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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: March 25, 2019 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 September 21, 2018 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-08 17 Abstract 19 This document is an extension to the base ALTO protocol [RFC7285]. 20 It extends the ALTO cost information service such that applications 21 decide not only 'where' to connect, but also 'when'. This is useful 22 for applications that need to perform bulk data transfer and would 23 like to schedule these transfers during an off-peak hour, for 24 example. This extension introduces ALTO Cost Calendars, with which 25 an ALTO Server exposes ALTO cost values in JSON arrays where each 26 value corresponds to a given time interval. The time intervals as 27 well as other Calendar attributes are specified in the Information 28 Resources Directory and ALTO Server responses. 30 Requirements Language 32 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 33 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 34 document are to be interpreted as described in RFC 2119 [RFC2119]. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at https://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on March 25, 2019. 53 Copyright Notice 55 Copyright (c) 2018 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (https://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 2. Overview of ALTO Cost Calendars . . . . . . . . . . . . . . . 4 72 2.1. ALTO Cost Calendar information features . . . . . . . . . 5 73 2.2. ALTO Calendar design characteristics . . . . . . . . . . 5 74 2.2.1. ALTO Cost Calendar for all cost modes . . . . . . . . 6 75 2.2.2. Compatibility with legacy ALTO Clients . . . . . . . 6 76 3. ALTO Calendar specification: IRD extensions . . . . . . . . . 7 77 3.1. Calendar attributes in the IRD resources capabilities . . 7 78 3.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 9 79 3.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 9 80 4. ALTO Calendar specification: Service Information Resources . 13 81 4.1. Calendar extensions for filtered cost maps . . . . . . . 13 82 4.1.1. Calendar extensions in Filtered Cost Map requests . . 13 83 4.1.2. Calendar extensions in Filtered Cost Map responses . 14 84 4.1.3. Use case and example: FCM with a bandwidth Calendar . 16 85 4.2. Calendar extensions in the Endpoint Cost Service . . . . 18 86 4.2.1. Calendar specific input in Endpoint Cost requests . 18 87 4.2.2. Calendar attributes in the Endpoint Cost response . . 18 88 4.2.3. Use case and example: ECS with a routingcost Calendar 19 89 4.2.4. Use case and example: ECS with a multi-cost calendar 90 for routingcost and owdelay . . . . . . . . . . . . . 22 91 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 92 6. Security Considerations . . . . . . . . . . . . . . . . . . . 24 93 7. Operational Considerations . . . . . . . . . . . . . . . . . 25 94 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 95 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 96 9.1. Normative References . . . . . . . . . . . . . . . . . . 25 97 9.2. Informative References . . . . . . . . . . . . . . . . . 26 98 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 100 1. Introduction 102 The ALTO protocol provides guidance to overlay applications needing 103 to select one or several hosts from a set of candidates able to 104 provide a desired resource. This guidance is based on parameters 105 that affect performance and efficiency of the data transmission 106 between the hosts such as the topological distance. The goal of ALTO 107 is to improve the Quality of Experience (QoE) in the application 108 while optimizing resource usage in the underlying network 109 infrastructure. 111 The ALTO protocol in [RFC7285] specifies a network map which defines 112 groupings of endpoints in provider-defined network regions (called 113 PIDs). The Cost Map Service, Endpoint Cost Service (ECS) and 114 Endpoint Ranking Service then provide ISP-defined costs and rankings 115 for connections among the specified endpoints and PIDs and thus 116 incentives for application clients to connect to ISP preferred 117 locations, e.g. to reduce their costs. ALTO intentionally avoids 118 provisioning realtime information as explained in the ALTO Problem 119 Statement [RFC5693] and ALTO Requirements [RFC5693]. Thus the 120 current Cost Map and Endpoint Cost Service are providing, for a given 121 Cost Type, exactly one path cost value. Applications have to query 122 one of these two services to retrieve the currently valid cost 123 values. They therefore need to plan their ALTO information requests 124 according to their own estimation of the frequency of cost value 125 change. 127 With [RFC7285], an ALTO client should interpret the returned costs as 128 those at the query moment. However, Network costs can fluctuate, 129 e.g. due to diurnal patterns of traffic demand or planned events such 130 as network maintenance, holidays or highly publicized events. 131 Providing network costs for only the current time thus may not be 132 sufficient, in particular for applications that can schedule their 133 traffic in a span of time, for example by deferring backups or other 134 background traffic to off-peak hours. 136 In case the ALTO Cost value changes are predictable over a certain 137 period of time and the application does not require immediate data 138 transfer, it can save time to get the whole set of cost values over 139 this period in one single ALTO response. Using this set to schedule 140 data transfers allows optimizing the network resources usage and QoE. 141 ALTO Clients and Servers can also minimize their workload by reducing 142 and accordingly scheduling their data exchanges. 