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Randriamasy 3 Internet-Draft Nokia Bell Labs 4 Intended status: Standards Track R. Yang 5 Expires: July 24, 2020 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 January 21, 2020 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-15 17 Abstract 19 This document is an extension to the base Application-Layer Traffic 20 Optimization (ALTO) protocol. It extends the ALTO cost information 21 service so that applications decide not only 'where' to connect, but 22 also 'when'. This is useful for applications that need to perform 23 bulk data transfer and would like to schedule these transfers during 24 an off-peak hour, for example. This extension introduces ALTO Cost 25 Calendar, with which an ALTO Server exposes ALTO cost values in JSON 26 arrays where each value corresponds to a given time interval. The 27 time intervals as well as other Calendar attributes, are specified in 28 the Information 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", "NOT RECOMMENDED", "MAY", and 34 "OPTIONAL" in this document are to be interpreted as described in 35 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 36 capitals, as shown here. 38 When the words appear in lower case, they are to be interpreted with 39 their natural language meanings. 41 Status of This Memo 43 This Internet-Draft is submitted in full conformance with the 44 provisions of BCP 78 and BCP 79. 46 Internet-Drafts are working documents of the Internet Engineering 47 Task Force (IETF). Note that other groups may also distribute 48 working documents as Internet-Drafts. The list of current Internet- 49 Drafts is at https://datatracker.ietf.org/drafts/current/. 51 Internet-Drafts are draft documents valid for a maximum of six months 52 and may be updated, replaced, or obsoleted by other documents at any 53 time. It is inappropriate to use Internet-Drafts as reference 54 material or to cite them other than as "work in progress." 56 This Internet-Draft will expire on July 24, 2020. 58 Copyright Notice 60 Copyright (c) 2020 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (https://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 76 2. Overview of ALTO Cost Calendars and terminology . . . . . . . 4 77 2.1. Some recent known uses . . . . . . . . . . . . . . . . . 4 78 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 79 2.3. ALTO Cost Calendar overview . . . . . . . . . . . . . . . 5 80 2.4. ALTO Cost Calendar information features . . . . . . . . . 6 81 2.5. ALTO Calendar design characteristics . . . . . . . . . . 7 82 2.5.1. ALTO Cost Calendar for all cost modes . . . . . . . . 8 83 2.5.2. Compatibility with legacy ALTO Clients . . . . . . . 8 84 3. ALTO Calendar specification: IRD extensions . . . . . . . . . 9 85 3.1. Calendar attributes in the IRD resource capabilities . . 9 86 3.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 10 87 3.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 11 88 4. ALTO Calendar specification: Service Information Resources . 14 89 4.1. Calendar extensions for Filtered Cost Maps (FCM) . . . . 14 90 4.1.1. Calendar extensions in Filtered Cost Map requests . . 14 91 4.1.2. Calendar extensions in Filtered Cost Map responses . 15 92 4.1.3. Use case and example: FCM with a bandwidth Calendar . 18 93 4.2. Calendar extensions in the Endpoint Cost Service . . . . 20 94 4.2.1. Calendar specific input in Endpoint Cost requests . 20 95 4.2.2. Calendar attributes in the Endpoint Cost response . . 20 96 4.2.3. Use case and example: ECS with a routingcost Calendar 21 97 4.2.4. Use case and example: ECS with a multi-cost Calendar 98 for routingcost and owdelay . . . . . . . . . . . . . 24 99 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 100 6. Security Considerations . . . . . . . . . . . . . . . . . . . 26 101 7. Operational Considerations . . . . . . . . . . . . . . . . . 27 102 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 103 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 104 9.1. Normative References . . . . . . . . . . . . . . . . . . 28 105 9.2. Informative References . . . . . . . . . . . . . . . . . 29 106 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 108 1. Introduction 110 The base Application-Layer Traffic Optimization (ALTO) protocol 111 specified in [RFC7285] provides guidance to overlay applications that 112 need to select one or several hosts from a set of candidates able to 113 provide a desired resource. This guidance is based on parameters 114 that affect performance and efficiency of the data transmission 115 between the hosts such as the topological distance. The goal of ALTO 116 is to improve the Quality of Experience (QoE) in the application 117 while optimizing resource usage in the underlying network 118 infrastructure. 120 The ALTO protocol in [RFC7285] specifies a network map which defines 121 groupings of endpoints in provider-defined network regions identified 122 by Provider-defined Identifiers (PIDs). The Cost Map Service, 123 Endpoint Cost Service (ECS) and Endpoint Ranking Service then provide 124 ISP-defined costs and rankings for connections among the specified 125 endpoints and PIDs and thus incentives for application clients to 126 connect to ISP preferred locations, for instance, to reduce their 127 costs. For the reasons outlined in the ALTO problem statement 128 [RFC5693] and requirement AR-14 of [RFC6708], ALTO does not 129 disseminate network metrics that change frequently. In a network, 130 the costs can fluctuate for many reasons having to do with 131 instantaneous traffic load or due to diurnal patterns of traffic 132 demand or planned events such as network maintenance, holidays or 133 highly publicized events. Thus, an ALTO application wishing to use 134 the Cost Map and Endpoint Cost Service at some future time will have 135 to estimate the state of the network at that time, a process that is, 136 at best, fragile and brittle since the application does not have any 137 visibility into the state of the network. Providing network costs 138 for only the current time thus may not be sufficient, in particular 139 for applications that can schedule their traffic in a span of time, 140 for example by deferring backups or other background traffic to off- 141 peak hours. 143 In case the ALTO Cost value changes are predictable over a certain 144 period of time and the application does not require immediate data 145 transfer, it can save time to get the whole set of cost values over 146 this period in one single ALTO response. Using this set to schedule 147 data transfers allows optimizing the network resources usage and QoE. 148 ALTO Clients and Servers can also minimize their workload by reducing 149 and accordingly scheduling their data exchanges. 151 This document extends [RFC7285] to allow an ALTO Server to provide 152 network costs for a given duration of time. A sequence of network 153 costs across a time span for a given pair of network locations is 154 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 155 Endpoint Cost Service are extended to provide Cost Calendars. In 156 addition to this functional ALTO enhancement, we expect to further 157 save network and storage resources by gathering multiple Cost Values 158 for one Cost Type into one single ALTO Server response. 