . . . . 10 68 3.2.1. Data Collection . . . . . . . . . . . . . . . . . . . 10 69 3.2.2. Reporting the PCN Data . . . . . . . . . . . . . . . . 11 70 3.2.3. Optional Report Suppression . . . . . . . . . . . . . 11 71 3.3. Behaviour at the Decision Point . . . . . . . . . . . . . 12 72 3.3.1. Flow Admission . . . . . . . . . . . . . . . . . . . . 12 73 3.3.2. Flow Termination . . . . . . . . . . . . . . . . . . . 13 74 3.3.3. Decision Point Action For Missing 75 PCN-Boundary-Node Reports . . . . . . . . . . . . . . 14 76 3.4. Behaviour of the Ingress Node . . . . . . . . . . . . . . 15 77 3.5. Summary of Timers and Associated Configurable Durations . 16 78 3.5.1. Recommended Values For the Configurable Durations . . 17 79 4. Specification of Diffserv Per-Domain Behaviour . . . . . . . . 18 80 4.1. Applicability . . . . . . . . . . . . . . . . . . . . . . 18 81 4.2. Technical Specification . . . . . . . . . . . . . . . . . 18 82 4.2.1. Classification and Traffic Conditioning . . . . . . . 18 83 4.2.2. PHB Configuration . . . . . . . . . . . . . . . . . . 18 84 4.3. Attributes . . . . . . . . . . . . . . . . . . . . . . . . 19 85 4.4. Parameters . . . . . . . . . . . . . . . . . . . . . . . . 19 86 4.5. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 19 87 4.6. Example Uses . . . . . . . . . . . . . . . . . . . . . . . 19 88 4.7. Environmental Concerns . . . . . . . . . . . . . . . . . . 19 89 4.8. Security Considerations . . . . . . . . . . . . . . . . . 20 90 5. Operational and Management Considerations . . . . . . . . . . 20 91 5.1. Deployment of the SM Edge Behaviour . . . . . . . . . . . 20 92 5.1.1. Selection of Deployment Options and Global 93 Parameters . . . . . . . . . . . . . . . . . . . . . . 20 94 5.1.2. Specification of Node- and Link-Specific Parameters . 21 95 5.1.3. Installation of Parameters and Policies . . . . . . . 22 96 5.1.4. Activation and Verification of All Behaviours . . . . 24 97 5.2. Management Considerations . . . . . . . . . . . . . . . . 24 98 5.2.1. Event Logging In the PCN Domain . . . . . . . . . . . 24 99 5.2.1.1. Logging Loss and Restoration of Contact . . . . . 25 100 5.2.1.2. Logging Flow Termination Events . . . . . . . . . 26 101 5.2.2. Provision and Use of Counters . . . . . . . . . . . . 27 102 6. Security Considerations . . . . . . . . . . . . . . . . . . . 29 103 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 104 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29 105 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 106 9.1. Normative References . . . . . . . . . . . . . . . . . . . 30 107 9.2. Informative References . . . . . . . . . . . . . . . . . . 30 109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 111 1. Introduction 113 The objective of Pre-Congestion Notification (PCN) is to protect the 114 quality of service (QoS) of inelastic flows within a Diffserv domain, 115 in a simple, scalable, and robust fashion. Two mechanisms are used: 116 admission control, to decide whether to admit or block a new flow 117 request, and (in abnormal circumstances) flow termination to decide 118 whether to terminate some of the existing flows. To achieve this, 119 the overall rate of PCN-traffic is metered on every link in the PCN- 120 domain, and PCN-packets are appropriately marked when certain 121 configured rates are exceeded. These configured rates are below the 122 rate of the link thus providing notification to PCN-boundary-nodes 123 about incipient overloads before any congestion occurs (hence the 124 "pre" part of "pre-congestion notification"). The level of marking 125 allows decisions to be made about whether to admit or terminate PCN- 126 flows. For more details see [RFC5559]. 128 This document describes an experimental edge node behaviour to 129 implement PCN in a network. The experiment may be run in a network 130 in which a substantial proportion of the traffic carried is in the 131 form of inelastic flows and where admission control of micro-flows is 132 applied at the edge. For the effects of PCN to be observable, the 133 committed bandwidth (i.e., level of non-best-effort traffic) on at 134 least some links of the network should be near or at link capacity. 135 The amount of effort required to prepare the network for the 136 experiment (see Section 5.1) may constrain the size of network to 137 which it is applied. The purposes of the experiment are: 139 o to validate the specification of the SM edge behaviour; 141 o to evaluate the effectiveness of the SM edge behaviour in 142 preserving quality of service for admitted flows; and 144 o to evaluate PCN's potential for reducing the amount of capital and 145 operational costs in comparison to alternative methods of assuring 146 quality of service. 148 For the first two objectives, the experiment should run long enough 149 for the network to experience sharp peaks of traffic in at least some 150 directions. It would also be desirable to observe PCN performance in 151 the face of failures in the network. A period in the order of a 152 month or two in busy season may be enough. The third objective is 153 more difficult, and could require observation over a period long 154 enough for traffic demand to grow to the point where additional 155 capacity must be provisioned at some points in the network. 157 Section 3 of this document specifies a detailed set of algorithms and 158 procedures used to implement the PCN mechanisms for the SM mode of 159 operation. Since the algorithms depend on specific metering and 160 marking behaviour at the interior nodes, it is also necessary to 161 specify the assumptions made about PCN-interior-node behaviour 162 (Section 2). Finally, because PCN uses DSCP values to carry its 163 markings, a specification of PCN-boundary-node behaviour must include 164 the per domain behaviour (PDB) template specified in [RFC3086], 165 filled out with the appropriate content (Section 4). 167 Note that the terms "block" or "terminate" actually translate to one 168 or more of several possible courses of action, as discussed in 169 Section 3.6 of [RFC5559]. The choice of which action to take for 170 blocked or terminated flows is a matter of local policy. 172 [RFC EDITOR'S NOTE: RFCyyyy is the published version of 173 draft-ietf-pcn-cl-edge-behaviour.] 175 A companion document [RFCyyyy] specifies the Controlled Load (CL) 176 PCN-boundary-node behaviour. This document and [RFCyyyy] have a 177 great deal of text in common. To simplify the task of the reader, 178 the text in the present document that is specific to the SM PCN- 179 boundary-node behaviour is preceded by the phrase: "[SM-specific]". 180 A similar distinction for CL-specific text is made in [RFCyyyy]. 182 1.1. Terminology 184 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 185 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 186 document are to be interpreted as described in [RFC2119]. 188 This document uses the following terms defined in Section 2 of 189 [RFC5559]: 191 o PCN-domain; 193 o PCN-ingress-node; 195 o PCN-egress-node; 197 o PCN-interior-node; 199 o PCN-boundary-node; 201 o PCN-flow; 203 o ingress-egress-aggregate (IEA); 205 o PCN-excess-rate; 206 o PCN-admissible-rate; 208 o PCN-supportable-rate; 210 o PCN-marked; 212 o excess-traffic-marked. 