144 This document extends [RFC7285] to allow an ALTO server to provide 145 network costs for a given duration of time. A sequence of network 146 costs across a time span for a given pair of network locations is 147 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 148 Endpoint Cost Service are extended to provide Cost Calendars. In 149 addition to this functional ALTO enhancement, we expect to further 150 save network and storage resources by gathering multiple Cost Values 151 for one Cost Type into one single ALTO Server response. 153 In this draft an "ALTO Cost Calendar" is specified by information 154 resources capabilities that are applicable to time-sensitive ALTO 155 metrics. An ALTO Cost Calendar exposes ALTO Cost Values in JSON 156 arrays where each value corresponds to a given time interval. The 157 time intervals as well as other Calendar attributes are specified in 158 the IRD and in the Server response to allow the ALTO Client to 159 interpret the received ALTO values. Last, the proposed extensions 160 for ALTO Calendars are applicable to any Cost Mode and they ensure 161 backwards compatibility with legacy ALTO clients. 163 In the rest of this document, Section 2 provides the design 164 characteristics. Sections 3 and 4 define the formal specifications 165 for the IRD and the information resources. IANA, security and 166 operational considerations are addressed respectively in sections 167 Section 5, Section 6 and Section 7. 169 2. Overview of ALTO Cost Calendars 171 An ALTO Cost calendar provided by the ALTO Server provides 2 172 information items: 174 o an array of values for a given metric, where each value 175 corresponds to a time interval, where the value array can 176 sometimes be a cyclic pattern that repeats a certain number of 177 times. 179 o attributes describing the time scope of the calendar such as the 180 size and number of the intervals and the date of the starting 181 point of the calendar, allowing an ALTO Client to properly 182 interpret the values. 184 An ALTO Cost Calendar can be used like a "time table" to figure out 185 the best time to schedule data transfers and also to proactively 186 manage application traffic given predictable events such as flash 187 crowds, traffic intensive holidays and network maintenance. It may 188 be viewed as a synthetic abstraction of real measurements that can be 189 historic or be a prediction for upcoming time periods. 191 Most likely, the ALTO Cost Calendar would be used for the Endpoint 192 Cost Service, assuming that a limited set of feasible Endpoints for a 193 non-real time application is already identified, that they do not 194 need to be accessed immediately and that their access can be 195 scheduled within a given time period. The Filtered Cost Map Service 196 is also applicable as long as the size of the Map allows it. 198 2.1. ALTO Cost Calendar information features 200 The Calendar attributes are provided in the Information Resources 201 Directory (IRD) and in ALTO Server responses. The IRD announces 202 attributes with dateless values in its information resources 203 capabilities, where as attributes with time dependent values are 204 provided in the "meta" of Server responses. The ALTO Cost Calendar 205 attributes provide the following information: 207 o attributes to interpret the time scope of the Calendar value 208 array: 210 * generic time zone, 212 * applicable time interval size for each calendar value: 213 combining a number and a time unit to reflect for example: 1 214 hour, 2 minutes, 10 seconds, 1 week, 1 month, 216 * duration of the Calendar: e.g. the number of intervals provided 217 in the calendar. 219 o "calendar-start-date": specifying when the calendar starts, that 220 is to which date the first value of the cost calendar is 221 applicable. 223 o "repeated": an optional attribute indicating for how many 224 iterations the provided calendar will have the same values. The 225 server may use it to allow the client to schedule its next request 226 and thus save its own workload by avoiding to process useless 227 requests. 229 2.2. ALTO Calendar design characteristics 231 To realize an ALTO Calendar, this document extends: the IRD, the ALTO 232 requests and responses for Cost Calendars. 234 This extension is designed to be light and ensure backwards 235 compatibility with base protocol ALTO Clients and with other 236 extensions. As recommended, it relies on section 8.3.7 "Parsing of 237 Unknown Fields" of [RFC7285] that writes: "Extensions may include 238 additional fields within JSON objects defined in this document. ALTO 239 implementations MUST ignore unknown fields when processing ALTO 240 messages." 242 The calendar-specific capabilities are integrated in the information 243 resources of the IRD and in the "meta" member of ALTO responses to 244 Cost Calendars requests. A calendar and its capabilities are 245 associated with a given information resource and within this 246 information resource with a given cost type. This design has several 247 advantages: 249 o it does not introduce a new mode, 251 o it does not introduce new media types, 253 o it allows an ALTO Server to offer calendar capabilities on a cost 254 type, with attributes values adapted to each information resource. 256 The Applicable Calendared information resources are: 258 o the Filtered Cost Map, 260 o the Endpoint Cost Map. 262 The ALTO Server can choose in which frequency it provides cost 263 Calendars to ALTO Clients. It may either provide calendar updates 264 starting at the request date, or carefully schedule its updates so as 265 to take profit from a potential repetition/periodicity of calendar 266 values. 