160 In this document, an "ALTO Cost Calendar" is specified in terms of 161 information resources capabilities that are applicable to time- 162 sensitive ALTO metrics. An ALTO Cost Calendar exposes ALTO Cost 163 Values in JSON arrays, see [RFC8259], where each value corresponds to 164 a given time interval. The time intervals as well as other Calendar 165 attributes are specified in the Information Resources Directory (IRD) 166 and in the Server response to allow the ALTO Client to interpret the 167 received ALTO values. Last, the extensions for ALTO Calendars are 168 applicable to any Cost Mode and they ensure backwards compatibility 169 with legacy ALTO Clients. 171 In the rest of this document, Section 2 provides the design 172 characteristics. Sections 3 and 4 define the formal specifications 173 for the IRD and the information resources. IANA, security and 174 operational considerations are addressed respectively in sections 175 Section 5, Section 6 and Section 7. 177 2. Overview of ALTO Cost Calendars and terminology 179 2.1. Some recent known uses 181 A potential use case is the SENSE project, see [SENSE-sdn-e2e-net], 182 who is implementing smart network services to dynamically build end- 183 to-end virtual guaranteed networks across administrative domains, 184 with no manual intervention. The initial SENSE services include 185 informing applications on the availability of bandwidth resources or 186 feasibility of some requested Time-Bandwidth-Product (TBP) during a 187 specific time period. ALTO Calendars can support these services if 188 the Calendar start date and duration cover the period of interest of 189 the requesting applications. 191 The need of future scheduling of large scale traffic that can be 192 addressed by the ALTO protocol is also motivated by Unicorn, a 193 unified resource orchestration framework for multi-domain, geo- 194 distributed data analytics, see 195 [draft-xiang-alto-multidomain-analytics]. 197 2.2. Terminology 199 o ALTO transaction: A request/response exchange between an ALTO 200 Client and an ALTO Server. 202 o Client: When used with a capital "C", this term refers to an ALTO 203 Client. 205 o Calendar, Cost Calendar: When used with capitalized words, these 206 terms refer to an ALTO Cost Calendar. 208 o Endpoint (EP): An endpoint is defined as in Section 2.1 of 209 [RFC7285]. It can be, for example, a peer, a CDN storage 210 location, a physical server involved in a virtual server-supported 211 application, a party in a resource-sharing swarm such as a 212 computation grid, or an online multi-party game. 214 o Server: When used with a capital "S", this term refers to an ALTO 215 Server. 217 2.3. ALTO Cost Calendar overview 219 An ALTO Cost Calendar provided by the ALTO Server provides 2 220 information items: 222 o an array of values for a given metric, where each value 223 corresponds to a time interval, where the value array can 224 sometimes be a cyclic pattern that repeats a certain number of 225 times. 227 o attributes describing the time scope of the Calendar such as the 228 size and number of the intervals and the date of the starting 229 point of the Calendar, allowing an ALTO Client to interpret the 230 values properly. 232 An ALTO Cost Calendar can be used like a "time table" to figure out 233 the best time to schedule data transfers and also to proactively 234 manage application traffic given predictable events such as expected 235 spike in traffic due to crowd gathering (concerts, sports, etc.), 236 traffic-intensive holidays and network maintenance. A Calendar may 237 be viewed as a synthetic abstraction of, for example, real 238 measurements gathered over previous periods on which statistics have 239 been computed. However, like for any schedule, unexpected network 240 incidents may require the current ALTO Calendar to be updated and re- 241 sent to the ALTO Clients needing it. To this end, this document 242 recommends that ALTO Servers providing ALTO Calendars also provide 243 the "ALTO Incremental Updates Using Server-Sent Events (SSE)" Service 244 that is specified in [draft-ietf-alto-incr-update-sse]. Likewise, 245 ALTO Clients capable of using ALTO Calendars should also use the SSE 246 Service. 248 Most likely, the ALTO Cost Calendar would be used for the Endpoint 249 Cost Service, assuming that a limited set of feasible Endpoints for a 250 non-real time application is already identified, that they do not 251 need to be accessed immediately and that their access can be 252 scheduled within a given time period. The Filtered Cost Map Service 253 is also applicable as long as the size of the Map allows it. 255 2.4. ALTO Cost Calendar information features 257 The Calendar attributes are provided in the Information Resources 258 Directory (IRD) and in ALTO Server responses. The IRD announces 259 attributes without date values in its information resources 260 capabilities, whereas attributes with time dependent values are 261 provided in the "meta" section of Server responses. The ALTO Cost 262 Calendar attributes provide the following information: 264 o attributes to describe the time scope of the Calendar value array: 266 * time zone (in UTC), 268 * applicable time interval size for each Calendar value, defined 269 in seconds, that can cover a wide range of values. 271 * duration of the Calendar: e.g., the number of intervals 272 provided in the Calendar. 274 o "calendar-start-date": specifying when the Calendar starts, that 275 is to which date the first value of the Cost Calendar is 276 applicable. 278 o "repeated": an optional attribute indicating how many iterations 279 of the provided Calendar will have the same values. The server 280 may use it to allow the client to schedule its next request and 281 thus save its own workload by reducing processing of similar 282 requests. 284 Attribute "repeated" may take a very high value if a Calendar 285 represents a cyclic value pattern that the Server considers valid for 286 a long period. In this case, the Server will only update the 287 Calendar values once this period has elapsed or if an unexpected 288 event occurs on the network. 290 2.5. ALTO Calendar design characteristics 292 The extensions in this document and encode requests and responses 293 using JSON [RFC8259]. 295 Formally, the cost entries in an ALTO cost map can be any type of 296 JSON value [RFC8259], (see the DstCosts object in Section 11.2.3.6 of 297 [RFC7285]). However, that section states that an implementation of 298 [RFC7285] SHOULD assume that the cost is a JSON number and fail to 299 parse if it is not, unless the implementation is using an extension 300 that signals a different data type. This document extends the 301 definition of a legacy cost map given in [RFC7285] to allow a cost 302 entry to be an array of values, one per time interval, instead of 303 just one number. 305 To realize an ALTO Calendar, this document extends: the IRD, the ALTO 306 requests and responses for Cost Calendars. 308 This extension is designed to be lightweight and to ensure backwards 309 compatibility with base protocol ALTO Clients and with other 310 extensions. It relies on section 8.3.7 "Parsing of Unknown Fields" 311 of [RFC7285] that writes: "Extensions may include additional fields 312 within JSON objects defined in this document. ALTO implementations 313 MUST ignore unknown fields when processing ALTO messages." 