214 It also uses the terms PCN-traffic and PCN-packet, for which the 215 definition is repeated from [RFC5559] because of their importance to 216 the understanding of the text that follows: 218 PCN-traffic, PCN-packets, PCN-BA 219 A PCN-domain carries traffic of different Diffserv behaviour 220 aggregates (BAs) [RFC2474]. The PCN-BA uses the PCN mechanisms to 221 carry PCN-traffic, and the corresponding packets are PCN-packets. 222 The same network will carry traffic of other Diffserv BAs. The 223 PCN-BA is distinguished by a combination of the Diffserv codepoint 224 and the ECN field. 226 This document uses the following term from [RFC5670]: 228 o excess-traffic-meter. 230 To complete the list of borrowed terms, this document reuses the 231 following terms and abbreviations defined in Section 3 of 232 [ID.pcn-3-in-1]: 234 o not-PCN codepoint; 236 o Not-marked (NM) codepoint; 238 o Excess-traffic-marked (ETM) codepoint. 240 This document defines the following additional terms: 242 Decision Point 243 The node that makes the decision about which flows to admit and to 244 terminate. In a given network deployment, this can be the PCN- 245 ingress-node or a centralized control node. In either case, the 246 PCN-ingress-node is the point where the decisions are enforced. 248 NM-rate 249 The rate of not-marked PCN-traffic received at a PCN-egress-node 250 for a given ingress-egress-aggregate in octets per second. For 251 further details see Section 3.2.1. 253 ETM-rate 254 The rate of excess-traffic-marked PCN-traffic received at a PCN- 255 egress-node for a given ingress-egress-aggregate in octets per 256 second. For further details see Section 3.2.1. 258 PCN-sent-rate 259 The rate of PCN-traffic received at a PCN-ingress-node and 260 destined for a given ingress-egress-aggregate in octets per 261 second. For further details see Section 3.4. 263 Congestion level estimate (CLE) 264 The ratio of PCN-marked to total PCN-traffic (measured in octets) 265 received for a given ingress-egress-aggregate during a given 266 measurement period. The CLE is used to derive the PCN-admission- 267 state (Section 3.3.1) and is also used by the report suppression 268 procedure (Section 3.2.3) if report suppression is activated. 270 PCN-admission-state 271 The state ("admit" or "block") derived by the Decision Point for a 272 given ingress-egress-aggregate based on PCN packet marking 273 statistics. The Decision Point decides to admit or block new 274 flows offered to the aggregate based on the current value of the 275 PCN-admission-state. For further details see Section 3.3.1. 277 Sustainable aggregate rate (SAR) 278 The estimated maximum rate of PCN-traffic that can be carried in a 279 given ingress-egress-aggregate at a given moment without risking 280 degradation of quality of service for the admitted flows. The 281 intention is that if the PCN-sent-rate of every ingress-egress- 282 aggregate passing through a given link is limited to its 283 sustainable aggregate rate, the total rate of PCN-traffic flowing 284 through the link will be limited to the PCN-supportable-rate for 285 that link. An estimate of the sustainable aggregate rate for a 286 given ingress-egress-aggregate is derived as part of the flow 287 termination procedure, and is used to determine how much PCN- 288 traffic needs to be terminated. For further details see 289 Section 3.3.2. 291 CLE-reporting-threshold 292 A configurable value against which the CLE is compared as part of 293 the report suppression procedure. For further details, see 294 Section 3.2.3. 296 CLE-limit 297 A configurable value against which the CLE is compared to 298 determine the PCN-admission-state for a given ingress-egress- 299 aggregate. For further details, see Section 3.3.1. 301 T_meas 302 A configurable time interval that defines the measurement period 303 over which the PCN-egress-node collects statistics relating to 304 PCN-traffic marking. At the end of the interval the PCN-egress- 305 node calculates the values NM-rate and ETM-rate as defined above 306 and sends a report to the Decision Point, subject to the operation 307 of the report suppression feature. For further details see 308 Section 3.2. 310 T_maxsuppress 311 A configurable time interval after which the PCN-egress-node MUST 312 send a report to the Decision Point for a given ingress-egress- 313 aggregate regardless of the most recent values of the CLE. This 314 mechanism provides the Decision Point with a periodic confirmation 315 of liveness when report suppression is activated. For further 316 details, see Section 3.2.3. 318 T_fail 319 An interval after which the Decision Point concludes that 320 communication from a given PCN-egress-node has failed if it has 321 received no reports from the PCN-egress-node during that interval. 322 For further details see Section 3.3.3. 324 T_crit 325 A configurable interval used in the calculation of T_fail. For 326 further details see Section 3.3.3. 328 2. [SM-Specific] Assumed Core Network Behaviour for SM 330 This section describes the assumed behaviour for PCN-interior-nodes 331 in the PCN-domain. The SM mode of operation assumes that: 333 o PCN-interior-nodes perform excess-traffic-marking of PCN-packets 334 according to the rules specified in [RFC5670]. 336 o for IP transport, excess-traffic-marking of PCN-packets uses the 337 excess-traffic-marked (ETM) codepoint defined in [ID.pcn-3-in-1]; 338 for MPLS transport, an equivalent marking is used as discussed in 339 [ID.pcn-3-in-1] Appendix C; 341 o on each link the reference rate for the excess-traffic-meter is 342 configured to be equal to the PCN-admissible-rate for the link; 344 o the set of valid codepoint transitions is as shown in Sections 345 5.2.1 and 5.2.3.1 of [ID.pcn-3-in-1]. 347 3. Node Behaviours 349 3.1. Overview 351 This section describes the behaviour of the PCN-ingress-node, PCN- 352 egress-node, and the Decision Point (which MAY be collocated with the 353 PCN-ingress-node). 355 The PCN-egress-node collects the rates of not-marked and excess- 356 traffic-marked PCN-traffic for each ingress-egress-aggregate and 357 reports them to the Decision Point. For a detailed description, see 358 Section 3.2. 360 The PCN-ingress-node enforces flow admission and termination 361 decisions. It also reports the rate of PCN-traffic sent to a given 362 ingress-egress-aggregate when requested by the Decision Point. For 363 details, see Section 3.4. 365 Finally, the Decision Point makes flow admission decisions and 366 selects flows to terminate based on the information provided by the 367 PCN-ingress-node and PCN-egress-node for a given ingress-egress- 368 aggregate. For details, see Section 3.3. 370 Specification of a signaling protocol to report rates to the Decision 371 Point is out of scope of this document. If the PCN-ingress-node is 372 chosen as the Decision Point, [I-D.tsvwg-rsvp-pcn] specifies an 373 appropriate signaling protocol. 375 Section 5.1.2 describes how to derive the filters by means of which 376 PCN-ingress-nodes and PCN-egress-nodes are able to classify incoming 377 packets into ingress-egress-aggregates. 