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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'TODO' is mentioned on line 965, but not defined == Missing Reference: 'OPTIONAL' is mentioned on line 662, but not defined ** Downref: Normative reference to an Informational RFC: RFC 5693 Summary: 3 errors (**), 0 flaws (~~), 9 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Randriamasy 3 Internet-Draft Nokia Bell Labs 4 Intended status: Standards Track R. Yang 5 Expires: December 13, 2018 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 June 11, 2018 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-04 17 Abstract 19 The goal of Application-Layer Traffic Optimization (ALTO) is to 20 bridge the gap between network and applications by provisioning 21 network related information in order to allow applications to make 22 network informed decisions. The present draft extends the ALTO cost 23 information so as to broaden the decision possibilities of 24 applications to not only decide 'where' to connect to, but also 25 'when'. This is useful to applications that need to schedule their 26 data transfers and connections and have a degree of freedom to do so. 27 ALTO guidance to schedule application traffic can also efficiently 28 help for load balancing and resources efficiency. Besides, the ALTO 29 Cost Calendar allows to schedule the ALTO requests themselves and 30 thus to save a number of ALTO transactions. 32 This draft proposes new capabilities and attributes on filtered cost 33 maps and endpoint cost maps enabling an ALTO Server to provide "Cost 34 Calendars". These capabilities are applicable to ALTO metrics with 35 time-varying values. With ALTO Cost Calendars, an ALTO Server 36 exposes ALTO cost values in JSON arrays where each value corresponds 37 to a given time interval. The time intervals as well as other 38 Calendar attributes are specified in the IRD and ALTO Server 39 responses. 41 Requirements Language 43 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 44 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 45 document are to be interpreted as described in RFC 2119 [RFC2119]. 47 Status of This Memo 49 This Internet-Draft is submitted in full conformance with the 50 provisions of BCP 78 and BCP 79. 52 Internet-Drafts are working documents of the Internet Engineering 53 Task Force (IETF). Note that other groups may also distribute 54 working documents as Internet-Drafts. The list of current Internet- 55 Drafts is at https://datatracker.ietf.org/drafts/current/. 57 Internet-Drafts are draft documents valid for a maximum of six months 58 and may be updated, replaced, or obsoleted by other documents at any 59 time. It is inappropriate to use Internet-Drafts as reference 60 material or to cite them other than as "work in progress." 62 This Internet-Draft will expire on December 13, 2018. 64 Copyright Notice 66 Copyright (c) 2018 IETF Trust and the persons identified as the 67 document authors. All rights reserved. 69 This document is subject to BCP 78 and the IETF Trust's Legal 70 Provisions Relating to IETF Documents 71 (https://trustee.ietf.org/license-info) in effect on the date of 72 publication of this document. Please review these documents 73 carefully, as they describe your rights and restrictions with respect 74 to this document. Code Components extracted from this document must 75 include Simplified BSD License text as described in Section 4.e of 76 the Trust Legal Provisions and are provided without warranty as 77 described in the Simplified BSD License. 79 Table of Contents 81 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 82 2. Overview of ALTO Cost Calendars . . . . . . . . . . . . . . . 4 83 2.1. ALTO Cost Calendar information features . . . . . . . . . 5 84 2.2. ALTO Calendar design characteristics . . . . . . . . . . 6 85 2.2.1. ALTO Cost Calendar for all cost modes . . . . . . . . 6 86 2.2.2. Compatibility with legacy ALTO Clients . . . . . . . 7 87 3. ALTO Calendar specification: IRD extensions . . . . . . . . . 7 88 3.1. Calendar attributes in the IRD resources capabilities . . 7 89 3.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 9 90 3.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 9 91 4. ALTO Calendar specification: Service Information Resources . 12 92 4.1. Calendar extensions for filtered cost maps . . . . . . . 12 93 4.1.1. Calendar extensions in Filtered Cost Map requests . . 13 94 4.1.2. Calendar extensions in Filtered Cost Map responses . 13 95 4.1.3. Use case and example: FCM with a bandwidth Calendar . 15 96 4.2. Calendar extensions in the Endpoint Cost Service . . . . 18 97 4.2.1. Calendar specific input in Endpoint Cost requests . 18 98 4.2.2. Calendar attributes in the Endpoint Cost response . . 18 99 4.2.3. Use case and example: ECS with a routingcost Calendar 19 100 4.2.4. Use case and example: ECS with a multi-cost calendar 101 for routingcost and latency . . . . . . . . . . . . . 22 102 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 103 5.1. Information for IANA on proposed Cost Types . . . . . . . 24 104 5.2. Information for IANA on proposed Endpoint Properties . . 24 105 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24 106 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 107 7.1. Normative References . . . . . . . . . . . . . . . . . . 24 108 7.2. Informative References . . . . . . . . . . . . . . . . . 