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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: September 10, 2020 Yale University 6 Q. Wu 7 Huawei 8 L. Deng 9 China Mobile 10 N. Schwan 11 Thales Deutschland 12 March 9, 2020 14 Application-Layer Traffic Optimization (ALTO) Cost Calendar 15 draft-ietf-alto-cost-calendar-20 17 Abstract 19 This document is an extension to the base Application-Layer Traffic 20 Optimization (ALTO) protocol. It extends the ALTO cost information 21 service so that applications decide not only 'where' to connect, but 22 also 'when'. This is useful for applications that need to perform 23 bulk data transfer and would like to schedule these transfers during 24 an off-peak hour, for example. This extension introduces ALTO Cost 25 Calendar, with which an ALTO Server exposes ALTO cost values in JSON 26 arrays where each value corresponds to a given time interval. The 27 time intervals as well as other Calendar attributes, are specified in 28 the Information Resources Directory and ALTO Server responses. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on September 10, 2020. 47 Copyright Notice 49 Copyright (c) 2020 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Some recent known uses . . . . . . . . . . . . . . . . . 4 66 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 67 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 68 3. Overview of ALTO Cost Calendars and terminology . . . . . . . 5 69 3.1. ALTO Cost Calendar overview . . . . . . . . . . . . . . . 5 70 3.2. ALTO Cost Calendar information features . . . . . . . . . 6 71 3.3. ALTO Calendar design characteristics . . . . . . . . . . 7 72 3.3.1. ALTO Cost Calendar for all cost modes . . . . . . . . 8 73 3.3.2. Compatibility with legacy ALTO Clients . . . . . . . 9 74 4. ALTO Calendar specification: IRD extensions . . . . . . . . . 9 75 4.1. Calendar attributes in the IRD resource capabilities . . 10 76 4.2. Calendars in a delegate IRD . . . . . . . . . . . . . . . 11 77 4.3. Example IRD with ALTO Cost Calendars . . . . . . . . . . 12 78 5. ALTO Calendar specification: Service Information Resources . 15 79 5.1. Calendar extensions for Filtered Cost Maps (FCM) . . . . 16 80 5.1.1. Calendar extensions in Filtered Cost Map requests . . 16 81 5.1.2. Calendar extensions in Filtered Cost Map responses . 17 82 5.1.3. Use case and example: FCM with a bandwidth Calendar . 19 83 5.2. Calendar extensions in the Endpoint Cost Service . . . . 21 84 5.2.1. Calendar specific input in Endpoint Cost requests . . 21 85 5.2.2. Calendar attributes in the Endpoint Cost response . . 22 86 5.2.3. Use case and example: ECS with a routingcost Calendar 23 87 5.2.4. Use case and example: ECS with a multi-cost Calendar 88 for routingcost and owdelay . . . . . . . . . . . . . 25 89 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 90 7. Security Considerations . . . . . . . . . . . . . . . . . . . 27 91 8. Operational Considerations . . . . . . . . . . . . . . . . . 29 92 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30 93 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 94 10.1. Normative References . . . . . . . . . . . . . . . . . . 30 95 10.2. Informative References . . . . . . . . . . . . . . . . . 31 96 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 98 1. Introduction 100 The base Application-Layer Traffic Optimization (ALTO) protocol 101 specified in [RFC7285] provides guidance to overlay applications that 102 need to select one or several hosts from a set of candidates able to 103 provide a desired resource. This guidance is based on parameters 104 that affect performance and efficiency of the data transmission 105 between the hosts such as the topological distance. The goal of ALTO 106 is to improve the Quality of Experience (QoE) in the application 107 while optimizing resource usage in the underlying network 108 infrastructure. 110 The ALTO protocol in [RFC7285] specifies a network map which defines 111 groupings of endpoints in provider-defined network regions identified 112 by Provider-defined Identifiers (PIDs). The Cost Map Service, 113 Endpoint Cost Service (ECS) and Endpoint Ranking Service then provide 114 ISP-defined costs and rankings for connections among the specified 115 endpoints and PIDs and thus incentives for application clients to 116 connect to ISP preferred locations, for instance, to reduce their 117 costs. For the reasons outlined in the ALTO problem statement 118 [RFC5693] and requirement AR-14 of [RFC6708], ALTO does not 119 disseminate network metrics that change frequently. In a network, 120 the costs can fluctuate for many reasons having to do with 121 instantaneous traffic load or due to diurnal patterns of traffic 122 demand or planned events such as network maintenance, holidays or 123 highly publicized events. Thus, an ALTO application wishing to use 124 the Cost Map and Endpoint Cost Service at some future time will have 125 to estimate the state of the network at that time, a process that is, 126 at best, fragile and brittle since the application does not have any 127 visibility into the state of the network. Providing network costs 128 for only the current time thus may not be sufficient, in particular 129 for applications that can schedule their traffic in a span of time, 130 for example by deferring backups or other background traffic to off- 131 peak hours. 133 In case the ALTO Cost value changes are predictable over a certain 134 period of time and the application does not require immediate data 135 transfer, it can save time to get the whole set of cost values over 136 this period in one single ALTO response. Using this set to schedule 137 data transfers allows optimizing the network resources usage and QoE. 138 ALTO Clients and Servers can also minimize their workload by reducing 139 and accordingly scheduling their data exchanges. 141 This document extends [RFC7285] to allow an ALTO Server to provide 142 network costs for a given duration of time. A sequence of network 143 costs across a time span for a given pair of network locations is 144 named an "ALTO Cost Calendar". The Filtered Cost Map Service and 145 Endpoint Cost Service are extended to provide Cost Calendars. In 146 addition to this functional ALTO enhancement, we expect to further 147 save network and storage resources by gathering multiple Cost Values 148 for one cost type into one single ALTO Server response. 150 In this document, an "ALTO Cost Calendar" is specified in terms of 151 information resource capabilities that are applicable to time- 152 sensitive ALTO metrics. An ALTO Cost Calendar exposes ALTO Cost 153 Values in JSON arrays, see [RFC8259], where each value corresponds to 154 a given time interval. The time intervals as well as other Calendar 155 attributes are specified in the Information Resources Directory (IRD) 156 and in the Server response to allow the ALTO Client to interpret the 157 received ALTO values. Last, the extensions for ALTO Calendars are 158 applicable to any Cost Mode and they ensure backwards compatibility 159 with legacy ALTO Clients - those that only support [RFC7285]. 161 In the rest of this document, Section 3 provides the design 162 characteristics. Sections Section 4 and Section 5 define the formal 163 specifications for the IRD and the information resources. IANA, 164 security and operational considerations are addressed respectively in 165 sections Section 6, Section 7 and Section 8. 167 1.1. Some recent known uses 169 A potential use case is implementing smart network services that 170 allow applications to dynamically build end-to-end, virtual networks, 171 to satisfy given demands, with no manual intervention. For example, 172 data-transfer automation applications may need a network service to 173 determine on the availability of bandwidth resources, to decide when 174 to transfer their data sets. The SENSE project [SENSE-sdn-e2e-net] 175 supports such applications by requiring that a network provides 176 services such as the Time-Bandwidth-Product (TBP) service, which 177 informs applications of bandwidth availability during a specific time 178 period. ALTO Calendars can support this service if the Calendar 179 start date and duration cover the period of interest of the 180 requesting application. 