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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 1321, 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: November 15, 2019 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 May 14, 2019 14 ALTO Cost Calendar 15 draft-ietf-alto-cost-calendar-12 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 November 15, 2019. 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 resources 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 a capital "C", these terms 187 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. It may be viewed 218 as a synthetic abstraction of, for example, real measurements 219 gathered over previous periods on which statistics have been 220 computed. However, like for any schedule, unexpected network 221 incidents may require the current ALTO Calendar to be updated and re- 222 sent to the ALTO Clients needing it. To this end, it is RECOMMENDED 223 that ALTO Servers providing ALTO Calendars also provide the "ALTO 224 Incremental Updates Using Server-Sent Events (SSE)" Service that is 225 specified in [draft-ietf-alto-incr-update-sse]. Likewise, ALTO 226 Clients capable of using ALTO Calendars SHOULD also use the SSE 227 Service. 229 Most likely, the ALTO Cost Calendar would be used for the Endpoint 230 Cost Service, assuming that a limited set of feasible Endpoints for a 231 non-real time application is already identified, that they do not 232 need to be accessed immediately and that their access can be 233 scheduled within a given time period. The Filtered Cost Map Service 234 is also applicable as long as the size of the Map allows it. 236 2.3. ALTO Cost Calendar information features 238 The Calendar attributes are provided in the Information Resources 239 Directory (IRD) and in ALTO Server responses. The IRD announces 240 attributes without date values in its information resources 241 capabilities, whereas attributes with time dependent values are 242 provided in the "meta" section of Server responses. The ALTO Cost 243 Calendar attributes provide the following information: 245 o attributes to describe the time scope of the Calendar value array: 247 * generic time zone, 249 * applicable time interval size for each Calendar value, defined 250 in seconds, that can cover a wide range of values. 252 * duration of the Calendar: e.g., the number of intervals 253 provided in the Calendar. 255 o "calendar-start-date": specifying when the Calendar starts, that 256 is to which date the first value of the Cost Calendar is 257 applicable. 259 o "repeated": an optional attribute indicating how many iterations 260 of the provided Calendar will have the same values. The server 261 may use it to allow the client to schedule its next request and 262 thus save its own workload by reducing processing of similar 263 requests. 265 Attribute "repeated" may take a very high value if a Calendar 266 represents a cyclic value pattern that the Server considers valid for 267 a long period. In this case, the Server will only update the 268 Calendar values once this period has elapsed or if an unexpected 269 event occurs on the network. 271 2.4. ALTO Calendar design characteristics 273 The extensions in this document and encode requests and responses 274 using JSON [RFC8259]. 276 Formally, the cost entries in an ALTO cost map can be any type of 277 JSON value [RFC8259], (see the DstCosts object in Section 11.2.3.6 of 278 [RFC7285]). However, that section states that an implementation of 279 [RFC7285] SHOULD assume that the cost is a JSON number and fail to 280 parse if it is not, unless the implementation is using an extension 281 that signals a different data type. This document extends the 282 definition of a legacy cost map given in [RFC7285] to allow a cost 283 entry to be an array of values, one per time interval, instead of 284 just one number. 286 To realize an ALTO Calendar, this document extends: the IRD, the ALTO 287 requests and responses for Cost Calendars. 289 This extension is designed to be light and to ensure backwards 290 compatibility with base protocol ALTO Clients and with other 291 extensions. It relies on section 8.3.7 "Parsing of Unknown Fields" 292 of [RFC7285] that writes: "Extensions may include additional fields 293 within JSON objects defined in this document. ALTO implementations 294 MUST ignore unknown fields when processing ALTO messages." 296 The Calendar-specific capabilities are integrated in the information 297 resources of the IRD and in the "meta" member of ALTO responses to 298 Cost Calendars requests. A Calendar and its capabilities are 299 associated with a given information resource and within this 300 information resource with a given cost type. This design has several 301 advantages: 303 o it does not introduce a new mode, 305 o it does not introduce new media types, 307 o it allows an ALTO Server to offer Calendar capabilities on a cost 308 type, with attributes values adapted to each information resource. 310 The applicable Calendared information resources are: 312 o the Filtered Cost Map, 314 o the Endpoint Cost Map. 316 The ALTO Server can choose in which frequency it provides cost 317 Calendars to ALTO Clients. It may either provide Calendar updates 318 starting at the request date, or carefully schedule its updates so as 319 to take profit from a potential repetition/periodicity of Calendar 320 values. 322 2.4.1. ALTO Cost Calendar for all cost modes 324 An ALTO Cost Calendar is well-suited for values encoded in the 325 "numerical" mode. Actually, a Calendar can also represent metrics in 326 other modes considered as compatible with time-varying values. For 327 example, types of Cost values such as JSONBool can also be 328 calendared, as their value may be 'true' or 'false' depending on 329 given time periods or likewise, values represented by strings, such 330 as "medium", "high", "low", "blue", "open". 332 Note also that a Calendar is suitable as well for time-varying 333 metrics provided in the "ordinal" mode, if these values are time- 334 varying and the ALTO Server provides updates of cost value based 335 preferences. 