379 3.2. Behaviour of the PCN-Egress-Node 381 3.2.1. Data Collection 383 The PCN-egress-node needs to meter the PCN-traffic it receives in 384 order to calculate the following rates for each ingress-egress- 385 aggregate passing through it. These rates SHOULD be calculated at 386 the end of each measurement period based on the PCN-traffic observed 387 during that measurement period. The duration of a measurement period 388 is equal to the configurable value T_meas. For further information 389 see Section 3.5. 391 o NM-rate: octets per second of PCN-traffic in PCN-packets that are 392 not-marked (i.e., marked with the NM codepoint); 394 o ETM-rate: octets per second of PCN-traffic in PCN-packets that are 395 excess-traffic-marked (i.e., marked with the ETM codepoint). 397 Note: metering the PCN-traffic continuously and using equal-length 398 measurement intervals minimizes the statistical variance 399 introduced by the measurement process itself. On the other hand, 400 the operation of PCN is not affected if the starting and ending 401 times of the measurement intervals for different ingress-egress- 402 aggregates are different. 404 3.2.2. Reporting the PCN Data 406 Unless the report suppression option described in Section 3.2.3 is 407 activated, the PCN-egress-node MUST report the latest values of NM- 408 rate and ETM-rate to the Decision Point each time that it calculates 409 them. 411 3.2.3. Optional Report Suppression 413 Report suppression MUST be provided as a configurable option, along 414 with two configurable parameters, the CLE-reporting-threshold and the 415 maximum report suppression interval T_maxsuppress. The default value 416 of the CLE-reporting-threshold is zero. The CLE-reporting-threshold 417 MUST NOT exceed the CLE-limit configured at the Decision Point. For 418 further information on T_maxsuppress see Section 3.5. 420 If the report suppression option is enabled, the PCN-egress-node MUST 421 apply the following procedure to decide whether to send a report to 422 the Decision Point, rather than sending a report automatically at the 423 end of each measurement interval. 425 1. As well as the quantities NM-rate and ETM-rate, the PCN-egress- 426 node MUST calculate the congestion level estimate (CLE) for each 427 measurement interval. The CLE is computed as: 429 [SM-specific] 430 CLE = ETM-rate / (NM-rate + ETM-rate) 432 if any PCN-traffic was observed, or CLE = 0 if all the rates are 433 zero. 435 2. If the CLE calculated for the latest measurement interval is 436 greater than the CLE-reporting-threshold and/or the CLE 437 calculated for the immediately previous interval was greater than 438 the CLE-reporting-threshold, then the PCN-egress-node MUST send a 439 report to the Decision Point. The contents of the report are 440 described below. 442 The reason for taking into account the CLE of the previous 443 interval is to ensure that the Decision Point gets immediate 444 feedback if the CLE has dropped below the CLE-reporting- 445 threshold. This is essential if the Decision Point is running 446 the flow termination procedure and observing whether (further) 447 flow termination is needed. See Section 3.3.2. 449 3. If an interval T_maxsuppress has elapsed since the last report 450 was sent to the Decision Point, then the PCN-egress-node MUST 451 send a report to the Decision Point regardless of the CLE value. 453 4. If neither of the preceding conditions holds, the PCN-egress-node 454 MUST NOT send a report for the latest measurement interval. 456 Each report sent to the Decision Point when report suppression has 457 been activated MUST contain the values of NM-rate, ETM-rate, and CLE 458 that were calculated for the most recent measurement interval. 460 The above procedure ensures that at least one report is sent per 461 interval (T_maxsuppress + T_meas). This demonstrates to the Decision 462 Point that both the PCN-egress-node and the communication path 463 between that node and the Decision Point are in operation. 465 3.3. Behaviour at the Decision Point 467 Operators can choose to use PCN procedures just for flow admission, 468 or just for flow termination, or for both. Decision Points MUST 469 implement both mechanisms, but configurable options MUST be provided 470 to activate or deactivate PCN-based flow admission and flow 471 termination independently of each other at a given Decision Point. 473 If PCN-based flow termination is enabled but PCN-based flow admission 474 is not, flow termination operates as specified in this document. 476 Logically, some other system of flow admission control is in 477 operation, but the description of such a system is out of scope of 478 this document and depends on local arrangements. 480 3.3.1. Flow Admission 482 The Decision Point determines the PCN-admission-state for a given 483 ingress-egress-aggregate each time it receives a report from the 484 egress node. It makes this determination on the basis of the 485 congestion level estimate (CLE). If the CLE is provided in the 486 egress node report, the Decision Point SHOULD use the reported value. 487 If the CLE was not provided in the report, the Decision Point MUST 488 calculate it based on the other values provided in the report, using 489 the formula: 491 [SM-specific] 492 CLE = ETM-rate / (NM-rate + ETM-rate) 494 if any PCN-traffic was observed, or CLE = 0 if all the rates are 495 zero. 497 The Decision Point MUST compare the reported or calculated CLE to a 498 configurable value, the CLE-limit. If the CLE is less than the CLE- 499 limit, the PCN-admission-state for that aggregate MUST be set to 500 "admit"; otherwise it MUST be set to "block". 502 If the PCN-admission-state for a given ingress-egress-aggregate is 503 "admit", the Decision Point SHOULD allow new flows to be admitted to 504 that aggregate. If the PCN-admission-state for a given ingress- 505 egress-aggregate is "block", the Decision Point SHOULD NOT allow new 506 flows to be admitted to that aggregate. These actions MAY be 507 modified by policy in specific cases, but such policy intervention 508 risks defeating the purpose of using PCN. 510 A performance study of this admission control method is presented in 511 [MeLe12]. 513 3.3.2. Flow Termination 515 [SM-specific] When the PCN-admission-state computed on the basis of 516 the CLE is "block" for the given ingress-egress-aggregate, the 517 Decision Point MUST request the PCN-ingress-node to provide an 518 estimate of the rate (PCN-sent-rate) at which the PCN-ingress-node is 519 receiving PCN-traffic that is destined for the given ingress-egress- 520 aggregate. 522 If the Decision Point is collocated with the PCN-ingress-node, the 523 request and response are internal operations. 525 The Decision Point MUST then wait, for both the requested rate from 526 the PCN-ingress-node and the next report from the PCN-egress-node for 527 the ingress-egress-aggregate concerned. If this next egress node 528 report also includes a non-zero value for the ETM-rate, the Decision 529 Point MUST determine the amount of PCN-traffic to terminate using the 530 following steps: 532 1. [SM-specific] The sustainable aggregate rate (SAR) for the given 533 ingress-egress-aggregate is estimated using the formula: 535 SAR = U * NM-Rate 537 for the latest reported interval, where U is a configurable 538 factor greater than one which is the same for all ingress-egress- 539 aggregates. In effect, the value of the PCN-supportable-rate for 540 each link is approximated by the expression 542 U*PCN-admissible-rate 544 rather than being calculated explicitly. 