182 The need of future scheduling of large scale traffic that can be 183 addressed by the ALTO protocol is also motivated by Unicorn, a 184 unified resource orchestration framework for multi-domain, geo- 185 distributed data analytics, see 186 [I-D.xiang-alto-multidomain-analytics]. 188 1.2. Terminology 190 o ALTO transaction: A request/response exchange between an ALTO 191 Client and an ALTO Server. 193 o Client: When used with a capital "C", this term refers to an ALTO 194 Client. 196 o Calendar, Cost Calendar: When used with capitalized words, these 197 terms refer to an ALTO Cost Calendar. 199 o Endpoint (EP): An endpoint is defined as in Section 2.1 of 200 [RFC7285]. It can be, for example, a peer, a CDN storage 201 location, a physical server involved in a virtual server-supported 202 application, a party in a resource-sharing swarm such as a 203 computation grid, or an online multi-party game. 205 o Server: When used with a capital "S", this term refers to an ALTO 206 Server. 208 2. Requirements Language 210 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 211 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 212 "OPTIONAL" in this document are to be interpreted as described in BCP 213 14 [RFC2119] [RFC8174] when, and only when, they appear in all 214 capitals, as shown here. 216 When the words appear in lower case, they are to be interpreted with 217 their natural language meanings. 219 3. Overview of ALTO Cost Calendars and terminology 221 This section gives a high-level overview of the design. It sets 222 rules to ensure backwards compatibility with legacy ALTO Clients in 223 Section 3.3.2 . It assumes the reader is familiar with the ALTO 224 protocol [RFC7285]. Normative specifications are given in the 225 following sections. 227 3.1. ALTO Cost Calendar overview 229 An ALTO Cost Calendar provided by the ALTO Server provides 2 230 information items: 232 o an array of values for a given metric, where each value specifies 233 the metric corresponding to a time interval, where the value array 234 can sometimes be a cyclic pattern that repeats a certain number of 235 times. 237 o attributes describing the time scope of the Calendar, including 238 the size and number of the intervals and the date of the starting 239 point of the Calendar, allowing an ALTO Client to interpret the 240 values properly. 242 An ALTO Cost Calendar can be used like a "time table" to figure out 243 the best time to schedule data transfers and also to proactively 244 manage application traffic given predictable events such as expected 245 spike in traffic due to crowd gathering (concerts, sports, etc.), 246 traffic-intensive holidays and network maintenance. A Calendar may 247 be viewed as a synthetic abstraction of, for example, real 248 measurements gathered over previous periods on which statistics have 249 been computed. However, like for any schedule, unexpected network 250 incidents may require the current ALTO Calendar to be updated and re- 251 sent to the ALTO Clients needing it. The "ALTO Incremental Updates 252 Using Server-Sent Events (SSE)" Service 253 [I-D.ietf-alto-incr-update-sse] can be used to directly update the 254 Calendar upon value changes, if supported by both the Server and the 255 Client. 257 Most likely, the ALTO Cost Calendar would be used for the Endpoint 258 Cost Service, assuming that a limited set of feasible Endpoints for a 259 non-real time application is already identified, that they do not 260 need to be accessed immediately and that their access can be 261 scheduled within a given time period. The Filtered Cost Map Service 262 is also applicable as long as the size of the Map allows it. 264 3.2. ALTO Cost Calendar information features 266 The Calendar attributes are provided in the Information Resources 267 Directory (IRD) and in ALTO Server responses. The IRD announces 268 attributes without date values in its information resources 269 capabilities, whereas attributes with time dependent values are 270 provided in the "meta" section of Server responses. The ALTO Cost 271 Calendar attributes provide the following information: 273 o attributes to describe the time scope of the Calendar value array: 275 * applicable time interval size for each Calendar value, defined 276 in seconds, that can cover a wide range of values. 278 * duration of the Calendar: e.g., the number of intervals 279 provided in the Calendar. 281 o "calendar-start-time": specifying when the Calendar starts, that 282 is to which date the first value of the Cost Calendar is 283 applicable. 285 o "repeated": an optional attribute indicating how many iterations 286 of the provided Calendar will have the same values. The Server 287 may use it to allow the Client to schedule its next request and 288 thus save its own workload by reducing processing of similar 289 requests. 291 Attribute "repeated" may take a very high value if a Calendar 292 represents a cyclic value pattern that the Server considers valid for 293 a long period. In this case, the Server will only update the 294 Calendar values once this period has elapsed or if an unexpected 295 event occurs on the network. See Section 8 for more discussion. 297 3.3. ALTO Calendar design characteristics 299 The extensions in this document encode requests and responses using 300 JSON [RFC8259]. 302 In the base protocol [RFC7285] section 11.2.3.6, an ALTO cost is 303 specified as a generic JSONValue [RFC8259], to allow extensions. 304 However, that section 11.2.3.6 states: "An implementation of the 305 protocol in this document ([RFC7285]) SHOULD assume that the cost is 306 a JSONNumber and fail to parse if it is not, unless the 307 implementation is using an extension to this document that indicates 308 when and how costs of other data types are signaled". 310 The present document extends the definition of a legacy cost map 311 given in [RFC7285] to allow a cost entry to be an array of values, 312 with one value one per time interval, instead of being just one 313 number. Therefore the implementor of this extension MUST consider 314 that a cost entry is an array of values. Specifically, an 315 implementation of this extension MUST parse the "number-of-intervals" 316 attribute of the "calendar-attributes" in an IRD entry announcing a 317 service providing Cost Calendar. The implementation then will know 318 that a cost entry of the service will be an array of values, and the 319 expected size of the array is that specified by the "number-of- 320 intervals" attribute. 322 To realize an ALTO Calendar, this document extends: the IRD and the 323 ALTO requests and responses for Cost Calendars. 325 This extension is designed to be lightweight and to ensure backwards 326 compatibility with base protocol ALTO Clients and with other 327 extensions. It relies on section 8.3.7 "Parsing of Unknown Fields" 328 of [RFC7285] that writes: "Extensions may include additional fields 329 within JSON objects defined in this document. ALTO implementations 330 MUST ignore unknown fields when processing ALTO messages." 331 The Calendar-specific capabilities are integrated in the information 332 resources of the IRD and in the "meta" member of ALTO responses to 333 Cost Calendars requests. A Calendar and its capabilities are 334 associated with a given information resource and within this 335 information resource with a given cost type. This design has several 336 advantages: 338 o it does not introduce a new mode, 340 o it does not introduce new media types, 342 o it allows an ALTO Server to offer Calendar capabilities on a cost 343 type, with attributes values adapted to each information resource. 345 The applicable Calendared information resources are: 347 o the Filtered Cost Map, 349 o the Endpoint Cost Map. 351 The ALTO Server can choose in which frequency it provides cost 352 Calendars to ALTO Clients. It may either provide Calendar updates 353 starting at the request date, or carefully schedule its updates so as 354 to take profit from a potential repetition/periodicity of Calendar 355 values. 