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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC5246' is defined on line 1363, but no explicit reference was found in the text -- Obsolete informational reference (is this intentional?): RFC 2818 (Obsoleted by RFC 9110) -- Obsolete informational reference (is this intentional?): RFC 5246 (Obsoleted by RFC 8446) -- Obsolete informational reference (is this intentional?): RFC 7159 (Obsoleted by RFC 8259) -- Obsolete informational reference (is this intentional?): RFC 7231 (Obsoleted by RFC 9110) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 5 comments (--). 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: August 10, 2020 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 February 7, 2020 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-16 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 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on August 10, 2020. 47 Copyright Notice 49 Copyright (c) 2020 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Some recent known uses . . . . . . . . . . . . . . . . . 4 66 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 67 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 68 3. Overview of ALTO Cost Calendars and terminology . . . . . . . 5 69 3.1. ALTO Cost Calendar overview . . . . . . . . . . . . . . . 5 70 3.2. ALTO Cost Calendar information features . . . . . . . . . 6 71 3.3. ALTO Calendar design characteristics . . . . . . . . . . 7 72 3.3.1. ALTO Cost Calendar for all cost modes . . . . . . . . 8 73 3.3.2. Compatibility with legacy ALTO Clients . . . . . . . 8 74 4. ALTO Calendar specification: IRD extensions . . . . . . . . . 9 75 4.1. Calendar attributes in the IRD resource capabilities . . 9 76 4.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 10 77 4.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 11 78 5. ALTO Calendar specification: Service Information Resources . 14 79 5.1. Calendar extensions for Filtered Cost Maps (FCM) . . . . 14 80 5.1.1. Calendar extensions in Filtered Cost Map requests . . 14 81 5.1.2. Calendar extensions in Filtered Cost Map responses . 15 82 5.1.3. Use case and example: FCM with a bandwidth Calendar . 18 83 5.2. Calendar extensions in the Endpoint Cost Service . . . . 20 84 5.2.1. Calendar specific input in Endpoint Cost requests . 20 85 5.2.2. Calendar attributes in the Endpoint Cost response . . 20 86 5.2.3. Use case and example: ECS with a routingcost Calendar 21 87 5.2.4. Use case and example: ECS with a multi-cost Calendar 88 for routingcost and owdelay . . . . . . . . . . . . . 24 89 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 90 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 91 8. Operational Considerations . . . . . . . . . . . . . . . . . 27 92 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 93 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 94 10.1. Normative References . . . . . . . . . . . . . . . . . . 28 95 10.2. Informative References . . . . . . . . . . . . . . . . . 29 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 98 1. Introduction 100 The base Application-Layer Traffic Optimization (ALTO) protocol 101 specified in [RFC7285] provides guidance to overlay applications that 102 need to select one or several hosts from a set of candidates able to 103 provide a desired resource. This guidance is based on parameters 104 that affect performance and efficiency of the data transmission 105 between the hosts such as the topological distance. The goal of ALTO 106 is to improve the Quality of Experience (QoE) in the application 107 while optimizing resource usage in the underlying network 108 infrastructure. 110 The ALTO protocol in [RFC7285] specifies a network map which defines 111 groupings of endpoints in provider-defined network regions identified 112 by Provider-defined Identifiers (PIDs). The Cost Map Service, 113 Endpoint Cost Service (ECS) and Endpoint Ranking Service then provide 114 ISP-defined costs and rankings for connections among the specified 115 endpoints and PIDs and thus incentives for application clients to 116 connect to ISP preferred locations, for instance, to reduce their 117 costs. For the reasons outlined in the ALTO problem statement 118 [RFC5693] and requirement AR-14 of [RFC6708], ALTO does not 119 disseminate network metrics that change frequently. In a network, 120 the costs can fluctuate for many reasons having to do with 121 instantaneous traffic load or due to diurnal patterns of traffic 122 demand or planned events such as network maintenance, holidays or 123 highly publicized events. Thus, an ALTO application wishing to use 124 the Cost Map and Endpoint Cost Service at some future time will have 125 to estimate the state of the network at that time, a process that is, 126 at best, fragile and brittle since the application does not have any 127 visibility into the state of the network. Providing network costs 128 for only the current time thus may not be sufficient, in particular 129 for applications that can schedule their traffic in a span of time, 130 for example by deferring backups or other background traffic to off- 131 peak hours. 133 In case the ALTO Cost value changes are predictable over a certain 134 period of time and the application does not require immediate data 135 transfer, it can save time to get the whole set of cost values over 136 this period in one single ALTO response. Using this set to schedule 137 data transfers allows optimizing the network resources usage and QoE. 138 ALTO Clients and Servers can also minimize their workload by reducing 139 and accordingly scheduling their data exchanges. 141 This document extends [RFC7285] to allow an ALTO Server to provide 142 network costs for a given duration of time. A sequence of network 143 costs across a time span for a given pair of network locations is 144 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 145 Endpoint Cost Service are extended to provide Cost Calendars. In 146 addition to this functional ALTO enhancement, we expect to further 147 save network and storage resources by gathering multiple Cost Values 148 for one Cost Type into one single ALTO Server response. 150 In this document, an "ALTO Cost Calendar" is specified in terms of 151 information resources capabilities that are applicable to time- 152 sensitive ALTO metrics. An ALTO Cost Calendar exposes ALTO Cost 153 Values in JSON arrays, see [RFC8259], where each value corresponds to 154 a given time interval. The time intervals as well as other Calendar 155 attributes are specified in the Information Resources Directory (IRD) 156 and in the Server response to allow the ALTO Client to interpret the 157 received ALTO values. Last, the extensions for ALTO Calendars are 158 applicable to any Cost Mode and they ensure backwards compatibility 159 with legacy ALTO Clients. 161 In the rest of this document, Section 2 provides the design 162 characteristics. Sections 3 and 4 define the formal specifications 163 for the IRD and the information resources. IANA, security and 164 operational considerations are addressed respectively in sections 165 Section 6, Section 7 and Section 8. 