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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Randriamasy 3 Internet-Draft Nokia Bell Labs 4 Intended status: Standards Track R. Yang 5 Expires: March 16, 2020 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 September 13, 2019 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-13 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 March 16, 2020. 58 Copyright Notice 60 Copyright (c) 2019 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 78 2.2. ALTO Cost Calendar overview . . . . . . . . . . . . . . . 5 79 2.3. ALTO Cost Calendar information features . . . . . . . . . 6 80 2.4. ALTO Calendar design characteristics . . . . . . . . . . 6 81 2.4.1. ALTO Cost Calendar for all cost modes . . . . . . . . 7 82 2.4.2. Compatibility with legacy ALTO Clients . . . . . . . 8 83 3. ALTO Calendar specification: IRD extensions . . . . . . . . . 8 84 3.1. Calendar attributes in the IRD resource capabilities . . 9 85 3.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 10 86 3.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 10 87 4. ALTO Calendar specification: Service Information Resources . 14 88 4.1. Calendar extensions for Filtered Cost Maps (FCM) . . . . 14 89 4.1.1. Calendar extensions in Filtered Cost Map requests . . 14 90 4.1.2. Calendar extensions in Filtered Cost Map responses . 15 91 4.1.3. Use case and example: FCM with a bandwidth Calendar . 18 92 4.2. Calendar extensions in the Endpoint Cost Service . . . . 20 93 4.2.1. Calendar specific input in Endpoint Cost requests . 20 94 4.2.2. Calendar attributes in the Endpoint Cost response . . 20 95 4.2.3. Use case and example: ECS with a routingcost Calendar 21 96 4.2.4. Use case and example: ECS with a multi-cost Calendar 97 for routingcost and owdelay . . . . . . . . . . . . . 24 98 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 99 6. Security Considerations . . . . . . . . . . . . . . . . . . . 26 100 7. Operational Considerations . . . . . . . . . . . . . . . . . 27 101 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 102 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 103 9.1. Normative References . . . . . . . . . . . . . . . . . . 28 104 9.2. Informative References . . . . . . . . . . . . . . . . . 29 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 107 1. Introduction 109 The base Application-Layer Traffic Optimization (ALTO) protocol 110 specified in [RFC7285] provides guidance to overlay applications that 111 need to select one or several hosts from a set of candidates able to 112 provide a desired resource. This guidance is based on parameters 113 that affect performance and efficiency of the data transmission 114 between the hosts such as the topological distance. The goal of ALTO 115 is to improve the Quality of Experience (QoE) in the application 116 while optimizing resource usage in the underlying network 117 infrastructure. 119 The ALTO protocol in [RFC7285] specifies a network map which defines 120 groupings of endpoints in provider-defined network regions identified 121 by Provider-defined Identifiers (PIDs). The Cost Map Service, 122 Endpoint Cost Service (ECS) and Endpoint Ranking Service then provide 123 ISP-defined costs and rankings for connections among the specified 124 endpoints and PIDs and thus incentives for application clients to 125 connect to ISP preferred locations, for instance, to reduce their 126 costs. For the reasons outlined in the ALTO problem statement 127 [RFC5693] and requirement AR-14 of [RFC6708], ALTO does not 128 disseminate network metrics that change frequently. In a network, 129 the costs can fluctuate for many reasons having to do with 130 instantaneous traffic load or due to diurnal patterns of traffic 131 demand or planned events such as network maintenance, holidays or 132 highly publicized events. Thus, an ALTO application wishing to use 133 the Cost Map and Endpoint Cost Service at some future time will have 134 to estimate the state of the network at that time, a process that is, 135 at best, fragile and brittle since the application does not have any 136 visibility into the state of the network. The need of such future 137 scheduling of large scale traffic that can be addressed by the ALTO 138 protocol is motivated by Unicorn, a unified resource orchestration 139 framework for multi-domain, geo-distributed data analytics, see 140 [draft-xiang-alto-multidomain-analytics]. 142 In case the ALTO Cost value changes are predictable over a certain 143 period of time and the application does not require immediate data 144 transfer, it can save time to get the whole set of cost values over 145 this period in one single ALTO response. Using this set to schedule 146 data transfers allows optimizing the network resources usage and QoE. 147 ALTO Clients and Servers can also minimize their workload by reducing 148 and accordingly scheduling their data exchanges. 150 This document extends [RFC7285] to allow an ALTO Server to provide 151 network costs for a given duration of time. A sequence of network 152 costs across a time span for a given pair of network locations is 153 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 154 Endpoint Cost Service are extended to provide Cost Calendars. In 155 addition to this functional ALTO enhancement, we expect to further 156 save network and storage resources by gathering multiple Cost Values 157 for one Cost Type into one single ALTO Server response. 159 In this draft, an "ALTO Cost Calendar" is specified in terms of 160 information resources capabilities that are applicable to time- 161 sensitive ALTO metrics. An ALTO Cost Calendar exposes ALTO Cost 162 Values in JSON arrays, see [RFC8259], where each value corresponds to 163 a given time interval. The time intervals as well as other Calendar 164 attributes are specified in the Information Resources Directory (IRD) 165 and in the Server response to allow the ALTO Client to interpret the 166 received ALTO values. Last, the extensions for ALTO Calendars are 167 applicable to any Cost Mode and they ensure backwards compatibility 168 with legacy ALTO Clients. 170 In the rest of this document, Section 2 provides the design 171 characteristics. Sections 3 and 4 define the formal specifications 172 for the IRD and the information resources. IANA, security and 173 operational considerations are addressed respectively in sections 174 Section 5, Section 6 and Section 7. 176 2. Overview of ALTO Cost Calendars and terminology 178 2.1. Terminology 180 o ALTO transaction: A request/response exchange between an ALTO 181 Client and an ALTO Server. 183 o Client: When used with a capital "C", this term refers to an ALTO 184 Client. 186 o Calendar, Cost Calendar: When used with capitalized words, these 187 terms refer to an ALTO Cost Calendar. 189 o Endpoint (EP): An endpoint is defined as in Section 2.1 of 190 [RFC7285]. It can be, for example, a peer, a CDN storage 191 location, a physical server involved in a virtual server-supported 192 application, a party in a resource-sharing swarm such as a 193 computation grid, or an online multi-party game. 195 o Server: When used with a capital "S", this term refers to an ALTO 196 Server. 