546 2. The amount of traffic to be terminated is the difference: 548 PCN-sent-rate - SAR, 550 where PCN-sent-rate is the value provided by the PCN-ingress- 551 node. 553 See Section 3.3.3 for a discussion of appropriate actions if the 554 Decision Point fails to receive a timely response to its request for 555 the PCN-sent-rate. 557 If the difference calculated in the second step is positive, the 558 Decision Point SHOULD select PCN-flows to terminate, until it 559 determines that the PCN-traffic admission rate will no longer be 560 greater than the estimated sustainable aggregate rate. If the 561 Decision Point knows the bandwidth required by individual PCN-flows 562 (e.g., from resource signalling used to establish the flows), it MAY 563 choose to complete its selection of PCN-flows to terminate in a 564 single round of decisions. 566 Alternatively, the Decision Point MAY spread flow termination over 567 multiple rounds to avoid over-termination. If this is done, it is 568 RECOMMENDED that enough time elapse between successive rounds of 569 termination to allow the effects of previous rounds to be reflected 570 in the measurements upon which the termination decisions are based. 571 (See [Satoh10] and sections 4.2 and 4.3 of [MeLe10].) 573 In general, the selection of flows for termination MAY be guided by 574 policy. 576 The Decision Point SHOULD log each round of termination as described 577 in Section 5.2.1.2. 579 3.3.3. Decision Point Action For Missing PCN-Boundary-Node Reports 581 The Decision Point SHOULD start a timer t_recvFail when it receives a 582 report from the PCN-egress-node. t_recvFail is reset each time a new 583 report is received from the PCN-egress-node. t_recvFail expires if it 584 reaches the value T_fail. T_fail is calculated according to the 585 following logic: 587 a. T_fail = the configurable duration T_crit, if report suppression 588 is not deployed; 590 b. T_fail = T_crit also if report suppression is deployed and the 591 last report received from the PCN-egress-node contained a CLE 592 value greater than CLE-reporting-threshold (Section 3.2.3); 594 c. T_fail = 3 * T_maxsuppress (Section 3.2.3) if report suppression 595 is deployed and the last report received from the PCN-egress-node 596 contained a CLE value less than or equal to CLE-reporting- 597 threshold. 599 If timer t_recvFail expires for a given PCN-egress-node, the Decision 600 Point SHOULD notify management. A log format is defined for that 601 purpose in Section 5.2.1.1. Other actions depend on local policy, 602 but MAY include blocking of new flows destined for the PCN-egress- 603 node concerned until another report is received from it. Termination 604 of already-admitted flows is also possible, but could be triggered by 605 "Destination unreachable" messages received at the PCN-ingress-node. 607 If a centralized Decision Point sends a request for the estimated 608 value of PCN-sent-rate to a given PCN-ingress-node and fails to 609 receive a response in a reasonable amount of time, the Decision Point 610 SHOULD repeat the request once. [SM-specific] If the second request 611 to the PCN-ingress-node also fails, the Decision Point SHOULD notify 612 management. The log format defined in Section 5.2.1.1 is also 613 suitable for this case. 615 The response timer t_sndFail with upper bound T_crit is specified 616 in Section 3.5. The use of T_crit is an approximation. A more 617 precise limit would be of the order of two round-trip times, plus 618 an allowance for processing at each end, plus an allowance for 619 variance in these values. 621 See Section 3.5 for suggested values of the configurable durations 622 T_crit and T_maxsuppress. 624 3.4. Behaviour of the Ingress Node 626 The PCN-ingress-node MUST provide the estimated current rate of PCN- 627 traffic received at that node and destined for a given ingress- 628 egress-aggregate in octets per second (the PCN-sent-rate) when the 629 Decision Point requests it. The way this rate estimate is derived is 630 a matter of implementation. 632 For example, the rate that the PCN-ingress-node supplies can be 633 based on a quick sample taken at the time the information is 634 required. 636 3.5. Summary of Timers and Associated Configurable Durations 638 Here is a summary of the timers used in the procedures just 639 described: 641 t_meas 643 Where used: PCN-egress-node. 645 Used in procedure: data collection (Section 3.2.1). 647 Incidence: one per ingress-egress-aggregate. 649 Reset: immediately on expiry. 651 Expiry: when it reaches the configurable duration T_meas. 653 Action on expiry: calculate NM-rate and ETM-rate and proceed to 654 the applicable reporting procedure (Section 3.2.2 or 655 Section 3.2.3). 657 t_maxsuppress 659 Where used: PCN-egress-node. 661 Used in procedure: report suppression (Section 3.2.3). 663 Incidence: one per ingress-egress-aggregate. 665 Reset: when the next report is sent, either after expiry or 666 because the CLE has exceeded the reporting threshold. 668 Expiry: when it reaches the configurable duration 669 T_maxsuppress. 671 Action on expiry: send a report to the Decision Point the next 672 time the reporting procedure (Section 3.2.3) is invoked, 673 regardless of the value of CLE. 675 t_recvFail 677 Where used: Decision Point. 679 Used in procedure: failure detection (Section 3.3.3). 681 Incidence: one per ingress-egress-aggregate. 683 Reset: when a report is received for the ingress-egress- 684 aggregate. 686 Expiry: when it reaches the calculated duration T_fail. As 687 described in Section 3.3.3, T_fail is equal either to the 688 configured duration T_crit or to the calculated value 3 * 689 T_maxsuppress, where T_maxsuppress is a configured duration. 691 Action on expiry: notify management, and possibly other 692 actions. 694 t_sndFail 696 Where used: centralized Decision Point. 698 Used in procedure: failure detection (Section 3.3.3). 700 Incidence: only as required, one per outstanding request to a 701 PCN-ingress-node. 703 Started: when a request for the value of PCN-sent-traffic for a 704 given ingress-egress-aggregate is sent to the PCN-ingress-node. 706 Terminated without action: when a response is received before 707 expiry. 709 Expiry: when it reaches the configured duration T_crit. 711 Action on expiry: as described in Section 3.3.3. 713 3.5.1. Recommended Values For the Configurable Durations 715 The timers just described depend on three configurable durations, 716 T_meas, T_maxsuppress, and T_crit. The recommendations given below 717 for the values of these durations are all related to the intended PCN 718 reaction time of 1 to 3 seconds. However, they are based on 719 judgement rather than operational experience or mathematical 720 derivation. 722 The value of T_meas is RECOMMENDED to be of the order of 100 to 500 723 ms to provide a reasonable tradeoff between demands on network 724 resources (PCN-egress-node and Decision Point processing, network 725 bandwidth) and the time taken to react to impending congestion. 