167 1.1. Some recent known uses 169 A potential use case is the SENSE project, see [SENSE-sdn-e2e-net], 170 who is implementing smart network services to dynamically build end- 171 to-end virtual guaranteed networks across administrative domains, 172 with no manual intervention. The initial SENSE services include 173 informing applications on the availability of bandwidth resources or 174 feasibility of some requested Time-Bandwidth-Product (TBP) during a 175 specific time period. ALTO Calendars can support these services if 176 the Calendar start date and duration cover the period of interest of 177 the requesting applications. 179 The need of future scheduling of large scale traffic that can be 180 addressed by the ALTO protocol is also motivated by Unicorn, a 181 unified resource orchestration framework for multi-domain, geo- 182 distributed data analytics, see 183 [draft-xiang-alto-multidomain-analytics]. 185 1.2. Terminology 187 o ALTO transaction: A request/response exchange between an ALTO 188 Client and an ALTO Server. 190 o Client: When used with a capital "C", this term refers to an ALTO 191 Client. 193 o Calendar, Cost Calendar: When used with capitalized words, these 194 terms refer to an ALTO Cost Calendar. 196 o Endpoint (EP): An endpoint is defined as in Section 2.1 of 197 [RFC7285]. It can be, for example, a peer, a CDN storage 198 location, a physical server involved in a virtual server-supported 199 application, a party in a resource-sharing swarm such as a 200 computation grid, or an online multi-party game. 202 o Server: When used with a capital "S", this term refers to an ALTO 203 Server. 205 2. Requirements Language 207 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 208 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 209 "OPTIONAL" in this document are to be interpreted as described in 210 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 211 capitals, as shown here. 213 When the words appear in lower case, they are to be interpreted with 214 their natural language meanings. 216 3. Overview of ALTO Cost Calendars and terminology 218 3.1. ALTO Cost Calendar overview 220 An ALTO Cost Calendar provided by the ALTO Server provides 2 221 information items: 223 o an array of values for a given metric, where each value 224 corresponds to a time interval, where the value array can 225 sometimes be a cyclic pattern that repeats a certain number of 226 times. 228 o attributes describing the time scope of the Calendar such as the 229 size and number of the intervals and the date of the starting 230 point of the Calendar, allowing an ALTO Client to interpret the 231 values properly. 233 An ALTO Cost Calendar can be used like a "time table" to figure out 234 the best time to schedule data transfers and also to proactively 235 manage application traffic given predictable events such as expected 236 spike in traffic due to crowd gathering (concerts, sports, etc.), 237 traffic-intensive holidays and network maintenance. A Calendar may 238 be viewed as a synthetic abstraction of, for example, real 239 measurements gathered over previous periods on which statistics have 240 been computed. However, like for any schedule, unexpected network 241 incidents may require the current ALTO Calendar to be updated and re- 242 sent to the ALTO Clients needing it. The "ALTO Incremental Updates 243 Using Server-Sent Events (SSE)" Service 244 [draft-ietf-alto-incr-update-sse] can be used to update the calendar 245 faster if supported by both the server and the client. 247 Most likely, the ALTO Cost Calendar would be used for the Endpoint 248 Cost Service, assuming that a limited set of feasible Endpoints for a 249 non-real time application is already identified, that they do not 250 need to be accessed immediately and that their access can be 251 scheduled within a given time period. The Filtered Cost Map Service 252 is also applicable as long as the size of the Map allows it. 254 3.2. ALTO Cost Calendar information features 256 The Calendar attributes are provided in the Information Resources 257 Directory (IRD) and in ALTO Server responses. The IRD announces 258 attributes without date values in its information resources 259 capabilities, whereas attributes with time dependent values are 260 provided in the "meta" section of Server responses. The ALTO Cost 261 Calendar attributes provide the following information: 263 o attributes to describe the time scope of the Calendar value array: 265 * time zone (in UTC), 267 * applicable time interval size for each Calendar value, defined 268 in seconds, that can cover a wide range of values. 270 * duration of the Calendar: e.g., the number of intervals 271 provided in the Calendar. 273 o "calendar-start-date": specifying when the Calendar starts, that 274 is to which date the first value of the Cost Calendar is 275 applicable. 277 o "repeated": an optional attribute indicating how many iterations 278 of the provided Calendar will have the same values. The server 279 may use it to allow the client to schedule its next request and 280 thus save its own workload by reducing processing of similar 281 requests. 283 Attribute "repeated" may take a very high value if a Calendar 284 represents a cyclic value pattern that the Server considers valid for 285 a long period. In this case, the Server will only update the 286 Calendar values once this period has elapsed or if an unexpected 287 event occurs on the network. 289 3.3. ALTO Calendar design characteristics 291 The extensions in this document and encode requests and responses 292 using JSON [RFC8259]. 294 Formally, the cost entries in an ALTO cost map can be any type of 295 JSON value [RFC8259], (see the DstCosts object in Section 11.2.3.6 of 296 [RFC7285]). However, that section states that an implementation of 297 [RFC7285] SHOULD assume that the cost is a JSON number and fail to 298 parse if it is not, unless the implementation is using an extension 299 that signals a different data type. This document extends the 300 definition of a legacy cost map given in [RFC7285] to allow a cost 301 entry to be an array of values, one per time interval, instead of 302 just one number. 304 To realize an ALTO Calendar, this document extends: the IRD, the ALTO 305 requests and responses for Cost Calendars. 307 This extension is designed to be lightweight and to ensure backwards 308 compatibility with base protocol ALTO Clients and with other 309 extensions. It relies on section 8.3.7 "Parsing of Unknown Fields" 310 of [RFC7285] that writes: "Extensions may include additional fields 311 within JSON objects defined in this document. ALTO implementations 312 MUST ignore unknown fields when processing ALTO messages." 314 The Calendar-specific capabilities are integrated in the information 315 resources of the IRD and in the "meta" member of ALTO responses to 316 Cost Calendars requests. A Calendar and its capabilities are 317 associated with a given information resource and within this 318 information resource with a given cost type. This design has several 319 advantages: 321 o it does not introduce a new mode, 323 o it does not introduce new media types, 325 o it allows an ALTO Server to offer Calendar capabilities on a cost 326 type, with attributes values adapted to each information resource. 