198 2.2. ALTO Cost Calendar overview 200 An ALTO Cost Calendar provided by the ALTO Server provides 2 201 information items: 203 o an array of values for a given metric, where each value 204 corresponds to a time interval, where the value array can 205 sometimes be a cyclic pattern that repeats a certain number of 206 times. 208 o attributes describing the time scope of the Calendar such as the 209 size and number of the intervals and the date of the starting 210 point of the Calendar, allowing an ALTO Client to interpret the 211 values properly. 213 An ALTO Cost Calendar can be used like a "time table" to figure out 214 the best time to schedule data transfers and also to proactively 215 manage application traffic given predictable events such as expected 216 spike in traffic due to crowd gathering (concerts, sports, etc.), 217 traffic-intensive holidays and network maintenance. A potential use 218 case is the SENSE project, see [SENSE-sdn-e2e-net], who is 219 implementing smart network services to dynamically build end-to-end 220 virtual guaranteed networks across administrative domains, with no 221 manual intervention. The initial SENSE services include informing 222 applications on the availability of bandwidth resources or 223 feasibility of some requested Time-Bandwidth-Product (TBP) during a 224 specific time period. ALTO Calendars can support these services if 225 the Calendar start date and duration cover the period of interest of 226 the requesting applications. A Calendar may be viewed as a synthetic 227 abstraction of, for example, real measurements gathered over previous 228 periods on which statistics have been computed. However, like for 229 any schedule, unexpected network incidents may require the current 230 ALTO Calendar to be updated and re-sent to the ALTO Clients needing 231 it. To this end, it is RECOMMENDED that ALTO Servers providing ALTO 232 Calendars also provide the "ALTO Incremental Updates Using Server- 233 Sent Events (SSE)" Service that is specified in 234 [draft-ietf-alto-incr-update-sse]. Likewise, ALTO Clients capable of 235 using ALTO Calendars SHOULD also use the SSE Service. 237 Most likely, the ALTO Cost Calendar would be used for the Endpoint 238 Cost Service, assuming that a limited set of feasible Endpoints for a 239 non-real time application is already identified, that they do not 240 need to be accessed immediately and that their access can be 241 scheduled within a given time period. The Filtered Cost Map Service 242 is also applicable as long as the size of the Map allows it. 244 2.3. ALTO Cost Calendar information features 246 The Calendar attributes are provided in the Information Resources 247 Directory (IRD) and in ALTO Server responses. The IRD announces 248 attributes without date values in its information resources 249 capabilities, whereas attributes with time dependent values are 250 provided in the "meta" section of Server responses. The ALTO Cost 251 Calendar attributes provide the following information: 253 o attributes to describe the time scope of the Calendar value array: 255 * generic time zone, 257 * applicable time interval size for each Calendar value, defined 258 in seconds, that can cover a wide range of values. 260 * duration of the Calendar: e.g., the number of intervals 261 provided in the Calendar. 263 o "calendar-start-date": specifying when the Calendar starts, that 264 is to which date the first value of the Cost Calendar is 265 applicable. 267 o "repeated": an optional attribute indicating how many iterations 268 of the provided Calendar will have the same values. The server 269 may use it to allow the client to schedule its next request and 270 thus save its own workload by reducing processing of similar 271 requests. 273 Attribute "repeated" may take a very high value if a Calendar 274 represents a cyclic value pattern that the Server considers valid for 275 a long period. In this case, the Server will only update the 276 Calendar values once this period has elapsed or if an unexpected 277 event occurs on the network. 279 2.4. ALTO Calendar design characteristics 281 The extensions in this document and encode requests and responses 282 using JSON [RFC8259]. 284 Formally, the cost entries in an ALTO cost map can be any type of 285 JSON value [RFC8259], (see the DstCosts object in Section 11.2.3.6 of 286 [RFC7285]). However, that section states that an implementation of 287 [RFC7285] SHOULD assume that the cost is a JSON number and fail to 288 parse if it is not, unless the implementation is using an extension 289 that signals a different data type. This document extends the 290 definition of a legacy cost map given in [RFC7285] to allow a cost 291 entry to be an array of values, one per time interval, instead of 292 just one number. 294 To realize an ALTO Calendar, this document extends: the IRD, the ALTO 295 requests and responses for Cost Calendars. 297 This extension is designed to be light and to ensure backwards 298 compatibility with base protocol ALTO Clients and with other 299 extensions. It relies on section 8.3.7 "Parsing of Unknown Fields" 300 of [RFC7285] that writes: "Extensions may include additional fields 301 within JSON objects defined in this document. ALTO implementations 302 MUST ignore unknown fields when processing ALTO messages." 304 The Calendar-specific capabilities are integrated in the information 305 resources of the IRD and in the "meta" member of ALTO responses to 306 Cost Calendars requests. A Calendar and its capabilities are 307 associated with a given information resource and within this 308 information resource with a given cost type. This design has several 309 advantages: 311 o it does not introduce a new mode, 313 o it does not introduce new media types, 315 o it allows an ALTO Server to offer Calendar capabilities on a cost 316 type, with attributes values adapted to each information resource. 318 The applicable Calendared information resources are: 320 o the Filtered Cost Map, 322 o the Endpoint Cost Map. 324 The ALTO Server can choose in which frequency it provides cost 325 Calendars to ALTO Clients. It may either provide Calendar updates 326 starting at the request date, or carefully schedule its updates so as 327 to take profit from a potential repetition/periodicity of Calendar 328 values. 330 2.4.1. ALTO Cost Calendar for all cost modes 332 An ALTO Cost Calendar is well-suited for values encoded in the 333 "numerical" mode. Actually, a Calendar can also represent metrics in 334 other modes considered as compatible with time-varying values. For 335 example, types of Cost values such as JSONBool can also be 336 calendared, as their value may be 'true' or 'false' depending on 337 given time periods or likewise, values represented by strings, such 338 as "medium", "high", "low", "blue", "open". 