315 The Calendar-specific capabilities are integrated in the information 316 resources of the IRD and in the "meta" member of ALTO responses to 317 Cost Calendars requests. A Calendar and its capabilities are 318 associated with a given information resource and within this 319 information resource with a given cost type. This design has several 320 advantages: 322 o it does not introduce a new mode, 324 o it does not introduce new media types, 326 o it allows an ALTO Server to offer Calendar capabilities on a cost 327 type, with attributes values adapted to each information resource. 329 The applicable Calendared information resources are: 331 o the Filtered Cost Map, 333 o the Endpoint Cost Map. 335 The ALTO Server can choose in which frequency it provides cost 336 Calendars to ALTO Clients. It may either provide Calendar updates 337 starting at the request date, or carefully schedule its updates so as 338 to take profit from a potential repetition/periodicity of Calendar 339 values. 341 2.5.1. ALTO Cost Calendar for all cost modes 343 An ALTO Cost Calendar is well-suited for values encoded in the 344 "numerical" mode. Actually, a Calendar can also represent metrics in 345 other modes considered as compatible with time-varying values. For 346 example, types of Cost values such as JSONBool can also be 347 calendared, as their value may be 'true' or 'false' depending on 348 given time periods or likewise, values represented by strings, such 349 as "medium", "high", "low", "blue", "open". 351 Note also that a Calendar is suitable as well for time-varying 352 metrics provided in the "ordinal" mode, if these values are time- 353 varying and the ALTO Server provides updates of cost value based 354 preferences. 356 2.5.2. Compatibility with legacy ALTO Clients 358 The ALTO protocol extensions for Cost Calendars have been defined so 359 as to ensure that Calendar capable ALTO Servers can provide legacy 360 ALTO Clients with legacy information resources as well. That is, a 361 legacy ALTO Client can request resources and receive responses as 362 specified in [RFC7285]. 364 A Calendar-aware ALTO Server MUST implement the base protocol 365 specified in [RFC7285]. 367 As a consequence, when a metric is available as a Calendar array, it 368 also MUST be available as a single value as required by [RFC7285]. 369 The Server, in this case, provides the current value of the metric to 370 either Calendar-aware Clients not interested in future or time-based 371 values, or Clients implementing [RFC7285] only. 373 For compatibility with legacy ALTO Clients specified in [RFC7285], 374 calendared information resources are not applicable for full cost 375 maps for the following reason: a legacy ALTO Client would receive a 376 calendared cost map via an HTTP 'GET' command. As specified in 377 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 378 indicated in the "meta" of the responses. Therefore, lacking 379 information on Calendar attributes, it will not be able to correctly 380 interpret and process the values of the received array of Calendar 381 cost values. 383 Therefore, calendared information resources MUST be requested via the 384 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 385 method. 387 3. ALTO Calendar specification: IRD extensions 389 The Calendar attributes in the IRD information resources capabilities 390 carry constant dateless values. A Calendar is associated with an 391 information resource rather than a cost type. For example, a Server 392 can provide a "routingcost" Calendar for the Filtered Cost Map 393 Service at a granularity of one day and a "routingcost" Calendar for 394 the Endpoint Cost Service at a finer granularity but for a limited 395 number of endpoints. An example IRD with Calendar specific features 396 is provided in Section 3.3. 398 3.1. Calendar attributes in the IRD resource capabilities 400 A Cost Calendar for a given Cost Type MUST be indicated in the IRD by 401 an object of type CalendarAttributes. A CalendarAttribute object is 402 represented by the "calendar-attributes" member of a resource entry. 403 Each CalendarAttributes object applies to a set of one or more cost 404 types. A Cost Type name MUST appear no more than once in the 405 "calendar-attributes" member of a resource entry; multiple 406 appearances of a Cost Type name in CalendarAttributes object of the 407 "calendar-attributes" member MUST cause the ALTO Client to ignore any 408 occurrences of this name beyond the first encountered occurrence. 410 It is RECOMMENDED for an ALTO Server that the time interval size 411 specified in the IRD is the smallest possible one that it can 412 provide. The Client can aggregate cost values on its own if it needs 413 a larger granularity. 415 The encoding format for object CalendarAttributes, using JSON 416 [RFC8259], is as follows: 418 CalendarAttributes calendar-attributes <1..*>; 420 object{ 421 JSONString cost-type-names <1..*>; 422 JSONNumber time-interval-size; 423 JSONNumber number-of-intervals; 424 } CalendarAttributes; 426 o "cost-type-names": 428 * An array of one or more elements indicating the cost-type-names 429 in the IRD entry to which the capabilities apply. 431 o "time-interval-size": 433 * is the duration of an ALTO Calendar time interval in seconds. 434 A "time-interval-size" value contains a JSONNumber. ALTO 435 Servers SHOULD use at least IEEE 754 double-precision floating 436 point [IEEE.754.2008] to store this value. Example values are: 437 300 , 7200, meaning that each Calendar value applies on a time 438 interval that lasts 5 minutes and 2 hours, respectively. 440 o "number-of-intervals": 442 * the integer number of values of the Cost Calendar array, at 443 least equal to 1. 445 - Attribute "cost-type-names" provides a better readability to the 446 Calendar attributes specified in the IRD and avoids confusion with 447 Calendar attributes of other cost-types. 449 - Multiplying 'time-interval-size' by 'number-of-intervals' provides 450 the duration of the provided Calendar. For example, an ALTO Server 451 may provide a Calendar for ALTO values changing every 'time-interval- 452 size' equal to 5 minutes. If 'number-of-intervals' has the value 12, 453 then the duration of the provided Calendar is "1 hour". 455 3.2. Calendars in a delegate IRD 457 It may be useful to distinguish IRD resources supported by the base 458 ALTO protocol from resources supported by its extensions. To achieve 459 this, one option, is that a "root" ALTO Server implementing base 460 protocol resources delegates "specialized" information resources such 461 as the ones providing Cost Calendars, to another ALTO Server running 462 in a subdomain that is specified with its URI in the "root" ALTO 463 Server. This option is described in Section 9.2.4 "Delegation using 464 IRDs" of [RFC7285]. 466 This document provides an example, where a "root" ALTO Server runs in 467 a domain called "alto.example.com". It delegates the announcement of 468 Calendars capabilities to an ALTO Server running in a subdomain 469 called "custom.alto.example.com". The location of the "delegate 470 Calendar IRD" is assumed to be indicated in the "root" IRD by the 471 resource entry: "custom-calendared-resources". 473 Another advantage is that some Cost Types for some resources may be 474 more advantageous as Cost Calendars and it makes few sense to get 475 them as a single value. For example, Cost Types with predictable and 476 frequently changing values, calendared in short time intervals such 477 as a minute. 