357 The ALTO Server does not support constraints on Calendars, provided 358 Calendars are requested for numerical values, for two main reasons: 360 o constraints on an array of values may be various: for instance, 361 some Clients may refuse Calendars with one single single values 362 violating a constraints, where as other ones may tolerate 363 Calendars with values violating constraints for example at given 364 times. Therefore, expressing constraints in a way that covers all 365 possible Client preferences is challenging, 367 o if constraints were to be supported, the processing overhead would 368 be substantial for the Server as it would have to parse alle the 369 values of the Calendar array before returning a response. 371 3.3.1. ALTO Cost Calendar for all cost modes 373 An ALTO Cost Calendar is well-suited for values encoded in the 374 "numerical" mode. Actually, a Calendar can also represent metrics in 375 other modes considered as compatible with time-varying values. For 376 example, types of Cost values such as JSONBool can also be 377 calendared, as their value may be 'true' or 'false' depending on 378 given time periods or likewise, values represented by strings, such 379 as "medium", "high", "low", "blue", "open". 381 Note also that a Calendar is suitable as well for time-varying 382 metrics provided in the "ordinal" mode, if these values are time- 383 varying and the ALTO Server provides updates of cost value based 384 preferences. 386 3.3.2. Compatibility with legacy ALTO Clients 388 The ALTO protocol extensions for Cost Calendars have been defined so 389 as to ensure that Calendar-capable ALTO Servers can provide legacy 390 ALTO Clients with legacy information resources as well. That is, a 391 legacy ALTO Client can request resources and receive responses as 392 specified in [RFC7285]. 394 A Calendar-aware ALTO Server MUST implement the base protocol 395 specified in [RFC7285]. 397 As a consequence, when a metric is available as a Calendar array, it 398 also MUST be available as a single value as required by [RFC7285]. 399 The Server, in this case, provides the current value of the metric to 400 either Calendar-aware Clients not interested in future or time-based 401 values, or Clients implementing [RFC7285] only. 403 For compatibility with legacy ALTO Clients specified in [RFC7285], 404 calendared information resources are not applicable for full cost 405 maps for the following reason: a legacy ALTO Client would receive a 406 calendared cost map via an HTTP 'GET' command. As specified in 407 section 8.3.7 of [RFC7285], it will ignore the Calendar Attributes 408 indicated in the "meta" of the responses. Therefore, lacking 409 information on Calendar attributes, it will not be able to correctly 410 interpret and process the values of the received array of Calendar 411 cost values. 413 Therefore, calendared information resources MUST be requested via the 414 Filtered Cost Map Service or the Endpoint Cost Service, using a POST 415 method. 417 4. ALTO Calendar specification: IRD extensions 419 The Calendar attributes in the IRD information resources capabilities 420 carry constant dateless values. A Calendar is associated with an 421 information resource rather than a cost type. For example, a Server 422 can provide a "routingcost" Calendar for the Filtered Cost Map 423 Service at a granularity of one day and a "routingcost" Calendar for 424 the Endpoint Cost Service at a finer granularity but for a limited 425 number of endpoints. An example IRD with Calendar specific features 426 is provided in Section 4.3. 428 4.1. Calendar attributes in the IRD resource capabilities 430 A Cost Calendar for a given cost type MUST be indicated in the IRD by 431 an object of type CalendarAttributes. A CalendarAttributes object is 432 represented by the "calendar-attributes" member of a resource entry. 433 Each CalendarAttributes object applies to a set of one or more cost 434 types. A cost type name MUST NOT appear more than once in the 435 "calendar-attributes" member of a resource entry; multiple 436 appearances of a cost type name in the CalendarAttributes object of 437 the "calendar-attributes" member MUST cause the ALTO Client to ignore 438 any occurrences of this name beyond the first encountered occurrence. 440 An ALTO Server SHOULD specify the "time-interval-size" in the IRD as 441 the smallest it is able to provide. A Client that needs a longer 442 interval can aggregate multiple cost values to obtain it. 444 The encoding format for object CalendarAttributes, using JSON 445 [RFC8259], is as follows: 447 CalendarAttributes calendar-attributes <1..*>; 449 object{ 450 JSONString cost-type-names <1..*>; 451 JSONNumber time-interval-size; 452 JSONNumber number-of-intervals; 453 } CalendarAttributes; 455 o "cost-type-names": 457 * An array of one or more elements indicating the cost-type-names 458 in the IRD entry to which the capabilities apply. 460 o "time-interval-size": 462 * is the duration of an ALTO Calendar time interval in a unit of 463 seconds. A "time-interval-size" value contains a non-negative 464 JSONNumber. Example values are: 300 and 7200, meaning that 465 each Calendar value applies on a time interval that lasts 5 466 minutes and 2 hours, respectively. Since an interval size 467 (e.g., 100 ms) can be smaller than the unit, the value 468 specified may be a floating point (e.g., 0.1). Both ALTO 469 Clients and Servers should be aware of potential precision 470 issues caused by using floating point numbers; for example, the 471 floating number 0.1 cannot be represented precisely using a 472 finite number of binary bits. To improve interoperability and 473 be consistent with [RFC7285] on the use of float point numbers, 474 the Server and the Client SHOULD use IEEE 754 double-precision 475 floating point [IEEE.754.2008] to store this value. 477 o "number-of-intervals": 479 * is a strictly positive integer (greater or equal to 1), that 480 indicates the number of values of the Cost Calendar array. 482 - Attribute "cost-type-names" is associated with "time-interval-size" 483 and "number-of-intervals", because multiple cost types may share the 484 same values for attributes "time-interval-size" and "number-of- 485 intervals". To avoid redundancies, cost type names sharing the same 486 values for "time-interval-size" and "number-of-intervals" are grouped 487 in the "cost-type-names" attribute. In the example IRD provided in 488 Section 4.3, the information resource "filtered-cost-map-calendar" 489 provides a Calendar for cost type names "num-routingcost", "num- 490 throughputrating" and "string-servicestatus". Cost type names "num- 491 routingcost" and "num-throughputrating" are grouped in the "cost- 492 type-names" attribute because they share the same values for "time- 493 interval-size" and "number-of-intervals", which are respectively 7200 494 and 12. 496 - Multiplying 'time-interval-size' by 'number-of-intervals' provides 497 the duration of the provided Calendar. For example, an ALTO Server 498 may provide a Calendar for ALTO values changing every 'time-interval- 499 size' equal to 5 minutes. If 'number-of-intervals' has the value 12, 500 then the duration of the provided Calendar is 1 hour. 502 4.2. Calendars in a delegate IRD 504 It may be useful to distinguish IRD resources supported by the base 505 ALTO protocol from resources supported by its extensions. To achieve 506 this, one option, is that a "root" ALTO Server implementing base 507 protocol resources and running at a given domain, delegates 508 "specialized" information resources such as the ones providing Cost 509 Calendars, to another ALTO Server running in a subdomain. The "root" 510 ALTO Server can provide a Calendar-specific resource entry where it 511 specifies the URI allowing to retrieve the location of a Calendar- 512 aware Server and relevant resources. This option is described in 513 Section 9.2.4 "Delegation using IRDs" of [RFC7285]. 515 This document provides an example, where a "root" ALTO Server runs in 516 a domain called "alto.example.com". It delegates the announcement of 517 Calendars capabilities to an ALTO Server running in a subdomain 518 called "custom.alto.example.com". The location of the "delegate 519 Calendar IRD" is assumed to be indicated in the "root" IRD by the 520 resource entry: "custom-calendared-resources". 