268 2.2.1. ALTO Cost Calendar for all cost modes 270 ALTO Calendars are well-suited for values encoded in the "numerical" 271 mode. Actually, Calendars can also represent metrics in other modes 272 considered as compatible with time-varying values. For example, 273 types of Cost values such as JSONBool can also be expressed as 274 calendars, as their value may be 'true' or 'false' depending on given 275 time periods or likewise, values represented by strings, such as 276 "medium", "high", "low", "blue", "open". 278 Note also that a Calendar is suitable as well for time-varying 279 metrics provided in the "ordinal" mode, if these values are time- 280 varying and their update is carefully managed by the ALTO Server. 282 2.2.2. Compatibility with legacy ALTO Clients 284 The ALTO protocol extensions for Cost Calendars have been defined so 285 as to ensure that Calendar capable ALTO Servers can provide legacy 286 ALTO Clients with legacy information resources as well. That is a 287 legacy ALTO Client can request resources and receive responses as 288 specified in [RFC7285]. 290 A Calendar-aware ALTO Server MUST implement the base protocol 291 specified in [RFC7285]. 293 When a metric is available as a calendar, it MUST be available as a 294 single value as well. 296 For compatibility with legacy ALTO Clients specified in [RFC7285], 297 calendared information resources are not applicable for full cost 298 maps for the following reason: a legacy ALTO client would receive a 299 calendared cost map via an HTTP 'GET' command. As specified in 300 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 301 indicated in the "meta" of the responses. Therefore, lacking 302 information on calendar attributes, it will not be able to correctly 303 interpret and process the values of the received array of calendar 304 cost values. 306 Therefore, calendared information resources MUST be requested via the 307 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 308 method. 310 3. ALTO Calendar specification: IRD extensions 312 The Calendar attributes in the IRD information resources capabilities 313 carry constant dateless values. A calendar is associated with an 314 information resource rather than a cost type. For example, a Server 315 can provide a "routingcost" calendar for the Filtered Cost Map 316 Service at a granularity of one day and a "routingcost" calendar for 317 the Endpoint Cost service at a finer granularity but for a limited 318 number of endpoints. 320 3.1. Calendar attributes in the IRD resources capabilities 322 When for an applicable resource, an ALTO Server provides a Cost 323 Calendar for a given Cost Type, it MUST indicate this in the IRD 324 capabilities of this resource, by an object of type 325 'CalendarAttributes', associated with this Cost Type and specified 326 below. 328 The capabilities of a Calendar-aware information resource entry have 329 a member named "calendar-attributes" which is an array of objects of 330 type CalendarAttributes. It is necessary to use an array because of 331 resources such as Filtered Cost Map and Endpoint Cost Map, for which 332 the member "cost-type-names" is an array of 1 or more values. 334 A member "calendar-attributes" MUST appear only once for each 335 applicable cost type name of a resource entry. If "calendar- 336 attributes" are specified several times for a same "cost-type-name" 337 in the capabilities of a resource entry, the ALTO client SHOULD 338 ignore any additional occurrence of "calendar-attributes", for this 339 cost type name. 341 An ALTO Client should assume that the time interval size specified in 342 the IRD is the smallest possible one that the ALTO Server can 343 provide. The Client can aggregate cost values on its own if it needs 344 a larger granularity. 346 CalendarAttributes calendar-attributes <1..*>; 348 object{ 349 JSONString cost-type-names <1..*>; 350 JSONString time-interval-size; 351 JSONNumber number-of-intervals; 352 } CalendarAttributes; 354 o "cost-type-names": 356 * An array of one or more elements indicating the cost-type-names 357 in the IRD entry to which the capabilities apply. 359 o "time-interval-size": 361 * is the duration of an ALTO calendar time interval. A "time- 362 interval-size" value contains 2 entities separated by exactly 363 one whitespace: a JSONNumber and a string representing a time 364 unit and taking values in {second, minute, hour, day, week, 365 month, year}. Example values are: "5 minute" , "2 hour", 366 meaning that each calendar value applies on a time interval 367 that lasts respectively 5 minutes and 2 hours. 369 o "number-of-intervals": 371 * the integer number of values of the cost calendar array, at 372 least equal to 1. 374 - Attribute "cost-type-name" , if used, provides a better readability 375 to the calendar attributes specified in the IRD and avoids confusion 376 with calendar attributes of other cost-types. 378 - Multiplying Attributes 'time-interval-size' and 'number-of- 379 intervals' provides the duration of the provided calendar. For 380 example an ALTO Server may provide a calendar for ALTO values 381 changing every 'time-interval-size' equal to 5 minutes. If 'number- 382 of-intervals' has the value 12, then the duration of the provided 383 calendar is "1 hour". 385 3.2. Calendars in a delegate IRD 387 One option to clarify IRD resources is that a "root" ALTO Server 388 implementing base protocol resources delegates "specialized" 389 information resources such as the ones providing Cost Calendars to 390 another ALTO Server running in a subdomain specified with its URI in 391 the "root" ALTO Server. This option is described in Section 9.2.4 392 "Delegation using IRDs" of [RFC7285]. 394 This document provides an example, where a "root" ALTO Server runs in 395 a domain called "alto.example.com". It delegates the announcement of 396 Calendars capabilities to an ALTO Server running in a subdomain 397 called "custom.alto.example.com". The location of the "delegate 398 Calendar IRD" is assumed to be indicated in the "root" IRD by the 399 resource entry: "custom-calendared-resources". 