328 The applicable Calendared information resources are: 330 o the Filtered Cost Map, 332 o the Endpoint Cost Map. 334 The ALTO Server can choose in which frequency it provides cost 335 Calendars to ALTO Clients. It may either provide Calendar updates 336 starting at the request date, or carefully schedule its updates so as 337 to take profit from a potential repetition/periodicity of Calendar 338 values. 340 3.3.1. ALTO Cost Calendar for all cost modes 342 An ALTO Cost Calendar is well-suited for values encoded in the 343 "numerical" mode. Actually, a Calendar can also represent metrics in 344 other modes considered as compatible with time-varying values. For 345 example, types of Cost values such as JSONBool can also be 346 calendared, as their value may be 'true' or 'false' depending on 347 given time periods or likewise, values represented by strings, such 348 as "medium", "high", "low", "blue", "open". 350 Note also that a Calendar is suitable as well for time-varying 351 metrics provided in the "ordinal" mode, if these values are time- 352 varying and the ALTO Server provides updates of cost value based 353 preferences. 355 3.3.2. Compatibility with legacy ALTO Clients 357 The ALTO protocol extensions for Cost Calendars have been defined so 358 as to ensure that Calendar capable ALTO Servers can provide legacy 359 ALTO Clients with legacy information resources as well. That is, a 360 legacy ALTO Client can request resources and receive responses as 361 specified in [RFC7285]. 363 A Calendar-aware ALTO Server MUST implement the base protocol 364 specified in [RFC7285]. 366 As a consequence, when a metric is available as a Calendar array, it 367 also MUST be available as a single value as required by [RFC7285]. 368 The Server, in this case, provides the current value of the metric to 369 either Calendar-aware Clients not interested in future or time-based 370 values, or Clients implementing [RFC7285] only. 372 For compatibility with legacy ALTO Clients specified in [RFC7285], 373 calendared information resources are not applicable for full cost 374 maps for the following reason: a legacy ALTO Client would receive a 375 calendared cost map via an HTTP 'GET' command. As specified in 376 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 377 indicated in the "meta" of the responses. Therefore, lacking 378 information on Calendar attributes, it will not be able to correctly 379 interpret and process the values of the received array of Calendar 380 cost values. 382 Therefore, calendared information resources MUST be requested via the 383 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 384 method. 386 4. ALTO Calendar specification: IRD extensions 388 The Calendar attributes in the IRD information resources capabilities 389 carry constant dateless values. A Calendar is associated with an 390 information resource rather than a cost type. For example, a Server 391 can provide a "routingcost" Calendar for the Filtered Cost Map 392 Service at a granularity of one day and a "routingcost" Calendar for 393 the Endpoint Cost Service at a finer granularity but for a limited 394 number of endpoints. An example IRD with Calendar specific features 395 is provided in Section 4.3. 397 4.1. Calendar attributes in the IRD resource capabilities 399 A Cost Calendar for a given Cost Type MUST be indicated in the IRD by 400 an object of type CalendarAttributes. A CalendarAttribute object is 401 represented by the "calendar-attributes" member of a resource entry. 402 Each CalendarAttributes object applies to a set of one or more cost 403 types. A Cost Type name MUST appear no more than once in the 404 "calendar-attributes" member of a resource entry; multiple 405 appearances of a Cost Type name in CalendarAttributes object of the 406 "calendar-attributes" member MUST cause the ALTO Client to ignore any 407 occurrences of this name beyond the first encountered occurrence. 409 It is RECOMMENDED for an ALTO Server that the time interval size 410 specified in the IRD is the smallest possible one that it can 411 provide. The Client can aggregate cost values on its own if it needs 412 a larger granularity. 414 The encoding format for object CalendarAttributes, using JSON 415 [RFC8259], is as follows: 417 CalendarAttributes calendar-attributes <1..*>; 419 object{ 420 JSONString cost-type-names <1..*>; 421 JSONNumber time-interval-size; 422 JSONNumber number-of-intervals; 423 } CalendarAttributes; 425 o "cost-type-names": 427 * An array of one or more elements indicating the cost-type-names 428 in the IRD entry to which the capabilities apply. 430 o "time-interval-size": 432 * is the duration of an ALTO Calendar time interval in seconds. 433 A "time-interval-size" value contains a JSONNumber. ALTO 434 Servers SHOULD use at least IEEE 754 double-precision floating 435 point [IEEE.754.2008] to store this value. Example values are: 436 300 , 7200, meaning that each Calendar value applies on a time 437 interval that lasts 5 minutes and 2 hours, respectively. 439 o "number-of-intervals": 441 * the integer number of values of the Cost Calendar array, at 442 least equal to 1. 444 - Attribute "cost-type-names" provides a better readability to the 445 Calendar attributes specified in the IRD and avoids confusion with 446 Calendar attributes of other cost-types. 448 - Multiplying 'time-interval-size' by 'number-of-intervals' provides 449 the duration of the provided Calendar. For example, an ALTO Server 450 may provide a Calendar for ALTO values changing every 'time-interval- 451 size' equal to 5 minutes. If 'number-of-intervals' has the value 12, 452 then the duration of the provided Calendar is "1 hour". 454 4.2. Calendars in a delegate IRD 456 It may be useful to distinguish IRD resources supported by the base 457 ALTO protocol from resources supported by its extensions. To achieve 458 this, one option, is that a "root" ALTO Server implementing base 459 protocol resources delegates "specialized" information resources such 460 as the ones providing Cost Calendars, to another ALTO Server running 461 in a subdomain that is specified with its URI in the "root" ALTO 462 Server. This option is described in Section 9.2.4 "Delegation using 463 IRDs" of [RFC7285]. 465 This document provides an example, where a "root" ALTO Server runs in 466 a domain called "alto.example.com". It delegates the announcement of 467 Calendars capabilities to an ALTO Server running in a subdomain 468 called "custom.alto.example.com". The location of the "delegate 469 Calendar IRD" is assumed to be indicated in the "root" IRD by the 470 resource entry: "custom-calendared-resources". 472 Another advantage is that some Cost Types for some resources may be 473 more advantageous as Cost Calendars and it makes few sense to get 474 them as a single value. For example, Cost Types with predictable and 475 frequently changing values, calendared in short time intervals such 476 as a minute. 478 4.3. Example IRD with ALTO Cost Calendars 480 This section provides an example ALTO Server IRD that supports 481 various cost metrics and cost modes. In particular, since [RFC7285] 482 makes it mandatory, the Server uses metric "routingcost" in the 483 "numerical" mode. 485 For illustrative purposes, this section introduces 3 other fictitious 486 example metrics and modes that should be understood as examples and 487 should not be used or considered as normative. 