337 2.4.2. Compatibility with legacy ALTO Clients 339 The ALTO protocol extensions for Cost Calendars have been defined so 340 as to ensure that Calendar capable ALTO Servers can provide legacy 341 ALTO Clients with legacy information resources as well. That is a 342 legacy ALTO Client can request resources and receive responses as 343 specified in [RFC7285]. 345 A Calendar-aware ALTO Server MUST implement the base protocol 346 specified in [RFC7285]. 348 As a consequence, when a metric is available as a Calendar array, it 349 also MUST be available as a single value as required by [RFC7285]. 350 The Server, in this case, provides the current value of the metric to 351 either Calendar-aware Clients not interested in future or time-based 352 values, or Clients implementing [RFC7285] only. 354 For compatibility with legacy ALTO Clients specified in [RFC7285], 355 calendared information resources are not applicable for full cost 356 maps for the following reason: a legacy ALTO client would receive a 357 calendared cost map via an HTTP 'GET' command. As specified in 358 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 359 indicated in the "meta" of the responses. Therefore, lacking 360 information on Calendar attributes, it will not be able to correctly 361 interpret and process the values of the received array of Calendar 362 cost values. 364 Therefore, calendared information resources MUST be requested via the 365 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 366 method. 368 3. ALTO Calendar specification: IRD extensions 370 The Calendar attributes in the IRD information resources capabilities 371 carry constant dateless values. A Calendar is associated with an 372 information resource rather than a cost type. For example, a Server 373 can provide a "routingcost" Calendar for the Filtered Cost Map 374 Service at a granularity of one day and a "routingcost" Calendar for 375 the Endpoint Cost Service at a finer granularity but for a limited 376 number of endpoints. An example IRD with Calendar specific features 377 is provided in Section 3.3. 379 3.1. Calendar attributes in the IRD resources capabilities 381 A Cost Calendar for a given Cost Type MUST be indicated in the IRD by 382 an object of type CalendarAttributes. A CalendarAttribute object is 383 represented by the "calendar-attributes" member of a resource entry. 384 Each CalendarAttributes object applies to a set of one or more cost 385 types. A Cost Type name MUST appear no more than once in the 386 "calendar-attributes" member of a resource entry; multiple 387 appearances of a Cost Type name in CalendarAttributes object of the 388 "calendar-attributes" member MUST cause the ALTO client to ignore any 389 occurrences of this name beyond the first encountered occurrence. 391 It is RECOMMENDED for an ALTO Server that the time interval size 392 specified in the IRD is the smallest possible one that it can 393 provide. The Client can aggregate cost values on its own if it needs 394 a larger granularity. 396 The encoding format for object CalendarAttributes, using JSON 397 [RFC8259], is as follows: 399 CalendarAttributes calendar-attributes <1..*>; 401 object{ 402 JSONString cost-type-names <1..*>; 403 JSONNumber time-interval-size; 404 JSONNumber number-of-intervals; 405 } CalendarAttributes; 407 o "cost-type-names": 409 * An array of one or more elements indicating the cost-type-names 410 in the IRD entry to which the capabilities apply. 412 o "time-interval-size": 414 * is the duration of an ALTO Calendar time interval in seconds. 415 A "time-interval-size" value contains a JSONNumber. ALTO 416 servers SHOULD use at least IEEE 754 double-precision floating 417 point [IEEE.754.2008] to store this value. Example values are: 418 300 , 7200, meaning that each Calendar value applies on a time 419 interval that lasts respectively 5 minutes and 2 hours. 421 o "number-of-intervals": 423 * the integer number of values of the Cost Calendar array, at 424 least equal to 1. 426 - Attribute "cost-type-names" provides a better readability to the 427 Calendar attributes specified in the IRD and avoids confusion with 428 Calendar attributes of other cost-types. 430 - Multiplying 'time-interval-size' by 'number-of-intervals' provides 431 the duration of the provided Calendar. For example, an ALTO Server 432 may provide a Calendar for ALTO values changing every 'time-interval- 433 size' equal to 5 minutes. If 'number-of-intervals' has the value 12, 434 then the duration of the provided Calendar is "1 hour". 436 3.2. Calendars in a delegate IRD 438 It may be useful to distinguish IRD resources supported by the base 439 ALTO protocol from resources supported by its extensions. To achieve 440 this, one option, is that a "root" ALTO Server implementing base 441 protocol resources delegates "specialized" information resources such 442 as the ones providing Cost Calendars, to another ALTO Server running 443 in a subdomain that is specified with its URI in the "root" ALTO 444 Server. This option is described in Section 9.2.4 "Delegation using 445 IRDs" of [RFC7285]. 447 This document provides an example, where a "root" ALTO Server runs in 448 a domain called "alto.example.com". It delegates the announcement of 449 Calendars capabilities to an ALTO Server running in a subdomain 450 called "custom.alto.example.com". The location of the "delegate 451 Calendar IRD" is assumed to be indicated in the "root" IRD by the 452 resource entry: "custom-calendared-resources". 454 Another advantage is that some Cost Types for some resources may be 455 more advantageous as Cost Calendars and it makes few sense to get 456 them as a single value. For example, Cost Types with predictable and 457 frequently changing values, calendared in short time intervals such 458 as a minute. 