522 Another benefit of delegation is that some cost types for some 523 resources may be more advantageous as Cost Calendars and it makes few 524 sense to get them as a single value. For example, if a cost type has 525 predictable and frequently changing values, calendared in short time 526 intervals such as a minute, it saves time and network resources to 527 track the cost values via a focused delegate Server rather than the 528 more general "root" Server. 530 4.3. Example IRD with ALTO Cost Calendars 532 This section provides an example ALTO Server IRD that supports 533 various cost metrics and cost modes. In particular, since [RFC7285] 534 makes it mandatory, the Server uses metric "routingcost" in the 535 "numerical" mode. 537 For illustrative purposes, this section introduces 3 other fictitious 538 example metrics and modes that should be understood as examples and 539 should not be used or considered as normative. 541 The cost type names used in the example IRD are as follows: 543 o "num-routingcost": refers to metric "routingcost" in the numerical 544 mode as defined in [RFC7285] and registered with IANA. 546 o "num-owdelay": refers to fictitious performance metric "owdelay" 547 in the "numerical" mode, to reflect the one-way packet 548 transmission delay on a path. A related performance metric is 549 currently under definition in [I-D.ietf-alto-performance-metrics]. 551 o "num-throughputrating": refers to fictitious metric 552 "throughputrating" in the "numerical" mode, to reflect the 553 provider preference in terms of end to end throughput. 555 o "string-servicestatus": refers to fictitious metric 556 "servicestatus" containing a string, to reflect the availability, 557 defined by the provider, of for instance path connectivity. 559 The example IRD includes 2 particular URIs providing Calendars: 561 o "https://custom.alto.example.com/calendar/costmap/filtered": a 562 filtered cost map in which Calendar capabilities are indicated for 563 cost type names: "num-routingcost", "num-throughputrating" and 564 "string-servicestatus", 566 o "https://custom.alto.example.com/calendar/endpointcost/lookup": an 567 endpoint cost map in which Calendar capabilities are indicated for 568 cost type names: "num-routingcost", "num-owdelay", "num- 569 throughputrating", "string-servicestatus". 571 The design of the Calendar capabilities allows some Calendars with 572 the same cost type name to be available in several information 573 resources with different Calendar Attributes. This is the case for 574 Calendars on "num-routingcost", "num-throughputrating" and "string- 575 servicestatus", available in both the Filtered Cost map and Endpoint 576 Cost Service, but with different time interval sizes for "num- 577 throughputrating" and "string-servicestatus". 579 --- Client to Server request for IRD ---------- 581 GET /calendars-directory HTTP/1.1 582 Host: custom.alto.example.com 583 Accept: application/alto-directory+json,application/alto-error+json 585 --- Server response to Client ----------------- 587 HTTP/1.1 200 OK 588 Content-Length: 2542 589 Content-Type: application/alto-directory+json 591 { 592 "meta" : { 593 "default-alto-network-map" : "my-default-network-map", 594 "cost-types": { 595 "num-routingcost": { 596 "cost-mode" : "numerical", 597 "cost-metric" : "routingcost" 598 }, 599 "num-owdelay": { 600 "cost-mode" : "numerical", 601 "cost-metric": "owdelay" 602 }, 603 "num-throughputrating": { 604 "cost-mode" : "numerical", 605 "cost-metric": "throughputrating" 606 }, 607 "string-servicestatus": { 608 "cost-mode" : "string", 609 "cost-metric": "servicestatus" 610 } 611 } 612 }, 613 "resources" : { 614 "filtered-cost-map-calendar" : { 615 "uri" : 616 "https://custom.alto.example.com/calendar/costmap/filtered", 617 "media-type" : "application/alto-costmap+json", 618 "accepts" : "application/alto-costmapfilter+json", 619 "capabilities" : { 620 "cost-constraints" : true, 621 "cost-type-names" : [ "num-routingcost", 622 "num-throughputrating", 623 "string-servicestatus" ], 624 "calendar-attributes" : [ 625 {"cost-type-names" : [ "num-routingcost", 626 "num-throughputrating" ], 627 "time-interval-size" : 7200, 628 "number-of-intervals" : 12 629 }, 630 {"cost-type-names" : [ "string-servicestatus" ], 631 "time-interval-size" : 1800, 632 "number-of-intervals" : 48 633 } 634 ] 635 }, 636 "uses": [ "my-default-network-map" ] 637 }, 638 "endpoint-cost-calendar-map" : { 639 "uri" : 640 "https://custom.alto.example.com/calendar/endpointcost/lookup", 641 "media-type" : "application/alto-endpointcost+json", 642 "accepts" : "application/alto-endpointcostparams+json", 643 "capabilities" : { 644 "cost-constraints" : true, 645 "cost-type-names" : [ "num-routingcost", 646 "num-owdelay", 647 "num-throughputrating", 648 "string-servicestatus" ], 649 "calendar-attributes" : [ 650 {"cost-type-names" : [ "num-routingcost" ], 651 "time-interval-size" : 3600, 652 "number-of-intervals" : 24 653 }, 654 {"cost-type-names" : [ "num-owdelay" ], 655 "time-interval-size" : 300, 656 "number-of-intervals" : 12 657 }, 658 {"cost-type-names" : [ "num-throughputrating" ], 659 "time-interval-size" : 60, 660 "number-of-intervals" : 60 661 }, 662 {"cost-type-names" : [ "string-servicestatus" ], 663 "time-interval-size" : 120, 664 "number-of-intervals" : 30 665 } 666 ] 668 } 669 } 670 } 671 } 673 In this example IRD, for the Filtered Cost Map Service: 675 o the Calendar for "num-routingcost" and "num-throughputrating" is 676 an array of 12 values each provided on a time interval lasting 677 7200 seconds (2 hours). 679 o the Calendar for "string-servicestatus": "is an array of 48 values 680 each provided on a time interval lasting 1800 seconds (30 681 minutes). 683 For the Endpoint Cost Service: 685 o the Calendar for "num-routingcost": is an array of 24 values each 686 provided on a time interval lasting 3600 seconds (1 hour). 688 o the Calendar for "owdelay": is an array of 12 values each provided 689 on a time interval lasting 300 seconds (5 minutes). 691 o the Calendar for "num-throughputrating": is an array of 60 values 692 each provided on a time interval lasting 60 seconds (1 minute). 694 o the Calendar for "string-servicestatus": "is an array of 30 values 695 each provided on a time interval lasting 120 seconds (2 minutes). 697 Note that in this example IRD, member "cost-constraints" is present 698 with a value set to "true" in both information resources "filtered- 699 cost-map-calendar" and "endpoint-cost-calendar-map". Although a 700 Calendar-aware ALTO Server does not support constraints for the 701 reasons explained in section Section 3.3, it MUST support constraints 702 on cost types that are not requested as Calendars but are requested 703 as specified in [RFC7285] and [RFC8189]. 705 5. ALTO Calendar specification: Service Information Resources 707 This section documents extensions to two basic ALTO information 708 resources (Filtered Cost Maps and Endpoint Cost Service) to provide 709 calendared information services for them. 711 Both extensions return calendar start time (calendar-start-time, a 712 point in time), which MUST be specified as an HTTP "Date" header 713 field using the IMF-fixdate format specified in Section 7.1.1.1 of 714 [RFC7231]. Note that the IMF-fixdate format uses "GMT", not "UTC", 715 to designate the time zone, as in this example: 717 Date: Tue, 15 Nov 2014 08:12:31 GMT 719 5.1. Calendar extensions for Filtered Cost Maps (FCM) 721 A legacy ALTO Client requests and gets Filtered Cost Map responses as 722 specified in [RFC7285]. 724 5.1.1. Calendar extensions in Filtered Cost Map requests 726 The input parameters of a "legacy" request for a filtered cost map, 727 defined by object ReqFilteredCostMap in section 11.3.2 of [RFC7285], 728 are augmented with one additional member. 730 A Calendar-aware ALTO Client requesting a Calendar on a given Cost 731 Type for a filtered cost map resource having Calendar capabilities 732 MUST add the following field to its input parameters: 734 JSONBoolean calendared<1..*>; 736 This field is an array of 1 to N boolean values, where N is the 737 number of requested metrics. Each entry corresponds to the requested 738 metric at the same array position. Each boolean value indicates 739 whether or not the ALTO Server should provide the values for this 740 cost type as a Calendar. The array MUST contain exactly N boolean 741 values, otherwise, the Server returns an error. 