727 The value of T_maxsuppress is RECOMMENDED to be on the order of 3 to 728 6 seconds, for similar reasons to those for the choice of T_meas. 730 The value of T_crit SHOULD NOT be less than 3 * T_meas. Otherwise it 731 could cause too many management notifications due to transient 732 conditions in the PCN-egress-node or along the signalling path. A 733 reasonable upper bound on T_crit is in the order of 3 seconds. 735 4. Specification of Diffserv Per-Domain Behaviour 737 This section provides the specification required by [RFC3086] for a 738 per-domain behaviour. 740 4.1. Applicability 742 This section quotes [RFC5559]. 744 The PCN SM boundary node behaviour specified in this document is 745 applicable to inelastic traffic (particularly video and voice) where 746 quality of service for admitted flows is protected primarily by 747 admission control at the ingress to the domain. 749 In exceptional circumstances (e.g., due to rerouting as a result of 750 network failures) already-admitted flows may be terminated to protect 751 the quality of service of the remaining flows. [SM-specific] The 752 performance results in, e.g., [MeLe10], indicate that the SM boundary 753 node behaviour is more likely to terminate too many flows under such 754 circumstances than the CL boundary node behaviour described in 755 [RFCyyyy]. 757 [RFC EDITOR'S NOTE: please replace RFCyyyy above by the reference to 758 the published version of draft-ietf-pcn-cl-edge-behaviour.] 760 4.2. Technical Specification 762 4.2.1. Classification and Traffic Conditioning 764 Packet classification and treatment at the PCN-ingress-node is 765 described in Section 5.1 of [ID.pcn-3-in-1]. 767 PCN packets are further classified as belonging or not belonging to 768 an admitted flow. PCN packets not belonging to an admitted flow are 769 "blocked". (See Section 1 for an understanding of how this term is 770 interpreted.) Packets belonging to an admitted flow are policed to 771 ensure that they adhere to the rate or flowspec that was negotiated 772 during flow admission. 774 4.2.2. PHB Configuration 776 The PCN SM boundary node behaviour is a metering and marking 777 behaviour rather than a scheduling behaviour. As a result, while the 778 encoding uses a single DSCP value, that value can vary from one 779 deployment to another. The PCN working group suggests using 780 admission control for the following service classes (defined in 781 [RFC4594]): 783 o Telephony (EF) 785 o Real-time interactive (CS4) 787 o Broadcast Video (CS3) 789 o Multimedia Conferencing (AF4) 791 For a fuller discussion, see Appendix A of [ID.pcn-3-in-1]. 793 4.3. Attributes 795 The purpose of this per-domain behaviour is to achieve low loss and 796 jitter for the target class of traffic. The design requirement for 797 PCN was that recovery from overloads through the use of flow 798 termination should happen within 1-3 seconds. PCN probably performs 799 better than that. 801 4.4. Parameters 803 The set of parameters that needs to be configured at each PCN-node 804 and at the Decision Point is described in Section 5.1. 806 4.5. Assumptions 808 It is assumed that a specific portion of link capacity has been 809 reserved for PCN-traffic. 811 4.6. Example Uses 813 The PCN SM behaviour may be used to carry real-time traffic, 814 particularly voice and video. 816 4.7. Environmental Concerns 818 The PCN SM per-domain behaviour could theoretically interfere with 819 the use of end-to-end ECN due to reuse of ECN bits for PCN marking. 820 Section 5.1 of [ID.pcn-3-in-1] describes the actions that can be 821 taken to protect ECN signalling. Appendix B of that document 822 provides further discussion of how ECN and PCN can co-exist. 824 4.8. Security Considerations 826 Please see the security considerations in [RFC5559] as well as those 827 in [RFC2474] and [RFC2475]. 829 5. Operational and Management Considerations 831 5.1. Deployment of the SM Edge Behaviour 833 Deployment of the PCN Single Marking edge behaviour requires the 834 following steps: 836 o selection of deployment options and global parameter values; 838 o derivation of per-node and per-link information; 840 o installation, but not activation, of parameters and policies at 841 all of the nodes in the PCN domain; 843 o activation and verification of all behaviours. 845 5.1.1. Selection of Deployment Options and Global Parameters 847 The first set of decisions affects the operation of the network as a 848 whole. To begin with, the operator needs to make basic design 849 decisions such as whether the Decision Point is centralized or 850 collocated with the PCN-ingress-nodes, and whether per-flow and 851 aggregate resource signalling as described in [I-D.tsvwg-rsvp-pcn] is 852 deployed in the network. After that, the operator needs to decide: 854 o whether PCN packets will be forwarded unencapsulated or in tunnels 855 between the PCN-ingress-node and the PCN-egress-node. 856 Encapsulation preserves incoming ECN settings and simplifies the 857 PCN-egress-node's job when it comes to relating incoming packets 858 to specific ingress-egress-aggregates, but lowers the path MTU and 859 imposes the extra labour of encapsulation/decapsulation on the 860 PCN-edge-nodes. 862 o which service classes will be subject to PCN control and what 863 Diffserv code point (DSCP) will be used for each. (See 864 [ID.pcn-3-in-1] Appendix A for advice on this topic.) 866 o the markings to be used at all nodes in the PCN domain to indicate 867 Not-Marked (NM) and Excess-Traffic-Marked (ETM) PCN packets; 869 o The marking rules for re-marking PCN-traffic leaving the PCN 870 domain; 872 o whether PCN-based flow admission is enabled; 874 o whether PCN-based flow termination is enabled. 876 The following parameters affect the operation of PCN itself. The 877 operator needs to choose: 879 o the value of CLE-limit if PCN-based flow admission is enabled. 880 [SM-specific] It is RECOMMENDED that the CLE-limit for SM be set 881 fairly low, in the order of 0.05. 883 o the value of the collection interval T_meas. For a recommended 884 range of values see Section 3.5.1 above. 886 o whether report suppression is to be enabled at the PCN-egress- 887 nodes and if so, the values of CLE-reporting-threshold and 888 T_maxsuppress. It is reasonable to leave CLE-reporting-threshold 889 at its default value (zero, as specified in Section 3.2.3). For a 890 recommended range of values of T_maxsuppress see Section 3.5.1 891 above. 893 o the value of the duration T_crit, which the Decision Point uses in 894 deciding whether communications with a given PCN-edge-node have 895 failed. For a recommended range of values of T_crit see 896 Section 3.5.1 above. 898 o [SM-specific] The factor U that is used in the flow termination 899 procedure (Section 3.3.2). An operational definition for U is 900 given in that section, but it may be thought of as a contingency 901 factor providing a buffer to handle flow peaks above the aggregate 902 levels expected when flows are admitted. A reasonable value for U 903 is between 1.2 and 2. Larger values of U tend to cause more over- 904 termination of traffic during peaks, but raise the average link 905 utilization level. 907 5.1.2. Specification of Node- and Link-Specific Parameters 909 Filters are required at both the PCN-ingress-node and the PCN-egress- 910 node to classify incoming PCN packets by ingress-egress-aggregate. 