479 3.3. Example IRD with ALTO Cost Calendars 481 This section provides an example ALTO Server IRD that supports 482 various cost metrics and cost modes. In particular, since [RFC7285] 483 makes it mandatory, the Server uses metric "routingcost" in the 484 "numerical" mode. 486 For illustrative purposes, this section introduces 3 other fictitious 487 example metrics and modes that should be understood as examples and 488 should not be used or considered as normative. 490 The cost type names used in the example IRD as thus as follows: 492 o "num-routingcost": refers to metric "routingcost" in the numerical 493 mode as defined in [RFC7285] and registered with IANA. 495 o "num-owdelay": refers to fictitious performance metric "owdelay" 496 in the "numerical" mode,to reflect the one-way packet transmission 497 delay on a path. A related performance metric is currently under 498 definition in [draft-ietf-alto-performance-metrics]. 500 o "num-throughputrating": refers to fictitious metric 501 "throughputrating" in the "numerical" mode, to reflect the 502 provider preference in terms of end to end throughput. 504 o "string-servicestatus": refers to fictitious metric 505 "servicestatus" containing a string, to reflect the availability, 506 defined by the provider, of for instance path connectivity. 508 The example IRD includes 2 particular URIs providing Calendars: 510 o "https://custom.alto.example.com/calendar/costmap/filtered": a 511 filtered cost map in which Calendar capabilities are indicated for 512 cost type names: "num-routingcost", "num-throughputrating" and 513 "string-servicestatus", 515 o "https://custom.alto.example.com/calendar/endpointcost/lookup": an 516 endpoint cost map in which Calendar capabilities are indicated for 517 cost type names: "num-routingcost", "num-owdelay", "num- 518 throughputrating", "string-servicestatus". 520 The design of the Calendar capabilities allows some Calendars with 521 the same cost type name to be available in several information 522 resources with different Calendar Attributes. This is the case for 523 Calendars on "num-routingcost", "num-throughputrating" and "string- 524 servicestatus", available in both the Filtered Cost map and Endpoint 525 Cost Service, but with different time interval sizes for "num- 526 throughputrating" and "string-servicestatus". 528 --- Client to Server request for IRD ---------- 530 GET /calendars-directory HTTP/1.1 531 Host: custom.alto.example.com 532 Accept: application/alto-directory+json,application/alto-error+json 534 --- Server response to Client ----------------- 536 HTTP/1.1 200 OK 537 Content-Length: 2542 538 Content-Type: application/alto-directory+json 540 { 541 "meta" : { 542 "default-alto-network-map" : "my-default-network-map", 543 "cost-types": { 544 "num-routingcost": { 545 "cost-mode" : "numerical", 546 "cost-metric" : "routingcost" 547 }, 548 "num-owdelay": { 549 "cost-mode" : "numerical", 550 "cost-metric": "owdelay" 551 }, 552 "num-throughputrating": { 553 "cost-mode" : "numerical", 554 "cost-metric": "throughputrating" 555 }, 556 "string-servicestatus": { 557 "cost-mode" : "string", 558 "cost-metric": "servicestatus" 559 } 560 } 561 }, 562 "resources" : { 563 "filtered-cost-map-calendar" : { 564 "uri" : 565 "https://custom.alto.example.com/calendar/costmap/filtered", 566 "media-type" : "application/alto-costmap+json", 567 "accepts" : "application/alto-costmapfilter+json", 568 "capabilities" : { 569 "cost-constraints" : true, 570 "cost-type-names" : [ "num-routingcost", 571 "num-throughputrating", 572 "string-servicestatus" ], 573 "calendar-attributes" : [ 574 {"cost-type-names" : [ "num-routingcost", 575 "num-throughputrating" ], 576 "time-interval-size" : 7200, 577 "number-of-intervals" : 12 578 }, 579 {"cost-type-names" : [ "string-servicestatus" ], 580 "time-interval-size" : 1800, 581 "number-of-intervals" : 48 582 } 583 ] 584 }, 585 "uses": [ "my-default-network-map" ] 586 }, 587 "endpoint-cost-calendar-map" : { 588 "uri" : 589 "https://custom.alto.example.com/calendar/endpointcost/lookup", 590 "media-type" : "application/alto-endpointcost+json", 591 "accepts" : "application/alto-endpointcostparams+json", 592 "capabilities" : { 593 "cost-constraints" : true, 594 "cost-type-names" : [ "num-routingcost", 595 "num-owdelay", 596 "num-throughputrating", 597 "string-servicestatus" ], 598 "calendar-attributes" : [ 599 {"cost-type-names" : [ "num-routingcost" ], 600 "time-interval-size" : 3600, 601 "number-of-intervals" : 24 602 }, 603 {"cost-type-names" : [ "num-owdelay" ], 604 "time-interval-size" : 300, 605 "number-of-intervals" : 12 606 }, 607 {"cost-type-names" : [ "num-throughputrating" ], 608 "time-interval-size" : 60, 609 "number-of-intervals" : 60 610 }, 611 {"cost-type-names" : [ "string-servicestatus" ], 612 "time-interval-size" : 120, 613 "number-of-intervals" : 30 614 } 615 ] 616 } 617 } 618 } 619 } 621 In this example IRD, for the Filtered Cost Map Service: 623 o the Calendar for "num-routingcost" and "num-throughputrating" is 624 an array of 12 values each provided on a time interval lasting 625 7200 seconds (2 hours). 627 o the Calendar for "string-servicestatus": "is an array of 48 values 628 each provided on a time interval lasting 1800 seconds (30 629 minutes). 631 For the Endpoint Cost Service: 633 o the Calendar for "num-routingcost": is an array of 24 values each 634 provided on a time interval lasting 3600 seconds (1 hour). 636 o the Calendar for "owdelay": is an array of 12 values each provided 637 on a time interval lasting 300 seconds (5 minutes). 639 o the Calendar for "num-throughputrating": is an array of 60 values 640 each provided on a time interval lasting 60 seconds (1 minute). 642 o the Calendar for "string-servicestatus": "is an array of 30 values 643 each provided on a time interval lasting 120 seconds (2 minutes). 645 4. ALTO Calendar specification: Service Information Resources 647 This section documents the individual information resources defined 648 to provide the calendared information services defined in this 649 document. 651 The reference time zone for the provided time values is UTC. The 652 option chosen to express the time format is the HTTP header fields 653 format specified in [RFC7231] where, however, timestamps are still 654 displayed with the acronym "GMT" rather than "UTC": 656 Date: Tue, 15 Nov 2014 08:12:31 GMT 658 The value of a Calendar time interval size is expressed in seconds. 660 4.1. Calendar extensions for Filtered Cost Maps (FCM) 662 A legacy ALTO Client requests and gets Filtered Cost Map responses as 663 specified in [RFC7285]. 665 4.1.1. Calendar extensions in Filtered Cost Map requests 667 The input parameters of a "legacy" request for a filtered cost map, 668 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 669 are augmented with one additional member. 671 A Calendar-aware ALTO Client requesting a Calendar on a given Cost 672 Type for a filtered cost map resource having Calendar capabilities 673 MUST add the following field to its input parameters: 675 JSONBoolean calendared<1..*>; 677 This field is an array of 1 to N boolean values, where N is the 678 number of requested metrics. Each entry corresponds to the requested 679 metric at the same array position. Each boolean value indicates 680 whether or not the ALTO Server should provide the values for this 681 Cost Type as a Calendar. The array MUST contain exactly N boolean 682 values, otherwise, the Server returns an error. 