401 Another advantage is that some Cost Types for some resources may be 402 more advantageous as Cost Calendars and it makes few sense to get 403 them as a single value. For example, Cost Types with predictable and 404 frequently changing values, calendared in short time intervals such 405 as a minute. 407 3.3. Example IRD with ALTO Cost Calendars 409 This section provides an example IRD with various cost metrics and 410 cost modes. As [RFC7285] makes it mandatory, it uses metric 411 "routingcost" in the "numerical" mode. 413 For illustrative purposes, this section introduces 3 other fictitious 414 example metrics and modes that should be understood as examples and 415 should not be used or considered as normative. 417 The cost type names used in the example IRD as thus as follows: 419 o "num-routingcost": refers to metric "routingcost" in the numerical 420 mode as defined in [RFC7285] and registered at the IANA. 422 o "num-owdelay": refers to some fictitious performance metric 423 "owdelay" in the "numerical" mode,to reflect the one way packet 424 transmission delay on a path. A related performance metric is 425 currently under definition in 426 [draft-ietf-alto-performance-metrics]. 428 o "num-throughputrating": refers to some fictitious metric 429 "throughputrating" in the "numerical" mode, to reflect the 430 provider preference in terms of end to end throughput. 432 o "string-servicestatus": refers to some fictitious metric 433 "servicestatus" in some example mode "string", to reflect the 434 availability, defined by the provider, of for instance path 435 connectivity. 437 The example IRD includes 2 particular URIs providing calendars: 439 o "http://custom.alto.example.com/calendar/costmap/filtered": a 440 filtered cost map in which calendar capabilities are indicated for 441 cost type names: "num-routingcost", "num-throughputrating" and 442 "string-servicestatus", 444 o "http://custom.alto.example.com/calendar/endpointcost/lookup": an 445 endpoint cost map in which calendar capabilities are indicated for 446 cost type names: "num-routingcost", "num-owdelay", "num- 447 throughputrating", "string-servicestatus". 449 The design of the Calendar capabilities allows that some calendars on 450 a cost type name are available in several information resources with 451 different Calendar Attributes. This is the case for calendars on 452 "num-routingcost", "num-throughputrating" and "string-servicestatus" 453 , available in both the Filtered Cost map and Endpoint Cost Service, 454 but with different time interval sizes for "num-throughputrating" and 455 "string-servicestatus". 457 GET /calendars-directory HTTP/1.1 458 Host: custom.alto.example.com 459 Accept: application/alto-directory+json,application/alto-error+json 460 --------------- 462 HTTP/1.1 200 OK 463 Content-Length: 2663 464 Content-Type: application/alto-directory+json 466 { 467 "meta" : { 468 "default-alto-network-map" : "my-default-network-map", 469 "cost-types": { 470 "num-routingcost": { 471 "cost-mode" : "numerical", 472 "cost-metric" : "routingcost" 473 }, 474 "num-owdelay": { 475 "cost-mode" : "numerical", 476 "cost-metric": "owdelay" 477 }, 478 "num-throughputrating": { 479 "cost-mode" : "numerical", 480 "cost-metric": "throughputrating", 481 }, 482 "string-servicestatus": { 483 "cost-mode" : "string", 484 "cost-metric": "servicestatus", 485 } 486 } 487 }, 488 "resources" : { 489 "filtered-cost-map-calendar" : { 490 "uri" : 491 "http://custom.alto.example.com/calendar/costmap/filtered", 492 "media-type" : "application/alto-costmap+json", 493 "accepts" : "application/alto-costmapfilter+json", 494 "capabilities" : { 495 "cost-constraints" : true, 496 "cost-type-names" : [ "num-routingcost", 497 "num-throughputrating", 498 "string-servicestatus" ], 499 "calendar-attributes" : [ 500 {"cost-type-names" : [ "num-routingcost", 501 "num-throughputrating" ], 502 "time-interval-size" : "1 hour", 503 "number-of-intervals" : 24 504 }, 505 {"cost-type-names" : [ "string-servicestatus" ], 506 "time-interval-size" : "30 minute", 507 "number-of-intervals" : 48 508 } 509 ] 510 } 511 "uses": [ "my-default-network-map" ] 512 }, 513 "endpoint-cost-calendar-map" : { 514 "uri" : 515 "http://custom.alto.example.com/calendar/endpointcost/lookup", 516 "media-type" : "application/alto-endpointcost+json", 517 "accepts" : "application/alto-endpointcostparams+json", 518 "capabilities" : { 519 "cost-constraints" : true, 520 "cost-type-names" : [ "num-routingcost", 521 "num-owdelay", 522 "num-throughputrating", 523 "string-servicestatus" ], 525 "calendar-attributes" : [ 526 {"cost-type-names" : [ "num-routingcost" ], 527 "time-interval-size" : "1 hour", 528 "number-of-intervals" : 24 529 }, 530 {"cost-type-names" : [ "num-owdelay" ], 531 "time-interval-size" : "5 minute", 532 "number-of-intervals" : 12 533 }, 534 {"cost-type-names" : [ "num-throughputrating" ], 535 "time-interval-size" : "1 minute", 536 "number-of-intervals" : 60 537 }, 538 {"cost-type-names" : [ "string-servicestatus" ], 539 "time-interval-size" : "2 minute", 540 "number-of-intervals" : 30 541 } 542 ] 543 } 544 } 545 } 546 } 548 In this example IRD, for the Filtered Cost map Service: 550 o the Calendar for "num-routingcost" and "num-throughputrating" is 551 an array of 24 values each provided on a time interval lasting 1 552 hour. 554 o the Calendar for "string-servicestatus": "is an array of 48 values 555 each provided on a time interval lasting 30 minutes. 557 For the Endpoint Cost service: 559 o the Calendar for "num-routingcost": is an array of 24 values each 560 provided on a time interval lasting 1 hour. 562 o the Calendar for "owdelay": is an array of 12 values each provided 563 on a time interval lasting 5 minutes. 565 o the Calendar for "num-throughputrating": is an array of 60 values 566 each provided on a time interval lasting 1 minute. 