340 Note also that a Calendar is suitable as well for time-varying 341 metrics provided in the "ordinal" mode, if these values are time- 342 varying and the ALTO Server provides updates of cost value based 343 preferences. 345 2.4.2. Compatibility with legacy ALTO Clients 347 The ALTO protocol extensions for Cost Calendars have been defined so 348 as to ensure that Calendar capable ALTO Servers can provide legacy 349 ALTO Clients with legacy information resources as well. That is a 350 legacy ALTO Client can request resources and receive responses as 351 specified in [RFC7285]. 353 A Calendar-aware ALTO Server MUST implement the base protocol 354 specified in [RFC7285]. 356 As a consequence, when a metric is available as a Calendar array, it 357 also MUST be available as a single value as required by [RFC7285]. 358 The Server, in this case, provides the current value of the metric to 359 either Calendar-aware Clients not interested in future or time-based 360 values, or Clients implementing [RFC7285] only. 362 For compatibility with legacy ALTO Clients specified in [RFC7285], 363 calendared information resources are not applicable for full cost 364 maps for the following reason: a legacy ALTO Client would receive a 365 calendared cost map via an HTTP 'GET' command. As specified in 366 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 367 indicated in the "meta" of the responses. Therefore, lacking 368 information on Calendar attributes, it will not be able to correctly 369 interpret and process the values of the received array of Calendar 370 cost values. 372 Therefore, calendared information resources MUST be requested via the 373 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 374 method. 376 3. ALTO Calendar specification: IRD extensions 378 The Calendar attributes in the IRD information resources capabilities 379 carry constant dateless values. A Calendar is associated with an 380 information resource rather than a cost type. For example, a Server 381 can provide a "routingcost" Calendar for the Filtered Cost Map 382 Service at a granularity of one day and a "routingcost" Calendar for 383 the Endpoint Cost Service at a finer granularity but for a limited 384 number of endpoints. An example IRD with Calendar specific features 385 is provided in Section 3.3. 387 3.1. Calendar attributes in the IRD resource capabilities 389 A Cost Calendar for a given Cost Type MUST be indicated in the IRD by 390 an object of type CalendarAttributes. A CalendarAttribute object is 391 represented by the "calendar-attributes" member of a resource entry. 392 Each CalendarAttributes object applies to a set of one or more cost 393 types. A Cost Type name MUST appear no more than once in the 394 "calendar-attributes" member of a resource entry; multiple 395 appearances of a Cost Type name in CalendarAttributes object of the 396 "calendar-attributes" member MUST cause the ALTO Client to ignore any 397 occurrences of this name beyond the first encountered occurrence. 399 It is RECOMMENDED for an ALTO Server that the time interval size 400 specified in the IRD is the smallest possible one that it can 401 provide. The Client can aggregate cost values on its own if it needs 402 a larger granularity. 404 The encoding format for object CalendarAttributes, using JSON 405 [RFC8259], is as follows: 407 CalendarAttributes calendar-attributes <1..*>; 409 object{ 410 JSONString cost-type-names <1..*>; 411 JSONNumber time-interval-size; 412 JSONNumber number-of-intervals; 413 } CalendarAttributes; 415 o "cost-type-names": 417 * An array of one or more elements indicating the cost-type-names 418 in the IRD entry to which the capabilities apply. 420 o "time-interval-size": 422 * is the duration of an ALTO Calendar time interval in seconds. 423 A "time-interval-size" value contains a JSONNumber. ALTO 424 Servers SHOULD use at least IEEE 754 double-precision floating 425 point [IEEE.754.2008] to store this value. Example values are: 426 300 , 7200, meaning that each Calendar value applies on a time 427 interval that lasts respectively 5 minutes and 2 hours. 429 o "number-of-intervals": 431 * the integer number of values of the Cost Calendar array, at 432 least equal to 1. 434 - Attribute "cost-type-names" provides a better readability to the 435 Calendar attributes specified in the IRD and avoids confusion with 436 Calendar attributes of other cost-types. 438 - Multiplying 'time-interval-size' by 'number-of-intervals' provides 439 the duration of the provided Calendar. For example, an ALTO Server 440 may provide a Calendar for ALTO values changing every 'time-interval- 441 size' equal to 5 minutes. If 'number-of-intervals' has the value 12, 442 then the duration of the provided Calendar is "1 hour". 444 3.2. Calendars in a delegate IRD 446 It may be useful to distinguish IRD resources supported by the base 447 ALTO protocol from resources supported by its extensions. To achieve 448 this, one option, is that a "root" ALTO Server implementing base 449 protocol resources delegates "specialized" information resources such 450 as the ones providing Cost Calendars, to another ALTO Server running 451 in a subdomain that is specified with its URI in the "root" ALTO 452 Server. This option is described in Section 9.2.4 "Delegation using 453 IRDs" of [RFC7285]. 455 This document provides an example, where a "root" ALTO Server runs in 456 a domain called "alto.example.com". It delegates the announcement of 457 Calendars capabilities to an ALTO Server running in a subdomain 458 called "custom.alto.example.com". The location of the "delegate 459 Calendar IRD" is assumed to be indicated in the "root" IRD by the 460 resource entry: "custom-calendared-resources". 462 Another advantage is that some Cost Types for some resources may be 463 more advantageous as Cost Calendars and it makes few sense to get 464 them as a single value. For example, Cost Types with predictable and 465 frequently changing values, calendared in short time intervals such 466 as a minute. 468 3.3. Example IRD with ALTO Cost Calendars 470 This section provides an example ALTO Server IRD that supports 471 various cost metrics and cost modes. In particular, since [RFC7285] 472 makes it mandatory, the Server uses metric "routingcost" in the 473 "numerical" mode. 475 For illustrative purposes, this section introduces 3 other fictitious 476 example metrics and modes that should be understood as examples and 477 should not be used or considered as normative. 479 The cost type names used in the example IRD as thus as follows: 481 o "num-routingcost": refers to metric "routingcost" in the numerical 482 mode as defined in [RFC7285] and registered with IANA. 484 o "num-owdelay": refers to fictitious performance metric "owdelay" 485 in the "numerical" mode,to reflect the one-way packet transmission 486 delay on a path. A related performance metric is currently under 487 definition in [draft-ietf-alto-performance-metrics]. 489 o "num-throughputrating": refers to fictitious metric 490 "throughputrating" in the "numerical" mode, to reflect the 491 provider preference in terms of end to end throughput. 