684 This field MUST NOT be included if no member "calendar-attributes" is 685 specified in this information resource. 687 If a value of field 'calendared' is 'true' for a cost type name for 688 which no Calendar attributes have been specified: an ALTO Server, 689 whether it implements the extensions of this document or only 690 implements [RFC7285], MUST ignore it and return a response with a 691 single cost value as specified in [RFC7285]. 693 If this field is not present, it MUST be assumed to have only values 694 equal to 'false'. 696 A Calendar-aware ALTO Client that supports requests for only one cost 697 type at a time and wants to request a Calendar MUST provide an array 698 of 1 element: 700 "calendared" : [true]; 702 A Calendar-aware ALTO Client that supports requests for more than one 703 Cost Types at a time, as specified in [RFC8189] MUST provide an array 704 of N values set to 'true' or 'false', depending whether it wants the 705 applicable Cost Type values as a single or calendared value. 707 4.1.2. Calendar extensions in Filtered Cost Map responses 709 In a calendared ALTO Filtered Cost Map, a cost value between a source 710 and a destination is a JSON array of JSON values. An ALTO Calendar 711 values array has a number of values equal to the value of member 712 "number-of-intervals" of the Calendar attributes that are indicated 713 in the IRD. These attributes will be conveyed as metadata in the 714 Filtered Cost Map response. Each element of the array is valid for 715 the time-interval that matches its array position. 717 The FCM response conveys metadata among which: 719 o some are not specific to Calendars and ensure compatibility with 720 [RFC7285] and [RFC8189] 722 o some are specific to Calendars. 724 The non Calendar specific "meta" fields of a calendared Filtered Cost 725 Map response MUST include at least: 727 o if the ALTO Client requests cost values for one Cost Type at a 728 time only: the "meta" fields specified in [RFC7285] for these 729 information service responses: 731 * "dependent-vtags ", 733 * "cost-type" field. 735 o if the ALTO Client implements the Multi-Cost ALTO extension 736 specified in [RFC8189] and requests cost values for several Cost 737 Types at a time: the "meta" fields specified in [RFC8189] for 738 these information service responses: 740 * "dependent-vtags ", 742 * "cost-type" field with value set to '{}', for backwards 743 compatibility with [RFC7285]. 745 * "multi-cost-types" field. 747 If the client request does not provide member "calendared" or if it 748 provides it with a value equal to 'false', for all the requested Cost 749 Types, then the ALTO Server response is exactly as specified in 750 [RFC7285] and [RFC8189]. 752 If the value of member "calendared" is equal to 'false' for a given 753 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 754 a single cost value as specified in [RFC7285]. 756 If the value of member "calendared" is equal to 'true' for a given 757 requested Cost Type, the ALTO Server returns, for this Cost Type, a 758 cost value Calendar as specified above in this section. In addition 759 to the above cited non Calendar specific "meta" members, the Server 760 MUST provide a Calendar specific metadata field. 762 The Calendar specific "meta" field that a calendared Filtered Cost 763 Map response MUST include is a member called "calendar-response- 764 attributes", that describes properties of the Calendar and where: 766 o member "calendar-response-attributes" is an array of one or more 767 objects of type "CalendarResponseAttributes". 769 o each "CalendarResponseAttributes" object in the array is specified 770 for one or more Cost Types for which the value of member 771 "calendared" is equal to 'true' and for which a Calendar is 772 provided for the requested information resource. 774 o the "CalendarResponseAttributes" object that applies to a cost 775 type name has a corresponding "CalendarAttributes" object defined 776 for this cost type name in the IRD capabilities of the requested 777 information resource. The members of a 778 "CalendarResponseAttributes" object include all the members of the 779 corresponding "CalendarAttributes" object. 781 The format of member "CalendarResponseAttributes is defined as 782 follows: 784 CalendarResponseAttributes calendar-response-attributes <1..*>; 786 object{ 787 [JSONString cost-type-names <1..*>]; 788 JSONString calendar-start-time; 789 JSONNumber time-interval-size; 790 JSONNumber number-of-intervals; 791 [JSONNumber repeated;] 792 } CalendarResponseAttributes; 794 Object CalendarResponseAttributes has the following attributes: 796 o "cost-type-names": is an array of one or more cost-type-names to 797 which the capabilities apply and for which a Calendar has been 798 requested. The value of this member is a subset of the "cost- 799 type-names" array specified in the corresponding IRD Calendar 800 attributes. 802 o "calendar-start-time": indicates the date at which the first value 803 of the Calendar applies. The value provided for the "calendar- 804 start-time" attribute SHOULD NOT be later than the request date. 806 o "time-interval-size": as specified in Section 3.1 and with the 807 same value. 809 o "number-of-intervals": as specified in Section 3.1 and with the 810 same value. 812 o "repeated": is an optional field provided for Calendars. It is an 813 integer N greater or equal to '1' that indicates how many 814 iterations of the Calendar value array starting at the date 815 indicated by "calendar-start-time" have the same values. The 816 number N includes the provided iteration. 818 For example: suppose the "calendar-start-time" member has value "Mon, 819 30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has 820 value '3600', the "number-of-intervals" member has value '24' and the 821 value of member "repeated" is equal to '4'. This means that the 822 Calendar values are the same on Monday, Tuesday, Wednesday and 823 Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO 824 Client thus may use the same Calendar for the next 4 days starting at 825 "calendar-start-time" and will only need to request a new one for 826 Friday July 4th at 00:00:00 GMT. 828 Attribute "repeated" may take a very high value if a Calendar 829 represents a cyclic value pattern that the Server considers valid for 830 a long period and hence will only update once this period has elapsed 831 or if an unexpected event occurs on the network. In the latter case, 832 the client will be notified if it uses the "ALTO Incremental Updates 833 Using Server-Sent Events (SSE)" Service, specified in 834 [draft-ietf-alto-incr-update-sse]. To this end, it is RECOMMENDED 835 that ALTO Servers providing ALTO Calendars also provide the "ALTO 836 Incremental Updates Using Server-Sent Events (SSE)" Service that is 837 specified in [draft-ietf-alto-incr-update-sse]. Likewise, ALTO 838 Clients capable of using ALTO Calendars SHOULD also use the SSE 839 Service. See also discussion in Section 7 "Operational 840 Considerations". 