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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ALTO WG G. Bernstein 3 Internet-Draft Grotto Networking 4 Intended status: Standards Track S. Chen 5 Expires: January 3, 2019 Tongji University 6 K. Gao 7 Tsinghua University 8 Y. Lee 9 Huawei 10 W. Roome 11 M. Scharf 12 Nokia 13 Y. Yang 14 Yale University 15 J. Zhang 16 Tongji University 17 July 2, 2018 19 ALTO Extension: Path Vector Cost Type 20 draft-ietf-alto-path-vector-04 22 Abstract 24 The Application-Layer Traffic Optimization (ALTO) protocol [RFC7285] 25 has defined cost maps and endpoint cost maps to provide basic network 26 information. However, they provide only scalar (numerical or 27 ordinal) cost mode values, which are insufficient to satisfy the 28 demands of solving more complex network optimization problems. This 29 document introduces an extension to the base ALTO protocol, namely 30 the path-vector extension, which allows ALTO clients to query 31 information such as capacity regions for a given set of flows. A 32 non-normative example called multi-flow scheduling is presented to 33 illustrate the limitations of existing ALTO endpoint cost maps. 34 After that, details of the extension are defined. 36 Requirements Language 38 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 39 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 40 document are to be interpreted as described in RFC 2119 [RFC2119]. 42 Status of This Memo 44 This Internet-Draft is submitted in full conformance with the 45 provisions of BCP 78 and BCP 79. 47 Internet-Drafts are working documents of the Internet Engineering 48 Task Force (IETF). Note that other groups may also distribute 49 working documents as Internet-Drafts. The list of current Internet- 50 Drafts is at https://datatracker.ietf.org/drafts/current/. 52 Internet-Drafts are draft documents valid for a maximum of six months 53 and may be updated, replaced, or obsoleted by other documents at any 54 time. It is inappropriate to use Internet-Drafts as reference 55 material or to cite them other than as "work in progress." 57 This Internet-Draft will expire on January 3, 2019. 59 Copyright Notice 61 Copyright (c) 2018 IETF Trust and the persons identified as the 62 document authors. All rights reserved. 64 This document is subject to BCP 78 and the IETF Trust's Legal 65 Provisions Relating to IETF Documents 66 (https://trustee.ietf.org/license-info) in effect on the date of 67 publication of this document. Please review these documents 68 carefully, as they describe your rights and restrictions with respect 69 to this document. Code Components extracted from this document must 70 include Simplified BSD License text as described in Section 4.e of 71 the Trust Legal Provisions and are provided without warranty as 72 described in the Simplified BSD License. 74 Table of Contents 76 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 77 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 78 3. Use Case: Capacity Region for Multi-Flow Scheduling . . . . . 5 79 4. Overview of Path Vector Extensions . . . . . . . . . . . . . 7 80 4.1. New Cost Type to Encode Path Vectors . . . . . . . . . . 7 81 4.2. New ALTO Entity Domain to Provide ANE Properties . . . . 8 82 4.3. Extended Cost Map/Endpoint Cost Service for Compound 83 Resources . . . . . . . . . . . . . . . . . . . . . . . . 8 84 5. Cost Type . . . . . . . . . . . . . . . . . . . . . . . . . . 8 85 5.1. Cost Mode: array . . . . . . . . . . . . . . . . . . . . 9 86 5.2. Cost Metric: ane-path . . . . . . . . . . . . . . . . . . 9 87 5.3. Path Vector Cost Type Semantics . . . . . . . . . . . . . 9 88 6. ANE Domain . . . . . . . . . . . . . . . . . . . . . . . . . 10 89 6.1. Domain Name . . . . . . . . . . . . . . . . . . . . . . . 10 90 6.2. Domain-Specific Entity Addresses . . . . . . . . . . . . 10 91 6.3. Hierarchy and Inheritance . . . . . . . . . . . . . . . . 10 92 7. Protocol Extensions for Path Vector Compound Query . . . . . 10 93 7.1. Filtered Cost Map Extensions . . . . . . . . . . . . . . 11 94 7.1.1. Capabilities . . . . . . . . . . . . . . . . . . . . 11 95 7.1.2. Accept Input Parameters . . . . . . . . . . . . . . . 12 96 7.1.3. Response . . . . . . . . . . . . . . . . . . . . . . 12 98 7.2. Endpoint Cost Service Extensions . . . . . . . . . . . . 12 99 7.2.1. Capabilities . . . . . . . . . . . . . . . . . . . . 13 100 7.2.2. Accept Input Parameters . . . . . . . . . . . . . . . 13 101 7.2.3. Response . . . . . . . . . . . . . . . . . . . . . . 13 102 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13 103 8.1. Workflow . . . . . . . . . . . . . . . . . . . . . . . . 13 104 8.2. Information Resource Directory Example . . . . . . . . . 14 105 8.3. Example # 1 . . . . . . . . . . . . . . . . . . . . . . . 16 106 8.4. Example # 2 . . . . . . . . . . . . . . . . . . . . . . . 18 107 8.5. Example #3 . . . . . . . . . . . . . . . . . . . . . . . 20 108 9. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 22 109 9.1. Compatibility with Legacy ALTO Clients/Servers . . . . . 22 110 9.2. Compatibility with Multi-Cost Extension . . . . . . . . . 23 111 9.3. Compatibility with Incremental Update . . . . . . . . . . 23 112 10. General Discussions . . . . . . . . . . . . . . . . . . . . . 23 113 10.1. Provide Calendar for Property Map . . . . . . . . . . . 23 114 10.2. Constraint Tests for General Cost Types . . . . . . . . 24 115 10.3. General Compound Resources Query . . . . . . . . . . . . 24 116 11. Security Considerations . . . . . . . . . . . . . . . . . . . 24 117 11.1. Privacy Concerns . . . . . . . . . . . . . . . . . . . . 24 118 11.2. Resource Consumption on ALTO Servers . . . . . . . . . . 25 119 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 120 12.1. ALTO Cost Mode Registry . . . . . . . . . . . . . . . . 25 121 12.2. ALTO Cost Metric Registry . . . . . . . . . . . . . . . 25 122 12.3. ALTO Domain Registry . . . . . . . . . . . . . . . . . . 25 123 12.4. ALTO Network Element Property Type Registry . . . . . . 26 124 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 125 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 126 14.1. Normative References . . . . . . . . . . . . . . . . . . 26 127 14.2. Informative References . . . . . . . . . . . . . . . . . 26 128 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 130 1. Introduction 132 The base ALTO protocol [RFC7285] is designed to expose network 133 information through services such as cost map and endpoint cost 134 service. These services use an extreme "single-node" network view 135 abstraction, which represents the whole network with a single node 136 and hosts with "endpoint groups" directly connected to the node. 138 Although the "single-node" network view abstraction works well in 139 many settings, it lacks the ability to support emerging use cases, 140 such as applications requiring large bandwidth or latency sensitivity 141 [I-D.bernstein-alto-topo], and inter-datacenter data transfers 142 [I-D.lee-alto-app-net-info-exchange]. For these use cases, 143 applications require a more powerful network view abstraction beyond 144 the "single-node" abstraction to support application capabilities, in 145 particular, the ability multi-flow scheduling. 147 To support capabilities like multi-flow scheduling, this document 148 uses a "path vector" abstraction to represent more detailed network 149 graph information like capacity regions. The path vector abstraction 150 uses path vectors with abstract network elements to provide network 151 graph view for applications. A path vector consists of a sequence of 152 Abstract Network Elements (ANEs) that end-to-end traffic goes 153 through. ANEs can be links, switches, middleboxes, their 154 aggregations, etc.; they have properties like "bandwidth", "delay", 155 etc. These information may help the application avoid network 156 congestion and achieve better application performance. 158 Providing path vector abstraction using ALTO introduces the following 159 additional requirements (ARs): 161 AR-1: The ALTO protocol SHOULD include the support for encoding 162 array-like cost values rather than scalar cost values in cost maps 163 or endpoint cost maps. 165 The ALTO server providing path vector abstraction SHOULD convey 166 sequences of ANEs between sources and destinations the ALTO client 167 requests. Theses information cannot be encoded by the scalar 168 types (numerical or ordinal) which the base ALTO protocol 169 supports. A new cost type is required to encode path vectors as 170 costs. 172 AR-2: The ALTO protocol SHOULD include the support for encoding 173 properties of ANEs. 175 Only the sequences of ANEs are not enough for most use cases 176 mentioned previously. The properties of ANEs like "bandwidth" and 177 "delay" are required by applications to build the capacity region 178 or realize the latency sensitivity. 180 AR-3: The ALTO server SHOULD allow the ALTO client to query path 181 vectors and the properties of abstract network elements 182 consistently. 184 Path vectors and the properties of abstract network elements are 185 correlated information, but can be separated into different ALTO 186 information resources. A mechanism to query both of them 187 consistently is necessary. 189 This document proposes the path vector extension which satisfies 190 these additional requirements to the ALTO protocol. Specifically, 191 the ALTO protocol encodes the array of ANEs over an end-to-end path 192 using a new cost type, and conveys the properties of ANEs using 193 unified property map [I-D.ietf-alto-unified-props-new]. We also 194 provide an optional solution to query separated path vectors and 195 properties of ANEs in a consistent way. But querying general 196 separated resources consistently is not the scope in this document. 198 The rest of this document is organized as follows. Section 3 gives 199 an example of multi-flow scheduling and illustrates the limitations 200 of the base ALTO protocol in such a use case. Section 4 gives an 201 overview of the path vector extension. Section 5 introduces a new 202 cost type. Section 6 registers a new domain in Domain Registry. 