493 o "string-servicestatus": refers to fictitious metric 494 "servicestatus" in some example mode "string", to reflect the 495 availability, defined by the provider, of for instance path 496 connectivity. 498 The example IRD includes 2 particular URIs providing Calendars: 500 o "https://custom.alto.example.com/calendar/costmap/filtered": a 501 filtered cost map in which Calendar capabilities are indicated for 502 cost type names: "num-routingcost", "num-throughputrating" and 503 "string-servicestatus", 505 o "https://custom.alto.example.com/calendar/endpointcost/lookup": an 506 endpoint cost map in which Calendar capabilities are indicated for 507 cost type names: "num-routingcost", "num-owdelay", "num- 508 throughputrating", "string-servicestatus". 510 The design of the Calendar capabilities allows that some Calendars on 511 a cost type name are available in several information resources with 512 different Calendar Attributes. This is the case for Calendars on 513 "num-routingcost", "num-throughputrating" and "string-servicestatus", 514 available in both the Filtered Cost map and Endpoint Cost Service, 515 but with different time interval sizes for "num-throughputrating" and 516 "string-servicestatus". 518 --- Client to Server request for IRD ---------- 520 GET /calendars-directory HTTP/1.1 521 Host: custom.alto.example.com 522 Accept: application/alto-directory+json,application/alto-error+json 524 --- Server response to Client ----------------- 525 HTTP/1.1 200 OK 526 Content-Length: 2542 527 Content-Type: application/alto-directory+json 529 { 530 "meta" : { 531 "default-alto-network-map" : "my-default-network-map", 532 "cost-types": { 533 "num-routingcost": { 534 "cost-mode" : "numerical", 535 "cost-metric" : "routingcost" 536 }, 537 "num-owdelay": { 538 "cost-mode" : "numerical", 539 "cost-metric": "owdelay" 540 }, 541 "num-throughputrating": { 542 "cost-mode" : "numerical", 543 "cost-metric": "throughputrating" 544 }, 545 "string-servicestatus": { 546 "cost-mode" : "string", 547 "cost-metric": "servicestatus" 548 } 549 } 550 }, 551 "resources" : { 552 "filtered-cost-map-calendar" : { 553 "uri" : 554 "https://custom.alto.example.com/calendar/costmap/filtered", 555 "media-type" : "application/alto-costmap+json", 556 "accepts" : "application/alto-costmapfilter+json", 557 "capabilities" : { 558 "cost-constraints" : true, 559 "cost-type-names" : [ "num-routingcost", 560 "num-throughputrating", 561 "string-servicestatus" ], 562 "calendar-attributes" : [ 563 {"cost-type-names" : [ "num-routingcost", 564 "num-throughputrating" ], 565 "time-interval-size" : 7200, 566 "number-of-intervals" : 12 567 }, 568 {"cost-type-names" : [ "string-servicestatus" ], 569 "time-interval-size" : 1800, 570 "number-of-intervals" : 48 571 } 572 ] 574 }, 575 "uses": [ "my-default-network-map" ] 576 }, 577 "endpoint-cost-calendar-map" : { 578 "uri" : 579 "https://custom.alto.example.com/calendar/endpointcost/lookup", 580 "media-type" : "application/alto-endpointcost+json", 581 "accepts" : "application/alto-endpointcostparams+json", 582 "capabilities" : { 583 "cost-constraints" : true, 584 "cost-type-names" : [ "num-routingcost", 585 "num-owdelay", 586 "num-throughputrating", 587 "string-servicestatus" ], 588 "calendar-attributes" : [ 589 {"cost-type-names" : [ "num-routingcost" ], 590 "time-interval-size" : 3600, 591 "number-of-intervals" : 24 592 }, 593 {"cost-type-names" : [ "num-owdelay" ], 594 "time-interval-size" : 300, 595 "number-of-intervals" : 12 596 }, 597 {"cost-type-names" : [ "num-throughputrating" ], 598 "time-interval-size" : 60, 599 "number-of-intervals" : 60 600 }, 601 {"cost-type-names" : [ "string-servicestatus" ], 602 "time-interval-size" : 120, 603 "number-of-intervals" : 30 604 } 605 ] 606 } 607 } 608 } 609 } 611 In this example IRD, for the Filtered Cost Map Service: 613 o the Calendar for "num-routingcost" and "num-throughputrating" is 614 an array of 12 values each provided on a time interval lasting 615 7200 seconds (2 hours). 617 o the Calendar for "string-servicestatus": "is an array of 48 values 618 each provided on a time interval lasting 1800 seconds (30 619 minutes). 621 For the Endpoint Cost Service: 623 o the Calendar for "num-routingcost": is an array of 24 values each 624 provided on a time interval lasting 3600 seconds (1 hour). 626 o the Calendar for "owdelay": is an array of 12 values each provided 627 on a time interval lasting 300 seconds (5 minutes). 629 o the Calendar for "num-throughputrating": is an array of 60 values 630 each provided on a time interval lasting 60 seconds (1 minute). 632 o the Calendar for "string-servicestatus": "is an array of 30 values 633 each provided on a time interval lasting 120 seconds (2 minutes). 635 4. ALTO Calendar specification: Service Information Resources 637 This section documents the individual information resources defined 638 to provide the calendared information services defined in this 639 document. 641 The reference time zone for the provided time values is UTC. The 642 option chosen to express the time format is the HTTP header fields 643 format specified in [RFC7231] where, however, timestamps are still 644 displayed with the acronym "GMT" rather than "UTC": 646 Date: Tue, 15 Nov 2014 08:12:31 GMT 648 The value of a Calendar time interval size is expressed in seconds. 650 4.1. Calendar extensions for Filtered Cost Maps (FCM) 652 A legacy ALTO Client requests and gets Filtered Cost Map responses as 653 specified in [RFC7285]. 655 4.1.1. Calendar extensions in Filtered Cost Map requests 657 The input parameters of a "legacy" request for a filtered cost map, 658 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 659 are augmented with one additional member. 661 A Calendar-aware ALTO Client requesting a Calendar on a given Cost 662 Type for a filtered cost map resource having Calendar capabilities 663 MUST add the following field to its input parameters: 665 JSONBoolean calendared<1..*>; 667 This field is an array of 1 to N boolean values, where N is the 668 number of requested metrics. Each entry corresponds to the requested 669 metric at the same array position. Each boolean value indicates 670 whether or not the ALTO Server should provide the values for this 671 Cost Type as a Calendar. The array MUST contain exactly N boolean 672 values, otherwise, the Server returns an error. 674 This field MUST NOT be included if no member "calendar-attributes" is 675 specified in this information resource. 677 If a value of field 'calendared' is 'true' for a cost type name for 678 which no Calendar attributes have been specified: an ALTO Server, 679 whether it implements the extensions of this document or only 680 implements [RFC7285], MUST ignore it and return a response with a 681 single cost value as specified in [RFC7285]. 683 If this field is not present, it MUST be assumed to have only values 684 equal to 'false'. 