460 3.3. Example IRD with ALTO Cost Calendars 462 This section provides an example ALTO Server IRD that supports 463 various cost metrics and cost modes. In particular, since [RFC7285] 464 makes it mandatory, the Server uses metric "routingcost" in the 465 "numerical" mode. 467 For illustrative purposes, this section introduces 3 other fictitious 468 example metrics and modes that should be understood as examples and 469 should not be used or considered as normative. 471 The cost type names used in the example IRD as thus as follows: 473 o "num-routingcost": refers to metric "routingcost" in the numerical 474 mode as defined in [RFC7285] and registered with IANA. 476 o "num-owdelay": refers to fictitious performance metric "owdelay" 477 in the "numerical" mode,to reflect the one-way packet transmission 478 delay on a path. A related performance metric is currently under 479 definition in [draft-ietf-alto-performance-metrics]. 481 o "num-throughputrating": refers to fictitious metric 482 "throughputrating" in the "numerical" mode, to reflect the 483 provider preference in terms of end to end throughput. 485 o "string-servicestatus": refers to fictitious metric 486 "servicestatus" in some example mode "string", to reflect the 487 availability, defined by the provider, of for instance path 488 connectivity. 490 The example IRD includes 2 particular URIs providing Calendars: 492 o "https://custom.alto.example.com/calendar/costmap/filtered": a 493 filtered cost map in which Calendar capabilities are indicated for 494 cost type names: "num-routingcost", "num-throughputrating" and 495 "string-servicestatus", 497 o "https://custom.alto.example.com/calendar/endpointcost/lookup": an 498 endpoint cost map in which Calendar capabilities are indicated for 499 cost type names: "num-routingcost", "num-owdelay", "num- 500 throughputrating", "string-servicestatus". 502 The design of the Calendar capabilities allows that some Calendars on 503 a cost type name are available in several information resources with 504 different Calendar Attributes. This is the case for Calendars on 505 "num-routingcost", "num-throughputrating" and "string-servicestatus", 506 available in both the Filtered Cost map and Endpoint Cost Service, 507 but with different time interval sizes for "num-throughputrating" and 508 "string-servicestatus". 510 --- Client to Server request for IRD ---------- 512 GET /calendars-directory HTTP/1.1 513 Host: custom.alto.example.com 514 Accept: application/alto-directory+json,application/alto-error+json 516 --- Server response to Client ----------------- 518 HTTP/1.1 200 OK 519 Content-Length: 2542 520 Content-Type: application/alto-directory+json 522 { 523 "meta" : { 524 "default-alto-network-map" : "my-default-network-map", 525 "cost-types": { 526 "num-routingcost": { 527 "cost-mode" : "numerical", 528 "cost-metric" : "routingcost" 529 }, 530 "num-owdelay": { 531 "cost-mode" : "numerical", 532 "cost-metric": "owdelay" 533 }, 534 "num-throughputrating": { 535 "cost-mode" : "numerical", 536 "cost-metric": "throughputrating" 537 }, 538 "string-servicestatus": { 539 "cost-mode" : "string", 540 "cost-metric": "servicestatus" 541 } 542 } 543 }, 544 "resources" : { 545 "filtered-cost-map-calendar" : { 546 "uri" : 547 "https://custom.alto.example.com/calendar/costmap/filtered", 548 "media-type" : "application/alto-costmap+json", 549 "accepts" : "application/alto-costmapfilter+json", 550 "capabilities" : { 551 "cost-constraints" : true, 552 "cost-type-names" : [ "num-routingcost", 553 "num-throughputrating", 554 "string-servicestatus" ], 555 "calendar-attributes" : [ 556 {"cost-type-names" : [ "num-routingcost", 557 "num-throughputrating" ], 558 "time-interval-size" : 7200, 559 "number-of-intervals" : 12 560 }, 561 {"cost-type-names" : [ "string-servicestatus" ], 562 "time-interval-size" : 1800, 563 "number-of-intervals" : 48 564 } 565 ] 566 }, 567 "uses": [ "my-default-network-map" ] 569 }, 570 "endpoint-cost-calendar-map" : { 571 "uri" : 572 "https://custom.alto.example.com/calendar/endpointcost/lookup", 573 "media-type" : "application/alto-endpointcost+json", 574 "accepts" : "application/alto-endpointcostparams+json", 575 "capabilities" : { 576 "cost-constraints" : true, 577 "cost-type-names" : [ "num-routingcost", 578 "num-owdelay", 579 "num-throughputrating", 580 "string-servicestatus" ], 581 "calendar-attributes" : [ 582 {"cost-type-names" : [ "num-routingcost" ], 583 "time-interval-size" : 3600, 584 "number-of-intervals" : 24 585 }, 586 {"cost-type-names" : [ "num-owdelay" ], 587 "time-interval-size" : 300, 588 "number-of-intervals" : 12 589 }, 590 {"cost-type-names" : [ "num-throughputrating" ], 591 "time-interval-size" : 60, 592 "number-of-intervals" : 60 593 }, 594 {"cost-type-names" : [ "string-servicestatus" ], 595 "time-interval-size" : 120, 596 "number-of-intervals" : 30 597 } 598 ] 599 } 600 } 601 } 602 } 604 In this example IRD, for the Filtered Cost Map Service: 606 o the Calendar for "num-routingcost" and "num-throughputrating" is 607 an array of 12 values each provided on a time interval lasting 608 7200 seconds (2 hours). 610 o the Calendar for "string-servicestatus": "is an array of 48 values 611 each provided on a time interval lasting 1800 seconds (30 612 minutes). 614 For the Endpoint Cost Service: 616 o the Calendar for "num-routingcost": is an array of 24 values each 617 provided on a time interval lasting 3600 seconds (1 hour). 619 o the Calendar for "owdelay": is an array of 12 values each provided 620 on a time interval lasting 300 seconds (5 minutes). 622 o the Calendar for "num-throughputrating": is an array of 60 values 623 each provided on a time interval lasting 60 seconds (1 minute). 625 o the Calendar for "string-servicestatus": "is an array of 30 values 626 each provided on a time interval lasting 120 seconds (2 minutes). 628 4. ALTO Calendar specification: Service Information Resources 630 This section documents the individual information resources defined 631 to provide the calendared information services defined in this 632 document. 