911 Because of the potential use of multi-path routing in domains 912 upstream of the PCN-domain, it is impossible to do such 913 classification reliably at the PCN-egress-node based on the packet 914 header contents as originally received at the PCN-ingress-node. 915 (Packets with the same header contents could enter the PCN-domain at 916 multiple PCN-ingress-nodes.) As a result, the only way to construct 917 such filters reliably is to tunnel the packets from the PCN-ingress- 918 node to the PCN-egress-node. 920 The PCN-ingress-node needs filters in order to place PCN packets into 921 the right tunnel in the first instance, and also to satisfy requests 922 from the Decision Point for admission rates into specific ingress- 923 egress-aggregates. These filters select the PCN-egress-node, but not 924 necessarily a specific path through the network to that node. As a 925 result, they are likely to be stable even in the face of failures in 926 the network, except when the PCN-egress-node itself becomes 927 unreachable. If all PCN packets will be tunneled, the PCN-ingress- 928 node also needs to know the address of the peer PCN-egress-node 929 associated with each filter. 931 Operators may wish to give some thought to the provisioning of 932 alternate egress points for some or all ingress-egress aggregates in 933 case of failure of the PCN-egress-node. This could require the 934 setting up of standby tunnels to these alternate egress points. 936 Each PCN-egress-node needs filters to classify incoming PCN packets 937 by ingress-egress-aggregate, in order to gather measurements on a 938 per-aggregate basis. If tunneling is used, these filters are 939 constructed on the basis of the identifier of the tunnel from which 940 the incoming packet has emerged (e.g. the source address in the outer 941 header if IP encapsulation is used). The PCN-egress-node also needs 942 to know the address of the Decision Point to which it sends reports 943 for each ingress-egress-aggregate. 945 A centralized Decision Point needs to have the address of the PCN- 946 ingress-node corresponding to each ingress-egress-aggregate. 947 Security considerations require that information also be prepared for 948 a centralized Decision Point and each PCN-edge-node to allow them to 949 authenticate each other. 951 Turning to link-specific parameters, the operator needs to derive a 952 value for the PCN-admissible-rate on each link in the network. The 953 first two paragraphs of Section 5.2.2 of [RFC5559] discuss how these 954 values may be derived. ([SM-specific] Confusingly, "PCN-admissible- 955 rate" in the present context corresponds to "PCN-threshold-rate" in 956 the cited paragraphs.) 958 5.1.3. Installation of Parameters and Policies 960 As discussed in the previous two sections, every PCN node needs to be 961 provisioned with a number of parameters and policies relating to its 962 behaviour in processing incoming packets. The Diffserv MIB [RFC3289] 963 can be useful for this purpose, although it needs to be extended in 964 some cases. This MIB covers packet classification, metering, 965 counting, policing and dropping, and marking. The required 966 extensions specifically include an encapsulation action following re- 967 classification by ingress-egress-aggregate. In addition, the MIB has 968 to be extended to include objects for marking the ECN field in the 969 outer header at the PCN-ingress-node and an extension to the 970 classifiers to include the ECN field at PCN-interior and PCN-egress- 971 nodes. Finally, a new object may need to be defined at the PCN- 972 interior-nodes to represent the packet-size-independent excess- 973 traffic-marking metering algorithm. 975 The value for the PCN-admissible-rate on each link on a node appears 976 as a metering parameter. Operators should take note of the need to 977 deploy excess-traffic meters either on the ingress side or the egress 978 of each interior link, but not both (Appendix B.2 of [RFC5670]. 980 The following additional information has to be configured by other 981 means (e.g., additional MIBs, NETCONF models). 983 At the PCN-egress-node: 985 o the measurement interval T_meas (units of ms, range 50 to 1000); 987 o whether report suppression is to be applied; 989 o if so, the interval T_maxsuppress (units of 100 ms, range 1 to 990 100) and the CLE-reporting-threshold (units of tenths of one 991 percent, range 0 to 1000, default value 0); 993 o the address of the PCN-ingress-node for each ingress-egress- 994 aggregate, if the Decision Point is collocated with the PCN- 995 ingress-node and [I-D.tsvwg-rsvp-pcn] is not deployed. 997 o the address of the centralized Decision Point to which it sends 998 its reports, if there is one. 1000 At the Decision Point: 1002 o whether PCN-based flow admission is enabled; 1004 o whether PCN-based flow termination is enabled. 1006 o the value of CLE-limit (units of tenths of one percent, range 0 to 1007 1000); 1009 o [SM-specific] the value of the factor U used in the flow 1010 termination procedure; 1012 o the value of the interval T_crit (units of 100 ms, range 1 to 1013 100); 1015 o whether report suppression is to be applied; 1017 o if so, the interval T_maxsuppress (units of 100 ms, range 1 to 1018 100) and the CLE-reporting-threshold (units of tenths of one 1019 percent, range 0 to 1000, default value 0). These MUST be the 1020 same values that are provisioned in the PCN-egress-nodes; 1022 o if the Decision Point is centralized, the address of the PCN- 1023 ingress-node (and any other information needed to establish a 1024 security association) for each ingress-egress-aggregate. 1026 Depending on the testing strategy, it may be necessary to install the 1027 new configuration data in stages. This is discussed further below. 1029 5.1.4. Activation and Verification of All Behaviours 1031 It is certainly not within the scope of this document to advise on 1032 testing strategy, which operators undoubtedly have well in hand. 1033 Quite possibly an operator will prefer an incremental approach to 1034 activation and testing. Implementing the PCN marking scheme at PCN- 1035 ingress-nodes, corresponding scheduling behaviour in downstream 1036 nodes, and re-marking at the PCN-egress-nodes is a large enough step 1037 in itself to require thorough testing before going further. 1039 Testing will probably involve the injection of packets at individual 1040 nodes and tracking of how the node processes them. This work can 1041 make use of the counter capabilities included in the Diffserv MIB. 1042 The application of these capabilities to the management of PCN is 1043 discussed in the next section. 1045 5.2. Management Considerations 1047 This section focuses on the use of event logging and the use of 1048 counters supported by the Diffserv MIB [RFC3289] for the various 1049 monitoring tasks involved in management of a PCN network. 1051 5.2.1. Event Logging In the PCN Domain 1053 It is anticipated that event logging using SYSLOG [RFC5424] will be 1054 needed for fault management and potentially for capacity management. 