489 The cost type names used in the example IRD as thus as follows: 491 o "num-routingcost": refers to metric "routingcost" in the numerical 492 mode as defined in [RFC7285] and registered with IANA. 494 o "num-owdelay": refers to fictitious performance metric "owdelay" 495 in the "numerical" mode,to reflect the one-way packet transmission 496 delay on a path. A related performance metric is currently under 497 definition in [draft-ietf-alto-performance-metrics]. 499 o "num-throughputrating": refers to fictitious metric 500 "throughputrating" in the "numerical" mode, to reflect the 501 provider preference in terms of end to end throughput. 503 o "string-servicestatus": refers to fictitious metric 504 "servicestatus" containing a string, to reflect the availability, 505 defined by the provider, of for instance path connectivity. 507 The example IRD includes 2 particular URIs providing Calendars: 509 o "https://custom.alto.example.com/calendar/costmap/filtered": a 510 filtered cost map in which Calendar capabilities are indicated for 511 cost type names: "num-routingcost", "num-throughputrating" and 512 "string-servicestatus", 514 o "https://custom.alto.example.com/calendar/endpointcost/lookup": an 515 endpoint cost map in which Calendar capabilities are indicated for 516 cost type names: "num-routingcost", "num-owdelay", "num- 517 throughputrating", "string-servicestatus". 519 The design of the Calendar capabilities allows some Calendars with 520 the same cost type name to be available in several information 521 resources with different Calendar Attributes. This is the case for 522 Calendars on "num-routingcost", "num-throughputrating" and "string- 523 servicestatus", available in both the Filtered Cost map and Endpoint 524 Cost Service, but with different time interval sizes for "num- 525 throughputrating" and "string-servicestatus". 527 --- Client to Server request for IRD ---------- 529 GET /calendars-directory HTTP/1.1 530 Host: custom.alto.example.com 531 Accept: application/alto-directory+json,application/alto-error+json 533 --- Server response to Client ----------------- 535 HTTP/1.1 200 OK 536 Content-Length: 2542 537 Content-Type: application/alto-directory+json 539 { 540 "meta" : { 541 "default-alto-network-map" : "my-default-network-map", 542 "cost-types": { 543 "num-routingcost": { 544 "cost-mode" : "numerical", 545 "cost-metric" : "routingcost" 546 }, 547 "num-owdelay": { 548 "cost-mode" : "numerical", 549 "cost-metric": "owdelay" 550 }, 551 "num-throughputrating": { 552 "cost-mode" : "numerical", 553 "cost-metric": "throughputrating" 554 }, 555 "string-servicestatus": { 556 "cost-mode" : "string", 557 "cost-metric": "servicestatus" 558 } 559 } 560 }, 561 "resources" : { 562 "filtered-cost-map-calendar" : { 563 "uri" : 564 "https://custom.alto.example.com/calendar/costmap/filtered", 565 "media-type" : "application/alto-costmap+json", 566 "accepts" : "application/alto-costmapfilter+json", 567 "capabilities" : { 568 "cost-constraints" : true, 569 "cost-type-names" : [ "num-routingcost", 570 "num-throughputrating", 571 "string-servicestatus" ], 572 "calendar-attributes" : [ 573 {"cost-type-names" : [ "num-routingcost", 574 "num-throughputrating" ], 575 "time-interval-size" : 7200, 576 "number-of-intervals" : 12 577 }, 578 {"cost-type-names" : [ "string-servicestatus" ], 579 "time-interval-size" : 1800, 580 "number-of-intervals" : 48 581 } 582 ] 583 }, 584 "uses": [ "my-default-network-map" ] 585 }, 586 "endpoint-cost-calendar-map" : { 587 "uri" : 588 "https://custom.alto.example.com/calendar/endpointcost/lookup", 589 "media-type" : "application/alto-endpointcost+json", 590 "accepts" : "application/alto-endpointcostparams+json", 591 "capabilities" : { 592 "cost-constraints" : true, 593 "cost-type-names" : [ "num-routingcost", 594 "num-owdelay", 595 "num-throughputrating", 596 "string-servicestatus" ], 597 "calendar-attributes" : [ 598 {"cost-type-names" : [ "num-routingcost" ], 599 "time-interval-size" : 3600, 600 "number-of-intervals" : 24 601 }, 602 {"cost-type-names" : [ "num-owdelay" ], 603 "time-interval-size" : 300, 604 "number-of-intervals" : 12 605 }, 606 {"cost-type-names" : [ "num-throughputrating" ], 607 "time-interval-size" : 60, 608 "number-of-intervals" : 60 609 }, 610 {"cost-type-names" : [ "string-servicestatus" ], 611 "time-interval-size" : 120, 612 "number-of-intervals" : 30 613 } 614 ] 615 } 616 } 617 } 618 } 620 In this example IRD, for the Filtered Cost Map Service: 622 o the Calendar for "num-routingcost" and "num-throughputrating" is 623 an array of 12 values each provided on a time interval lasting 624 7200 seconds (2 hours). 626 o the Calendar for "string-servicestatus": "is an array of 48 values 627 each provided on a time interval lasting 1800 seconds (30 628 minutes). 630 For the Endpoint Cost Service: 632 o the Calendar for "num-routingcost": is an array of 24 values each 633 provided on a time interval lasting 3600 seconds (1 hour). 635 o the Calendar for "owdelay": is an array of 12 values each provided 636 on a time interval lasting 300 seconds (5 minutes). 638 o the Calendar for "num-throughputrating": is an array of 60 values 639 each provided on a time interval lasting 60 seconds (1 minute). 641 o the Calendar for "string-servicestatus": "is an array of 30 values 642 each provided on a time interval lasting 120 seconds (2 minutes). 644 5. ALTO Calendar specification: Service Information Resources 646 This section documents the individual information resources defined 647 to provide the calendared information services defined in this 648 document. 650 The reference time zone for the provided time values is UTC. The 651 option chosen to express the time format is the HTTP header fields 652 format specified in [RFC7231] where, however, timestamps are still 653 displayed with the acronym "GMT" rather than "UTC": 655 Date: Tue, 15 Nov 2014 08:12:31 GMT 657 The value of a Calendar time interval size is expressed in seconds. 659 5.1. Calendar extensions for Filtered Cost Maps (FCM) 661 A legacy ALTO Client requests and gets Filtered Cost Map responses as 662 specified in [RFC7285]. 664 5.1.1. Calendar extensions in Filtered Cost Map requests 666 The input parameters of a "legacy" request for a filtered cost map, 667 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 668 are augmented with one additional member. 670 A Calendar-aware ALTO Client requesting a Calendar on a given Cost 671 Type for a filtered cost map resource having Calendar capabilities 672 MUST add the following field to its input parameters: 674 JSONBoolean calendared<1..*>; 676 This field is an array of 1 to N boolean values, where N is the 677 number of requested metrics. Each entry corresponds to the requested 678 metric at the same array position. Each boolean value indicates 679 whether or not the ALTO Server should provide the values for this 680 Cost Type as a Calendar. The array MUST contain exactly N boolean 681 values, otherwise, the Server returns an error. 683 This field MUST NOT be included if no member "calendar-attributes" is 684 specified in this information resource. 686 If a value of field 'calendared' is 'true' for a cost type name for 687 which no Calendar attributes have been specified: an ALTO Server, 688 whether it implements the extensions of this document or only 689 implements [RFC7285], MUST ignore it and return a response with a 690 single cost value as specified in [RFC7285]. 