634 The reference time zone for the provided time values is UTC. The 635 option chosen to express the time format is the HTTP header fields 636 format specified in [RFC7231] where, however, timestamps are still 637 displayed with the acronym "GMT" rather than "UTC": 639 Date: Tue, 15 Nov 2014 08:12:31 GMT 641 The value of a Calendar time interval size is expressed in seconds. 643 4.1. Calendar extensions for Filtered Cost Maps (FCM) 645 A legacy ALTO client requests and gets Filtered Cost Map responses as 646 specified in [RFC7285]. 648 4.1.1. Calendar extensions in Filtered Cost Map requests 650 The input parameters of a "legacy" request for a filtered cost map, 651 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 652 are augmented with one additional member. 654 A Calendar-aware ALTO client requesting a Calendar on a given Cost 655 Type for a filtered cost map resource having Calendar capabilities 656 MUST add the following field to its input parameters: 658 JSONBoolean calendared<1..*>; 660 This field is an array of 1 to N boolean values, where N is the 661 number of requested metrics. Each entry corresponds to the requested 662 metric at the same array position. Each boolean value indicates 663 whether or not the ALTO Server should provide the values for this 664 Cost Type as a Calendar. The array MUST contain exactly N boolean 665 values, otherwise, the Server returns an error. 667 This field MUST NOT be included if no member "calendar-attributes" is 668 specified in this information resource. 670 If a value of field 'calendared' is 'true' for a cost type name for 671 which no Calendar attributes have been specified: an ALTO Server, 672 whether it implements the extensions of this document or only 673 implements [RFC7285], MUST ignore it and return a response with a 674 single cost value as specified in [RFC7285]. 676 If this field is not present, it MUST be assumed to have only values 677 equal to 'false'. 679 A Calendar-aware ALTO client that supports requests for only one cost 680 type at a time and wants to request a Calendar MUST provide an array 681 of 1 element: 683 "calendared" : [true]; 685 A Calendar-aware ALTO client that supports requests for more than one 686 Cost Types at a time, as specified in [RFC8189] MUST provide an array 687 of N values set to 'true' or 'false', depending whether it wants the 688 applicable Cost Type values as a single or calendared value. 690 4.1.2. Calendar extensions in Filtered Cost Map responses 692 In a calendared ALTO Filtered Cost Map, a cost value between a source 693 and a destination is a JSON array of JSON values. An ALTO Calendar 694 values array has a number of values equal to the value of member 695 "number-of-intervals" of the Calendar attributes that are indicated 696 in the IRD. These attributes will be conveyed as metadata in the 697 Filtered Cost Map response. Each element of the array is valid for 698 the time-interval that matches its array position. 700 The FCM response conveys metadata among which: 702 o some are not specific to Calendars and ensure compatibility with 703 [RFC7285] and [RFC8189] 705 o some are specific to Calendars. 707 The non Calendar specific "meta" fields of a calendared Filtered Cost 708 Map response MUST include at least: 710 o if the ALTO Client requests cost values for one Cost Type at a 711 time only: the "meta" fields specified in [RFC7285] for these 712 information service responses: 714 * "dependent-vtags ", 716 * "cost-type" field. 718 o if the ALTO Client implements the Multi-Cost ALTO extension 719 specified in [RFC8189] and requests cost values for several Cost 720 Types at a time: the "meta" fields specified in [RFC8189] for 721 these information service responses: 723 * "dependent-vtags ", 725 * "cost-type" field with value set to '{}', for backwards 726 compatibility with [RFC7285]. 728 * "multi-cost-types" field. 730 If the client request does not provide member "calendared" or if it 731 provides it with a value equal to 'false', for all the requested Cost 732 Types, then the ALTO Server response is exactly as specified in 733 [RFC7285] and [RFC8189]. 735 If the value of member "calendared" is equal to 'false' for a given 736 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 737 a single cost value as specified in [RFC7285]. 739 If the value of member "calendared" is equal to 'true' for a given 740 requested Cost Type, the ALTO Server returns, for this Cost Type, a 741 cost value Calendar as specified above in this section. In addition 742 to the above cited non Calendar specific "meta" members, the Server 743 MUST provide a Calendar specific metadata field. 745 The Calendar specific "meta" field that a calendared Filtered Cost 746 Map response MUST include is a member called "calendar-response- 747 attributes", that describes properties of the Calendar and where: 749 o member "calendar-response-attributes" is an array of one or more 750 objects of type "CalendarResponseAttributes". 752 o each "CalendarResponseAttributes" object in the array is specified 753 for one or more Cost Types for which the value of member 754 "calendared" is equal to 'true' and for which a Calendar is 755 provided for the requested information resource. 757 o the "CalendarResponseAttributes" object that applies to a cost 758 type name has a corresponding "CalendarAttributes" object defined 759 for this cost type name in the IRD capabilities of the requested 760 information resource. The members of a 761 "CalendarResponseAttributes" object include all the members of the 762 corresponding "CalendarAttributes" object. 764 The format of member "CalendarResponseAttributes is defined as 765 follows: 767 CalendarResponseAttributes calendar-response-attributes <1..*>; 769 object{ 770 [JSONString cost-type-names <1..*>]; 771 JSONString calendar-start-time; 772 JSONNumber time-interval-size; 773 JSONNumber number-of-intervals; 774 [JSONNumber repeated;] 775 } CalendarResponseAttributes; 777 Object CalendarResponseAttributes has the following attributes: 779 o "cost-type-names": is an array of one or more cost-type-names to 780 which the capabilities apply and for which a Calendar has been 781 requested. The value of this member is a subset of the "cost- 782 type-names" array specified in the corresponding IRD Calendar 783 attributes. 