25 109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 111 1. Introduction 113 IETF is currently standardizing the ALTO protocol which aims at 114 providing guidance to overlay applications needing to select one or 115 several hosts from a set of candidates able to provide a desired 116 resource. This guidance is based on parameters that affect 117 performance and efficiency of the data transmission between the hosts 118 such as the topological distance. The goal of ALTO is to improve the 119 Quality of Experience (QoE) in the application while optimizing 120 resource usage in the underlying network infrastructure. 122 The ALTO protocol in [RFC7285] specifies a network map which defines 123 groupings of endpoints in provider-defined network regions (called 124 PIDs). The Cost Map Service, Endpoint Cost Service (ECS) and 125 Endpoint Ranking Service then provide ISP-defined costs and rankings 126 for connections among the specified endpoints and PIDs and thus 127 incentives for application clients to connect to ISP preferred 128 locations, e.g. to reduce their costs. ALTO intentionally avoids 129 provisioning realtime information as explained in the ALTO Problem 130 Statement [RFC5693] and ALTO Requirements [RFC5693].Thus the current 131 Cost Map and Endpoint Cost Service are providing, for a given Cost 132 Type, exactly one path cost value. Applications have to query one of 133 these two services to retrieve the currently valid cost values. They 134 therefore need to plan their ALTO information requests according to 135 their own estimation of the frequency of cost value change. 137 With [RFC7285], an ALTO client should interpret the returned costs as 138 those at the query moment. However, Network costs can fluctuate, 139 e.g. due to diurnal patterns of traffic demand or planned events such 140 as network maintenance, holidays or highly publicized events. 141 Providing network costs for only the current time thus may not be 142 sufficient, in particular for applications that can schedule their 143 traffic in a span of time, for example by deferring backup to night 144 during traffic trough. 146 In case the ALTO Cost value changes are predictable over a certain 147 period of time and the application does not require immediate data 148 transfer, it can save time to get the whole set of cost values over 149 this period in one single ALTO response. Using this set to schedule 150 data transfers allows optimizing the network resources usage and QoE. 151 ALTO Clients and Servers can also minimize their workload by reducing 152 and accordingly scheduling their data exchanges. 154 This document extends RFC7285 to allow an ALTO server to provide 155 network costs for a given duration of time. A sequence of network 156 costs across a time span for a given pair of network locations is 157 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 158 Endpoint Cost Service are extended to provide Cost Calendars. In 159 addition to this functional ALTO enhancement, we expect to further 160 gain on storage and on the wire data exchange by gathering multiple 161 Cost Values for one Cost Type into one single ALTO Server response. 163 In this draft an "ALTO Cost Calendar" is specified by information 164 resources capabilities that are applicable to time-sensitive ALTO 165 metrics. An ALTO Cost Calendar exposes ALTO Cost Values in JSON 166 arrays where each value corresponds to a given time interval. The 167 time intervals as well as other Calendar attributes are specified in 168 the IRD and in the Server response to allow the ALTO Client to 169 interpret the received ALTO values. Last, the proposed extensions 170 for ALTO Calendars are applicable to any Cost Mode and they ensure 171 backwards compatibility with legacy ALTO clients. 173 In the rest of this document, Section 2 provides the design 174 characteristics. Sections 3 and 4 define the formal specifications 175 for the IRD and the information resources. Section 5 provides non- 176 normative use cases to illustrate the usage of cost calendars. IANA 177 considerations and security considerations will be completed in 178 further versions. 180 2. Overview of ALTO Cost Calendars 182 An ALTO Cost calendar provided by the ALTO Server provides 2 183 information items: 185 o an array of values for a given metric, where each value 186 corresponds to a time interval, where the value array can 187 sometimes be a cyclic pattern that repeats a certain number of 188 times. 190 o attributes describing the time scope of the calendar such as the 191 size and number of the intervals and the date of the starting 192 point of the calendar, allowing an ALTO Client to properly 193 interpret the values. 195 An ALTO Cost Calendar can be used like a "time table" to figure out 196 the best time to schedule data transfers and also to proactively 197 manage application traffic given predictable events such as flash 198 crowds, traffic intensive holidays and network maintenance. It may 199 be viewed as a synthetic abstraction of real measurements that can be 200 historic or be a prediction for upcoming time periods. 202 Most likely, the ALTO Cost Calendar would be used for the Endpoint 203 Cost Service, assuming that a limited set of feasible Endpoints for a 204 non-real time application is already identified, that they do not 205 need to be accessed immediately and that their access can be 206 scheduled within a given time period. The Filtered Cost Map Service 207 is also applicable as long as the size of the Map allows it. 209 2.1. ALTO Cost Calendar information features 211 The Calendar attributes are provided in the IRD and in ALTO Server 212 responses. The IRD announces attributes with dateless values in its 213 information resources capabilities, where as attributes with time 214 dependent values are provided in the "meta" of Server responses. The 215 ALTO Cost Calendar attributes provide the following information: 217 o attributes to interpret the time scope of the Calendar value 218 array: 220 * generic time zone, 222 * applicable time interval size for each calendar value: 223 combining a number and a time unit to reflect for example: 1 224 hour, 2 minutes, 10 seconds, 1 week, 1 month, 226 * duration of the Calendar: e.g. the number of intervals provided 227 in the calendar. 