842 4.1.3. Use case and example: FCM with a bandwidth Calendar 844 An example of non-real time information that can be provisioned in a 845 Calendar is the expected path throughput. While the transmission 846 rate can be measured in real time by end systems, the operator of a 847 data center is in the position of formulating preferences for given 848 paths, at given time periods to avoid traffic peaks due to diurnal 849 usage patterns. In this example, we assume that an ALTO Client 850 requests a Calendar of network provider defined throughput ratings, 851 as specified in the IRD, to schedule its bulk data transfers as 852 described in the use cases. 854 In the example IRD, Calendars for cost type name "num- 855 throughputrating" are available for the information resources: 856 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 857 ALTO Client requests a Calendar for "num-throughputrating" via a POST 858 request for a filtered cost map. 860 We suppose in the present example that the ALTO Client sends its 861 request on Tuesday July 1st 2014 at 13:15. The Server returns 862 Calendars with arrays of 12 numbers for each source and destination 863 pair. The values for metric "throughputrating", in this example, are 864 assumed to be encoded in 2 digits. 866 POST /calendar/costmap/filtered HTTP/1.1 867 Host: alto.example.com 868 Content-Length: 208 869 Content-Type: application/alto-costmapfilter+json 870 Accept: application/alto-costmap+json,application/alto-error+json 872 { 873 "cost-type" : {"cost-mode" : "numerical", 874 "cost-metric" : "throughputrating"}, 875 "calendared" : [true], 876 "pids" : { 877 "srcs" : [ "PID1", "PID2" ], 878 "dsts" : [ "PID1", "PID2", "PID3" ] 879 } 880 } 882 HTTP/1.1 200 OK 883 Content-Length: 1013 884 Content-Type: application/alto-costmap+json 886 { 887 "meta" : { 888 "dependent-vtags" : [ 889 {"resource-id": "my-default-network-map", 890 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 891 } 892 ], 893 "cost-type" : {"cost-mode" : "numerical", 894 "cost-metric" : "throughputrating"}, 895 "calendar-response-attributes" : [ 896 {"calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 897 "time-interval-size" : 7200, 898 "number-of-intervals" : 12} 899 ] 900 }, 901 "cost-map" : { 902 "PID1": { "PID1": [ 1, 12, 14, 18, 14, 14, 903 14, 18, 19, 20, 11, 12], 904 "PID2": [13, 4, 15, 16, 17, 18, 905 19, 20, 11, 12, 13, 14], 906 "PID3": [20, 20, 18, 14, 12, 12, 907 14, 14, 12, 12, 14, 16] }, 908 "PID2": { "PID1": [17, 18, 19, 10, 11, 12, 909 13, 14, 15, 16, 17, 18], 910 "PID2": [20, 20, 18, 16, 14, 14, 911 14, 16, 16, 16, 14, 16], 912 "PID3": [20, 20, 18, 14, 12, 12, 913 14, 14, 12, 12, 14, 16] } 914 } 915 } 917 4.2. Calendar extensions in the Endpoint Cost Service 919 This document extends the Endpoint Cost Service, as defined in 920 {11.5.1} of [RFC7285], by adding new input parameters and 921 capabilities, and by returning JSONArrays instead of JSONNumbers as 922 the cost values. The media type {11.5.1.1} and HTTP method 923 {11.5.1.2} are unchanged. 925 4.2.1. Calendar specific input in Endpoint Cost requests 927 The extensions to the requests for calendared Endpoint Cost Maps are 928 the same as for the Filtered Cost Map Service, specified in section 929 Section 4.1.1 of this draft. 931 The ReqEndpointCostMap object for a calendared ECM request will have 932 the following format: 934 object { 935 [CostType cost-type;] 936 [CostType multi-cost-types<1..*>;] 937 [JSONBoolean calendared<1..*>;] 938 EndpointFilter endpoints; 939 } ReqEndpointCostMap; 941 object { 942 [TypedEndpointAddr srcs<0..*>;] 943 [TypedEndpointAddr dsts<0..*>;] 944 } EndpointFilter; 946 4.2.2. Calendar attributes in the Endpoint Cost response 948 The "meta" field of a calendared Endpoint Cost response MUST include 949 at least: 951 o if the ALTO Client supports cost values for one Cost Type at a 952 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 953 for the Endpoint Cost response: 955 * "cost-type" field. 957 o if the ALTO Client supports cost values for several Cost Types at 958 a time, as specified in [RFC8189] : the "meta" fields specified in 959 [RFC8189] for the the Endpoint Cost response: 961 * "cost-type" field with value set to '{}', for backwards 962 compatibility with [RFC7285]. 964 * "multi-cost-types" field. 966 If the client request does not provide member "calendared" or if it 967 provides it with a value equal to 'false', for all the requested Cost 968 Types, then the ALTO Server response is exactly as specified in 969 [RFC7285] and [RFC8189]. 971 If the ALTO Client provides member "calendared" in the input 972 parameters with a value equal to 'true' for given requested Cost 973 Types, the "meta" member of a calendared Endpoint Cost response MUST 974 include, for these Cost Types, an additional member "calendar- 975 response-attributes", the contents of which obey the same rules as 976 for the Filtered Cost Map Service, specified in Section 4.1.2. The 977 Server response is thus changed as follows, w.r.t [RFC7285] and 978 [RFC8189]: 980 o the "meta" member has one additional field 981 "CalendarResponseAttributes", as specified for the Filtered Cost 982 Map Service, 984 o the calendared costs are JSONArrays instead of the JSONNumbers 985 format used by legacy ALTO implementations. All arrays have a 986 number of values equal to 'number-of-intervals'. 988 If the value of member "calendared" is equal to 'false' for a given 989 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 990 a single cost value as specified in [RFC7285]. 992 4.2.3. Use case and example: ECS with a routingcost Calendar 994 Let us assume an Application Client is located in an end system with 995 limited resources and having access to the network that is either 996 intermittent or provides an acceptable quality in limited but 997 predictable time periods. Therefore, it needs to both schedule its 998 resource-greedy networking activities and its ALTO transactions. 1000 The Application Client has the choice to trade content or resources 1001 with a set of Endpoints and needs to decide with which one it will 1002 connect and at what time. For instance, the Endpoints are spread in 1003 different time-zones, or have intermittent access. In this example, 1004 the 'routingcost' is assumed to be time-varying, with values provided 1005 as ALTO Calendars. 1007 The ALTO Client associated with the Application Client queries an 1008 ALTO Calendar on 'routingcost' and will get the Calendar covering the 1009 24 hours time period "containing" the date and time of the ALTO 1010 client request. 1012 For Cost Type "num-routingcost", the solicited ALTO Server has 1013 defined 3 different daily patterns each represented by a Calendar, to 1014 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 1016 - C1 for Monday, Tuesday, Wednesday, Thursday, (weekdays) 1018 - C2 for Saturday, Sunday, (weekend) 1020 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 1021 to 04:00:00 GMT, or big holiday such as New Year evening). 1023 In the following example, the ALTO Client sends its request on 1024 Tuesday July 1st 2014 at 13:15. 1026 The "routingcost" values are assumed to be encoded in 3 digits. 