785 o "calendar-start-time": indicates the date at which the first value 786 of the Calendar applies. The value provided for the "calendar- 787 start-time" attribute SHOULD NOT be later than the request date. 789 o "time-interval-size": as specified in Section 3.1 and with the 790 same value. 792 o "number-of-intervals": as specified in Section 3.1 and with the 793 same value. 795 o "repeated": is an optional field provided for Calendars. It is an 796 integer N greater or equal to '1' that indicates how many 797 iterations of the Calendar value array starting at the date 798 indicated by "calendar-start-time" have the same values. The 799 number N includes the provided iteration. 801 For example: suppose the "calendar-start-time" member has value "Mon, 802 30 Jun 2014 at 00:00:00 GMT", the "time-interval-size" member has 803 value '3600', the "number-of-intervals" member has value '24' and the 804 value of member "repeated" is equal to '4'. This means that the 805 Calendar values are the same on Monday, Tuesday, Wednesday and 806 Thursday on a period of 24 hours starting at 00:00:00 GMT. The ALTO 807 Client thus may use the same Calendar for the next 4 days starting at 808 "calendar-start-time" and will only need to request a new one for 809 Friday July 4th at 00:00:00 GMT. 811 Attribute "repeated" may take a very high value if a Calendar 812 represents a cyclic value pattern that the Server considers valid for 813 a long period and hence will only update once this period has elapsed 814 or if an unexpected event occurs on the network. In the latter case, 815 the client will be notified if it uses the "ALTO Incremental Updates 816 Using Server-Sent Events (SSE)" Service, specified in 817 [draft-ietf-alto-incr-update-sse]. See also discussion in Section 7 818 "Operational Considerations". 820 4.1.3. Use case and example: FCM with a bandwidth Calendar 822 An example of non-real time information that can be provisioned in a 823 Calendar is the expected path throughput. While the transmission 824 rate can be measured in real time by end systems, the operator of a 825 data center is in the position of formulating preferences for given 826 paths, at given time periods to avoid traffic peaks due to diurnal 827 usage patterns. In this example, we assume that an ALTO Client 828 requests a Calendar of network provider defined throughput ratings, 829 as specified in the IRD, to schedule its bulk data transfers as 830 described in the use cases. 832 In the example IRD, Calendars for cost type name "num- 833 throughputrating" are available for the information resources: 834 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 835 ALTO Client requests a Calendar for "num-throughputrating" via a POST 836 request for a filtered cost map. 838 We suppose in the present example that the ALTO Client sends its 839 request on Tuesday July 1st 2014 at 13:15. The Server returns 840 Calendars with arrays of 12 numbers for each source and destination 841 pair. The values for metric "throughputrating", in this example, are 842 assumed to be encoded in 2 digits. For representation brevity, the 843 arrays in the provided example are symbolized by expression "[v1,v2, 844 ... v12]", that is otherwise not valid in JSON. The value of field 845 "Content-Length" in the responses is computed as if 846 "throughputrating" values were encoded in 2 digits. The same type of 847 symbolization is used in the other example Server responses in 848 Section 4.2.3 and Section 4.2.4 of this document. 850 POST /calendar/costmap/filtered HTTP/1.1 851 Host: alto.example.com 852 Content-Length: 208 853 Content-Type: application/alto-costmapfilter+json 854 Accept: application/alto-costmap+json,application/alto-error+json 856 { 857 "cost-type" : {"cost-mode" : "numerical", 858 "cost-metric" : "throughputrating"}, 859 "calendared" : [true], 860 "pids" : { 861 "srcs" : [ "PID1", "PID2" ], 862 "dsts" : [ "PID1", "PID2", "PID3" ] 863 } 864 } 866 HTTP/1.1 200 OK 867 Content-Length: 815 868 Content-Type: application/alto-costmap+json 870 { 871 "meta" : { 872 "dependent-vtags" : [ 873 {"resource-id": "my-default-network-map", 874 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 875 } 876 ], 877 "cost-type" : {"cost-mode" : "numerical", 878 "cost-metric" : "throughputrating"}, 879 "calendar-response-attributes" : [ 880 {"calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 881 "time-interval-size" : 7200, 882 "number-of-intervals" : 12} 883 ] 884 }, 885 "cost-map" : { 886 "PID1": { "PID1": [v1,v2, ... v12], 887 "PID2": [v1,v2, ... v12], 888 "PID3": [v1,v2, ... v12] }, 889 "PID2": { "PID1": [v1,v2, ... v12], 890 "PID2": [v1,v2, ... v12], 891 "PID3": [v1,v2, ... v12] } 892 } 893 } 895 4.2. Calendar extensions in the Endpoint Cost Service 897 This document extends the Endpoint Cost Service, as defined in 898 {11.5.1} of [RFC7285], by adding new input parameters and 899 capabilities, and by returning JSONArrays instead of JSONNumbers as 900 the cost values. The media type {11.5.1.1} and HTTP method 901 {11.5.1.2} are unchanged. 903 4.2.1. Calendar specific input in Endpoint Cost requests 905 The extensions to the requests for calendared Endpoint Cost Maps are 906 the same as for the Filtered Cost Map Service, specified in section 907 Section 4.1.1 of this draft. 909 The ReqEndpointCostMap object for a calendared ECM request will have 910 the following format: 912 object { 913 [CostType cost-type;] 914 [CostType multi-cost-types<1..*>;] 915 [JSONBoolean calendared<1..*>;] 916 EndpointFilter endpoints; 917 } ReqEndpointCostMap; 919 object { 920 [TypedEndpointAddr srcs<0..*>;] 921 [TypedEndpointAddr dsts<0..*>;] 922 } EndpointFilter; 924 4.2.2. Calendar attributes in the Endpoint Cost response 926 The "meta" field of a calendared Endpoint Cost response MUST include 927 at least: 929 o if the ALTO Client supports cost values for one Cost Type at a 930 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 931 for the Endpoint Cost response: 933 * "cost-type" field. 