743 This field MUST NOT be included if no member "calendar-attributes" is 744 specified in this information resource. 746 If a value of field 'calendared' is 'true' for a cost type name for 747 which no Calendar attributes have been specified: an ALTO Server, 748 whether it implements the extensions of this document or only 749 implements [RFC7285], MUST ignore it and return a response with a 750 single cost value as specified in [RFC7285]. 752 If this field is not present, it MUST be assumed to have only values 753 equal to 'false'. 755 A Calendar-aware ALTO Client that supports requests for only one cost 756 type at a time and wants to request a Calendar MUST provide an array 757 of 1 element: 759 "calendared" : [true]; 761 A Calendar-aware ALTO Client that supports requests for more than one 762 cost types at a time, as specified in [RFC8189] MUST provide an array 763 of N values set to 'true' or 'false', depending whether it wants the 764 applicable cost type values as a single or calendared value. 766 5.1.2. Calendar extensions in Filtered Cost Map responses 768 In a calendared ALTO Filtered Cost Map, a cost value between a source 769 and a destination is a JSON array of JSON values. An ALTO Calendar 770 values array has a number of values equal to the value of member 771 "number-of-intervals" of the Calendar attributes that are indicated 772 in the IRD. These attributes will be conveyed as metadata in the 773 Filtered Cost Map response. Each element of the array is valid for 774 the time-interval that matches its array position. 776 The FCM response conveys metadata among which: 778 o some are not specific to Calendars and ensure compatibility with 779 [RFC7285] and [RFC8189] 781 o some are specific to Calendars. 783 The non Calendar specific "meta" fields of a calendared Filtered Cost 784 Map response MUST include at least: 786 o if the ALTO Client requests cost values for one cost type at a 787 time only: the "meta" fields specified in [RFC7285] for these 788 information service responses: 790 * "dependent-vtags ", 792 * "cost-type" field. 794 o if the ALTO Client implements the Multi-Cost ALTO extension 795 specified in [RFC8189] and requests cost values for several Cost 796 Types at a time: the "meta" fields specified in [RFC8189] for 797 these information service responses: 799 * "dependent-vtags ", 801 * "cost-type" field with value set to '{}', for backwards 802 compatibility with [RFC7285]. 804 * "multi-cost-types" field. 806 If the Client request does not provide member "calendared" or if it 807 provides it with a value equal to 'false', for all the requested Cost 808 Types, then the ALTO Server response is exactly as specified in 809 [RFC7285] and [RFC8189]. 811 If the value of member "calendared" is equal to 'false' for a given 812 requested cost type, the ALTO Server MUST return, for this cost type, 813 a single cost value as specified in [RFC7285]. 815 If the value of member "calendared" is equal to 'true' for a given 816 requested cost type, the ALTO Server returns, for this cost type, a 817 cost value Calendar as specified above in this section. In addition 818 to the above cited non Calendar specific "meta" members, the Server 819 MUST provide a Calendar specific metadata field. 821 The Calendar specific "meta" field that a calendared Filtered Cost 822 Map response MUST include is a member called "calendar-response- 823 attributes", that describes properties of the Calendar and where: 825 o member "calendar-response-attributes" is an array of one or more 826 objects of type "CalendarResponseAttributes". 828 o each "CalendarResponseAttributes" object in the array is specified 829 for one or more cost types for which the value of member 830 "calendared" is equal to 'true' and for which a Calendar is 831 provided for the requested information resource. 833 o the "CalendarResponseAttributes" object that applies to a cost 834 type name has a corresponding "CalendarAttributes" object defined 835 for this cost type name in the IRD capabilities of the requested 836 information resource. The members of a 837 "CalendarResponseAttributes" object include all the members of the 838 corresponding "CalendarAttributes" object. 840 The format of member "CalendarResponseAttributes is defined as 841 follows: 843 CalendarResponseAttributes calendar-response-attributes <1..*>; 845 object{ 846 [JSONString cost-type-names <1..*>]; 847 JSONString calendar-start-time; 848 JSONNumber time-interval-size; 849 JSONNumber number-of-intervals; 850 [JSONNumber repeated;] 851 } CalendarResponseAttributes; 853 Object CalendarResponseAttributes has the following attributes: 855 o "cost-type-names": is an array of one or more cost-type-names to 856 which the capabilities apply and for which a Calendar has been 857 requested. The value of this member is a subset of the "cost- 858 type-names" array specified in the corresponding IRD Calendar 859 attributes. 861 o "calendar-start-time": indicates the date at which the first value 862 of the Calendar applies. The value provided for the "calendar- 863 start-time" attribute SHOULD NOT be later than the request date. 865 o "time-interval-size": as specified in Section 4.1 and with the 866 same value. 868 o "number-of-intervals": as specified in Section 4.1 and with the 869 same value. 871 o "repeated": is an optional field provided for Calendars. It is an 872 integer N greater or equal to '1' that indicates how many 873 iterations of the Calendar value array starting at the date 874 indicated by "calendar-start-time" have the same values. The 875 number N includes the iteration provided in the returned response. 877 For example: suppose the "calendar-start-time" member has value "Mon, 878 30 Jun 2014 00:00:00 GMT", the "time-interval-size" member has value 879 '3600', the "number-of-intervals" member has value '24' and the value 880 of member "repeated" is equal to '4'. This means that the Calendar 881 values are the same on Monday, Tuesday, Wednesday and Thursday on a 882 period of 24 hours starting at 00:00:00 GMT. The ALTO Client thus 883 may use the same Calendar for the next 4 days starting at "calendar- 884 start-time" and will only need to request a new one for Friday July 885 4th at 00:00:00 GMT. 887 Attribute "repeated" may take a very high value if a Calendar 888 represents a cyclic value pattern that the Server considers valid for 889 a long period and hence will only update once this period has elapsed 890 or if an unexpected event occurs on the network. In the latter case, 891 the Client will be notified if it uses the "ALTO Incremental Updates 892 Using Server-Sent Events (SSE)" Service, specified in 893 [I-D.ietf-alto-incr-update-sse]. To this end, it is RECOMMENDED that 894 ALTO Servers providing ALTO Calendars also provide the "ALTO 895 Incremental Updates Using Server-Sent Events (SSE)" Service that is 896 specified in [I-D.ietf-alto-incr-update-sse]. Likewise, ALTO Clients 897 capable of using ALTO Calendars SHOULD also use the SSE Service. See 898 also discussion in Section 8 "Operational Considerations". 900 5.1.3. Use case and example: FCM with a bandwidth Calendar 902 An example of non-real time information that can be provisioned in a 903 Calendar is the expected path throughput. While the transmission 904 rate can be measured in real time by end systems, the operator of a 905 data center is in the position of formulating preferences for given 906 paths, at given time periods to avoid traffic peaks due to diurnal 907 usage patterns. In this example, we assume that an ALTO Client 908 requests a Calendar of network provider defined throughput ratings, 909 as specified in the IRD, to schedule its bulk data transfers as 910 described in the use cases. 