1028 POST /calendar/endpointcost/lookup HTTP/1.1 1029 Host: alto.example.com 1030 Content-Length: 290 1031 Content-Type: application/alto-endpointcostparams+json 1032 Accept: application/alto-endpointcost+json,application/alto-error+json 1034 { 1035 "cost-type" : {"cost-mode" : "numerical", 1036 "cost-metric" : "routingcost"}, 1037 "calendared" : [true], 1038 "endpoints" : { 1039 "srcs": [ "ipv4:192.0.2.2" ], 1040 "dsts": [ 1041 "ipv4:192.0.2.89", 1042 "ipv4:198.51.100.34", 1043 "ipv4:203.0.113.45", 1044 "ipv6:2001:db8::10" 1045 ] 1046 } 1047 } 1049 HTTP/1.1 200 OK 1050 Content-Length: 1318 1051 Content-Type: application/alto-endpointcost+json 1053 { 1054 "meta" : { 1055 "cost-type" : {"cost-mode" : "numerical", 1056 "cost-metric" : "routingcost"}, 1057 "calendar-response-attributes" : [ 1058 {"calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1059 "time-interval-size" : 3600, 1060 "number-of-intervals" : 24, 1061 "repeated": 4 1062 } 1063 ] 1064 }, 1065 "endpoint-cost-map" : { 1066 "ipv4:192.0.2.2": { 1067 "ipv4:192.0.2.89" : [100, 100, 100, 100, 100, 150, 1068 200, 300, 300, 300, 300, 250, 1069 250, 300, 300, 300, 300, 300, 1070 400, 250, 250, 200, 150, 150], 1071 "ipv4:198.51.100.34" : [ 80, 80, 80, 80, 150, 150, 1072 250, 400, 400, 450, 400, 200, 1073 200, 350, 400, 400, 400, 350, 1074 500, 200, 200, 200, 100, 100], 1075 "ipv4:203.0.113.45" : [300, 400, 250, 250, 200, 150, 1076 150, 100, 100, 100, 100, 100, 1077 100, 100, 100, 100, 100, 150, 1078 200, 300, 300, 300, 300, 250], 1079 "ipv6:2001:db8::10" : [200, 250, 300, 300, 300, 300, 1080 250, 300, 300, 300, 300, 350, 1081 300, 400, 250, 150, 100, 100, 1082 100, 150, 200, 250, 250, 300] 1083 } 1084 } 1085 } 1087 When the Client gets the Calendar for "routingcost", it sees that the 1088 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 1089 equal to '4'. It understands that the provided values are valid 1090 until Thursday included and will only need to get a Calendar update 1091 on Friday. 1093 4.2.4. Use case and example: ECS with a multi-cost Calendar for 1094 routingcost and owdelay 1096 In this example, it is assumed that the ALTO Server implements multi- 1097 cost capabilities, as specified in [RFC8189] . That is, an ALTO 1098 Client can request and receive values for several cost types in one 1099 single transaction. An illustrating use case is a path selection 1100 done on the basis of 2 metrics: routing cost and owdelay. 1102 As in the previous example, the IRD indicates that the ALTO Server 1103 provides "routingcost" Calendars in terms of 24 time intervals of 1 1104 hour (3600 seconds) each. 1106 For metric "owdelay", the IRD indicates that the ALTO Server provides 1107 Calendars in terms of 12 time intervals values lasting each 5 minutes 1108 (300 seconds). 1110 In the following example transaction, the ALTO Client sends its 1111 request on Tuesday July 1st 2014 at 13:15. 1113 This example assumes that the values of metric "owdelay" and 1114 "routingcost" are encoded in 3 digits. 1116 POST calendar/endpointcost/lookup HTTP/1.1 1117 Host: alto.example.com 1118 Content-Length: 373 1119 Content-Type: application/alto-endpointcostparams+json 1120 Accept: application/alto-endpointcost+json,application/alto-error+json 1122 { 1123 "cost-type" : {}, 1124 "multi-cost-types" : [ 1125 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1126 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1127 ], 1128 "calendared" : [true, true], 1129 "endpoints" : { 1130 "srcs": [ "ipv4:192.0.2.2" ], 1131 "dsts": [ 1132 "ipv4:192.0.2.89", 1133 "ipv4:198.51.100.34", 1134 "ipv4:203.0.113.45", 1135 "ipv6:2001:db8::10" 1136 ] 1137 } 1138 } 1139 HTTP/1.1 200 OK 1140 Content-Length: 2111 1141 Content-Type: application/alto-endpointcost+json 1143 { 1144 "meta" : { 1145 "multi-cost-types" : [ 1146 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1147 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1148 ], 1149 "calendar-response-attributes" : [ 1150 {"cost-type-names" : "num-routingcost", 1151 "calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1152 "time-interval-size" : 3600, 1153 "number-of-intervals" : 24, 1154 "repeated": 4 }, 1155 {"cost-type-names" : "num-owdelay", 1156 "calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 1157 "time-interval-size" : 300, 1158 "number-of-intervals" : 12} 1159 ] 1160 }, 1161 "endpoint-cost-map" : { 1162 "ipv4:192.0.2.2": { 1163 "ipv4:192.0.2.89" : [[100, 100, 100, 100, 100, 150, 1164 200, 300, 300, 300, 300, 250, 1165 250, 300, 300, 300, 300, 300, 1166 400, 250, 250, 200, 150, 150], 1167 [ 20, 400, 20, 80, 80, 90, 1168 100, 90, 60, 40, 30, 20]], 1169 "ipv4:198.51.100.34" : [[ 80, 80, 80, 80, 150, 150, 1170 250, 400, 400, 450, 400, 200, 1171 200, 350, 400, 400, 400, 350, 1172 500, 200, 200, 200, 100, 100], 1173 [ 20, 20, 50, 30, 30, 30, 1174 30, 40, 40, 30, 20, 20]], 1175 "ipv4:203.0.113.45" : [[300, 400, 250, 250, 200, 150, 1176 150, 100, 100, 100, 100, 100, 1177 100, 100, 100, 100, 100, 150, 1178 200, 300, 300, 300, 300, 250], 1179 [100, 90, 80, 60, 50, 50, 1180 40, 40, 60, 90, 100, 80]], 1181 "ipv6:2001:db8::10" : [[200, 250, 300, 300, 300, 300, 1182 250, 300, 300, 300, 300, 350, 1183 300, 400, 250, 150, 100, 100, 1184 100, 150, 200, 250, 250, 300], 1185 [ 40, 40, 40, 40, 50, 50, 1186 50, 20, 10, 15, 30, 40]] 1188 } 1189 } 1190 } 1192 When receiving the response, the client sees that the Calendar values 1193 for metric "routingcost" are repeated for 4 iterations. Therefore, 1194 in its next requests until the "routingcost" Calendar is expected to 1195 change, the client will only need to request a Calendar for 1196 "owdelay". 1198 Without the ALTO Calendar extensions, the ALTO Client would have no 1199 clue on the dynamicity of the metric value change and would spend 1200 needless time requesting values at an inappropriate pace. In 1201 addition, without the Multi-Cost ALTO capabilities, the ALTO Client 1202 would duplicate this waste of time as it would need to send one 1203 request per cost metric. 1205 5. IANA Considerations 1207 This document does not define any new media types or introduce any 1208 new IANA considerations. 1210 6. Security Considerations 1212 As an extension of the base ALTO protocol [RFC7285], this document 1213 fits into the architecture of the base protocol, and hence the 1214 Security Considerations (Section 15) of the base protocol fully apply 1215 when this extension is provided by an ALTO Server. For example, the 1216 same authenticity and integrity considerations (Section 15.1 of 1217 [RFC7285] still fully apply; the same considerations for the privacy 1218 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1220 The calendaring information provided by this extension requires 1221 additional considerations on three security considerations discussed 1222 in the base protocol: potential undesirable guidance to clients 1223 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1224 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1225 of [RFC7285]). For example, by providing network information in the 1226 future in a Calendar, this extension may improve availability of 1227 ALTO, when the ALTO Server is unavailable but related information is 1228 already provided in the Calendar. 1230 For confidentiality of ALTO information, an operator should be 1231 cognizant that this extension may introduce a new risk: an ALTO 1232 Client may get information for future events that are scheduled 1233 through Calendaring. Possessing such information, the client may use 1234 it to achieve its goal: (1) initiating connections only at 1235 advantageous network costs, leading to unexpected network load; (2) 1236 generating massive connections to the network at times where its load 1237 is expected to be high. 1239 To mitigate this risk, the operator should address the risk of ALTO 1240 information being leaked to malicious clients or third parties. As 1241 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1242 the ALTO Server should authenticate ALTO Clients and use the 1243 Transport Layer Security (TLS) protocol so that Man In The Middle 1244 (MITM) attacks to intercept an ALTO Calendar are not possible. 