568 o the Calendar for "string-servicestatus": "is an array of 30 values 569 each provided on a time interval lasting 2 minutes. 571 4. ALTO Calendar specification: Service Information Resources 573 This section documents the individual information resources defined 574 to provide the Calendared information services defined in this 575 document. 577 The reference time zone for the provided time values is GMT because 578 the option chosen to express the time format is the HTTP header 579 fields format: 581 Date: Tue, 15 Nov 2014 08:12:31 GMT 583 4.1. Calendar extensions for filtered cost maps 585 A legacy ALTO client requests and gets Filtered Cost Map responses as 586 specified in [RFC7285]. 588 4.1.1. Calendar extensions in Filtered Cost Map requests 590 The input parameters of a "legacy" request for a filtered cost map, 591 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 592 are augmented with one additional member. 594 A Calendar-aware ALTO client requesting a Calendar on a given Cost 595 Type for a filtered cost map resource having Calendar capabilities 596 MUST add the following field to its input parameters: 598 JSONBoolean calendared<1..*>; 600 This field is an array of 1 to N boolean values, where N is the 601 number of requested metrics. Each boolean value indicates whether or 602 not the ALTO Server should provide the values for this Cost Type as a 603 calendar. The array MUST contain exactly N boolean values, otherwise 604 the server returns an error. 606 This field SHOULD NOT be specified if no member "calendar-attributes" 607 is specified in this information resource. 609 If a value of field 'calendared' is 'true' for a cost type name for 610 which no calendar attributes have been specified: a Calendar-aware 611 Server will return a response with a single cost value as specified 612 in [RFC7285]. 614 If this field is not present, it MUST be assumed to have only values 615 equal to 'false'. 617 A Calendar-aware ALTO client supporting single cost type values, as 618 specified in [RFC7285], that aims to request a Calendar MUST provide 619 an array of 1 element: 621 "calendared" : [true]; 623 A Calendar-aware ALTO client that is also Multi-Cost aware MUST 624 provide an array of N values set to 'true' or 'false', depending 625 whether it wants the applicable Cost Type values as a single or 626 calendared value. 628 4.1.2. Calendar extensions in Filtered Cost Map responses 630 The calendared costs are JSONArrays instead of JSONNumbers for the 631 legacy ALTO implementation. All arrays have a number of values equal 632 to 'number-of-intervals'. 634 The "meta" field of a Calendared Filtered Cost Map response MUST 635 include at least: 637 o if the ALTO Client supports cost values for one Cost Type at a 638 time only: the "meta" fields specified in [RFC7285] for these 639 information service responses: 641 * "dependent-vtags ", 643 * "cost-type" field. 645 o if the ALTO Client supports cost values for several Cost Types at 646 a time, as specified in [RFC8189] : the "meta" fields specified in 647 [RFC8189] for these information service responses: 649 * "dependent-vtags ", 651 * "cost-type" field with value set to '{}', for backwards 652 compatibility with [RFC7285]. 654 * "multi-cost-types" field. 656 o If the client request does not provide member "calendared" or if 657 it provides it with a value equal to 'false', for all the 658 requested Cost Types, then the ALTO Server response is exactly as 659 specified in [RFC7285] and [RFC8189]. 661 o If the value of member "calendared" is equal to 'false' for a 662 given requested Cost Type, the ALTO Server must return, for these 663 Cost Types, a single cost value as specified in [RFC7285]. 665 In addition, the "meta" field of a Calendared Filtered Cost map 666 response MUST include the member "calendar-response-attributes" for 667 the requested information resource, together with the values provided 668 by the ALTO Server for these attributes. This member is an array of 669 objects of type "CalendarResponseAttributes", defined as follows: 671 CalendarResponseAttributes calendar-response-attributes <1..*>; 673 object{ 674 [JSONString cost-type-names <1..*>]; 675 JSONString calendar-start-time; 676 JSONString time-interval-size; 677 JSONNumber number-of-intervals; 678 [JSONNumber repeated;] 679 } CalendarResponseAttributes; 681 Object CalendarResponseAttributes has the following attributes: 683 o "cost-type-names": member indicating the cost-type-names to which 684 the capabilities apply. This field MUST appear in responses to 685 Multi-Cost ALTO requests. 687 o "calendar-start-time": indicates the date at which the first value 688 of the calendar applies. By default, the value provided for the 689 "calendar-start-time" attribute SHOULD be no later than the 690 request date. 692 o "time-interval-size": as specified in section "Calendar attributes 693 in the IRD resources capabilities", 695 o "number-of-intervals": as specified in section "Calendar 696 attributes in the IRD resources capabilities", 698 o "repeated": is an optional field provided for Calendars. It is an 699 integer N greater or equal to '1' that indicates how many 700 iterations of the calendar value array starting at the date 701 indicated by "calendar-start-time" have the same values. The 702 number N includes the provided iteration. 