229 o "calendar-start-date": specifying when the calendar starts, that 230 is to which date the first value of the cost calendar is 231 applicable. 233 o "repeated": an optional attribute indicating for how many 234 iterations the provided calendar will have the same values. The 235 server may use it to allow the client to schedule its next request 236 and thus save its own workload by avoiding to process useless 237 requests. 239 2.2. ALTO Calendar design characteristics 241 The protocol extension placeholders for an ALTO Calendar are: the 242 IRD, the ALTO requests and responses for Cost calendars. 244 Extensions are designed to be light and ensure backwards 245 compatibility with base protocol ALTO Clients and with other 246 extensions. It uses section 8.3.7 "Parsing of Unknown Fields" of 247 RFC7285 that writes: "Extensions may include additional fields within 248 JSON objects defined in this document. ALTO implementations MUST 249 ignore unknown fields when processing ALTO messages." 251 The calendar-specific capabilities are integrated in the information 252 resources of the IRD and in the "meta" member of ALTO responses to 253 Cost Calendars requests. A calendar and its capabilities are 254 associated with a given information resource and within this 255 information resource with a given cost type. This design has several 256 advantages: 258 o it does not introduce a new mode, 260 o it does not introduce new media types, 262 o it allows an ALTO Server to offer calendar capabilities on a cost 263 type, with attributes values adapted to each information resource. 265 The Applicable Calendared information resources are: 267 o the Filtered Cost Map, 269 o the Endpoint Cost Map. 271 The ALTO Server can choose in which frequency it provides cost 272 Calendars to ALTO Clients. It may either provide calendar updates 273 starting at the request date, or carefully schedule its updates so as 274 to take profit from a potential repetition/periodicity of calendar 275 values. 277 2.2.1. ALTO Cost Calendar for all cost modes 279 ALTO Calendars are well-suited for values encoded in the "numerical" 280 mode. Actually, Calendars can also represent metrics in other modes 281 and having considered as time-varying values. For example, types of 282 Cost values such as JSONBool can also be expressed as calendars, as 283 their value may be 'true' or 'false' depending on given time periods 284 or likewise, values represented by strings, such as "medium", "high", 285 "low", "blue", "open" . 287 Note also that a Calendar is suitable as well for time-varying 288 metrics provided in the "ordinal" mode, if these values are time- 289 varying and their update is carefully managed by the ALTO Server. 291 2.2.2. Compatibility with legacy ALTO Clients 293 The ALTO protocol extensions for Cost Calendars have been defined so 294 as to ensure that Calendar capable ALTO Servers can provide legacy 295 ALTO Clients with legacy information resources as well. That is a 296 legacy ALTO Client can request resources and receive responses as 297 specified in RFC7285. 299 A Calendar-aware ALTO Server MUST implement the base protocol 300 specified in RFC7285. 302 When a metric is available as a calendar, it MUST be available as a 303 single value as well. 305 For compatibility with legacy ALTO Clients specified in RFC7285, 306 calendared information resources are not applicable for full cost 307 maps for the following reason: a legacy ALTO client would receive a 308 calendared cost map via an HTTP 'GET' command. As specified in 309 section 8.3.7 of RFC7285, it will ignore the Calendar Attributes 310 indicated in the "meta" of the responses. Therefore, lacking 311 information on calendar attributes, it will not be able to correctly 312 interpret and process the values of the received array of calendar 313 cost values. 315 Therefore, calendared information resources MUST be requested via the 316 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 317 method. 319 3. ALTO Calendar specification: IRD extensions 321 The Calendar attributes in the IRD information resources capabilities 322 carry constant dateless values. A calendar is associated with an 323 information resource rather than a cost type. For example, a Server 324 can provide a "routingcost" calendar for the Filtered Cost Map 325 Service at a granularity of one day and a "routingcost" calendar for 326 the Endpoint Cost service at a finer granularity but for a limited 327 number of endpoints. 329 3.1. Calendar attributes in the IRD resources capabilities 331 When for an applicable resource, an ALTO Server provides a Cost 332 Calendar for a given Cost Type, it MUST indicate this in the IRD 333 capabilities of this resource, by an object of type 334 'CalendarAttributes', associated with this Cost Type and specified 335 below. 337 The capabilities of a Calendar-aware information resource entry have 338 a member named "calendar-attributes" which is an array of objects of 339 type CalendarAttributes. It is necessary to use an array because of 340 resources such as Filtered Cost Map and Endpoint Cost Map, for which 341 the member "cost-type-names" is an array of 1 or more values. 