1245 [RFC7285] ensures the availability of such a solution in its 1246 Section 8.3.5. "Authentication and Encryption", which specifies 1247 that: "ALTO Server implementations as well as ALTO Client 1248 implementations MUST support the "https" URI scheme of [RFC2818] and 1249 Transport Layer Security (TLS) of [RFC5246]". 1251 [RFC8446] specifies TLS 1.3 and writes in its section 1: "While TLS 1252 1.3 is not directly compatible with previous versions, all versions 1253 of TLS incorporate a versioning mechanism which allows clients and 1254 servers to interoperably negotiate a common version if one is 1255 supported by both peers". So ALTO Clients and servers MAY use newer 1256 versions (e.g., 1.3) of TLS as long as the negotiation process 1257 succeeds. To ensure backward compatibility with [RFC7285], it is 1258 RECOMMENDED for both Calendar-aware Clients and Servers to both 1259 support at least TLS 1.2, until it gets deprecated. 1261 To avoid malicious or erroneous guidance from ALTO information, an 1262 ALTO Client should be cognizant that using calendaring information 1263 can have risks: (1) Calendar values, especially in "repeated" 1264 Calendars may be only statistical, and (2) future events may change. 1265 Hence, a more robust ALTO Client should adapt and extend protection 1266 strategies specified in Section 15.2 of the base protocol. For 1267 example, to be notified immediately when a particular ALTO value that 1268 the client depends on changes, it is RECOMMENDED that both the ALTO 1269 Client and ALTO Server using this extension support "ALTO Incremental 1270 Updates Using Server-Sent Events(SSE)" Service [draft-ietf-alto-incr- 1271 update-sse]. 1273 7. Operational Considerations 1275 Conveying ALTO Cost Calendars tends to reduce the on-the-wire data 1276 exchange volume compared to multiple single cost ALTO transactions. 1277 An application using Calendars has a set of time-dependent values 1278 upon which it can plan its connections in advance with no need for 1279 the ALTO Client to query information at each time. Additionally, the 1280 Calendar response attribute "repeated", when provided, saves 1281 additional data exchanges in that it indicates that the ALTO Client 1282 does not need to query Calendars during a period indicated by this 1283 attribute. Unexpected changes during this period can be handled by 1284 using the SSE Service as discussed in Section 6, if the Server and 1285 the Client support it. 1287 High-resolution intervals may be needed when values change, sometimes 1288 during very small time intervals but in a significant manner. A way 1289 to avoid conveying too many entries is to leverage on the "repeated" 1290 feature. A server can smartly set the Calendar start time and number 1291 of intervals so as to declare them "repeated" for a large number of 1292 periods, until the Calendar values change and are conveyed to 1293 requesting Clients. 1295 Clients and Servers supporting ALTO Calendars use [RFC8259]. 1296 [RFC7285] encodes its requests and responses using the JSON Data 1297 Interchange Format specified in [RFC7159]. In the meantime, 1298 [RFC7159] has been obsoleted by [RFC8259], that among others makes 1299 UTF-8 mandatory for text encoding to improve interoperability. 1300 Therefore, ALTO Clients and Servers implementations using UTF-{16,32} 1301 need to be cognizant of the subsequent interoperability risks and it 1302 is RECOMMENDED for them to switch to UTF-8 encoding, if they want to 1303 interoperate with Calendar-aware Servers and Clients. 1305 8. Acknowledgements 1307 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1308 Peng and Haibin Song for fruitful discussions and feedback on earlier 1309 draft versions. Dawn Chan, Kai Gao, Vijay Gurbani, Yichen Qian and 1310 Jensen Zhang provided substantial review feedback and suggestions to 1311 the protocol design. 1313 9. References 1315 9.1. Normative References 1317 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1318 Requirement Levels", BCP 14, RFC 2119, 1319 DOI 10.17487/RFC2119, March 1997, 1320 . 1322 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1323 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1324 "Application-Layer Traffic Optimization (ALTO) Protocol", 1325 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1326 . 1328 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1329 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1330 May 2017, . 1332 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1333 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1334 DOI 10.17487/RFC8189, October 2017, 1335 . 1337 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1338 Interchange Format", STD 90, RFC 8259, 1339 DOI 10.17487/RFC8259, December 2017, 1340 . 1342 9.2. Informative References 1344 [draft-ietf-alto-incr-update-sse] 1345 "ALTO Incremental Updates Using Server-Sent Events (SSE) 1346 (work in progress)", December 2018. 1348 [draft-ietf-alto-performance-metrics] 1349 "ALTO Performance Cost Metrics (work in progress)", June 1350 2018. 1352 [draft-xiang-alto-multidomain-analytics] 1353 "Unicorn: Resource Orchestration for Multi-Domain, Geo- 1354 Distributed Data Analytics", July 2018. 1356 [IEEE.754.2008] 1357 "Standard for Binary Floating-Point Arithmetic, IEEE 1358 Standard 754", August 2008. 1360 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1361 DOI 10.17487/RFC2818, May 2000, 1362 . 1364 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1365 (TLS) Protocol Version 1.2", RFC 5246, 1366 DOI 10.17487/RFC5246, August 2008, 1367 . 1369 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1370 Optimization (ALTO) Problem Statement", RFC 5693, 1371 DOI 10.17487/RFC5693, October 2009, 1372 . 1374 [RFC6708] Kiesel, S., Ed., Previdi, S., Stiemerling, M., Woundy, R., 1375 and Y. Yang, "Application-Layer Traffic Optimization 1376 (ALTO) Requirements", RFC 6708, DOI 10.17487/RFC6708, 1377 September 2012, . 1379 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1380 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1381 2014, . 1383 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1384 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1385 DOI 10.17487/RFC7231, June 2014, 1386 . 1388 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1389 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1390 . 1392 [SENSE-sdn-e2e-net] 1393 "SDN for End-to-End Networked Science at the Exascale 1394 (SENSE), http://sense.es.net/overview". 1396 Authors' Addresses 1398 Sabine Randriamasy 1399 Nokia Bell Labs 1400 Route de Villejust 1401 NOZAY 91460 1402 FRANCE 1404 Email: Sabine.Randriamasy@nokia-bell-labs.com 1406 Richard Yang 1407 Yale University 1408 51 Prospect st 1409 New Haven, CT 06520 1410 USA 1412 Email: yry@cs.yale.edu 1414 Qin Wu 1415 Huawei 1416 101 Software Avenue, Yuhua District 1417 Nanjing, Jiangsu 210012 1418 China 1420 Email: sunseawq@huawei.com 1421 Lingli Deng 1422 China Mobile 1423 China 1425 Email: denglingli@chinamobile.com 1427 Nico Schwan 1428 Thales Deutschland 1429 Lorenzstrasse 10 1430 Stuttgart 70435 1431 Germany 1433 Email: nico.schwan@thalesgroup.com