912 In the example IRD, Calendars for cost type name "num- 913 throughputrating" are available for the information resources: 914 "filtered-cost-calendar-map" and "endpoint-cost-calendar-map". The 915 ALTO Client requests a Calendar for "num-throughputrating" via a POST 916 request for a filtered cost map. 918 We suppose in the present example that the ALTO Client sends its 919 request on Tuesday July 1st 2014 at 13:15. The Server returns 920 Calendars with arrays of 12 numbers for each source and destination 921 pair. The values for metric "throughputrating", in this example, are 922 assumed to be encoded in 2 digits. 924 POST /calendar/costmap/filtered HTTP/1.1 925 Host: alto.example.com 926 Content-Length: 208 927 Content-Type: application/alto-costmapfilter+json 928 Accept: application/alto-costmap+json,application/alto-error+json 930 { 931 "cost-type" : {"cost-mode" : "numerical", 932 "cost-metric" : "throughputrating"}, 933 "calendared" : [true], 934 "pids" : { 935 "srcs" : [ "PID1", "PID2" ], 936 "dsts" : [ "PID1", "PID2", "PID3" ] 937 } 938 } 940 HTTP/1.1 200 OK 941 Content-Length: 1013 942 Content-Type: application/alto-costmap+json 944 { 945 "meta" : { 946 "dependent-vtags" : [ 947 {"resource-id": "my-default-network-map", 948 "tag": "3ee2cb7e8d63d9fab71b9b34cbf764436315542e" 949 } 950 ], 951 "cost-type" : {"cost-mode" : "numerical", 952 "cost-metric" : "throughputrating"}, 953 "calendar-response-attributes" : [ 954 {"calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 955 "time-interval-size" : 7200, 956 "number-of-intervals" : 12} 958 ] 959 }, 960 "cost-map" : { 961 "PID1": { "PID1": [ 1, 12, 14, 18, 14, 14, 962 14, 18, 19, 20, 11, 12], 963 "PID2": [13, 4, 15, 16, 17, 18, 964 19, 20, 11, 12, 13, 14], 965 "PID3": [20, 20, 18, 14, 12, 12, 966 14, 14, 12, 12, 14, 16] }, 967 "PID2": { "PID1": [17, 18, 19, 10, 11, 12, 968 13, 14, 15, 16, 17, 18], 969 "PID2": [20, 20, 18, 16, 14, 14, 970 14, 16, 16, 16, 14, 16], 971 "PID3": [20, 20, 18, 14, 12, 12, 972 14, 14, 12, 12, 14, 16] } 973 } 974 } 976 5.2. Calendar extensions in the Endpoint Cost Service 978 This document extends the Endpoint Cost Service, as defined in 979 {11.5.1} of [RFC7285], by adding new input parameters and 980 capabilities, and by returning JSONArrays instead of JSONNumbers as 981 the cost values. The media type {11.5.1.1} and HTTP method 982 {11.5.1.2} are unchanged. 984 5.2.1. Calendar specific input in Endpoint Cost requests 986 The extensions to the requests for calendared Endpoint Cost Maps are 987 the same as for the Filtered Cost Map Service, specified in section 988 Section 5.1.1 of this draft. 990 The ReqEndpointCostMap object for a calendared ECM request will have 991 the following format: 993 object { 994 [CostType cost-type;] 995 [CostType multi-cost-types<1..*>;] 996 [JSONBoolean calendared<1..*>;] 997 EndpointFilter endpoints; 998 } ReqEndpointCostMap; 1000 object { 1001 [TypedEndpointAddr srcs<0..*>;] 1002 [TypedEndpointAddr dsts<0..*>;] 1003 } EndpointFilter; 1004 For the reasons explained in section Section 3.3, a Calendar-aware 1005 ALTO Server does not support constraints. Therefore, member 1006 "[constraints]" is not present in the ReqEndpointCostMap object and 1007 member "constraints" MUST NOT be present in the input parameters of a 1008 request for an Endpoint Cost Calendar. If this member is present, 1009 the Server MUST ignore it. 1011 5.2.2. Calendar attributes in the Endpoint Cost response 1013 The "meta" field of a calendared Endpoint Cost response MUST include 1014 at least: 1016 o if the ALTO Client supports cost values for one cost type at a 1017 time only: the "meta" fields specified in {11.5.1.6} of [RFC7285] 1018 for the Endpoint Cost response: 1020 * "cost-type" field. 1022 o if the ALTO Client supports cost values for several cost types at 1023 a time, as specified in [RFC8189] : the "meta" fields specified in 1024 [RFC8189] for the the Endpoint Cost response: 1026 * "cost-type" field with value set to '{}', for backwards 1027 compatibility with [RFC7285]. 1029 * "multi-cost-types" field. 1031 If the Client request does not provide member "calendared" or if it 1032 provides it with a value equal to 'false', for all the requested Cost 1033 Types, then the ALTO Server response is exactly as specified in 1034 [RFC7285] and [RFC8189]. 1036 If the ALTO Client provides member "calendared" in the input 1037 parameters with a value equal to 'true' for given requested Cost 1038 Types, the "meta" member of a calendared Endpoint Cost response MUST 1039 include, for these cost types, an additional member "calendar- 1040 response-attributes", the contents of which obey the same rules as 1041 for the Filtered Cost Map Service, specified in Section 5.1.2. The 1042 Server response is thus changed as follows, with respect to [RFC7285] 1043 and [RFC8189]: 1045 o the "meta" member has one additional field 1046 "CalendarResponseAttributes", as specified for the Filtered Cost 1047 Map Service, 1049 o the calendared costs are JSONArrays instead of the JSONNumbers 1050 format used by legacy ALTO implementations. All arrays have a 1051 number of values equal to 'number-of-intervals'. 1053 If the value of member "calendared" is equal to 'false' for a given 1054 requested cost type, the ALTO Server MUST return, for this cost type, 1055 a single cost value as specified in [RFC7285]. 1057 5.2.3. Use case and example: ECS with a routingcost Calendar 1059 Let us assume an Application Client is located in an end system with 1060 limited resources and having access to the network that is either 1061 intermittent or provides an acceptable quality in limited but 1062 predictable time periods. Therefore, it needs to schedule both its 1063 resource-greedy networking activities and its ALTO transactions. 1065 The Application Client has the choice to trade content or resources 1066 with a set of Endpoints and needs to decide with which one it will 1067 connect and at what time. For instance, the Endpoints are spread in 1068 different time-zones, or have intermittent access. In this example, 1069 the 'routingcost' is assumed to be time-varying, with values provided 1070 as ALTO Calendars. 1072 The ALTO Client associated with the Application Client queries an 1073 ALTO Calendar on 'routingcost' and will get the Calendar covering the 1074 24 hours time period "containing" the date and time of the ALTO 1075 Client request. 1077 For cost type "num-routingcost", the solicited ALTO Server has 1078 defined 3 different daily patterns each represented by a Calendar, to 1079 cover the week of Monday June 30th at 00:00 to Sunday July 6th 23:59: 1081 o C1 for Monday, Tuesday, Wednesday, Thursday, (weekdays) 1083 o C2 for Saturday, Sunday, (weekend) 1085 o C3 for Friday (maintenance outage on July 4, 2014 from 02:00:00 1086 GMT to 04:00:00 GMT, or big holiday such as New Year evening). 1088 In the following example, the ALTO Client sends its request on 1089 Tuesday July 1st 2014 at 13:15. 1091 The "routingcost" values are assumed to be encoded in 3 digits. 1093 POST /calendar/endpointcost/lookup HTTP/1.1 1094 Host: alto.example.com 1095 Content-Length: 290 1096 Content-Type: application/alto-endpointcostparams+json 1097 Accept: application/alto-endpointcost+json,application/alto-error+json 1099 { 1100 "cost-type" : {"cost-mode" : "numerical", 1101 "cost-metric" : "routingcost"}, 1102 "calendared" : [true], 1103 "endpoints" : { 1104 "srcs": [ "ipv4:192.0.2.2" ], 1105 "dsts": [ 1106 "ipv4:192.0.2.89", 1107 "ipv4:198.51.100.34", 1108 "ipv4:203.0.113.45", 1109 "ipv6:2001:db8::10" 1110 ] 1111 } 1112 } 1114 HTTP/1.1 200 OK 1116 Content-Length: 1318 1117 Content-Type: application/alto-endpointcost+json 1119 { 1120 "meta" : { 1121 "cost-type" : {"cost-mode" : "numerical", 1122 "cost-metric" : "routingcost"}, 1123 "calendar-response-attributes" : [ 1124 {"calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1125 "time-interval-size" : 3600, 1126 "number-of-intervals" : 24, 1127 "repeated": 4 1128 } 1129 ] 1130 }, 1131 "endpoint-cost-map" : { 1132 "ipv4:192.0.2.2": { 1133 "ipv4:192.0.2.89" : [100, 100, 100, 100, 100, 150, 1134 200, 300, 300, 300, 300, 250, 1135 250, 300, 300, 300, 300, 300, 1136 400, 250, 250, 200, 150, 150], 1137 "ipv4:198.51.100.34" : [ 80, 80, 80, 80, 150, 150, 1138 250, 400, 400, 450, 400, 200, 1139 200, 350, 400, 400, 400, 350, 1140 500, 200, 200, 200, 100, 100], 1141 "ipv4:203.0.113.45" : [300, 400, 250, 250, 200, 150, 1142 150, 100, 100, 100, 100, 100, 1143 100, 100, 100, 100, 100, 150, 1144 200, 300, 300, 300, 300, 250], 1145 "ipv6:2001:db8::10" : [200, 250, 300, 300, 300, 300, 1146 250, 300, 300, 300, 300, 350, 1147 300, 400, 250, 150, 100, 100, 1148 100, 150, 200, 250, 250, 300] 1150 } 1151 } 1152 } 1154 When the Client gets the Calendar for "routingcost", it sees that the 1155 "calendar-start-time" is Monday at 00h00 GMT and member "repeated" is 1156 equal to '4'. It understands that the provided values are valid 1157 until Thursday included and will only need to get a Calendar update 1158 on Friday. 