692 If this field is not present, it MUST be assumed to have only values 693 equal to 'false'. 695 A Calendar-aware ALTO Client that supports requests for only one cost 696 type at a time and wants to request a Calendar MUST provide an array 697 of 1 element: 699 "calendared" : [true]; 701 A Calendar-aware ALTO Client that supports requests for more than one 702 Cost Types at a time, as specified in [RFC8189] MUST provide an array 703 of N values set to 'true' or 'false', depending whether it wants the 704 applicable Cost Type values as a single or calendared value. 706 5.1.2. Calendar extensions in Filtered Cost Map responses 708 In a calendared ALTO Filtered Cost Map, a cost value between a source 709 and a destination is a JSON array of JSON values. An ALTO Calendar 710 values array has a number of values equal to the value of member 711 "number-of-intervals" of the Calendar attributes that are indicated 712 in the IRD. These attributes will be conveyed as metadata in the 713 Filtered Cost Map response. Each element of the array is valid for 714 the time-interval that matches its array position. 716 The FCM response conveys metadata among which: 718 o some are not specific to Calendars and ensure compatibility with 719 [RFC7285] and [RFC8189] 721 o some are specific to Calendars. 723 The non Calendar specific "meta" fields of a calendared Filtered Cost 724 Map response MUST include at least: 726 o if the ALTO Client requests cost values for one Cost Type at a 727 time only: the "meta" fields specified in [RFC7285] for these 728 information service responses: 730 * "dependent-vtags ", 732 * "cost-type" field. 734 o if the ALTO Client implements the Multi-Cost ALTO extension 735 specified in [RFC8189] and requests cost values for several Cost 736 Types at a time: the "meta" fields specified in [RFC8189] for 737 these information service responses: 739 * "dependent-vtags ", 741 * "cost-type" field with value set to '{}', for backwards 742 compatibility with [RFC7285]. 744 * "multi-cost-types" field. 746 If the client request does not provide member "calendared" or if it 747 provides it with a value equal to 'false', for all the requested Cost 748 Types, then the ALTO Server response is exactly as specified in 749 [RFC7285] and [RFC8189]. 751 If the value of member "calendared" is equal to 'false' for a given 752 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 753 a single cost value as specified in [RFC7285]. 755 If the value of member "calendared" is equal to 'true' for a given 756 requested Cost Type, the ALTO Server returns, for this Cost Type, a 757 cost value Calendar as specified above in this section. In addition 758 to the above cited non Calendar specific "meta" members, the Server 759 MUST provide a Calendar specific metadata field. 761 The Calendar specific "meta" field that a calendared Filtered Cost 762 Map response MUST include is a member called "calendar-response- 763 attributes", that describes properties of the Calendar and where: 765 o member "calendar-response-attributes" is an array of one or more 766 objects of type "CalendarResponseAttributes". 768 o each "CalendarResponseAttributes" object in the array is specified 769 for one or more Cost Types for which the value of member 770 "calendared" is equal to 'true' and for which a Calendar is 771 provided for the requested information resource. 773 o the "CalendarResponseAttributes" object that applies to a cost 774 type name has a corresponding "CalendarAttributes" object defined 775 for this cost type name in the IRD capabilities of the requested 776 information resource. The members of a 777 "CalendarResponseAttributes" object include all the members of the 778 corresponding "CalendarAttributes" object. 780 The format of member "CalendarResponseAttributes is defined as 781 follows: 783 CalendarResponseAttributes calendar-response-attributes <1..*>; 785 object{ 786 [JSONString cost-type-names <1..*>]; 787 JSONString calendar-start-time; 788 JSONNumber time-interval-size; 789 JSONNumber number-of-intervals; 790 [JSONNumber repeated;] 791 } CalendarResponseAttributes; 793 Object CalendarResponseAttributes has the following attributes: 795 o "cost-type-names": is an array of one or more cost-type-names to 796 which the capabilities apply and for which a Calendar has been 797 requested. The value of this member is a subset of the "cost- 798 type-names" array specified in the corresponding IRD Calendar 799 attributes. 801 o "calendar-start-time": indicates the date at which the first value 802 of the Calendar applies. The value provided for the "calendar- 803 start-time" attribute SHOULD NOT be later than the request date. 805 o "time-interval-size": as specified in Section 4.1 and with the 806 same value. 808 o "number-of-intervals": as specified in Section 4.1 and with the 809 same value. 811 o "repeated": is an optional field provided for Calendars. It is an 812 integer N greater or equal to '1' that indicates how many 813 iterations of the Calendar value array starting at the date 814 indicated by "calendar-start-time" have the same values. The 815 number N includes the provided iteration. 817 For example: suppose the "calendar-start-time" member has value "Mon, 818 30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has 819 value '3600', the "number-of-intervals" member has value '24' and the 820 value of member "repeated" is equal to '4'. This means that the 821 Calendar values are the same on Monday, Tuesday, Wednesday and 822 Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO 823 Client thus may use the same Calendar for the next 4 days starting at 824 "calendar-start-time" and will only need to request a new one for 825 Friday July 4th at 00:00:00 GMT. 827 Attribute "repeated" may take a very high value if a Calendar 828 represents a cyclic value pattern that the Server considers valid for 829 a long period and hence will only update once this period has elapsed 830 or if an unexpected event occurs on the network. In the latter case, 831 the client will be notified if it uses the "ALTO Incremental Updates 832 Using Server-Sent Events (SSE)" Service, specified in 833 [draft-ietf-alto-incr-update-sse]. To this end, it is RECOMMENDED 834 that ALTO Servers providing ALTO Calendars also provide the "ALTO 835 Incremental Updates Using Server-Sent Events (SSE)" Service that is 836 specified in [draft-ietf-alto-incr-update-sse]. Likewise, ALTO 837 Clients capable of using ALTO Calendars SHOULD also use the SSE 838 Service. See also discussion in Section 8 "Operational 839 Considerations". 841 5.1.3. Use case and example: FCM with a bandwidth Calendar 843 An example of non-real time information that can be provisioned in a 844 Calendar is the expected path throughput. While the transmission 845 rate can be measured in real time by end systems, the operator of a 846 data center is in the position of formulating preferences for given 847 paths, at given time periods to avoid traffic peaks due to diurnal 848 usage patterns. In this example, we assume that an ALTO Client 849 requests a Calendar of network provider defined throughput ratings, 850 as specified in the IRD, to schedule its bulk data transfers as 851 described in the use cases. 