343 A member "calendar-attributes" MUST appear only once for each 344 applicable cost type name of a resource entry. If "calendar- 345 attributes" are specified several times for a same "cost-type-name" 346 in the capabilities of a resource entry, the ALTO client SHOULD 347 ignore any additional occurrence of "calendar-attributes", for this 348 cost type name. 350 An ALTO Client should assume that the time interval size specified in 351 the IRD is the smallest possible one that the ALTO Server can 352 provide. The Client can aggregate cost values on its own if it needs 353 a larger granularity. 355 CalendarAttributes calendar-attributes <1..*>; 357 object{ 358 JSONString cost-type-names <1..*>; 359 JSONString time-interval-size; 360 JSONNumber number-of-intervals; 361 } CalendarAttributes; 363 o "cost-type-names": 365 * An array of one or more elements indicating the cost-type-names 366 in the IRD entry to which the capabilities apply. 368 o "time-interval-size": 370 * is the duration of an ALTO calendar time interval. A "time- 371 interval-size" value contains 2 entities separated by exactly 372 one whitespace: a JSONNumber and a string representing a time 373 unit and taking values in {second, minute, hour, day, week, 374 month, year}. Example values are: "5 minute" , "2 hour", 375 meaning that each calendar value applies on a time interval 376 that lasts respectively 5 minutes and 2 hours. 378 o "number-of-intervals": 380 * the integer number of values of the cost calendar array, at 381 least equal to 1. 383 - Attribute "cost-type-name" , if used, provides a better readability 384 to the calendar attributes specified in the IRD and avoids confusion 385 with calendar attributes of other cost-types. 387 - Multiplying Attributes 'time-interval-size' and 'number-of- 388 intervals' provides the duration of the provided calendar. For 389 example an ALTO Server may provide a calendar for ALTO values 390 changing every 'time-interval-size' equal to 5 minutes. If 'number- 391 of-intervals' has the value 12, then the duration of the provided 392 calendar is "1 hour". 394 3.2. Calendars in a delegate IRD 396 One option to clarify IRD resources is that a "root" ALTO Server 397 implementing base protocol resources delegates "specialized" 398 information resources such as the ones providing Cost Calendars to 399 another ALTO Server running in a subdomain specified with its URI in 400 the "root" ALTO Server. This option is described in Section 9.2.4 401 "Delegation using IRDs" of RFC7285. 403 This document provides an example, where a "root" ALTO Server runs in 404 a domain called "alto.example.com". It delegates the announcement of 405 Calendars capabilities to an ALTO Server running in a subdomain 406 called "custom.alto.example.com". The location of the "delegate 407 Calendar IRD" is assumed to be indicated in the "root" IRD by the 408 resource entry: "custom-calendared-resources". 410 Another advantage is that some Cost Types for some resources may be 411 more advantageous as Cost Calendars and it makes few sense to get 412 them as a single value. For example, Cost Types with predictable and 413 frequently changing values, calendared in short time intervals such 414 as a minute. 416 3.3. Example IRD with ALTO Cost Calendars 418 The cost types in this example are either specified in the base ALTO 419 protocol or may be specified in other drafts see 420 [draft-ietf-alto-performance-metrics] or defined in this draft for 421 illustrative purposes. In this example, the available cost metrics 422 are indicated in the "meta" field by cost type names "num- 423 routingcost", "num-latency", "num-pathbandwidth" and "string-quality- 424 status". Metrics "routingcost", "latency" and "bandwidthscore" are 425 available in the "numerical" Cost Mode. Metric "quality-status" is 426 available in the "string" Cost Mode. 428 The example IRD includes 2 particular URIs providing calendars: 430 o "http://custom.alto.example.com/calendar/costmap/filtered": a 431 filtered cost map in which calendar capabilities are indicated for 432 cost type names: "num-routingcost", "num-pathbandwidth" and 433 "string-service-status", 435 o "http://custom.alto.example.com/calendar/endpointcost/lookup": an 436 endpoint cost map in which calendar capabilities are indicated for 437 cost type names: "num-routingcost", "num-latency", "num- 438 pathbandwidth", "string-service-status". 440 The design of the Calendar capabilities allows that some calendars on 441 a cost type name are available in several information resources with 442 different Calendar Attributes. This is the case for calendars on 443 "num-routingcost", "num-pathbandwidth" and "string-service-status" , 444 available in both the Filtered Cost map and Endpoint Cost Service, 445 but with different time interval sizes for "num-pathbandwidth" and 446 "string-service-status". 448 GET /calendars-directory HTTP/1.1 449 Host: custom.alto.example.com 450 Accept: application/alto-directory+json,application/alto-error+json 451 --------------- 453 HTTP/1.1 200 OK 454 Content-Length: [TODO] 455 Content-Type: application/alto-directory+json 457 { 458 "meta" : { 459 "cost-types": { 460 "num-routingcost": { 461 "cost-mode" : "numerical", 462 "cost-metric" : "routingcost" 463 }, 464 "num-latency": { 465 "cost-mode" : "numerical", 466 "cost-metric": "latency" 467 }, 468 "num-pathbandwidth": { 469 "cost-mode" : "numerical", 470 "cost-metric": "bandwidthscore", 471 }, 472 "string-qual-status": { 473 "cost-mode" : "string", 474 "cost-metric": "quality-status", 475 } 476 ... other meta ... 