935 o if the ALTO Client supports cost values for several Cost Types at 936 a time, as specified in [RFC8189] : the "meta" fields specified in 937 [RFC8189] for the the Endpoint Cost response: 939 * "cost-type" field with value set to '{}', for backwards 940 compatibility with [RFC7285]. 942 * "multi-cost-types" field. 944 If the client request does not provide member "calendared" or if it 945 provides it with a value equal to 'false', for all the requested Cost 946 Types, then the ALTO Server response is exactly as specified in 947 [RFC7285] and [RFC8189]. 949 If the ALTO client provides member "calendared" in the input 950 parameters with a value equal to 'true' for given requested Cost 951 Types, the "meta" member of a calendared Endpoint Cost response MUST 952 include, for these Cost Types, an additional member "calendar- 953 response-attributes", the contents of which obey the same rules as 954 for the Filtered Cost Map Service, specified in Section 4.1.2. The 955 Server response is thus changed as follows, w.r.t [RFC7285] and 956 [RFC8189]: 958 o the "meta" member has one additional field 959 "CalendarResponseAttributes", as specified for the Filtered Cost 960 Map Service, 962 o the calendared costs are JSONArrays instead of the JSONNumbers 963 format used by legacy ALTO implementations. All arrays have a 964 number of values equal to 'number-of-intervals'. 966 If the value of member "calendared" is equal to 'false' for a given 967 requested Cost Type, the ALTO Server MUST return, for this Cost Type, 968 a single cost value as specified in [RFC7285]. 970 4.2.3. Use case and example: ECS with a routingcost Calendar 972 Let us assume an Application Client is located in an end system with 973 limited resources and having access to the network that is either 974 intermittent or provides an acceptable quality in limited but 975 predictable time periods. Therefore, it needs to both schedule its 976 resource-greedy networking activities and its ALTO transactions. 978 The Application Client has the choice to trade content or resources 979 with a set of Endpoints and needs to decide with which one it will 980 connect and at what time. For instance, the Endpoints are spread in 981 different time-zones, or have intermittent access. In this example, 982 the 'routingcost' is assumed to be time-varying, with values provided 983 as ALTO Calendars. 985 The ALTO Client associated with the Application Client queries an 986 ALTO Calendar on 'routingcost' and will get the Calendar covering the 987 24 hours time period "containing" the date and time of the ALTO 988 client request. 990 For Cost Type "num-routingcost", the solicited ALTO Server has 991 defined 3 different daily patterns each represented by a Calendar, to 992 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 994 - C1 for Monday, Tuesday, Wednesday, Thursday, (weekdays) 996 - C2 for Saturday, Sunday, (weekend) 998 - C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 GMT 999 to 04:00:00 GMT, or big holiday such as New Year evening). 1001 In the following example, the ALTO Client sends its request on 1002 Tuesday July 1st 2014 at 13:15. 1004 The "routingcost" values are assumed to be encoded in 3 digits. 1006 For representation brevity, the arrays in the provided example are 1007 symbolized by expression "[v1,v2, ... v24]", that is otherwise not 1008 valid in JSON. The value of field "Content-Length" in the responses 1009 is computed as if "routingcost" values were encoded in 3 digits. 1011 POST /calendar/endpointcost/lookup HTTP/1.1 1012 Host: alto.example.com 1013 Content-Length: 290 1014 Content-Type: application/alto-endpointcostparams+json 1015 Accept: application/alto-endpointcost+json,application/alto-error+json 1017 { 1018 "cost-type" : {"cost-mode" : "numerical", 1019 "cost-metric" : "routingcost"}, 1020 "calendared" : [true], 1021 "endpoints" : { 1022 "srcs": [ "ipv4:192.0.2.2" ], 1023 "dsts": [ 1024 "ipv4:192.0.2.89", 1025 "ipv4:198.51.100.34", 1026 "ipv4:203.0.113.45", 1027 "ipv6:2001:db8::10" 1028 ] 1029 } 1030 } 1032 HTTP/1.1 200 OK 1033 Content-Length: 877 1034 Content-Type: application/alto-endpointcost+json 1036 { 1037 "meta" : { 1038 "cost-type" : {"cost-mode" : "numerical", 1039 "cost-metric" : "routingcost"}, 1040 "calendar-response-attributes" : [ 1041 {"calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1042 "time-interval-size" : 3600, 1043 "number-of-intervals" : 24, 1044 "repeated": 4 1045 } 1046 ] 1047 }, 1048 "endpoint-cost-map" : { 1049 "ipv4:192.0.2.2": { 1050 "ipv4:192.0.2.89" : [v1, v2, ... v24], 1051 "ipv4:198.51.100.34" : [v1, v2, ... v24], 1052 "ipv4:203.0.113.45" : [v1, v2, ... v24], 1053 "ipv6:2001:db8::10" : [v1, v2, ... v24] 1054 } 1055 } 1056 } 1057 When the Client gets the Calendar for "routingcost", it sees that the 1058 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 1059 equal to '4'. It understands that the provided values are valid 1060 until Thursday included and will only need to get a Calendar update 1061 on Friday. 1063 4.2.4. Use case and example: ECS with a multi-cost Calendar for 1064 routingcost and owdelay 1066 In this example, it is assumed that the ALTO Server implements multi- 1067 cost capabilities, as specified in [RFC8189] . That is, an ALTO 1068 client can request and receive values for several cost types in one 1069 single transaction. An illustrating use case is a path selection 1070 done on the basis of 2 metrics: routing cost and owdelay. 1072 As in the previous example, the IRD indicates that the ALTO Server 1073 provides "routingcost" Calendars in terms of 24 time intervals of 1 1074 hour (3600 seconds) each. 1076 For metric "owdelay", the IRD indicates that the ALTO Server provides 1077 Calendars in terms of 12 time intervals values lasting each 5 minutes 1078 (300 seconds). 1080 In the following example transaction, the ALTO Client sends its 1081 request on Tuesday July 1st 2014 at 13:15. 1083 This example assumes that the values of metric "owdelay" and 1084 "routingcost" are encoded in 3 digits. 