1055 Implementations MUST be capable of generating logs for the following 1056 events: 1058 o detection of loss of contact between a Decision Point and a PCN- 1059 edge-node, as described in Section 3.3.3; 1061 o successful receipt of a report from a PCN-egress-node, following 1062 detection of loss of contact with that node; 1064 o flow termination events. 1066 All of these logs are generated by the Decision Point. There is a 1067 strong likelihood in the first and third cases that the events are 1068 correlated with network failures at a lower level. This has 1069 implications for how often specific event types should be reported, 1070 so as not to contribute unnecessarily to log buffer overflow. 1071 Recommendations on this topic follow for each event report type. 1073 The field names (e.g., HOSTNAME, STRUCTURED-DATA) used in the 1074 following subsections are defined in [RFC5424]. 1076 5.2.1.1. Logging Loss and Restoration of Contact 1078 Section 3.3.3 describes the circumstances under which the Decision 1079 Point may determine that it has lost contact, either with a PCN- 1080 ingress-node or a PCN-egress-node, due to failure to receive an 1081 expected report. Loss of contact with a PCN-ingress-node is a case 1082 primarily applicable when the Decision Point is in a separate node. 1083 However, implementations MAY implement logging in the collocated case 1084 if the implementation is such that non-response to a request from the 1085 Decision Point function can occasionally occur due to processor load 1086 or other reasons. 1088 The log reporting the loss of contact with a PCN-ingress-node or PCN- 1089 egress-node MUST include the following content: 1091 o The HOSTNAME field MUST identify the Decision Point issuing the 1092 log. 1094 o A STRUCTURED-DATA element MUST be present, containing parameters 1095 identifying the node for which an expected report has not been 1096 received and the type of report lost (ingress or egress). It is 1097 RECOMMENDED that the SD-ID for the STRUCTURED-DATA element have 1098 the form "PCNNode" (without the quotes), which has been registered 1099 with IANA. The node identifier PARAM-NAME is RECOMMENDED to be 1100 "ID" (without the quotes). The identifier itself is subject to 1101 the preferences expressed in Section 6.2.4 of [RFC5424] for the 1102 HOSTNAME field. The report type PARAM-NAME is RECOMMENDED to be 1103 "RTyp" (without the quotes). The PARAM-VALUE for the RTyp field 1104 MUST be either "ingr" or "egr". 1106 The following values are also RECOMMENDED for the indicated fields in 1107 this log, subject to local practice: 1109 o PRI initially set to 115, representing a Facility value of (14) 1110 "log alert" and a Severity level of (3) "Error Condition". Note 1111 that loss of contact with a PCN-egress-node implies that no new 1112 flows will be admitted to one or more ingress-egress-aggregates 1113 until contact is restored. The reason a higher severity level 1114 (lower value) is not proposed for the initial log is because any 1115 corrective action would probably be based on alerts at a lower 1116 subsystem level. 1118 o APPNAME set to "PCN" (without the quotes). 1120 o MSGID set to "LOST" (without the quotes). 1122 If contact is not regained with a PCN-egress-node in a reasonable 1123 period of time (say, one minute), the log SHOULD be repeated, this 1124 time with a PRI value of 113, implying a Facility value of (14) "log 1125 alert" and a Severity value of (1) "Alert: action must be taken 1126 immediately". The reasoning is that by this time, any more general 1127 conditions should have been cleared, and the problem lies 1128 specifically with the PCN-egress-node concerned and the PCN 1129 application in particular. 1131 Whenever a loss-of-contact log is generated for a PCN-egress-node, a 1132 log indicating recovery SHOULD be generated when the Decision Point 1133 next receives a report from the node concerned. The log SHOULD have 1134 the same content as just described for the loss-of-contact log, with 1135 the following differences: 1137 o PRI changes to 117, indicating a Facility value of (14) "log 1138 alert" and a Severity of (5) "Notice: normal but significant 1139 condition". 1141 o MSGID changes to "RECVD" (without the quotes). 1143 5.2.1.2. Logging Flow Termination Events 1145 Section 3.3.2 describes the process whereby the Decision Point 1146 decides that flow termination is required for a given ingress-egress- 1147 aggregate, calculates how much flow to terminate, and selects flows 1148 for termination. This section describes a log that SHOULD be 1149 generated each time such an event occurs. (In the case where 1150 termination occurs in multiple rounds, one log SHOULD be generated 1151 per round.) The log may be useful in fault management, to indicate 1152 the service impact of a fault occuring in a lower-level subsystem. 1153 In the absence of network failures, it may also be used as an 1154 indication of an urgent need to review capacity utilization along the 1155 path of the ingress-egress-aggregate concerned. 1157 The log reporting a flow termination event MUST include the following 1158 content: 1160 o The HOSTNAME field MUST identify the Decision Point issuing the 1161 log. 1163 o A STRUCTURED-DATA element MUST be present, containing parameters 1164 identifying the ingress and egress nodes for the ingress-egress- 1165 aggregate concerned, indicating the total amount of flow being 1166 terminated, and giving the number of flows terminated to achieve 1167 that objective. 1169 It is RECOMMENDED that the SD-ID for the STRUCTURED-DATA element 1170 have the form: "PCNTerm" (without the quotes), which has been 1171 registered with IANA. The parameter identifying the ingress node 1172 for the ingress-egress-aggregate is RECOMMENDED to have PARAM-NAME 1173 "IngrID" (without the quotes). This parameter MAY be omitted if 1174 the Decision Point is collocated with that PCN-ingress-node. The 1175 parameter identifying the egress node for the ingress-egress- 1176 aggregate is RECOMMENDED to have PARAM-NAME "EgrID" (without the 1177 quotes). Both identifiers are subject to the preferences 1178 expressed in Section 6.2.4 of [RFC5424] for the HOSTNAME field. 1180 The parameter giving the total amount of flow being terminated is 1181 RECOMMENDED to have PARAM-NAME "TermRate" (without the quotes). 1182 The PARAM-VALUE MUST be the target rate as calculated according to 1183 the procedures of Section 3.3.2, as an integer value in thousands 1184 of octets per second. The parameter giving the number of flows 1185 selected for termination is RECOMMENDED to have PARAM-NAME "FCnt" 1186 (without the quotes). The PARAM-VALUE for this parameter MUST be 1187 an integer, the number of flows selected. 1189 The following values are also RECOMMENDED for the indicated fields in 1190 this log, subject to local practice: 1192 o PRI initially set to 116, representing a Facility value of (14) 1193 "log alert" and a Severity level of (4) "Warning: warning 1194 conditions". 1196 o APPNAME set to "PCN" (without the quotes). 1198 o MSGID set to "TERM" (without the quotes). 1200 5.2.2. Provision and Use of Counters 1202 The Diffserv MIB [RFC3289] allows for the provision of counters along 1203 the various possible processing paths associated with an interface 1204 and flow direction. It is RECOMMENDED that the PCN-nodes be 1205 instrumented as described below. It is assumed that the cumulative 1206 counts so obtained will be collected periodically for use in 1207 debugging, fault management, and capacity management. 