477 }, 479 "resources" : { 480 "filtered-cost-map-calendar" : { 481 "uri" : "http://custom.alto.example.com/calendar/costmap/filtered", 482 "media-type" : "application/alto-costmap+json", 483 "accepts" : "application/alto-costmapfilter+json", 484 "capabilities" : { 485 "cost-constraints" : true, 486 "cost-type-names" : [ "num-routingcost", "num-pathbandwidth", 487 "string-service-status" ], 488 "calendar-attributes" : [ 489 {"cost-type-names" : [ "num-routingcost", "num-pathbandwidth" ], 490 "time-interval-size" : "1 hour", 491 "number-of-intervals" : 24 492 }, 493 {"cost-type-names" : [ "string-service-status" ], 494 "time-interval-size" : "30 minute", 495 "number-of-intervals" : 48 496 } 497 ] // end calendar-attributes 498 "uses": [ "my-default-network-map" ] 499 } 500 }, 502 "endpoint-cost-calendar-map" : { 503 "uri" : "http://custom.alto.example.com/calendar/endpointcost/lookup", 504 "media-type" : "application/alto-endpointcost+json", 505 "accepts" : "application/alto-endpointcostparams+json", 506 "capabilities" : { 507 "cost-constraints" : true, 508 "cost-type-names" : [ "num-routingcost", "num-latency", 509 "num-pathbandwidth", "string-service-status" ], 510 "calendar-attributes" : [ 511 {"cost-type-names" : [ "num-routingcost" ], 512 "time-interval-size" : "1 hour", 513 "number-of-intervals" : 24 514 }, 515 {"cost-type-names" : [ "num-latency" ], 516 "time-interval-size" : "5 minute", 517 "number-of-intervals" : 12 518 }, 519 {"cost-type-names" : [ "num-pathbandwidth" ], 520 "time-interval-size" : "1 minute", 521 "number-of-intervals" : 60 522 }, 523 {"cost-type-names" : [ "string-service-status" ], 524 "time-interval-size" : "2 minute", 525 "number-of-intervals" : 30 526 } 528 ] // Calendar attributes 529 } // ECM capab 530 } //info resource N 531 } // ressources 533 In this example IRD, for the Filtered Cost map Service: 535 o the Calendar for 'num-routingcost' and 'num-pathbandwidth' is an 536 array of 24 values each provided on a time interval lasting 1 537 hour. 539 o the Calendar for "string-service-status": "is an array of 48 540 values each provided on a time interval lasting 30 minutes. 542 For the Endpoint Cost service: 544 o the Calendar for 'num-routingcost': is an array of 24 values each 545 provided on a time interval lasting 1 hour. 547 o the Calendar for 'latency': is an array of 12 values each provided 548 on a time interval lasting 5 minutes. 550 o the Calendar for 'num-pathbandwidth': is an array of 60 values 551 each provided on a time interval lasting 1 minute. 553 o the Calendar for "string-service-status": "is an array of 30 554 values each provided on a time interval lasting 2 minutes. 556 4. ALTO Calendar specification: Service Information Resources 558 This section documents the individual information resources defined 559 to provide the Calendared information services defined in this 560 document. 562 The reference time zone for the provided time values is GMT because 563 the option chosen to express the time format is the HTTP header 564 fields format: 566 Date: Tue, 15 Nov 2014 08:12:31 GMT 568 4.1. Calendar extensions for filtered cost maps 570 A legacy ALTO client requests and gets Filtered Cost Map responses as 571 specified in RFC7285. 573 4.1.1. Calendar extensions in Filtered Cost Map requests 575 The input parameters of a "legacy" request for a filtered cost map, 576 defined by object ReqFilteredCostMap in section 11.3.2 of RFC7285, 577 are augmented with one additional member. 579 A Calendar-aware ALTO client requesting a Calendar on a given Cost 580 Type for a filtered cost map resource having Calendar capabilities 581 MUST add the following field to its input parameters: 583 JSONBoolean calendared<1..*>; 585 This field is an array of 1 to N boolean values, where N is the 586 number of requested metrics. Each boolean value indicates whether or 587 not the ALTO Server should provide the values for this Cost Type as a 588 calendar. The array MUST contain exactly N boolean values, otherwise 589 the server returns an error. 591 This field SHOULD NOT be specified if no member "calendar-attributes" 592 is specified in this information resource. 594 If a value of field 'calendared' is 'true' for a cost type name for 595 which no calendar attributes have been specified: a Calendar-aware 596 Server will return a response with a single cost value as specified 597 in RFC 7285. 599 If this field is not present, it MUST be assumed to have only values 600 equal to 'false'. 602 A Calendar-aware ALTO client supporting single cost type values, as 603 specified in RFC7285, MUST provide an array of 1 element: 605 "calendared" : [true]; 607 A Calendar-aware ALTO client that is also Multi-Cost aware MUST 608 provide an array of N values set to 'true' or 'false', depending 609 whether it wants the applicable Cost Type values as a single or 610 calendared value. 612 4.1.2. Calendar extensions in Filtered Cost Map responses 614 The calendared costs are JSONArrays instead of JSONNumbers for the 615 legacy ALTO implementation. All arrays have a number of values equal 616 to 'number-of-intervals'. 618 The "meta" field of a Calendared Filtered Cost Map response MUST 619 include at least: 621 o if the ALTO Client supports cost values for one Cost Type at a 622 time only: the "meta" fields specified in RFC 7285 for these 623 information service responses: 625 * "dependent-vtags ", 627 * "cost-type" field. 629 o if the ALTO Client supports cost values for several Cost Types at 630 a time, as specified in [RFC8189] : the "meta" fields specified in 631 [RFC8189] for these information service responses: 633 * "dependent-vtags ", 635 * "cost-type" field with value set to '{}', for backwards 636 compatibility with RFC7285. 