686 A Calendar-aware ALTO Client that supports requests for only one cost 687 type at a time and wants to request a Calendar MUST provide an array 688 of 1 element: 690 "calendared" : [true]; 692 A Calendar-aware ALTO Client that supports requests for more than one 693 Cost Types at a time, as specified in [RFC8189] MUST provide an array 694 of N values set to 'true' or 'false', depending whether it wants the 695 applicable Cost Type values as a single or calendared value. 697 4.1.2. Calendar extensions in Filtered Cost Map responses 699 In a calendared ALTO Filtered Cost Map, a cost value between a source 700 and a destination is a JSON array of JSON values. An ALTO Calendar 701 values array has a number of values equal to the value of member 702 "number-of-intervals" of the Calendar attributes that are indicated 703 in the IRD. These attributes will be conveyed as metadata in the 704 Filtered Cost Map response. Each element of the array is valid for 705 the time-interval that matches its array position. 707 The FCM response conveys metadata among which: 709 o some are not specific to Calendars and ensure compatibility with 710 [RFC7285] and [RFC8189] 712 o some are specific to Calendars. 714 The non Calendar specific "meta" fields of a calendared Filtered Cost 715 Map response MUST include at least: 717 o if the ALTO Client requests cost values for one Cost Type at a 718 time only: the "meta" fields specified in [RFC7285] for these 719 information service responses: 721 * "dependent-vtags ", 723 * "cost-type" field. 725 o if the ALTO Client implements the Multi-Cost ALTO extension 726 specified in [RFC8189] and requests cost values for several Cost 727 Types at a time: the "meta" fields specified in [RFC8189] for 728 these information service responses: 730 * "dependent-vtags ", 732 * "cost-type" field with value set to '{}', for backwards 733 compatibility with [RFC7285]. 735 * "multi-cost-types" field. 737 If the client request does not provide member "calendared" or if it 738 provides it with a value equal to 'false', for all the requested Cost 739 Types, then the ALTO Server response is exactly as specified in 740 [RFC7285] and [RFC8189]. 742 If the value of member "calendared" is equal to 'false' for a given 743 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 744 a single cost value as specified in [RFC7285]. 746 If the value of member "calendared" is equal to 'true' for a given 747 requested Cost Type, the ALTO Server returns, for this Cost Type, a 748 cost value Calendar as specified above in this section. In addition 749 to the above cited non Calendar specific "meta" members, the Server 750 MUST provide a Calendar specific metadata field. 752 The Calendar specific "meta" field that a calendared Filtered Cost 753 Map response MUST include is a member called "calendar-response- 754 attributes", that describes properties of the Calendar and where: 756 o member "calendar-response-attributes" is an array of one or more 757 objects of type "CalendarResponseAttributes". 759 o each "CalendarResponseAttributes" object in the array is specified 760 for one or more Cost Types for which the value of member 761 "calendared" is equal to 'true' and for which a Calendar is 762 provided for the requested information resource. 764 o the "CalendarResponseAttributes" object that applies to a cost 765 type name has a corresponding "CalendarAttributes" object defined 766 for this cost type name in the IRD capabilities of the requested 767 information resource. The members of a 768 "CalendarResponseAttributes" object include all the members of the 769 corresponding "CalendarAttributes" object. 771 The format of member "CalendarResponseAttributes is defined as 772 follows: 774 CalendarResponseAttributes calendar-response-attributes <1..*>; 776 object{ 777 [JSONString cost-type-names <1..*>]; 778 JSONString calendar-start-time; 779 JSONNumber time-interval-size; 780 JSONNumber number-of-intervals; 781 [JSONNumber repeated;] 782 } CalendarResponseAttributes; 784 Object CalendarResponseAttributes has the following attributes: 786 o "cost-type-names": is an array of one or more cost-type-names to 787 which the capabilities apply and for which a Calendar has been 788 requested. The value of this member is a subset of the "cost- 789 type-names" array specified in the corresponding IRD Calendar 790 attributes. 792 o "calendar-start-time": indicates the date at which the first value 793 of the Calendar applies. The value provided for the "calendar- 794 start-time" attribute SHOULD NOT be later than the request date. 796 o "time-interval-size": as specified in Section 3.1 and with the 797 same value. 799 o "number-of-intervals": as specified in Section 3.1 and with the 800 same value. 802 o "repeated": is an optional field provided for Calendars. It is an 803 integer N greater or equal to '1' that indicates how many 804 iterations of the Calendar value array starting at the date 805 indicated by "calendar-start-time" have the same values. The 806 number N includes the provided iteration. 808 For example: suppose the "calendar-start-time" member has value "Mon, 809 30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has 810 value '3600', the "number-of-intervals" member has value '24' and the 811 value of member "repeated" is equal to '4'. This means that the 812 Calendar values are the same on Monday, Tuesday, Wednesday and 813 Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO 814 Client thus may use the same Calendar for the next 4 days starting at 815 "calendar-start-time" and will only need to request a new one for 816 Friday July 4th at 00:00:00 GMT. 818 Attribute "repeated" may take a very high value if a Calendar 819 represents a cyclic value pattern that the Server considers valid for 820 a long period and hence will only update once this period has elapsed 821 or if an unexpected event occurs on the network. In the latter case, 822 the client will be notified if it uses the "ALTO Incremental Updates 823 Using Server-Sent Events (SSE)" Service, specified in 824 [draft-ietf-alto-incr-update-sse]. See also discussion in Section 7 825 "Operational Considerations". 827 4.1.3. Use case and example: FCM with a bandwidth Calendar 829 An example of non-real time information that can be provisioned in a 830 Calendar is the expected path throughput. While the transmission 831 rate can be measured in real time by end systems, the operator of a 832 data center is in the position of formulating preferences for given 833 paths, at given time periods to avoid traffic peaks due to diurnal 834 usage patterns. In this example, we assume that an ALTO Client 835 requests a Calendar of network provider defined throughput ratings, 836 as specified in the IRD, to schedule its bulk data transfers as 837 described in the use cases. 839 In the example IRD, Calendars for cost type name "num- 840 throughputrating" are available for the information resources: 841 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 842 ALTO Client requests a Calendar for "num-throughputrating" via a POST 843 request for a filtered cost map. 845 We suppose in the present example that the ALTO Client sends its 846 request on Tuesday July 1st 2014 at 13:15. The Server returns 847 Calendars with arrays of 12 numbers for each source and destination 848 pair. The values for metric "throughputrating", in this example, are 849 assumed to be encoded in 2 digits. 