853 In the example IRD, Calendars for cost type name "num- 854 throughputrating" are available for the information resources: 855 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 856 ALTO Client requests a Calendar for "num-throughputrating" via a POST 857 request for a filtered cost map. 859 We suppose in the present example that the ALTO Client sends its 860 request on Tuesday July 1st 2014 at 13:15. The Server returns 861 Calendars with arrays of 12 numbers for each source and destination 862 pair. The values for metric "throughputrating", in this example, are 863 assumed to be encoded in 2 digits. 865 POST /calendar/costmap/filtered HTTP/1.1 866 Host: alto.example.com 867 Content-Length: 208 868 Content-Type: application/alto-costmapfilter+json 869 Accept: application/alto-costmap+json,application/alto-error+json 871 { 872 "cost-type" : {"cost-mode" : "numerical", 873 "cost-metric" : "throughputrating"}, 874 "calendared" : [true], 875 "pids" : { 876 "srcs" : [ "PID1", "PID2" ], 877 "dsts" : [ "PID1", "PID2", "PID3" ] 878 } 879 } 881 HTTP/1.1 200 OK 882 Content-Length: 1013 883 Content-Type: application/alto-costmap+json 885 { 886 "meta" : { 887 "dependent-vtags" : [ 888 {"resource-id": "my-default-network-map", 889 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 890 } 891 ], 892 "cost-type" : {"cost-mode" : "numerical", 893 "cost-metric" : "throughputrating"}, 894 "calendar-response-attributes" : [ 895 {"calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 896 "time-interval-size" : 7200, 897 "number-of-intervals" : 12} 898 ] 899 }, 900 "cost-map" : { 901 "PID1": { "PID1": [ 1, 12, 14, 18, 14, 14, 902 14, 18, 19, 20, 11, 12], 903 "PID2": [13, 4, 15, 16, 17, 18, 904 19, 20, 11, 12, 13, 14], 905 "PID3": [20, 20, 18, 14, 12, 12, 906 14, 14, 12, 12, 14, 16] }, 907 "PID2": { "PID1": [17, 18, 19, 10, 11, 12, 908 13, 14, 15, 16, 17, 18], 909 "PID2": [20, 20, 18, 16, 14, 14, 910 14, 16, 16, 16, 14, 16], 911 "PID3": [20, 20, 18, 14, 12, 12, 912 14, 14, 12, 12, 14, 16] } 913 } 914 } 916 5.2. Calendar extensions in the Endpoint Cost Service 918 This document extends the Endpoint Cost Service, as defined in 919 {11.5.1} of [RFC7285], by adding new input parameters and 920 capabilities, and by returning JSONArrays instead of JSONNumbers as 921 the cost values. The media type {11.5.1.1} and HTTP method 922 {11.5.1.2} are unchanged. 924 5.2.1. Calendar specific input in Endpoint Cost requests 926 The extensions to the requests for calendared Endpoint Cost Maps are 927 the same as for the Filtered Cost Map Service, specified in section 928 Section 5.1.1 of this draft. 930 The ReqEndpointCostMap object for a calendared ECM request will have 931 the following format: 933 object { 934 [CostType cost-type;] 935 [CostType multi-cost-types<1..*>;] 936 [JSONBoolean calendared<1..*>;] 937 EndpointFilter endpoints; 938 } ReqEndpointCostMap; 940 object { 941 [TypedEndpointAddr srcs<0..*>;] 942 [TypedEndpointAddr dsts<0..*>;] 943 } EndpointFilter; 945 5.2.2. Calendar attributes in the Endpoint Cost response 947 The "meta" field of a calendared Endpoint Cost response MUST include 948 at least: 950 o if the ALTO Client supports cost values for one Cost Type at a 951 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 952 for the Endpoint Cost response: 954 * "cost-type" field. 956 o if the ALTO Client supports cost values for several Cost Types at 957 a time, as specified in [RFC8189] : the "meta" fields specified in 958 [RFC8189] for the the Endpoint Cost response: 960 * "cost-type" field with value set to '{}', for backwards 961 compatibility with [RFC7285]. 963 * "multi-cost-types" field. 965 If the client request does not provide member "calendared" or if it 966 provides it with a value equal to 'false', for all the requested Cost 967 Types, then the ALTO Server response is exactly as specified in 968 [RFC7285] and [RFC8189]. 970 If the ALTO Client provides member "calendared" in the input 971 parameters with a value equal to 'true' for given requested Cost 972 Types, the "meta" member of a calendared Endpoint Cost response MUST 973 include, for these Cost Types, an additional member "calendar- 974 response-attributes", the contents of which obey the same rules as 975 for the Filtered Cost Map Service, specified in Section 5.1.2. The 976 Server response is thus changed as follows, w.r.t [RFC7285] and 977 [RFC8189]: 979 o the "meta" member has one additional field 980 "CalendarResponseAttributes", as specified for the Filtered Cost 981 Map Service, 983 o the calendared costs are JSONArrays instead of the JSONNumbers 984 format used by legacy ALTO implementations. All arrays have a 985 number of values equal to 'number-of-intervals'. 987 If the value of member "calendared" is equal to 'false' for a given 988 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 989 a single cost value as specified in [RFC7285]. 991 5.2.3. Use case and example: ECS with a routingcost Calendar 993 Let us assume an Application Client is located in an end system with 994 limited resources and having access to the network that is either 995 intermittent or provides an acceptable quality in limited but 996 predictable time periods. Therefore, it needs to both schedule its 997 resource-greedy networking activities and its ALTO transactions. 999 The Application Client has the choice to trade content or resources 1000 with a set of Endpoints and needs to decide with which one it will 1001 connect and at what time. For instance, the Endpoints are spread in 1002 different time-zones, or have intermittent access. In this example, 1003 the 'routingcost' is assumed to be time-varying, with values provided 1004 as ALTO Calendars. 1006 The ALTO Client associated with the Application Client queries an 1007 ALTO Calendar on 'routingcost' and will get the Calendar covering the 1008 24 hours time period "containing" the date and time of the ALTO 1009 client request. 1011 For Cost Type "num-routingcost", the solicited ALTO Server has 1012 defined 3 different daily patterns each represented by a Calendar, to 1013 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 1015 - C1 for Monday, Tuesday, Wednesday, Thursday, (weekdays) 1017 - C2 for Saturday, Sunday, (weekend) 1019 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 1020 to 04:00:00 GMT, or big holiday such as New Year evening). 1022 In the following example, the ALTO Client sends its request on 1023 Tuesday July 1st 2014 at 13:15. 1025 The "routingcost" values are assumed to be encoded in 3 digits. 