638 * "multi-cost-types" field. 640 o If the client request does not provide member "calendared" or if 641 it provides it with a value equal to 'false', for all the 642 requested Cost Types, then the ALTO Server response is exactly as 643 specified in RFC 7285 [RFC7285] and [RFC8189]. 645 o If the value of member "calendared" is equal to 'false' for a 646 given requested Cost Type, the ALTO Server must return, for these 647 Cost Types, a single cost value as specified in RFC 7285. 649 In addition, the "meta" field of a Calendared Filtered Cost map 650 response MUST include the member "calendar-response-attributes" for 651 the requested information resource, together with the values provided 652 by the ALTO Server for these attributes. This member is an array of 653 objects of type "CalendarResponseAttributes", defined as follows: 655 CalendarResponseAttributes calendar-response-attributes <1..*>; 657 object{ 658 [JSONString cost-type-names <1..*>]; 659 JSONString calendar-start-time; 660 JSONString time-interval-size; 661 JSONNumber number-of-intervals; 662 [JSONNumber repeated;] [OPTIONAL] 663 } CalendarResponseAttributes; 665 Object CalendarResponseAttributes has the following attributes: 667 o "cost-type-names": member indicating the cost-type-names to which 668 the capabilities apply. This field MUST appear in responses to 669 Multi-Cost ALTO requests. 671 o "calendar-start-time": indicates the date at which the first value 672 of the calendar applies. By default, the value provided for the 673 "calendar-start-time" attribute SHOULD be no later than the 674 request date. 676 o "time-interval-size": as specified in section "Calendar attributes 677 in the IRD resources capabilities", 679 o "number-of-intervals": as specified in section "Calendar 680 attributes in the IRD resources capabilities", 682 o "repeated": is an optional field provided for Calendars. It is an 683 integer N greater or equal to '1' that indicates how many 684 iterations of the calendar value array starting at the date 685 indicated by "calendar-start-time" have the same values. The 686 number N includes the provided iteration. 688 Using the member "repeated" helps minimizing on the wire data 689 exchange: by providing it, an ALTO Server will avoid unecessary 690 processing of requests for Calendars with unchanged values while it 691 allows ALTO Clients to save their resources as well. 693 For example: if the "calendar-start-time" member has value "Mon, 30 694 Jun 2014 at 00:00:00 GMT" and if the value of member "repeated" is 695 equal to 4, it means that the calendar values are the same values on 696 Monday, Tuesday, Wednesday and Thursday. The ALTO Client thus may 697 use the same calendar for the next 4 duration periods following 698 "calendar-start-time". 700 4.1.3. Use case and example: FCM with a bandwidth Calendar 702 An example of non-real time information that can be provisioned in a 703 'calendar' is the expected path bandwidth. While the transmission 704 rate can be measured in real time by end systems, the operator of a 705 data center is in the position of formulating preferences for given 706 paths, at given time periods for example to avoid traffic peaks due 707 to diurnal usage patterns. In this example, we assume that an ALTO 708 Client requests a bandwidth calendar as specified in the IRD to 709 schedule its bulk data transfers as described in the use cases. 711 In the example IRD, calendars for cost type name "num-pathbandwidth" 712 are available for the information resources: "filtered-cost-calendar- 713 map" and "endpoint-cost-calendar-map". The ALTO Client requests a 714 calendar for "num-pathbandwidth" via a POST request for a filtered 715 cost map. 717 We suppose in this example that the ALTO Client sends its request on 718 Tuesday July 1st 2014 at 13:15 720 POST /calendar/costmap/filtered HTTP/1.1 721 Host: alto.example.com 722 Content-Length: [TODO] 723 Content-Type: application/alto-costmapfilter+json 724 Accept: application/alto-costmap+json,application/alto-error+json 726 { 727 "cost-type" : {"cost-mode" : "numerical", "cost-metric" : "bandwidthscore"}, 728 "calendared" : [true], 730 "pids" : { 731 "srcs" : [ "PID1", "PID2" ], 732 "dsts" : [ "PID1", "PID2", "PID3" ] 733 } 734 } 736 HTTP/1.1 200 OK 737 Content-Length: [TODO] 738 Content-Type: application/alto-costmap+json 740 { 741 "meta" : { 742 "dependent-vtags" : [...], 743 "cost-type" : {"cost-mode" : "numerical", "cost-metric" : "bandwidthscore"}, 744 "calendar-response-attributes" : [ 745 "calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT, 746 "time-interval-size" : "2 hour", 747 "number-of-intervals" : 12 748 ] 749 }, 751 "cost-map" : { 752 "PID1": { "PID1": [v1,v2, ... v12], 753 "PID2": [v1,v2, ... v12], 754 "PID3": [v1,v2, ... v12] }, 755 "PID2": { "PID1": [v1,v2, ... v12], 756 "PID2": [v1,v2, ... v12], 757 "PID3": [v1,v2, ... v12] } 758 } 759 } 761 4.2. Calendar extensions in the Endpoint Cost Service 763 This document extends the Endpoint Cost Service, as defined in 764 {11.5.1} of [RFC7285], by adding new input parameters and 765 capabilities, and by returning JSONArrays instead of JSONNumbers as 766 the cost values. The media type {11.5.1.1} and HTTP method 767 {11.5.1.2} are unchanged. 769 4.2.1. Calendar specific input in Endpoint Cost requests 771 The extensions to the requests for calendared Endpoint Cost Maps are 772 the same as for the Filtered Cost Map Service, specified in section 773 Section 4.1.1 of this draft. 