851 POST /calendar/costmap/filtered HTTP/1.1 852 Host: alto.example.com 853 Content-Length: 208 854 Content-Type: application/alto-costmapfilter+json 855 Accept: application/alto-costmap+json,application/alto-error+json 857 { 858 "cost-type" : {"cost-mode" : "numerical", 859 "cost-metric" : "throughputrating"}, 860 "calendared" : [true], 861 "pids" : { 862 "srcs" : [ "PID1", "PID2" ], 863 "dsts" : [ "PID1", "PID2", "PID3" ] 864 } 865 } 867 HTTP/1.1 200 OK 868 Content-Length: 815 869 Content-Type: application/alto-costmap+json 871 { 872 "meta" : { 873 "dependent-vtags" : [ 874 {"resource-id": "my-default-network-map", 875 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 876 } 877 ], 878 "cost-type" : {"cost-mode" : "numerical", 879 "cost-metric" : "throughputrating"}, 880 "calendar-response-attributes" : [ 881 {"calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 882 "time-interval-size" : 7200, 883 "number-of-intervals" : 12} 884 ] 885 }, 886 "cost-map" : { 887 "PID1": { "PID1": [01, 12, 14, 18, 14, 14, 14, 18, 19, 20, 11, 12], 888 "PID2": [13, 04, 15, 16, 17, 18, 19, 20, 11, 12, 13, 14], 889 "PID3": [20, 20, 18, 14, 12, 12, 14, 14, 12, 12, 14, 16] }, 890 "PID2": { "PID1": [17, 18, 19, 10, 11, 12, 13, 14, 15, 16, 17, 18], 891 "PID2": [20, 20, 18, 16, 14, 14, 14, 16, 16, 16, 14, 16] 892 "PID3": [20, 20, 18, 14, 12, 12, 14, 14, 12, 12, 14, 16] } 893 } 894 } 896 4.2. Calendar extensions in the Endpoint Cost Service 898 This document extends the Endpoint Cost Service, as defined in 899 {11.5.1} of [RFC7285], by adding new input parameters and 900 capabilities, and by returning JSONArrays instead of JSONNumbers as 901 the cost values. The media type {11.5.1.1} and HTTP method 902 {11.5.1.2} are unchanged. 904 4.2.1. Calendar specific input in Endpoint Cost requests 906 The extensions to the requests for calendared Endpoint Cost Maps are 907 the same as for the Filtered Cost Map Service, specified in section 908 Section 4.1.1 of this draft. 910 The ReqEndpointCostMap object for a calendared ECM request will have 911 the following format: 913 object { 914 [CostType cost-type;] 915 [CostType multi-cost-types<1..*>;] 916 [JSONBoolean calendared<1..*>;] 917 EndpointFilter endpoints; 918 } ReqEndpointCostMap; 920 object { 921 [TypedEndpointAddr srcs<0..*>;] 922 [TypedEndpointAddr dsts<0..*>;] 923 } EndpointFilter; 925 4.2.2. Calendar attributes in the Endpoint Cost response 927 The "meta" field of a calendared Endpoint Cost response MUST include 928 at least: 930 o if the ALTO Client supports cost values for one Cost Type at a 931 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 932 for the Endpoint Cost response: 934 * "cost-type" field. 936 o if the ALTO Client supports cost values for several Cost Types at 937 a time, as specified in [RFC8189] : the "meta" fields specified in 938 [RFC8189] for the the Endpoint Cost response: 940 * "cost-type" field with value set to '{}', for backwards 941 compatibility with [RFC7285]. 943 * "multi-cost-types" field. 945 If the client request does not provide member "calendared" or if it 946 provides it with a value equal to 'false', for all the requested Cost 947 Types, then the ALTO Server response is exactly as specified in 948 [RFC7285] and [RFC8189]. 950 If the ALTO Client provides member "calendared" in the input 951 parameters with a value equal to 'true' for given requested Cost 952 Types, the "meta" member of a calendared Endpoint Cost response MUST 953 include, for these Cost Types, an additional member "calendar- 954 response-attributes", the contents of which obey the same rules as 955 for the Filtered Cost Map Service, specified in Section 4.1.2. The 956 Server response is thus changed as follows, w.r.t [RFC7285] and 957 [RFC8189]: 959 o the "meta" member has one additional field 960 "CalendarResponseAttributes", as specified for the Filtered Cost 961 Map Service, 963 o the calendared costs are JSONArrays instead of the JSONNumbers 964 format used by legacy ALTO implementations. All arrays have a 965 number of values equal to 'number-of-intervals'. 967 If the value of member "calendared" is equal to 'false' for a given 968 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 969 a single cost value as specified in [RFC7285]. 971 4.2.3. Use case and example: ECS with a routingcost Calendar 973 Let us assume an Application Client is located in an end system with 974 limited resources and having access to the network that is either 975 intermittent or provides an acceptable quality in limited but 976 predictable time periods. Therefore, it needs to both schedule its 977 resource-greedy networking activities and its ALTO transactions. 979 The Application Client has the choice to trade content or resources 980 with a set of Endpoints and needs to decide with which one it will 981 connect and at what time. For instance, the Endpoints are spread in 982 different time-zones, or have intermittent access. In this example, 983 the 'routingcost' is assumed to be time-varying, with values provided 984 as ALTO Calendars. 986 The ALTO Client associated with the Application Client queries an 987 ALTO Calendar on 'routingcost' and will get the Calendar covering the 988 24 hours time period "containing" the date and time of the ALTO 989 client request. 991 For Cost Type "num-routingcost", the solicited ALTO Server has 992 defined 3 different daily patterns each represented by a Calendar, to 993 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 995 - C1 for Monday, Tuesday, Wednesday, Thursday, (weekdays) 997 - C2 for Saturday, Sunday, (weekend) 999 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 1000 to 04:00:00 GMT, or big holiday such as New Year evening). 1002 In the following example, the ALTO Client sends its request on 1003 Tuesday July 1st 2014 at 13:15. 1005 The "routingcost" values are assumed to be encoded in 3 digits. 1007 For representation brevity, the arrays in the provided example are 1008 symbolized by expression "[v1,v2, ... v24]", that is otherwise not 1009 valid in JSON. The value of field "Content-Length" in the responses 1010 is computed as if "routingcost" values were encoded in 3 digits. 