1027 POST /calendar/endpointcost/lookup HTTP/1.1 1028 Host: alto.example.com 1029 Content-Length: 290 1030 Content-Type: application/alto-endpointcostparams+json 1031 Accept: application/alto-endpointcost+json,application/alto-error+json 1033 { 1034 "cost-type" : {"cost-mode" : "numerical", 1035 "cost-metric" : "routingcost"}, 1036 "calendared" : [true], 1037 "endpoints" : { 1038 "srcs": [ "ipv4:192.0.2.2" ], 1039 "dsts": [ 1040 "ipv4:192.0.2.89", 1041 "ipv4:198.51.100.34", 1042 "ipv4:203.0.113.45", 1043 "ipv6:2001:db8::10" 1044 ] 1045 } 1046 } 1048 HTTP/1.1 200 OK 1049 Content-Length: 1318 1050 Content-Type: application/alto-endpointcost+json 1052 { 1053 "meta" : { 1054 "cost-type" : {"cost-mode" : "numerical", 1055 "cost-metric" : "routingcost"}, 1056 "calendar-response-attributes" : [ 1057 {"calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1058 "time-interval-size" : 3600, 1059 "number-of-intervals" : 24, 1060 "repeated": 4 1061 } 1062 ] 1063 }, 1064 "endpoint-cost-map" : { 1065 "ipv4:192.0.2.2": { 1066 "ipv4:192.0.2.89" : [100, 100, 100, 100, 100, 150, 1067 200, 300, 300, 300, 300, 250, 1068 250, 300, 300, 300, 300, 300, 1069 400, 250, 250, 200, 150, 150], 1070 "ipv4:198.51.100.34" : [ 80, 80, 80, 80, 150, 150, 1071 250, 400, 400, 450, 400, 200, 1072 200, 350, 400, 400, 400, 350, 1073 500, 200, 200, 200, 100, 100], 1074 "ipv4:203.0.113.45" : [300, 400, 250, 250, 200, 150, 1075 150, 100, 100, 100, 100, 100, 1076 100, 100, 100, 100, 100, 150, 1077 200, 300, 300, 300, 300, 250], 1078 "ipv6:2001:db8::10" : [200, 250, 300, 300, 300, 300, 1079 250, 300, 300, 300, 300, 350, 1080 300, 400, 250, 150, 100, 100, 1081 100, 150, 200, 250, 250, 300] 1082 } 1083 } 1084 } 1086 When the Client gets the Calendar for "routingcost", it sees that the 1087 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 1088 equal to '4'. It understands that the provided values are valid 1089 until Thursday included and will only need to get a Calendar update 1090 on Friday. 1092 5.2.4. Use case and example: ECS with a multi-cost Calendar for 1093 routingcost and owdelay 1095 In this example, it is assumed that the ALTO Server implements multi- 1096 cost capabilities, as specified in [RFC8189] . That is, an ALTO 1097 Client can request and receive values for several cost types in one 1098 single transaction. An illustrating use case is a path selection 1099 done on the basis of 2 metrics: routing cost and owdelay. 1101 As in the previous example, the IRD indicates that the ALTO Server 1102 provides "routingcost" Calendars in terms of 24 time intervals of 1 1103 hour (3600 seconds) each. 1105 For metric "owdelay", the IRD indicates that the ALTO Server provides 1106 Calendars in terms of 12 time intervals values lasting each 5 minutes 1107 (300 seconds). 1109 In the following example transaction, the ALTO Client sends its 1110 request on Tuesday July 1st 2014 at 13:15. 1112 This example assumes that the values of metric "owdelay" and 1113 "routingcost" are encoded in 3 digits. 1115 POST calendar/endpointcost/lookup HTTP/1.1 1116 Host: alto.example.com 1117 Content-Length: 373 1118 Content-Type: application/alto-endpointcostparams+json 1119 Accept: application/alto-endpointcost+json,application/alto-error+json 1121 { 1122 "cost-type" : {}, 1123 "multi-cost-types" : [ 1124 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1125 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1126 ], 1127 "calendared" : [true, true], 1128 "endpoints" : { 1129 "srcs": [ "ipv4:192.0.2.2" ], 1130 "dsts": [ 1131 "ipv4:192.0.2.89", 1132 "ipv4:198.51.100.34", 1133 "ipv4:203.0.113.45", 1134 "ipv6:2001:db8::10" 1135 ] 1136 } 1137 } 1138 HTTP/1.1 200 OK 1139 Content-Length: 2111 1140 Content-Type: application/alto-endpointcost+json 1142 { 1143 "meta" : { 1144 "multi-cost-types" : [ 1145 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1146 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1147 ], 1148 "calendar-response-attributes" : [ 1149 {"cost-type-names" : "num-routingcost", 1150 "calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1151 "time-interval-size" : 3600, 1152 "number-of-intervals" : 24, 1153 "repeated": 4 }, 1154 {"cost-type-names" : "num-owdelay", 1155 "calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 1156 "time-interval-size" : 300, 1157 "number-of-intervals" : 12} 1158 ] 1159 }, 1160 "endpoint-cost-map" : { 1161 "ipv4:192.0.2.2": { 1162 "ipv4:192.0.2.89" : [[100, 100, 100, 100, 100, 150, 1163 200, 300, 300, 300, 300, 250, 1164 250, 300, 300, 300, 300, 300, 1165 400, 250, 250, 200, 150, 150], 1166 [ 20, 400, 20, 80, 80, 90, 1167 100, 90, 60, 40, 30, 20]], 1168 "ipv4:198.51.100.34" : [[ 80, 80, 80, 80, 150, 150, 1169 250, 400, 400, 450, 400, 200, 1170 200, 350, 400, 400, 400, 350, 1171 500, 200, 200, 200, 100, 100], 1172 [ 20, 20, 50, 30, 30, 30, 1173 30, 40, 40, 30, 20, 20]], 1174 "ipv4:203.0.113.45" : [[300, 400, 250, 250, 200, 150, 1175 150, 100, 100, 100, 100, 100, 1176 100, 100, 100, 100, 100, 150, 1177 200, 300, 300, 300, 300, 250], 1178 [100, 90, 80, 60, 50, 50, 1179 40, 40, 60, 90, 100, 80]], 1180 "ipv6:2001:db8::10" : [[200, 250, 300, 300, 300, 300, 1181 250, 300, 300, 300, 300, 350, 1182 300, 400, 250, 150, 100, 100, 1183 100, 150, 200, 250, 250, 300], 1184 [ 40, 40, 40, 40, 50, 50, 1185 50, 20, 10, 15, 30, 40]] 1187 } 1188 } 1189 } 1191 When receiving the response, the client sees that the Calendar values 1192 for metric "routingcost" are repeated for 4 iterations. Therefore, 1193 in its next requests until the "routingcost" Calendar is expected to 1194 change, the client will only need to request a Calendar for 1195 "owdelay". 1197 Without the ALTO Calendar extensions, the ALTO Client would have no 1198 clue on the dynamicity of the metric value change and would spend 1199 needless time requesting values at an inappropriate pace. In 1200 addition, without the Multi-Cost ALTO capabilities, the ALTO Client 1201 would duplicate this waste of time as it would need to send one 1202 request per cost metric. 1204 6. IANA Considerations 1206 This document does not define any new media types or introduce any 1207 new IANA considerations. 1209 7. Security Considerations 1211 As an extension of the base ALTO protocol [RFC7285], this document 1212 fits into the architecture of the base protocol, and hence the 1213 Security Considerations (Section 15) of the base protocol fully apply 1214 when this extension is provided by an ALTO Server. For example, the 1215 same authenticity and integrity considerations (Section 15.1 of 1216 [RFC7285] still fully apply; the same considerations for the privacy 1217 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1219 The calendaring information provided by this extension requires 1220 additional considerations on three security considerations discussed 1221 in the base protocol: potential undesirable guidance to clients 1222 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1223 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1224 of [RFC7285]). For example, by providing network information in the 1225 future in a Calendar, this extension may improve availability of 1226 ALTO, when the ALTO Server is unavailable but related information is 1227 already provided in the Calendar. 1229 For confidentiality of ALTO information, an operator should be 1230 cognizant that this extension may introduce a new risk: an ALTO 1231 Client may get information for future events that are scheduled 1232 through Calendaring. Possessing such information, the client may use 1233 it to achieve its goal: (1) initiating connections only at 1234 advantageous network costs, leading to unexpected network load; (2) 1235 generating massive connections to the network at times where its load 1236 is expected to be high. 1238 To mitigate this risk, the operator should address the risk of ALTO 1239 information being leaked to malicious clients or third parties. As 1240 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1241 the ALTO Server should authenticate ALTO Clients and use the 1242 Transport Layer Security (TLS) protocol so that Man In The Middle 1243 (MITM) attacks to intercept an ALTO Calendar are not possible. 