775 The ReqEndpointCostMap object for a Calendared ECM request will have 776 the following format: 778 object { 779 [CostType cost-type;] 780 [CostType multi-cost-types<1..*>;] 781 [JSONBoolean calendared<1..*>;] 782 EndpointFilter endpoints; 783 } ReqEndpointCostMap; 785 object { 786 [TypedEndpointAddr srcs<0..*>;] 787 [TypedEndpointAddr dsts<0..*>;] 788 } EndpointFilter; 790 4.2.2. Calendar attributes in the Endpoint Cost response 792 The "meta" field of a Calendared Endpoint Cost response MUST include 793 at least: 795 o if the ALTO Client supports cost values for one Cost Type at a 796 time only: the "meta" fields specified in {11.5.1.6} of RFC 7285 797 for the Endpoint Cost response: 799 * "cost-type" field. 801 o if the ALTO Client supports cost values for several Cost Types at 802 a time, as specified in [RFC8189] : the "meta" fields specified in 803 [RFC8189] for the the Endpoint Cost response: 805 * "cost-type" field with value set to '{}', for backwards 806 compatibility with RFC7285. 808 * "multi-cost-types" field. 810 If the client request does not provide member "calendared" or if it 811 provides it with a value equal to 'false', for all the requested Cost 812 Types, then the ALTO Server response is exactly as specified in RFC 813 7285 [RFC7285] and [RFC8189]. 815 If the ALTO client provides member "calendared" in the input 816 parameters with a value equal to 'true' for given requested Cost 817 Types, the "meta" member of a Calendared Endpoint Cost response MUST 818 include, for these Cost Types, the same additional member "calendar- 819 response-attributes", as specified for the Filtered Cost Map Service. 820 The Server response is thus changed as follows, w.r.t RFC 7285 and 821 [RFC8189]: 823 o the "meta" member has one additional field 824 "CalendarResponseAttributes", as specified for the Filtered Cost 825 Map Service, 827 o the calendared costs are JSONArrays instead of JSONNumbers for the 828 legacy ALTO implementation. All arrays have a number of values 829 equal to 'number-of-intervals'. 831 If the value of member "calendared" is equal to 'false' for a given 832 requested Cost Type, the ALTO Server must return, for these Cost 833 Types, a single cost value as specified in RFC 7285. 835 4.2.3. Use case and example: ECS with a routingcost Calendar 837 Let us assume an Application Client is located in an end system with 838 limited resources and having an access to the network that is either 839 intermittent or provides an acceptable quality in limited but 840 predictable time periods. Therefore, it needs to both schedule its 841 resources greedy networking activities and its ALTO transactions. 843 The Application Client has the choice to trade content or resources 844 with a set of Endpoints and needs to decide with which one it will 845 connect and at what time. For instance, the Endpoints are spread in 846 different time-zones, or have intermittent access. In this example, 847 the 'routingcost' is assumed to be time-varying, with values provided 848 as ALTO Calendars. 850 The ALTO Client associated with the Application Client queries an 851 ALTO Calendar on 'routingcost' and will get the Calendar covering the 852 24 hours time period "containing" the date and time of the ALTO 853 client request. 855 For Cost Type 'num-routingcost', the solicited ALTO Server has 856 defined 3 different daily patterns each represented by a Calendar, to 857 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 859 - C1 for Monday, Tuesday, Wednesday, Thursday, (week days) 861 - C2 for Saturday, Sunday, (week end) 863 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 864 to 04:00:00 GMT, or big holiday such as New Year evening). 866 In the following example, the ALTO Client sends its request on 867 Tuesday July 1st 2014 at 13:15. 869 POST /calendar/endpointcost/lookup HTTP/1.1 870 Host: alto.example.com 871 Content-Length: [TODO] 872 Content-Type: application/alto-endpointcostparams+json 873 Accept: application/alto-endpointcost+json,application/alto-error+json 875 { 876 "cost-type" : {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 877 "calendared" : [true], 878 "endpoints" : { 879 "srcs": [ "ipv4:192.0.2.2" ], 880 "dsts": [ 881 "ipv4:192.0.2.89", 882 "ipv4:198.51.100.34", 883 "ipv4:203.0.113.45", 884 "ipv6:2000::1:2345:6789:abcd" 885 ] 886 } 887 } 889 HTTP/1.1 200 OK 890 Content-Length: [TODO] 891 Content-Type: application/alto-endpointcost+json 893 { 894 "meta" : { 895 "cost-type" : {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 896 "calendar-response-attributes" : [ 897 { "calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT, 898 "time-interval-size" : "1 hour", 899 "number-of-intervals" : 24, 900 "repeated": 4 } 901 ], 902 } // end meta 904 "endpoint-cost-map" : { 905 "ipv4:192.0.2.2": { 906 "ipv4:192.0.2.89" : [v1, v2, ... v24], 907 "ipv4:198.51.100.34" : [v1, v2, ... v24], 908 "ipv4:203.0.113.45" : [v1, v2, ... v24], 909 "ipv6:2000::1:2345:6789:abcd" : [v1, v2, ... v24] 910 } 911 } 912 } 913 When the Client gets the Calendar for "routingcost", it sees that the 914 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 915 equal to '4'. It understands that the provided values are valid 916 until Thursday included and will only need to get a Calendar update 917 on Friday. 919 4.2.4. Use case and example: ECS with a multi-cost calendar for 920 routingcost and latency 922 In this example, it is assumed that the ALTO Server implements multi- 923 cost capabilities, as specified in [RFC8189] . That is, an ALTO 924 client can request and receive values for several cost types in one 925 single transaction. An illustrating use case is a path selection 926 done on the basis of 2 metrics: routing cost and latency. 