1012 POST /calendar/endpointcost/lookup HTTP/1.1 1013 Host: alto.example.com 1014 Content-Length: 290 1015 Content-Type: application/alto-endpointcostparams+json 1016 Accept: application/alto-endpointcost+json,application/alto-error+json 1018 { 1019 "cost-type" : {"cost-mode" : "numerical", 1020 "cost-metric" : "routingcost"}, 1021 "calendared" : [true], 1022 "endpoints" : { 1023 "srcs": [ "ipv4:192.0.2.2" ], 1024 "dsts": [ 1025 "ipv4:192.0.2.89", 1026 "ipv4:198.51.100.34", 1027 "ipv4:203.0.113.45", 1028 "ipv6:2001:db8::10" 1029 ] 1030 } 1031 } 1033 HTTP/1.1 200 OK 1034 Content-Length: 877 1035 Content-Type: application/alto-endpointcost+json 1037 { 1038 "meta" : { 1039 "cost-type" : {"cost-mode" : "numerical", 1040 "cost-metric" : "routingcost"}, 1041 "calendar-response-attributes" : [ 1042 {"calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1043 "time-interval-size" : 3600, 1044 "number-of-intervals" : 24, 1045 "repeated": 4 1046 } 1047 ] 1048 }, 1049 "endpoint-cost-map" : { 1050 "ipv4:192.0.2.2": { 1051 "ipv4:192.0.2.89" : [v1, v2, ... v24], 1052 "ipv4:198.51.100.34" : [v1, v2, ... v24], 1053 "ipv4:203.0.113.45" : [v1, v2, ... v24], 1054 "ipv6:2001:db8::10" : [v1, v2, ... v24] 1055 } 1056 } 1057 } 1058 When the Client gets the Calendar for "routingcost", it sees that the 1059 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 1060 equal to '4'. It understands that the provided values are valid 1061 until Thursday included and will only need to get a Calendar update 1062 on Friday. 1064 4.2.4. Use case and example: ECS with a multi-cost Calendar for 1065 routingcost and owdelay 1067 In this example, it is assumed that the ALTO Server implements multi- 1068 cost capabilities, as specified in [RFC8189] . That is, an ALTO 1069 Client can request and receive values for several cost types in one 1070 single transaction. An illustrating use case is a path selection 1071 done on the basis of 2 metrics: routing cost and owdelay. 1073 As in the previous example, the IRD indicates that the ALTO Server 1074 provides "routingcost" Calendars in terms of 24 time intervals of 1 1075 hour (3600 seconds) each. 1077 For metric "owdelay", the IRD indicates that the ALTO Server provides 1078 Calendars in terms of 12 time intervals values lasting each 5 minutes 1079 (300 seconds). 1081 In the following example transaction, the ALTO Client sends its 1082 request on Tuesday July 1st 2014 at 13:15. 1084 This example assumes that the values of metric "owdelay" and 1085 "routingcost" are encoded in 3 digits. 1087 For representation brevity, the arrays in the provided example are 1088 symbolized by expression "[[r1, r2, ... r24], [o1, o2, ... o12]]", 1089 that is otherwise not valid in JSON. The value of field "Content- 1090 Length" in the responses is computed as if "routingcost" and 1091 "owdelay" values were encoded in 3 digits. 1093 POST calendar/endpointcost/lookup HTTP/1.1 1094 Host: alto.example.com 1095 Content-Length: 373 1096 Content-Type: application/alto-endpointcostparams+json 1097 Accept: application/alto-endpointcost+json,application/alto-error+json 1099 { 1100 "cost-type" : {}, 1101 "multi-cost-types" : [ 1102 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1103 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1104 ], 1105 "calendared" : [true, true], 1106 "endpoints" : { 1107 "srcs": [ "ipv4:192.0.2.2" ], 1108 "dsts": [ 1109 "ipv4:192.0.2.89", 1110 "ipv4:198.51.100.34", 1111 "ipv4:203.0.113.45", 1112 "ipv6:2001:db8::10" 1113 ] 1114 } 1115 } 1117 HTTP/1.1 200 OK 1118 Content-Length: 1377 1119 Content-Type: application/alto-endpointcost+json 1121 { 1122 "meta" : { 1123 "multi-cost-types" : [ 1124 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1125 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1126 ], 1127 "calendar-response-attributes" : [ 1128 {"cost-type-names" : "num-routingcost", 1129 "calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1130 "time-interval-size" : 3600, 1131 "number-of-intervals" : 24, 1132 "repeated": 4 }, 1133 {"cost-type-names" : "num-owdelay" 1134 "calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 1135 "time-interval-size" : 300, 1136 "number-of-intervals" : 12} 1137 ], 1138 }, 1139 "endpoint-cost-map" : { 1140 "ipv4:192.0.2.2": { 1141 "ipv4:192.0.2.89" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1142 "ipv4:198.51.100.34" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1143 "ipv4:203.0.113.45" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1144 "ipv6:2001:db8::10" : [[r1, r2, ... r24], [o1, o2, ... o12]] 1145 } 1146 } 1147 } 1149 When receiving the response, the client sees that the Calendar values 1150 for metric "routingcost" are repeated for 4 iterations. Therefore, 1151 in its next requests until the "routingcost" Calendar is expected to 1152 change, the client will only need to request a Calendar for 1153 "owdelay". 1155 Without the ALTO Calendar extensions, the ALTO Client would have no 1156 clue on the dynamicity of the metric value change and would spend 1157 needless time requesting values at an inappropriate pace. In 1158 addition, without the Multi-Cost ALTO capabilities, the ALTO Client 1159 would duplicate this waste of time as it would need to send one 1160 request per cost metric. 1162 5. IANA Considerations 1164 This document does not define any new media types or introduce any 1165 new IANA considerations. 1167 6. Security Considerations 1169 As an extension of the base ALTO protocol [RFC7285], this document 1170 fits into the architecture of the base protocol, and hence the 1171 Security Considerations (Section 15) of the base protocol fully apply 1172 when this extension is provided by an ALTO Server. For example, the 1173 same authenticity and integrity considerations (Section 15.1 of 1174 [RFC7285] still fully apply; the same considerations for the privacy 1175 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1177 The calendaring information provided by this extension requires 1178 additional considerations on three security considerations discussed 1179 in the base protocol: potential undesirable guidance to clients 1180 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1181 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1182 of [RFC7285]). For example, by providing network information in the 1183 future in a Calendar, this extension may improve availability of 1184 ALTO, when the ALTO Server is unavailable but related information is 1185 already provided in the Calendar. 1187 For confidentiality of ALTO information, an operator should be 1188 cognizant that this extension may introduce a new risk: an ALTO 1189 Client may get information for future events that are scheduled 1190 through Calendaring. Possessing such information, the client may use 1191 it to achieve its goal: (1) initiating connections only at 1192 advantageous network costs, leading to unexpected network load; (2) 1193 generating massive connections to the network at times where its load 1194 is expected to be high. 1196 To mitigate this risk, the operator should address the risk of ALTO 1197 information being leaked to malicious clients or third parties. As 1198 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1199 the ALTO Server should authenticate ALTO Clients and use the 1200 Transport Layer Security (TLS) protocol so that Man In The Middle 1201 (MITM) attacks to intercept an ALTO Calendar are not possible. 1202 [RFC7285] ensures the availability of such a solution in its 1203 Section 8.3.5. "Authentication and Encryption", which specifies 1204 that: "ALTO Server implementations as well as ALTO Client 1205 implementations MUST support the "https" URI scheme of [RFC2818] and 1206 Transport Layer Security (TLS) of [RFC5246]". 