1086 For representation brevity, the arrays in the provided example are 1087 symbolized by expression "[[r1, r2, ... r24], [o1, o2, ... o12]]", 1088 that is otherwise not valid in JSON. The value of field "Content- 1089 Length" in the responses is computed as if "routingcost" and 1090 "owdelay" values were encoded in 3 digits. 1092 POST calendar/endpointcost/lookup HTTP/1.1 1093 Host: alto.example.com 1094 Content-Length: 373 1095 Content-Type: application/alto-endpointcostparams+json 1096 Accept: application/alto-endpointcost+json,application/alto-error+json 1098 { 1099 "cost-type" : {}, 1100 "multi-cost-types" : [ 1101 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1102 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1103 ], 1104 "calendared" : [true, true], 1105 "endpoints" : { 1106 "srcs": [ "ipv4:192.0.2.2" ], 1107 "dsts": [ 1108 "ipv4:192.0.2.89", 1109 "ipv4:198.51.100.34", 1110 "ipv4:203.0.113.45", 1111 "ipv6:2001:db8::10" 1112 ] 1113 } 1114 } 1116 HTTP/1.1 200 OK 1117 Content-Length: 1377 1118 Content-Type: application/alto-endpointcost+json 1120 { 1121 "meta" : { 1122 "multi-cost-types" : [ 1123 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1124 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1125 ], 1126 "calendar-response-attributes" : [ 1127 {"cost-type-names" : "num-routingcost", 1128 "calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1129 "time-interval-size" : 3600, 1130 "number-of-intervals" : 24, 1131 "repeated": 4 }, 1132 {"cost-type-names" : "num-owdelay" 1133 "calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 1134 "time-interval-size" : 300, 1135 "number-of-intervals" : 12} 1136 ], 1137 }, 1138 "endpoint-cost-map" : { 1139 "ipv4:192.0.2.2": { 1140 "ipv4:192.0.2.89" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1141 "ipv4:198.51.100.34" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1142 "ipv4:203.0.113.45" : [[r1, r2, ... r24], [o1, o2, ... o12]], 1143 "ipv6:2001:db8::10" : [[r1, r2, ... r24], [o1, o2, ... o12]] 1144 } 1145 } 1146 } 1148 When receiving the response, the client sees that the Calendar values 1149 for 'routing cost' are repeated for 4 iterations. Therefore, in its 1150 next requests until the routing cost Calendar is expected to change, 1151 the client will only need to request a Calendar for "owdelay". 1153 Without the ALTO Calendar extensions, the ALTO client would have no 1154 clue on the dynamicity of the metric value change and would spend 1155 needless time requesting values at an inappropriate pace. In 1156 addition, without the Multi-Cost ALTO capabilities, the ALTO client 1157 would duplicate this waste of time as it would need to send one 1158 request per cost metric. 1160 5. IANA Considerations 1162 This document does not define any new media types or introduce any 1163 new IANA considerations. 1165 6. Security Considerations 1167 As an extension of the base ALTO protocol [RFC7285], this document 1168 fits into the architecture of the base protocol, and hence the 1169 Security Considerations (Section 15) of the base protocol fully apply 1170 when this extension is provided by an ALTO server. For example, the 1171 same authenticity and integrity considerations (Section 15.1 of 1172 [RFC7285] still fully apply; the same considerations for the privacy 1173 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1175 The calendaring information provided by this extension requires 1176 additional considerations on three security considerations discussed 1177 in the base protocol: potential undesirable guidance to clients 1178 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1179 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1180 of [RFC7285]). For example, by providing network information in the 1181 future in a Calendar, this extension may improve availability of 1182 ALTO, when the ALTO server is unavailable but related information is 1183 already provided in the Calendar. 1185 For confidentiality of ALTO information, an operator should be 1186 cognizant that this extension may introduce a new risk: an ALTO 1187 client may get information for future events that are scheduled 1188 through Calendaring. Possessing such information, the client may use 1189 it to achieve its goal: (1) initiating connections only at 1190 advantageous network costs, leading to unexpected network load; (2) 1191 generating massive connections to the network at times where its load 1192 is expected to be high. 1194 To mitigate this risk, the operator should address the risk of ALTO 1195 information being leaked to malicious clients or third parties. As 1196 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1197 the ALTO server should authenticate ALTO clients and use the 1198 Transport Layer Security (TLS) protocol so that Man In The Middle 1199 (MITM) attacks to intercept an ALTO Calendar are not possible. 1200 [RFC7285] ensures the availability of such a solution in its 1201 Section 8.3.5. "Authentication and Encryption", which specifies 1202 that: "ALTO server implementations as well as ALTO client 1203 implementations MUST support the "https" URI scheme of [RFC2818] and 1204 Transport Layer Security (TLS) of [RFC5246]". 1206 [RFC8446] specifies TLS 1.3 and writes in its section 1: "While TLS 1207 1.3 is not directly compatible with previous versions, all versions 1208 of TLS incorporate a versioning mechanism which allows clients and 1209 servers to interoperably negotiate a common version if one is 1210 supported by both peers". So ALTO clients and servers MAY use newer 1211 versions (e.g., 1.3) of TLS as long as the negotiation process 1212 succeeds. To ensure backward compatibility with [RFC7285], it is 1213 RECOMMENDED for both Calendar-aware Clients and Servers to both 1214 support at least TLS 1.2, until it gets deprecated. 1216 To avoid malicious or erroneous guidance from ALTO information, an 1217 ALTO client should be cognizant that using calendaring information 1218 can have risks: (1) Calendar values, especially in "repeated" 1219 Calendars may be only statistical, and (2) future events may change. 