1160 5.2.4. Use case and example: ECS with a multi-cost Calendar for 1161 routingcost and owdelay 1163 In this example, it is assumed that the ALTO Server implements multi- 1164 cost capabilities, as specified in [RFC8189] . That is, an ALTO 1165 Client can request and receive values for several cost types in one 1166 single transaction. An illustrating use case is a path selection 1167 done on the basis of 2 metrics: routing cost and owdelay. 1169 As in the previous example, the IRD indicates that the ALTO Server 1170 provides "routingcost" Calendars in terms of 24 time intervals of 1 1171 hour (3600 seconds) each. 1173 For metric "owdelay", the IRD indicates that the ALTO Server provides 1174 Calendars in terms of 12 time intervals values lasting each 5 minutes 1175 (300 seconds). 1177 In the following example transaction, the ALTO Client sends its 1178 request on Tuesday July 1st 2014 at 13:15. 1180 This example assumes that the values of metric "owdelay" and 1181 "routingcost" are encoded in 3 digits. 1183 POST calendar/endpointcost/lookup HTTP/1.1 1184 Host: alto.example.com 1185 Content-Length: 373 1186 Content-Type: application/alto-endpointcostparams+json 1187 Accept: application/alto-endpointcost+json,application/alto-error+json 1189 { 1190 "cost-type" : {}, 1191 "multi-cost-types" : [ 1192 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1193 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1194 ], 1195 "calendared" : [true, true], 1196 "endpoints" : { 1197 "srcs": [ "ipv4:192.0.2.2" ], 1198 "dsts": [ 1199 "ipv4:192.0.2.89", 1200 "ipv4:198.51.100.34", 1201 "ipv4:203.0.113.45", 1202 "ipv6:2001:db8::10" 1203 ] 1204 } 1205 } 1207 HTTP/1.1 200 OK 1208 Content-Length: 2111 1209 Content-Type: application/alto-endpointcost+json 1211 { 1212 "meta" : { 1213 "multi-cost-types" : [ 1214 {"cost-mode" : "numerical", "cost-metric" : "routingcost"}, 1215 {"cost-mode" : "numerical", "cost-metric" : "owdelay"} 1216 ], 1217 "calendar-response-attributes" : [ 1218 {"cost-type-names" : "num-routingcost", 1219 "calendar-start-time" : "Mon, 30 Jun 2014 00:00:00 GMT", 1220 "time-interval-size" : 3600, 1221 "number-of-intervals" : 24, 1222 "repeated": 4 }, 1223 {"cost-type-names" : "num-owdelay", 1224 "calendar-start-time" : "Tue, 1 Jul 2014 13:00:00 GMT", 1225 "time-interval-size" : 300, 1226 "number-of-intervals" : 12} 1227 ] 1228 }, 1229 "endpoint-cost-map" : { 1230 "ipv4:192.0.2.2": { 1231 "ipv4:192.0.2.89" : [[100, 100, 100, 100, 100, 150, 1232 200, 300, 300, 300, 300, 250, 1233 250, 300, 300, 300, 300, 300, 1234 400, 250, 250, 200, 150, 150], 1235 [ 20, 400, 20, 80, 80, 90, 1236 100, 90, 60, 40, 30, 20]], 1237 "ipv4:198.51.100.34" : [[ 80, 80, 80, 80, 150, 150, 1238 250, 400, 400, 450, 400, 200, 1239 200, 350, 400, 400, 400, 350, 1240 500, 200, 200, 200, 100, 100], 1241 [ 20, 20, 50, 30, 30, 30, 1242 30, 40, 40, 30, 20, 20]], 1243 "ipv4:203.0.113.45" : [[300, 400, 250, 250, 200, 150, 1244 150, 100, 100, 100, 100, 100, 1245 100, 100, 100, 100, 100, 150, 1246 200, 300, 300, 300, 300, 250], 1247 [100, 90, 80, 60, 50, 50, 1248 40, 40, 60, 90, 100, 80]], 1249 "ipv6:2001:db8::10" : [[200, 250, 300, 300, 300, 300, 1250 250, 300, 300, 300, 300, 350, 1251 300, 400, 250, 150, 100, 100, 1252 100, 150, 200, 250, 250, 300], 1253 [ 40, 40, 40, 40, 50, 50, 1254 50, 20, 10, 15, 30, 40]] 1255 } 1256 } 1257 } 1259 When receiving the response, the Client sees that the Calendar values 1260 for metric "routingcost" are repeated for 4 iterations. Therefore, 1261 in its next requests until the "routingcost" Calendar is expected to 1262 change, the Client will only need to request a Calendar for 1263 "owdelay". 1265 Without the ALTO Calendar extensions, the ALTO Client would have no 1266 clue on the dynamicity of the metric value change and would spend 1267 needless time requesting values at an inappropriate pace. In 1268 addition, without the Multi-Cost ALTO capabilities, the ALTO Client 1269 would duplicate this waste of time as it would need to send one 1270 request per cost metric. 1272 6. IANA Considerations 1274 This document does not define any new media types or introduce any 1275 new IANA considerations. 1277 7. Security Considerations 1279 As an extension of the base ALTO protocol [RFC7285], this document 1280 fits into the architecture of the base protocol, and hence the 1281 Security Considerations (Section 15) of the base protocol fully apply 1282 when this extension is provided by an ALTO Server. For example, the 1283 same authenticity and integrity considerations (Section 15.1 of 1284 [RFC7285] still fully apply; the same considerations for the privacy 1285 of ALTO users (Section 15.4 of [RFC7285]) also still fully apply. 1287 The calendaring information provided by this extension requires 1288 additional considerations on three security considerations discussed 1289 in the base protocol: potential undesirable guidance to Clients 1290 (Section 15.2 of [RFC7285]), confidentiality of ALTO information 1291 (Section 15.2 of [RFC7285]), and availability of ALTO (Section 15.5 1292 of [RFC7285]). For example, by providing network information in the 1293 future in a Calendar, this extension may improve availability of 1294 ALTO, when the ALTO Server is unavailable but related information is 1295 already provided in the Calendar. 1297 For confidentiality of ALTO information, an operator should be 1298 cognizant that this extension may introduce a new risk: a malicious 1299 ALTO Client may get information for future events that are scheduled 1300 through Calendaring. Possessing such information, the malicious 1301 Client may use it to generate massive connections to the network at 1302 times where its load is expected to be high. 1304 To mitigate this risk, the operator should address the risk of ALTO 1305 information being leaked to malicious Clients or third parties. As 1306 specified in Section 15.3.2 ("Protection Strategies") of [RFC7285], 1307 the ALTO Server should authenticate ALTO Clients and use the 1308 Transport Layer Security (TLS) protocol so that Man In The Middle 1309 (MITM) attacks to intercept an ALTO Calendar are not possible. 1310 [RFC7285] ensures the availability of such a solution in its 1311 Section 8.3.5. "Authentication and Encryption", which specifies 1312 that: "ALTO Server implementations as well as ALTO Client 1313 implementations MUST support the "https" URI scheme of [RFC2818] and 1314 Transport Layer Security (TLS) of [RFC5246]". 1316 [RFC8446] specifies TLS 1.3 and writes in its section 1: "While TLS 1317 1.3 is not directly compatible with previous versions, all versions 1318 of TLS incorporate a versioning mechanism which allows Clients and 1319 Servers to interoperably negotiate a common version if one is 1320 supported by both peers". ALTO Clients and Servers SHOULD support 1321 both TLS 1.3 [RFC8446] and TLS 1.2 [RFC5246], and MAY support and use 1322 newer versions of TLS as long as the negotiation process succeeds. 1324 The operator should be cognizant that the preceding mechanisms do not 1325 address all security risks. In particular, they will not help in the 1326 case of "malicious Clients" possessing valid credentials to 1327 authenticate. The threat here can be that legitimate Clients have 1328 become subverted by an attacker and are now 'bots' being asked to 1329 participate in a DDoS attack. The Calendar information would be 1330 valuable information for when to persecute a DDoS attack. A 1331 mechanism such as a monitoring system that detects abnormal behaviors 1332 may still be needed. 1334 To avoid malicious or erroneous guidance from ALTO information, an 1335 ALTO Client should be cognizant that using calendaring information 1336 can have risks: (1) Calendar values, especially in "repeated" 1337 Calendars may be only statistical, and (2) future events may change. 