1208 [RFC8446] specifies TLS 1.3 and writes in its section 1: "While TLS 1209 1.3 is not directly compatible with previous versions, all versions 1210 of TLS incorporate a versioning mechanism which allows clients and 1211 servers to interoperably negotiate a common version if one is 1212 supported by both peers". So ALTO Clients and servers MAY use newer 1213 versions (e.g., 1.3) of TLS as long as the negotiation process 1214 succeeds. To ensure backward compatibility with [RFC7285], it is 1215 RECOMMENDED for both Calendar-aware Clients and Servers to both 1216 support at least TLS 1.2, until it gets deprecated. 1218 To avoid malicious or erroneous guidance from ALTO information, an 1219 ALTO Client should be cognizant that using calendaring information 1220 can have risks: (1) Calendar values, especially in "repeated" 1221 Calendars may be only statistical, and (2) future events may change. 1222 Hence, a more robust ALTO Client should adapt and extend protection 1223 strategies specified in Section 15.2 of the base protocol: it should 1224 develop self-check and also ensure information update, to reduce the 1225 impact of this risk. To address the risk of unexpected ALTO Values 1226 changes that the ALTO Client would be unaware of, it is RECOMMENDED 1227 that Servers supporting Calendars also support the "ALTO Incremental 1228 Updates Using Server-Sent Events (SSE)" Service, specified in 1229 [draft-ietf-alto-incr-update-sse]. Likewise, it is RECOMMENDED that 1230 Clients using Calendars also support the SSE Service. 1232 7. Operational Considerations 1234 Conveying ALTO Cost Calendars tends to reduce the on-the-wire data 1235 exchange volume compared to multiple single cost ALTO transactions. 1236 An application using Calendars has a set of time-dependent values 1237 upon which it can plan its connections in advance with no need for 1238 the ALTO Client to query information at each time. Additionally, the 1239 Calendar response attribute "repeated", when provided, saves 1240 additional data exchanges in that it indicates that the ALTO Client 1241 does not need to query Calendars during a period indicated by this 1242 attribute. Unexpected changes during this period can be handled by 1243 using the SSE Service as discussed in Section 6, if the Server and 1244 the Client support it. 1246 High-resolution intervals may be needed when values change, sometimes 1247 during very small time intervals but in a significant manner. A way 1248 to avoid conveying too many entries is to leverage on the "repeated" 1249 feature. A server can smartly set the Calendar start time and number 1250 of intervals so as to declare them "repeated" for a large number of 1251 periods, until the Calendar values change and are conveyed to 1252 requesting Clients. 1254 Clients and Servers supporting ALTO Calendars use [RFC8259]. 1255 [RFC7285] encodes its requests and responses using the JSON Data 1256 Interchange Format specified in [RFC7159]. In the meantime, 1257 [RFC7159] has been obsoleted by [RFC8259], that among others makes 1258 UTF-8 mandatory for text encoding to improve interoperability. 1259 Therefore, ALTO Clients and Servers implementations using UTF-{16,32} 1260 need to be cognizant of the subsequent interoperability risks and it 1261 is RECOMMENDED for them to switch to UTF-8 encoding, if they want to 1262 interoperate with Calendar-aware Servers and Clients. 1264 8. Acknowledgements 1266 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1267 Peng and Haibin Song for fruitful discussions and feedback on earlier 1268 draft versions. Dawn Chan, Kai Gao, Vijay Gurbani, Yichen Qian and 1269 Jensen Zhang provided substantial review feedback and suggestions to 1270 the protocol design. 1272 9. References 1274 9.1. Normative References 1276 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1277 Requirement Levels", BCP 14, RFC 2119, 1278 DOI 10.17487/RFC2119, March 1997, 1279 . 1281 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1282 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1283 "Application-Layer Traffic Optimization (ALTO) Protocol", 1284 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1285 . 1287 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1288 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1289 May 2017, . 1291 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1292 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1293 DOI 10.17487/RFC8189, October 2017, 1294 . 1296 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1297 Interchange Format", STD 90, RFC 8259, 1298 DOI 10.17487/RFC8259, December 2017, 1299 . 1301 9.2. Informative References 1303 [draft-ietf-alto-incr-update-sse] 1304 "ALTO Incremental Updates Using Server-Sent Events (SSE) 1305 (work in progress)", December 2018. 1307 [draft-ietf-alto-performance-metrics] 1308 "ALTO Performance Cost Metrics (work in progress)", June 1309 2018. 1311 [draft-xiang-alto-multidomain-analytics] 1312 "Unicorn: Resource Orchestration for Multi-Domain, Geo- 1313 Distributed Data Analytics", July 2018. 1315 [IEEE.754.2008] 1316 "Standard for Binary Floating-Point Arithmetic, IEEE 1317 Standard 754", August 2008. 1319 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1320 DOI 10.17487/RFC2818, May 2000, 1321 . 1323 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1324 (TLS) Protocol Version 1.2", RFC 5246, 1325 DOI 10.17487/RFC5246, August 2008, 1326 . 1328 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1329 Optimization (ALTO) Problem Statement", RFC 5693, 1330 DOI 10.17487/RFC5693, October 2009, 1331 . 1333 [RFC6708] Kiesel, S., Ed., Previdi, S., Stiemerling, M., Woundy, R., 1334 and Y. Yang, "Application-Layer Traffic Optimization 1335 (ALTO) Requirements", RFC 6708, DOI 10.17487/RFC6708, 1336 September 2012, . 1338 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1339 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1340 2014, . 1342 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1343 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1344 DOI 10.17487/RFC7231, June 2014, 1345 . 1347 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1348 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1349 . 1351 [SENSE-sdn-e2e-net] 1352 "SDN for End-to-End Networked Science at the Exascale 1353 (SENSE), http://sense.es.net/overview". 1355 Authors' Addresses 1357 Sabine Randriamasy 1358 Nokia Bell Labs 1359 Route de Villejust 1360 NOZAY 91460 1361 FRANCE 1363 Email: Sabine.Randriamasy@nokia-bell-labs.com 1365 Richard Yang 1366 Yale University 1367 51 Prospect st 1368 New Haven, CT 06520 1369 USA 1371 Email: yry@cs.yale.edu 1373 Qin Wu 1374 Huawei 1375 101 Software Avenue, Yuhua District 1376 Nanjing, Jiangsu 210012 1377 China 1379 Email: sunseawq@huawei.com 1380 Lingli Deng 1381 China Mobile 1382 China 1384 Email: denglingli@chinamobile.com 1386 Nico Schwan 1387 Thales Deutschland 1388 Lorenzstrasse 10 1389 Stuttgart 70435 1390 Germany 1392 Email: nico.schwan@thalesgroup.com