928 As in the previous example, the IRD indicates that the ALTO Server 929 provides "routingcost" Calendars in terms of 24 time intervals of 1 930 hour each. 932 For metric "latency", the IRD indicates that the ALTO Server provides 933 Calendars in terms of 12 time intervals values lasting each 5 934 minutes. 936 In the following example transaction, the ALTO Client sends its 937 request on Tuesday July 1st 2014 at 13:15. 939 POST calendar/endpointcost/lookup HTTP/1.1 940 Host: alto.example.com 941 Content-Length: [TODO] 942 Content-Type: application/alto-endpointcostparams+json 943 Accept: application/alto-endpointcost+json,application/alto-error+json 945 { 946 "cost-type" : {}, 947 "multi-cost-types" : [ 948 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 949 {"cost-mode" : "numerical", "cost-metric" : "latency"} 950 ], 951 "calendared" : [true, true], 952 "endpoints" : { 953 "srcs": [ "ipv4:192.0.2.2" ], 954 "dsts": [ 955 "ipv4:192.0.2.89", 956 "ipv4:198.51.100.34", 957 "ipv4:203.0.113.45", 958 "ipv6:2000::1:2345:6789:abcd" 959 ] 960 } 962 } 964 HTTP/1.1 200 OK 965 Content-Length: [TODO] 966 Content-Type: application/alto-endpointcost+json 968 { 969 "meta" : { 970 "multi-cost-types" : [ 971 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 972 {"cost-mode" : "numerical", "cost-metric" : "latency"} 973 ], 974 "calendar-response-attributes" : [ 975 { "cost-type-name : num-routingcost" 976 "calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT, 977 "time-interval-size" : "1 hour", 978 "number-of-intervals" : 24, 979 "repeated": 4 }, 980 { "cost-type-name : num-latency" 981 "calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT, 982 "time-interval-size" : "5 minute", 983 "number-of-intervals" : 12} 984 ], 985 } // end meta 987 "endpoint-cost-map" : { 988 "ipv4:192.0.2.2": { 989 "ipv4:192.0.2.89" : [[r1, r2, ... r24], [l1, l2, ... l12]], 990 "ipv4:198.51.100.34" : [[r1, r2, ... r24], [l1, l2, ... l12]], 991 "ipv4:203.0.113.45" : [[r1, r2, ... r24], [l1, l2, ... l12]], 992 "ipv6:2000::1:2345:6789:abcd" : [[r1, r2, ... r24], [l1, l2, ... l12]] 993 } 994 } 995 } 997 When receiving the response, the client sees that the calendar values 998 for 'routing cost' are repeated for 4 iterations. Therefore, in its 999 next requests until the routing cost calendar is expected to change, 1000 the client will only need to request a calendar for "latency". 1002 Without the ALTO Calendar extensions, the ALTO client would have no 1003 clue on the dynamicity of the metric value change and would spend 1004 needless time requesting values at an inappropriate pace. In 1005 addition, without the Multi-Cost ALTO capabilities, the ALTO client 1006 would duplicate this waste of time as it would need to send one 1007 request per cost metric. 1009 5. IANA Considerations 1011 Information for the ALTO Endpoint property registry maintained by the 1012 IANA and related to the new Endpoints supported by the acting ALTO 1013 server. These definitions will be formulated according to the syntax 1014 defined in Section on "ALTO Endpoint Property Registry" of [RFC7285]. 1016 Information for the ALTO Cost Type Registry maintained by the IANA 1017 and related to the new Cost Types supported by the acting ALTO 1018 server. These definitions will be formulated according to the syntax 1019 defined in Section on "ALTO Cost Type Registry" of [RFC7285]. 1021 5.1. Information for IANA on proposed Cost Types 1023 When a new ALTO Cost Type is defined, accepted by the ALTO working 1024 group and requests for IANA registration MUST include the following 1025 information, detailed in Section 11.2: Identifier, Intended 1026 Semantics, Security Considerations. 1028 5.2. Information for IANA on proposed Endpoint Properties 1030 Likewise, an ALTO Endpoint Property Registry could serve the same 1031 purposes as the ALTO Cost Type registry. Application to IANA 1032 registration for Endpoint Properties would follow a similar process. 1034 6. Acknowledgements 1036 Many thanks to Diego Lopez, He Peng, Haibin Song, Dawn Chan, Li Geng, 1037 Yichen Qian and Jensen Zhang for fruitful discussions and review 1038 feedback. 1040 7. References 1042 7.1. Normative References 1044 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1045 Requirement Levels", BCP 14, RFC 2119, 1046 DOI 10.17487/RFC2119, March 1997, 1047 . 1049 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1050 Optimization (ALTO) Problem Statement", RFC 5693, 1051 DOI 10.17487/RFC5693, October 2009, 1052 . 1054 [RFC7285] R. Alimi, R. Yang, R. Penno, Eds., "ALTO Protocol, IETF 1055 RFC 7285", September 2014. 1057 [RFC8189] S. Randriamasy, W. Roome, N. Schwan, "Multi-Cost 1058 Application-Layer Traffic Optimization (ALTO), IETF RFC 1059 8189", October 2017. 1061 7.2. Informative References 1063 [draft-ietf-alto-performance-metrics] 1064 Q. Wu, Y. Yang, Y. Lee, D. Dhody, S. Randriamasy, "ALTO 1065 Performance Cost Metrics (work in progress)", July 2017. 1067 Authors' Addresses 1069 Sabine Randriamasy 1070 Nokia Bell Labs 1071 Route de Villejust 1072 NOZAY 91460 1073 FRANCE 1075 Email: Sabine.Randriamasy@nokia-bell-labs.com 1077 Richard Yang 1078 Yale University 1079 51 Prospect st 1080 New Haven, CT 06520 1081 USA 1083 Email: yry@cs.yale.edu 1085 Qin Wu 1086 Huawei 1087 101 Software Avenue, Yuhua District 1088 Nanjing, Jiangsu 210012 1089 China 1091 Email: sunseawq@huawei.com 1093 Lingli Deng 1094 China Mobile 1095 China 1097 Email: denglingli@chinamobile.com 1098 Nico Schwan 1099 Thales Deutschland 1101 Email: nico.schwan@thalesgroup.com