1338 Hence, a more robust ALTO Client should adapt and extend protection 1339 strategies specified in Section 15.2 of the base protocol. For 1340 example, to be notified immediately when a particular ALTO value that 1341 the Client depends on changes, it is RECOMMENDED that both the ALTO 1342 Client and ALTO Server using this extension support "ALTO Incremental 1343 Updates Using Server-Sent Events(SSE)" Service 1344 [I-D.ietf-alto-incr-update-sse]. 1346 8. Operational Considerations 1348 It is important that both the operator of the network and the 1349 operator of the applications consider both the feedback aspect and 1350 the prediction-based (uncertainty) aspect of using the Cost Calendar. 1352 First consider the feedback aspect and consider the Cost Calendar as 1353 a traffic-aware map service (e.g., Google Maps). Using the service 1354 without considering its own effect, a large fleet can turn a not- 1355 congested road into a congested one; a large number of individual 1356 cars each choosing a road with light traffic ("cheap link") can also 1357 result in congestion or result in a less optimal global outcome 1358 (e.g., the Braess' Paradox [Braess-paradox]). 1360 Next consider the prediction aspect. Conveying ALTO Cost Calendars 1361 tends to reduce the on-the-wire data exchange volume compared to 1362 multiple single cost ALTO transactions. An application using 1363 Calendars has a set of time-dependent values upon which it can plan 1364 its connections in advance with no need for the ALTO Client to query 1365 information at each time. Additionally, the Calendar response 1366 attribute "repeated", when provided, saves additional data exchanges 1367 in that it indicates that the ALTO Client does not need to query 1368 Calendars during a period indicated by this attribute. The preceding 1369 is true only when "accidents" do not happen. 1371 Although individual network operators and application operators can 1372 choose their own approaches to address the aforementioned issues, 1373 this document recommends the following considerations. First, a 1374 typical approach to reducing instability and handling uncertainty is 1375 to ensure timely update of information. The SSE Service as discussed 1376 in Section 7 can handle updates, if supported by both the Server and 1377 the Client. Second, when a network operator updates the Cost 1378 Calendar and when an application reacts to the update, they should 1379 consider the feedback effects. This is the best approach even though 1380 there is theoretical analysis [Selfish-routing-Roughgarden-thesis] 1381 and Internet based evaluation [Selfish-routing-Internet-eval] showing 1382 that uncoordinated behaviors do not always cause substantial sub- 1383 optimal results. 1385 High-resolution intervals may be needed when values change, sometimes 1386 during very small time intervals but in a significant manner. A way 1387 to avoid conveying too many entries is to leverage on the "repeated" 1388 feature. A Server can smartly set the Calendar start time and number 1389 of intervals so as to declare them "repeated" for a large number of 1390 periods, until the Calendar values change and are conveyed to 1391 requesting Clients. 1393 The newer JSON Data Interchange Format specification [RFC8259] used 1394 in ALTO Calendars replaces the older one [RFC7159] used in the base 1395 ALTO protocol [RFC7285]. The newer JSON mandates UTF-8 text encoding 1396 to improve interoperability. Therefore, ALTO Clients and Servers 1397 implementations using UTF-{16,32} need to be cognizant of the 1398 subsequent interoperability risks and MUST switch to UTF-8 encoding, 1399 if they want to interoperate with Calendar-aware Servers and Clients. 1401 9. Acknowledgements 1403 The authors would like to thank Fred Baker, Li Geng, Diego Lopez, He 1404 Peng and Haibin Song for fruitful discussions and feedback on earlier 1405 draft versions. Dawn Chan, Kai Gao, Vijay Gurbani, Yichen Qian, 1406 Juergen Schoenwaelder, and Brian Weis and Jensen Zhang provided 1407 substantial review feedback and suggestions to the protocol design. 1409 10. References 1411 10.1. Normative References 1413 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1414 Requirement Levels", BCP 14, RFC 2119, 1415 DOI 10.17487/RFC2119, March 1997, 1416 . 1418 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1419 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1420 DOI 10.17487/RFC7231, June 2014, 1421 . 1423 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1424 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1425 "Application-Layer Traffic Optimization (ALTO) Protocol", 1426 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1427 . 1429 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1430 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1431 May 2017, . 1433 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1434 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1435 DOI 10.17487/RFC8189, October 2017, 1436 . 1438 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1439 Interchange Format", STD 90, RFC 8259, 1440 DOI 10.17487/RFC8259, December 2017, 1441 . 1443 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1444 (TLS) Protocol Version 1.2", RFC 5246, 1445 DOI 10.17487/RFC5246, August 2008, 1446 . 1448 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 1449 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 1450 . 1452 [I-D.ietf-alto-incr-update-sse] 1453 Roome, W. and Y. Yang, "ALTO Incremental Updates Using 1454 Server-Sent Events (SSE)", draft-ietf-alto-incr-update- 1455 sse-20 (work in progress), February 2020. 1457 [IEEE.754.2008] 1458 "Standard for Binary Floating-Point Arithmetic, IEEE 1459 Standard 754", August 2008. 1461 10.2. Informative References 1463 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1464 DOI 10.17487/RFC2818, May 2000, 1465 . 1467 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 1468 Optimization (ALTO) Problem Statement", RFC 5693, 1469 DOI 10.17487/RFC5693, October 2009, 1470 . 1472 [RFC6708] Kiesel, S., Ed., Previdi, S., Stiemerling, M., Woundy, R., 1473 and Y. Yang, "Application-Layer Traffic Optimization 1474 (ALTO) Requirements", RFC 6708, DOI 10.17487/RFC6708, 1475 September 2012, . 1477 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1478 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1479 2014, . 1481 [I-D.ietf-alto-performance-metrics] 1482 WU, Q., Yang, Y., Lee, Y., Dhody, D., and S. Randriamasy, 1483 "ALTO Performance Cost Metrics", draft-ietf-alto- 1484 performance-metrics-08 (work in progress), November 2019. 1486 [I-D.xiang-alto-multidomain-analytics] 1487 Xiang, Q., Le, F., Yang, Y., Newman, H., and H. Du, 1488 "Unicorn: Resource Orchestration for Multi-Domain, Geo- 1489 Distributed Data Analytics", draft-xiang-alto-multidomain- 1490 analytics-02 (work in progress), July 2018. 1492 [SENSE-sdn-e2e-net] 1493 "SDN for End-to-End Networked Science at the Exascale 1494 (SENSE), http://sense.es.net/overview". 1496 [Braess-paradox] 1497 Steinberg, R. and W. Zangwill, "The Prevalence of Braess' 1498 Paradox", Transportation Science Vol. 17 No. 3, August 1499 1983. 1501 [Selfish-routing-Roughgarden-thesis] 1502 Roughgarden, T., "Selfish Routing", Dissertation Thesis, 1503 Cornell 2002, May 2002. 1505 [Selfish-routing-Internet-eval] 1506 Qiu, L., Yang, Y., Zhang, Y., and S. Shenker, "Selfish 1507 Routing in Internet-LIke Environments", Proceedings of ACM 1508 SIGCOMM 2001, August 2001. 1510 Authors' Addresses 1512 Sabine Randriamasy 1513 Nokia Bell Labs 1514 Route de Villejust 1515 NOZAY 91460 1516 FRANCE 1518 Email: Sabine.Randriamasy@nokia-bell-labs.com 1520 Richard Yang 1521 Yale University 1522 51 Prospect st 1523 New Haven, CT 06520 1524 USA 1526 Email: yry@cs.yale.edu 1527 Qin Wu 1528 Huawei 1529 101 Software Avenue, Yuhua District 1530 Nanjing, Jiangsu 210012 1531 China 1533 Email: sunseawq@huawei.com 1535 Lingli Deng 1536 China Mobile 1537 China 1539 Email: denglingli@chinamobile.com 1541 Nico Schwan 1542 Thales Deutschland 1543 Lorenzstrasse 10 1544 Stuttgart 70435 1545 Germany 1547 Email: nico.schwan@thalesgroup.com