1244 [RFC7285] ensures the availability of such a solution in its 1245 Section 8.3.5. "Authentication and Encryption", which specifies 1246 that: "ALTO Server implementations as well as ALTO Client 1247 implementations MUST support the "https" URI scheme of [RFC2818] and 1248 Transport Layer Security (TLS) of [RFC5246]". 1250 [RFC8446] specifies TLS 1.3 and writes in its section 1: "While TLS 1251 1.3 is not directly compatible with previous versions, all versions 1252 of TLS incorporate a versioning mechanism which allows clients and 1253 servers to interoperably negotiate a common version if one is 1254 supported by both peers". So ALTO Clients and servers MAY use newer 1255 versions (e.g., 1.3) of TLS as long as the negotiation process 1256 succeeds. To ensure backward compatibility with [RFC7285], it is 1257 RECOMMENDED for both Calendar-aware Clients and Servers to both 1258 support at least TLS 1.2, until it gets deprecated. 1260 To avoid malicious or erroneous guidance from ALTO information, an 1261 ALTO Client should be cognizant that using calendaring information 1262 can have risks: (1) Calendar values, especially in "repeated" 1263 Calendars may be only statistical, and (2) future events may change. 1264 Hence, a more robust ALTO Client should adapt and extend protection 1265 strategies specified in Section 15.2 of the base protocol. For 1266 example, to be notified immediately when a particular ALTO value that 1267 the client depends on changes, it is RECOMMENDED that both the ALTO 1268 Client and ALTO Server using this extension support "ALTO Incremental 1269 Updates Using Server-Sent Events(SSE)" Service [draft-ietf-alto-incr- 1270 update-sse]. 1272 8. Operational Considerations 1274 Conveying ALTO Cost Calendars tends to reduce the on-the-wire data 1275 exchange volume compared to multiple single cost ALTO transactions. 1276 An application using Calendars has a set of time-dependent values 1277 upon which it can plan its connections in advance with no need for 1278 the ALTO Client to query information at each time. Additionally, the 1279 Calendar response attribute "repeated", when provided, saves 1280 additional data exchanges in that it indicates that the ALTO Client 1281 does not need to query Calendars during a period indicated by this 1282 attribute. Unexpected changes during this period can be handled by 1283 using the SSE Service as discussed in Section 7, if the Server and 1284 the Client support it. 1286 High-resolution intervals may be needed when values change, sometimes 1287 during very small time intervals but in a significant manner. A way 1288 to avoid conveying too many entries is to leverage on the "repeated" 1289 feature. A server can smartly set the Calendar start time and number 1290 of intervals so as to declare them "repeated" for a large number of 1291 periods, until the Calendar values change and are conveyed to 1292 requesting Clients. 1294 Clients and Servers supporting ALTO Calendars use [RFC8259]. 1295 [RFC7285] encodes its requests and responses using the JSON Data 1296 Interchange Format specified in [RFC7159]. In the meantime, 1297 [RFC7159] has been obsoleted by [RFC8259], that among others makes 1298 UTF-8 mandatory for text encoding to improve interoperability. 1299 Therefore, ALTO Clients and Servers implementations using UTF-{16,32} 1300 need to be cognizant of the subsequent interoperability risks and it 1301 is RECOMMENDED for them to switch to UTF-8 encoding, if they want to 1302 interoperate with Calendar-aware Servers and Clients. 1304 9. Acknowledgements 1306 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1307 Peng and Haibin Song for fruitful discussions and feedback on earlier 1308 draft versions. Dawn Chan, Kai Gao, Vijay Gurbani, Yichen Qian and 1309 Jensen Zhang provided substantial review feedback and suggestions to 1310 the protocol design. 1312 10. References 1314 10.1. Normative References 1316 [draft-ietf-alto-incr-update-sse] 1317 "ALTO Incremental Updates Using Server-Sent Events (SSE) 1318 (work in progress)", January 2020. 1320 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1321 Requirement Levels", BCP 14, RFC 2119, 1322 DOI 10.17487/RFC2119, March 1997, 1323 . 1325 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1326 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1327 "Application-Layer Traffic Optimization (ALTO) Protocol", 1328 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1329 . 1331 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1332 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1333 May 2017, . 1335 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1336 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1337 DOI 10.17487/RFC8189, October 2017, 1338 . 1340 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1341 Interchange Format", STD 90, RFC 8259, 1342 DOI 10.17487/RFC8259, December 2017, 1343 . 1345 10.2. Informative References 1347 [draft-ietf-alto-performance-metrics] 1348 "ALTO Performance Cost Metrics (work in progress)", 1349 November 2019. 1351 [draft-xiang-alto-multidomain-analytics] 1352 "Unicorn: Resource Orchestration for Multi-Domain, Geo- 1353 Distributed Data Analytics", July 2018. 1355 [IEEE.754.2008] 1356 "Standard for Binary Floating-Point Arithmetic, IEEE 1357 Standard 754", August 2008. 1359 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1360 DOI 10.17487/RFC2818, May 2000, 1361 . 1363 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1364 (TLS) Protocol Version 1.2", RFC 5246, 1365 DOI 10.17487/RFC5246, August 2008, 1366 . 1368 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1369 Optimization (ALTO) Problem Statement", RFC 5693, 1370 DOI 10.17487/RFC5693, October 2009, 1371 . 1373 [RFC6708] Kiesel, S., Ed., Previdi, S., Stiemerling, M., Woundy, R., 1374 and Y. Yang, "Application-Layer Traffic Optimization 1375 (ALTO) Requirements", RFC 6708, DOI 10.17487/RFC6708, 1376 September 2012, . 1378 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1379 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1380 2014, . 1382 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1383 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1384 DOI 10.17487/RFC7231, June 2014, 1385 . 1387 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1388 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1389 . 1391 [SENSE-sdn-e2e-net] 1392 "SDN for End-to-End Networked Science at the Exascale 1393 (SENSE), http://sense.es.net/overview". 1395 Authors' Addresses 1397 Sabine Randriamasy 1398 Nokia Bell Labs 1399 Route de Villejust 1400 NOZAY 91460 1401 FRANCE 1403 Email: Sabine.Randriamasy@nokia-bell-labs.com 1405 Richard Yang 1406 Yale University 1407 51 Prospect st 1408 New Haven, CT 06520 1409 USA 1411 Email: yry@cs.yale.edu 1413 Qin Wu 1414 Huawei 1415 101 Software Avenue, Yuhua District 1416 Nanjing, Jiangsu 210012 1417 China 1419 Email: sunseawq@huawei.com 1420 Lingli Deng 1421 China Mobile 1422 China 1424 Email: denglingli@chinamobile.com 1426 Nico Schwan 1427 Thales Deutschland 1428 Lorenzstrasse 10 1429 Stuttgart 70435 1430 Germany 1432 Email: nico.schwan@thalesgroup.com