1209 PCN-ingress-nodes SHOULD provide the following counts for each 1210 ingress-egress-aggregate. Since the Diffserv MIB installs counters 1211 by interface and direction, aggregation of counts over multiple 1212 interfaces may be necessary to obtain total counts by ingress-egress- 1213 aggregate. It is expected that such aggregation will be performed by 1214 a central system rather than at the PCN-ingress-node. 1216 o total PCN packets and octets received for that ingress-egress- 1217 aggregate but dropped; 1219 o total PCN packets and octets admitted to that aggregate. 1221 PCN-interior-nodes SHOULD provide the following counts for each 1222 interface, noting that a given packet MUST NOT be counted more than 1223 once as it passes through the node: 1225 o total PCN packets and octets dropped; 1227 o total PCN packets and octets forwarded without re-marking; 1229 o total PCN packets and octets re-marked to Excess-Traffic-Marked. 1231 PCN-egress-nodes SHOULD provide the following counts for each 1232 ingress-egress-aggregate. As with the PCN-ingress-node, so with the 1233 PCN-egress-node it is expected that any necessary aggregation over 1234 multiple interfaces will be done by a central system. 1236 o total Not-Marked PCN packets and octets received; 1238 o total Excess-Traffic-Marked PCN packets and octets received. 1240 The following continuously cumulative counters SHOULD be provided as 1241 indicated, but require new MIBs to be defined. If the Decision Point 1242 is not collocated with the PCN-ingress-node, the latter SHOULD 1243 provide a count of the number of requests for PCN-sent-rate received 1244 from the Decision Point and the number of responses returned to the 1245 Decision Point. The PCN-egress-node SHOULD provide a count of the 1246 number of reports sent to each Decision Point. Each Decision Point 1247 SHOULD provide the following: 1249 o total number of requests for PCN-sent-rate sent to each PCN- 1250 ingress-node with which it is not collocated; 1252 o total number of reports received from each PCN-egress-node; 1254 o total number of loss-of-contact events detected for each PCN- 1255 boundary-node; 1257 o total cumulative duration of "block" state in hundreds of 1258 milliseconds for each ingress-egress-aggregate; 1260 o total number of rounds of flow termination exercised for each 1261 ingress-egress-aggregate. 1263 6. Security Considerations 1265 [RFC5559] provides a general description of the security 1266 considerations for PCN. This memo introduces one new consideration, 1267 related to the use of a centralized Decision Point. The Decision 1268 Point itself is a trusted entity. However, its use implies the 1269 existence of an interface on the PCN-ingress-node through which 1270 communication of policy decisions takes place. That interface is a 1271 point of vulnerability which must be protected from denial of service 1272 attacks. 1274 7. IANA Considerations 1276 This memo includes no request to IANA. 1278 8. Acknowledgements 1280 Ruediger Geib, Philip Eardley, and Bob Briscoe have helped to shape 1281 the present document with their comments. Toby Moncaster gave a 1282 careful review to get it into shape for Working Group Last Call. 1284 Amongst the authors, Michael Menth deserves special mention for his 1285 constant and careful attention to both the technical content of this 1286 document and the manner in which it was expressed. 1288 David Harrington's careful AD review resulted not only in necessary 1289 changes throughout the document, but also the addition of the 1290 operations and management considerations (Section 5). 1292 Finally, reviews by Joel Halpern and Brian Carpenter helped to 1293 clarify how ingress-egress-aggregates are distinguished (Joel) and 1294 handling of packets that cannot be carried successfully as PCN- 1295 packets (Brian). They also made other suggestions to improve the 1296 document, as did Stephen Farrell, Sean Turner, and Pete Resnick. 1298 9. References 1299 9.1. Normative References 1301 [ID.pcn-3-in-1] 1302 Briscoe, B., Moncaster, T., and M. Menth, "Encoding 3 PCN- 1303 States in the IP header using a single DSCP", March 2012. 1305 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1306 Requirement Levels", BCP 14, RFC 2119, March 1997. 1308 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1309 "Definition of the Differentiated Services Field (DS 1310 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1311 December 1998. 1313 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 1314 and W. Weiss, "An Architecture for Differentiated 1315 Services", RFC 2475, December 1998. 1317 [RFC3086] Nichols, K. and B. Carpenter, "Definition of 1318 Differentiated Services Per Domain Behaviors and Rules for 1319 their Specification", RFC 3086, April 2001. 1321 [RFC3289] Baker, F., Chan, K., and A. Smith, "Management Information 1322 Base for the Differentiated Services Architecture", 1323 RFC 3289, May 2002. 1325 [RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009. 1327 [RFC5559] Eardley, P., "Pre-Congestion Notification (PCN) 1328 Architecture", RFC 5559, June 2009. 1330 [RFC5670] Eardley, P., "Metering and Marking Behaviour of PCN- 1331 Nodes", RFC 5670, November 2009. 1333 9.2. Informative References 1335 [I-D.tsvwg-rsvp-pcn] 1336 Karagiannis, G. and A. Bhargava, "Generic Aggregation of 1337 Resource ReSerVation Protocol (RSVP) for IPv4 And IPv6 1338 Reservations over PCN domains (Work in progress)", 1339 July 2011. 1341 [MeLe10] Menth, M. and F. Lehrieder, "PCN-Based Measured Rate 1342 Termination", Computer Networks Journal (Elsevier) vol. 1343 54, no. 13, pages 2099 - 2116, September 2010. 1345 [MeLe12] Menth, M. and F. Lehrieder, "Performance of PCN-Based 1346 Admission Control under Challenging Conditions, IEEE/ACM 1347 Transactions on Networking, vol. 20, no. 2", April 2012. 1349 [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration 1350 Guidelines for DiffServ Service Classes", RFC 4594, 1351 August 2006. 1353 [RFCyyyy] Charny, A., Karagiannis, G., Menth, M., Huang, F., and T. 1354 Taylor, "PCN Boundary Node Behaviour for the Controlled 1355 Load (CL) Mode of Operation (Work in progress)", 1356 February 2012. 1358 [Satoh10] Satoh, D. and H. Ueno, ""Cause and Countermeasure of 1359 Overtermination for PCN-Based Flow Termination", 1360 Proceedings of IEEE Symposium on Computers and 1361 Communications (ISCC '10), pp. 155-161, Riccione, Italy", 1362 June 2010. 1364 Authors' Addresses 1366 Anna Charny 1367 Cisco Systems 1368 USA 1370 Email: anna@mwsm.com 1372 Xinyan (Joy) Zhang 1373 Cisco Systems 1374 300 Apollo Drive 1375 Chelmsford, MA 01824 1376 USA 1378 Email: joyzhang@cisco.com 1380 Georgios Karagiannis 1381 U. Twente 1383 Phone: 1384 Email: karagian@cs.utwente.nl 1385 Michael Menth 1386 University of Tuebingen 1387 Sand 13 1388 Tuebingen D-72076 1389 Germany 1391 Phone: +49-7071-2970505 1392 Email: menth@informatik.uni-tuebingen.de 1394 Tom Taylor (editor) 1395 Huawei Technologies 1396 Ottawa, Ontario 1397 Canada 1399 Email: tom.taylor.stds@gmail.com