1220 Hence, a more robust ALTO client should adapt and extend protection 1221 strategies specified in Section 15.2 of the base protocol: it should 1222 develop self-check and also ensure information update, to reduce the 1223 impact of this risk. To address the risk of unexpected ALTO Values 1224 changes that the ALTO Client would be unaware of, it is RECOMMENDED 1225 that Servers supporting Calendars also support the "ALTO Incremental 1226 Updates Using Server-Sent Events (SSE)" Service, specified in 1227 [draft-ietf-alto-incr-update-sse]. Likewise, it is RECOMMENDED that 1228 Clients using Calendars also support the SSE Service. 1230 7. Operational Considerations 1232 Conveying ALTO Cost Calendars tends to reduce the on-the-wire data 1233 exchange volume compared to multiple single cost ALTO transactions. 1234 An application using Calendars has a set of time-dependent values 1235 upon which it can plan its connections in advance with no need for 1236 the ALTO Client to query information at each time. Additionally, the 1237 Calendar response attribute "repeated", when provided, saves 1238 additional data exchanges in that it indicates that the ALTO Client 1239 does not need to query Calendars during a period indicated by this 1240 attribute. Unexpected changes during this period can be handled by 1241 using the SSE Service as discussed in Section 6, if the Server and 1242 the Client support it. 1244 High-resolution intervals may be needed when values change, sometimes 1245 during very small time intervals but in a significant manner. A way 1246 to avoid conveying too many entries is to leverage on the "repeated" 1247 feature. A server can smartly set the Calendar start time and number 1248 of intervals so as to declare them "repeated" for a large number of 1249 periods, until the Calendar values change and are conveyed to 1250 requesting Clients. 1252 Clients and Servers supporting ALTO Calendars use [RFC8259]. 1253 [RFC7285] encodes its requests and responses using the JSON Data 1254 Interchange Format specified in [RFC7159]. In the meantime, 1255 [RFC7159] has been obsoleted by [RFC8259], that among others makes 1256 UTF-8 mandatory for text encoding to improve interoperability. 1257 Therefore, ALTO Clients and Servers implementations using UTF-{16,32} 1258 need to be cognizant of the subsequent interoperability risks and it 1259 is RECOMMENDED for them to switch to UTF-8 encoding, if they want to 1260 interoperate with Calendar-aware Servers and Clients. 1262 8. Acknowledgements 1264 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1265 Peng and Haibin Song for fruitful discussions and feedback on earlier 1266 draft versions. Dawn Chan, Kai Gao, Vijay Gurbani, Yichen Qian and 1267 Jensen Zhang provided substantial review feedback and suggestions to 1268 the protocol design. 1270 9. References 1272 9.1. Normative References 1274 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1275 Requirement Levels", BCP 14, RFC 2119, 1276 DOI 10.17487/RFC2119, March 1997, 1277 . 1279 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1280 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1281 "Application-Layer Traffic Optimization (ALTO) Protocol", 1282 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1283 . 1285 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1286 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1287 May 2017, . 1289 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1290 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1291 DOI 10.17487/RFC8189, October 2017, 1292 . 1294 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1295 Interchange Format", STD 90, RFC 8259, 1296 DOI 10.17487/RFC8259, December 2017, 1297 . 1299 9.2. Informative References 1301 [draft-ietf-alto-incr-update-sse] 1302 "ALTO Incremental Updates Using Server-Sent Events (SSE) 1303 (work in progress)", December 2018. 1305 [draft-ietf-alto-performance-metrics] 1306 "ALTO Performance Cost Metrics (work in progress)", June 1307 2018. 1309 [draft-xiang-alto-multidomain-analytics] 1310 "Unicorn: Resource Orchestration for Multi-Domain, Geo- 1311 Distributed Data Analytics", July 2018. 1313 [IEEE.754.2008] 1314 "Standard for Binary Floating-Point Arithmetic, IEEE 1315 Standard 754", August 2008. 1317 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1318 DOI 10.17487/RFC2818, May 2000, 1319 . 1321 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1322 (TLS) Protocol Version 1.2", RFC 5246, 1323 DOI 10.17487/RFC5246, August 2008, 1324 . 1326 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1327 Optimization (ALTO) Problem Statement", RFC 5693, 1328 DOI 10.17487/RFC5693, October 2009, 1329 . 1331 [RFC6708] Kiesel, S., Ed., Previdi, S., Stiemerling, M., Woundy, R., 1332 and Y. Yang, "Application-Layer Traffic Optimization 1333 (ALTO) Requirements", RFC 6708, DOI 10.17487/RFC6708, 1334 September 2012, . 1336 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1337 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1338 2014, . 1340 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1341 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1342 DOI 10.17487/RFC7231, June 2014, 1343 . 1345 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1346 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1347 . 1349 Authors' Addresses 1351 Sabine Randriamasy 1352 Nokia Bell Labs 1353 Route de Villejust 1354 NOZAY 91460 1355 FRANCE 1357 Email: Sabine.Randriamasy@nokia-bell-labs.com 1359 Richard Yang 1360 Yale University 1361 51 Prospect st 1362 New Haven, CT 06520 1363 USA 1365 Email: yry@cs.yale.edu 1367 Qin Wu 1368 Huawei 1369 101 Software Avenue, Yuhua District 1370 Nanjing, Jiangsu 210012 1371 China 1373 Email: sunseawq@huawei.com 1375 Lingli Deng 1376 China Mobile 1377 China 1379 Email: denglingli@chinamobile.com 1380 Nico Schwan 1381 Thales Deutschland 1382 Lorenzstrasse 10 1383 Stuttgart 70435 1384 Germany 1386 Email: nico.schwan@thalesgroup.com