704 For example: suppose the "calendar-start-time" member has value "Mon, 705 30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has 706 value "1 hour", the "number-of-intervals" member has value "24" and 707 the value of member "repeated" is equal to 4. This means that the 708 calendar values are the same on Monday, Tuesday, Wednesday and 709 Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO 710 Client thus may use the same calendar for the next 4 days starting at 711 "calendar-start-time" and will only need to request a new one for 712 Friday July 4th at 00:00:00 GMT. 714 4.1.3. Use case and example: FCM with a bandwidth Calendar 716 An example of non-real time information that can be provisioned in a 717 'calendar' is the expected path throughput. While the transmission 718 rate can be measured in real time by end systems, the operator of a 719 data center is in the position of formulating preferences for given 720 paths, at given time periods for example to avoid traffic peaks due 721 to diurnal usage patterns. In this example, we assume that an ALTO 722 Client requests a calendar of network provider defined throughput 723 ratings, as specified in the IRD, to schedule its bulk data transfers 724 as described in the use cases. 726 In the example IRD, calendars for cost type name "num- 727 throughputrating" are available for the information resources: 728 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 729 ALTO Client requests a calendar for "num-throughputrating" via a POST 730 request for a filtered cost map. 732 We suppose in this example that the ALTO Client sends its request on 733 Tuesday July 1st 2014 at 13:15 and, to calculate the Content-Length 734 in the server response, that the values for metric "throughputrating" 735 are encoded in 2 digits. 737 POST /calendar/costmap/filtered HTTP/1.1 738 Host: alto.example.com 739 Content-Length: 218 740 Content-Type: application/alto-costmapfilter+json 741 Accept: application/alto-costmap+json,application/alto-error+json 743 { 744 "cost-type" : {"cost-mode" : "numerical", 745 "cost-metric" : "throughputrating"}, 746 "calendared" : [true], 747 "pids" : { 748 "srcs" : [ "PID1", "PID2" ], 749 "dsts" : [ "PID1", "PID2", "PID3" ] 750 } 751 } 753 HTTP/1.1 200 OK 754 Content-Length: 904 755 Content-Type: application/alto-costmap+json 757 { 758 "meta" : { 759 "dependent-vtags" : [ 760 {"resource-id": "my-default-network-map", 761 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 762 } 763 ], 764 "cost-type" : {"cost-mode" : "numerical", 765 "cost-metric" : "throughputrating"}, 766 "calendar-response-attributes" : [ 767 "calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT, 768 "time-interval-size" : "2 hour", 769 "number-of-intervals" : 12 770 ] 771 }, 772 "cost-map" : { 773 "PID1": { "PID1": [v1,v2, ... v12], 774 "PID2": [v1,v2, ... v12], 775 "PID3": [v1,v2, ... v12] }, 776 "PID2": { "PID1": [v1,v2, ... v12], 777 "PID2": [v1,v2, ... v12], 778 "PID3": [v1,v2, ... v12] } 779 } 780 } 782 4.2. Calendar extensions in the Endpoint Cost Service 784 This document extends the Endpoint Cost Service, as defined in 785 {11.5.1} of [RFC7285], by adding new input parameters and 786 capabilities, and by returning JSONArrays instead of JSONNumbers as 787 the cost values. The media type {11.5.1.1} and HTTP method 788 {11.5.1.2} are unchanged. 790 4.2.1. Calendar specific input in Endpoint Cost requests 792 The extensions to the requests for calendared Endpoint Cost Maps are 793 the same as for the Filtered Cost Map Service, specified in section 794 Section 4.1.1 of this draft. 796 The ReqEndpointCostMap object for a Calendared ECM request will have 797 the following format: 799 object { 800 [CostType cost-type;] 801 [CostType multi-cost-types<1..*>;] 802 [JSONBoolean calendared<1..*>;] 803 EndpointFilter endpoints; 804 } ReqEndpointCostMap; 806 object { 807 [TypedEndpointAddr srcs<0..*>;] 808 [TypedEndpointAddr dsts<0..*>;] 809 } EndpointFilter; 811 4.2.2. Calendar attributes in the Endpoint Cost response 813 The "meta" field of a Calendared Endpoint Cost response MUST include 814 at least: 816 o if the ALTO Client supports cost values for one Cost Type at a 817 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 818 for the Endpoint Cost response: 820 * "cost-type" field. 822 o if the ALTO Client supports cost values for several Cost Types at 823 a time, as specified in [RFC8189] : the "meta" fields specified in 824 [RFC8189] for the the Endpoint Cost response: 826 * "cost-type" field with value set to '{}', for backwards 827 compatibility with [RFC7285]. 829 * "multi-cost-types" field. 831 If the client request does not provide member "calendared" or if it 832 provides it with a value equal to 'false', for all the requested Cost 833 Types, then the ALTO Server response is exactly as specified in 834 [RFC7285] and [RFC8189]. 836 If the ALTO client provides member "calendared" in the input 837 parameters with a value equal to 'true' for given requested Cost 838 Types, the "meta" member of a Calendared Endpoint Cost response MUST 839 include, for these Cost Types, the same additional member "calendar- 840 response-attributes", as specified for the Filtered Cost Map Service. 841 The Server response is thus changed as follows, w.r.t [RFC7285] and 842 [RFC8189]: 844 o the "meta" member has one additional field 845 "CalendarResponseAttributes", as specified for the Filtered Cost 846 Map Service, 848 o the calendared costs are JSONArrays instead of JSONNumbers for the 849 legacy ALTO implementation. All arrays have a number of values 850 equal to 'number-of-intervals'. 852 If the value of member "calendared" is equal to 'false' for a given 853 requested Cost Type, the ALTO Server MUST return, for these Cost 854 Types, a single cost value as specified in [RFC7285]. 856 4.2.3. Use case and example: ECS with a routingcost Calendar 858 Let us assume an Application Client is located in an end system with 859 limited resources and having an access to the network that is either 860 intermittent or provides an acceptable quality in limited but 861 predictable time periods. Therefore, it needs to both schedule its 862 resources greedy networking activities and its ALTO transactions. 864 The Application Client has the choice to trade content or resources 865 with a set of Endpoints and needs to decide with which one it will 866 connect and at what time. For instance, the Endpoints are spread in 867 different time-zones, or have intermittent access. In this example, 868 the 'routingcost' is assumed to be time-varying, with values provided 869 as ALTO Calendars. 871 The ALTO Client associated with the Application Client queries an 872 ALTO Calendar on 'routingcost' and will get the Calendar covering the 873 24 hours time period "containing" the date and time of the ALTO 874 client request. 876 For Cost Type "num-routingcost", the solicited ALTO Server has 877 defined 3 different daily patterns each represented by a Calendar, to 878 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 880 - C1 for Monday, Tuesday, Wednesday, Thursday, (week days) 882 - C2 for Saturday, Sunday, (week end) 884 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 885 to 04:00:00 GMT, or big holiday such as New Year evening). 887 In the following example, the ALTO Client sends its request on 888 Tuesday July 1st 2014 at 13:15. 890 To calculate the Content-Length in the server response, the 891 "routingcost" values are assumed to be encoded in 3 digits. 893 POST /calendar/endpointcost/lookup HTTP/1.1 894 Host: alto.example.com 895 Content-Length: 316 896 Content-Type: application/alto-endpointcostparams+json 897 Accept: application/alto-endpointcost+json,application/alto-error+json 899 { 900 "cost-type" : {"cost-mode" : "numerical", 901 "cost-metric" : "routingcost"}, 902 "calendared" : [true], 903 "endpoints" : { 904 "srcs": [ "ipv4:192.0.2.2" ], 905 "dsts": [ 906 "ipv4:192.0.2.89", 907 "ipv4:198.51.100.34", 908 "ipv4:203.0.113.45", 909 "ipv6:2000::1:2345:6789:abcd" 910 ] 911 } 912 } 914 HTTP/1.1 200 OK 915 Content-Length: 1007 916 Content-Type: application/alto-endpointcost+json 918 { 919 "meta" : { 920 "cost-type" : {"cost-mode" : "numerical", 921 "cost-metric" : "routingcost"}, 922 "calendar-response-attributes" : [ 923 {"calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT, 924 "time-interval-size" : "1 hour", 925 "number-of-intervals" : 24, 926 "repeated": 4 927 } 928 ], 929 } 930 "endpoint-cost-map" : { 931 "ipv4:192.0.2.2": { 932 "ipv4:192.0.2.89" : [v1, v2, ... v24], 933 "ipv4:198.51.100.34" : [v1, v2, ... v24], 934 "ipv4:203.0.113.45" : [v1, v2, ... v24], 935 "ipv6:2000::1:2345:6789:abcd" : [v1, v2, ... v24] 936 } 937 } 938 } 939 When the Client gets the Calendar for "routingcost", it sees that the 940 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 941 equal to '4'. It understands that the provided values are valid 942 until Thursday included and will only need to get a Calendar update 943 on Friday. 945 4.2.4. Use case and example: ECS with a multi-cost calendar for 946 routingcost and owdelay 948 In this example, it is assumed that the ALTO Server implements multi- 949 cost capabilities, as specified in [RFC8189] . That is, an ALTO 950 client can request and receive values for several cost types in one 951 single transaction. An illustrating use case is a path selection 952 done on the basis of 2 metrics: routing cost and owdelay. 954 As in the previous example, the IRD indicates that the ALTO Server 955 provides "routingcost" Calendars in terms of 24 time intervals of 1 956 hour each. 958 For metric "owdelay", the IRD indicates that the ALTO Server provides 959 Calendars in terms of 12 time intervals values lasting each 5 960 minutes. 962 In the following example transaction, the ALTO Client sends its 963 request on Tuesday July 1st 2014 at 13:15. 965 This example assumes that the values of metric "owdelay" are encoded 966 in 3 digits. 968 POST calendar/endpointcost/lookup HTTP/1.1 969 Host: alto.example.com 970 Content-Length: 401 971 Content-Type: application/alto-endpointcostparams+json 972 Accept: application/alto-endpointcost+json,application/alto-error+json 974 { 975 "cost-type" : {}, 976 "multi-cost-types" : [ 977 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 978 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 979 ], 980 "calendared" : [true, true], 981 "endpoints" : { 982 "srcs": [ "ipv4:192.0.2.2" ], 983 "dsts": [ 984 "ipv4:192.0.2.89", 985 "ipv4:198.51.100.34", 986 "ipv4:203.0.113.45", 987 "ipv6:2000::1:2345:6789:abcd" 988 ] 989 } 990 } 992 HTTP/1.1 200 OK 993 Content-Length: 1597 994 Content-Type: application/alto-endpointcost+json 996 { 997 "meta" : { 998 "multi-cost-types" : [ 999 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1000 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1001 ], 1002 "calendar-response-attributes" : [ 1003 {"cost-type-name : num-routingcost" 1004 "calendar-start-time" : Mon, 30 Jun 2014 00:00:00 GMT, 1005 "time-interval-size" : "1 hour", 1006 "number-of-intervals" : 24, 1007 "repeated": 4 }, 1008 {"cost-type-name : num-owdelay" 1009 "calendar-start-time" : Tue, 1 Jul 2014 13:00:00 GMT, 1010 "time-interval-size" : "5 minute", 1011 "number-of-intervals" : 12} 1012 ], 1013 } 1014 "endpoint-cost-map" : { 1015 "ipv4:192.0.2.2": { 1016 "ipv4:192.0.2.89" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1017 "ipv4:198.51.100.34" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1018 "ipv4:203.0.113.45" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1019 "ipv6:2000::1:2345:6789:abcd" : [[r1, r2, ... r24], 1020 [o1, o2, ... o12]] 1021 } 1022 } 1023 } 1025 When receiving the response, the client sees that the calendar values 1026 for 'routing cost' are repeated for 4 iterations. Therefore, in its 1027 next requests until the routing cost calendar is expected to change, 1028 the client will only need to request a calendar for "owdelay". 1030 Without the ALTO Calendar extensions, the ALTO client would have no 1031 clue on the dynamicity of the metric value change and would spend 1032 needless time requesting values at an inappropriate pace. In 1033 addition, without the Multi-Cost ALTO capabilities, the ALTO client 1034 would duplicate this waste of time as it would need to send one 1035 request per cost metric. 1037 5. IANA Considerations 1039 This document does not define any new media types or introduce any 1040 new IANA considerations. 1042 6. Security Considerations 1044 As an extension of the base ALTO protocol [RFC7285], this document 1045 fits into the architecture of the base protocol, and hence the 1046 Security Considerations (Section 15) of the base protocol fully apply 1047 when this extension is provided by an ALTO server. For example, the 1048 same authenticity and integrity considerations (Section 15.1 of 1049 [RFC7285] still fully apply; the same considerations for the privacy 1050 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1052 The calendaring information provided by this extension requires 1053 additional considerations on three security considerations discussed 1054 in the base protocol: potential undesirable guidance to clients 1055 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1056 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1057 of [RFC7285]). For example, by providing network information in the 1058 future in a calendar, this extension may improve availability of 1059 ALTO, when the ALTO server is unavailable but related information is 1060 already provided in the calendar. 1062 For confidentiality of ALTO information, an operator should be 1063 cognizant that this extension may introduce a new risk: an ALTO 1064 client may get information for future events that are scheduled 1065 through calendaring. Possessing such information, the client may use 1066 it to achieve its goal: (1) initiating connections only at 1067 advantageous network costs, leading to unexpected network load; (2) 1068 generating massive connections to the network at times where its load 1069 is expected to be high. 1071 To mitigate this risk, the operator should address the risk of ALTO 1072 information being leaked to malicious clients or third parties. As 1073 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1074 the ALTO server should authenticate ALTO clients and use the 1075 Transport Layer Security (TLS) protocol so that Man In The Middle 1076 (MITM) attacks to intercept an ALTO Calendar are not possible. 1077 [RFC7285] ensures the availability of such a solution in its 1078 Section 8.3.5. "Authentication and Encryption", which specifies that 1079 "ALTO server implementations as well as ALTO client implementations 1080 MUST support the "https" URI scheme [RFC2818] and Transport Layer 1081 Security (TLS) [RFC5246]". 1083 For potential undesirable guidance of ALTO information, an ALTO 1084 client should be cognizant that using calendaring information can 1085 have risks: (1) a repeat pattern may be only statistical, and (2) 1086 future events may change. Hence, a more robust ALTO client should 1087 adapt and extend protection strategies specified in Section 15.2 of 1088 the base protocol: it should develop self check and also ensure 1089 information update, to reduce the impact of this risk. 1091 7. Operational Considerations 1093 Conveying ALTO Cost Calendars tends to reduce the on-the-wire data 1094 exchange volume compared to multiple single cost ALTO transactions, 1095 as an application has a set of time-dependent values upon which it 1096 can plan its connections in advance with no need for the ALTO Client 1097 to query information at each time. Additionally, the Calendar 1098 response attribute "repeated", when provided, saves additional data 1099 exchanges in that it indicates that the ALTO Client does not need to 1100 query Calendars during a period indicated by this attribute. 1102 8. Acknowledgements 1104 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1105 Peng and Haibin Song for fruitful discussions and feedback on earlier 1106 draft versions. Dawn Chan, Vijay Gurbani, Yichen Qian and Jensen 1107 Zhang provided substantial review feedback and suggestions to the 1108 protocol design. 1110 9. References 1112 9.1. Normative References 1114 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1115 Requirement Levels", BCP 14, RFC 2119, 1116 DOI 10.17487/RFC2119, March 1997, 1117 . 1119 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1120 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1121 "Application-Layer Traffic Optimization (ALTO) Protocol", 1122 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1123 . 1125 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1126 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1127 DOI 10.17487/RFC8189, October 2017, 1128 . 1130 9.2. Informative References 1132 [draft-ietf-alto-performance-metrics] 1133 Q. Wu, Y. Yang, Y. Lee, D. Dhody, S. Randriamasy, "ALTO 1134 Performance Cost Metrics (work in progress)", June 2018. 1136 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1137 DOI 10.17487/RFC2818, May 2000, 1138 . 1140 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1141 (TLS) Protocol Version 1.2", RFC 5246, 1142 DOI 10.17487/RFC5246, August 2008, 1143 . 1145 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1146 Optimization (ALTO) Problem Statement", RFC 5693, 1147 DOI 10.17487/RFC5693, October 2009, 1148 . 1150 Authors' Addresses 1152 Sabine Randriamasy 1153 Nokia Bell Labs 1154 Route de Villejust 1155 NOZAY 91460 1156 FRANCE 1158 Email: Sabine.Randriamasy@nokia-bell-labs.com 1160 Richard Yang 1161 Yale University 1162 51 Prospect st 1163 New Haven, CT 06520 1164 USA 1166 Email: yry@cs.yale.edu 1167 Qin Wu 1168 Huawei 1169 101 Software Avenue, Yuhua District 1170 Nanjing, Jiangsu 210012 1171 China 1173 Email: sunseawq@huawei.com 1175 Lingli Deng 1176 China Mobile 1177 China 1179 Email: denglingli@chinamobile.com 1181 Nico Schwan 1182 Thales Deutschland 1183 Lorenzstrasse 10 1184 Stuttgart 70435 1185 Germany 1187 Email: nico.schwan@thalesgroup.com