203 Section 7 extends Filtered Cost Map and Endpoint Cost Service to 204 support the compound resource query. Section 8 presents several 205 examples. Section 9 and Section 10 discusses compatibility issues 206 with other existing ALTO extensions and design decisions. Section 11 207 and Section 12 review the security and IANA considerations. 209 2. Terminology 211 Besides the terms defined in [RFC7285] and 212 [I-D.ietf-alto-unified-props-new], this document also uses the 213 following additional terms: Abstract Network Element, Path Vector. 215 o Abstract Network Element (ANE): An abstract network element is an 216 abstraction of network components; it can be an aggregation of 217 links, middle boxes, virtualized network function (VNF), etc. An 218 abstract network element has two types of attributes: a name and a 219 set of properties. 221 o Path Vector: A path vector is an array of ANEs. It presents an 222 abstract network path between source/destination points such as 223 PIDs or endpoints. 225 3. Use Case: Capacity Region for Multi-Flow Scheduling 227 Assume that an application has control over a set of flows, which may 228 go through shared links or switches and share a bottleneck. The 229 application hopes to schedule the traffic among multiple flows to get 230 better performance. The capacity region information for those flows 231 will benefit the scheduling. However, existing cost maps can not 232 reveal such information. 234 Specifically, consider a network as shown in Figure 1. The network 235 has 7 switches (sw1 to sw7) forming a dumb-bell topology. Switches 236 sw1/sw3 provide access on one side, sw2/sw4 provide access on the 237 other side, and sw5-sw7 form the backbone. Endhosts eh1 to eh4 are 238 connected to access switches sw1 to sw4 respectively. Assume that 239 the bandwidth of link eh1 -> sw1 and link sw1 -> sw5 are 150 Mbps, 240 and the bandwidth of the rest links are 100 Mbps. 242 +------+ 243 | | 244 --+ sw6 +-- 245 / | | \ 246 PID1 +-----+ / +------+ \ +-----+ PID2 247 eh1__| |_ / \ ____| |__eh2 248 | sw1 | \ +--|---+ +---|--+ / | sw2 | 249 +-----+ \ | | | |/ +-----+ 250 \_| sw5 +---------+ sw7 | 251 PID3 +-----+ / | | | |\ +-----+ PID4 252 eh3__| |__/ +------+ +------+ \____| |__eh4 253 | sw3 | | sw4 | 254 +-----+ +-----+ 256 Figure 1: Raw Network Topology. 258 The single-node ALTO topology abstraction of the network is shown in 259 Figure 2. 261 +----------------------+ 262 {eh1} | | {eh2} 263 PID1 | | PID2 264 +------+ +------+ 265 | | 266 | | 267 {eh3} | | {eh4} 268 PID3 | | PID4 269 +------+ +------+ 270 | | 271 +----------------------+ 273 Figure 2: Base Single-Node Topology Abstraction. 275 Consider an application overlay (e.g., a large data analysis system) 276 which wants to schedule the traffic among a set of end host source- 277 destination pairs, say eh1 -> eh2 and eh1 -> eh4. The application 278 can request a cost map providing end-to-end available bandwidth, 279 using "availbw" as cost-metric and "numerical" as cost-mode. 281 The application will receive from ALTO server that the bandwidth of 282 eh1 -> eh2 and eh1 -> eh4 are both 100 Mbps. But this information is 283 not enough. Consider the following two cases: 285 o Case 1: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw6 -> 286 sw7 -> sw2 -> eh2 and eh1 -> eh4 uses path eh1 -> sw1 -> sw5 -> 287 sw7 -> sw4 -> eh4, then the application will obtain 150 Mbps at 288 most. 290 o Case 2: If eh1 -> eh2 uses the path eh1 -> sw1 -> sw5 -> sw7 -> 291 sw2 -> eh2 and eh1 -> eh4 uses the path eh1 -> sw1 -> sw5 -> sw7 292 -> sw4 -> eh4, then the application will obtain only 100 Mbps at 293 most. 295 To allow applications to distinguish the two aforementioned cases, 296 the network needs to provide more details. In particular: 298 o The network needs to expose more detailed routing information to 299 show the shared bottlenecks. 301 o The network needs to provide the necessary abstraction to hide the 302 real topology information while providing enough information to 303 applications. 305 The path vector extension defined in this document propose a solution 306 to provide these details. 308 See [I-D.bernstein-alto-topo] for a more comprehensive survey of use 309 cases where extended network topology information is needed. 311 4. Overview of Path Vector Extensions 313 This section presents an overview of approaches adopted by the path 314 vector extension. It assumes the readers are familiar with cost map 315 and endpoint cost service defined in [RFC7285]. The path vector 316 extension also requires the support of Filtered Property Map defined 317 in [I-D.ietf-alto-unified-props-new]. 319 The path vector extension is composed of three building blocks: (1) a 320 new cost type to encode path vectors; (2) a new ALTO entity domain 321 for unified property extension [I-D.ietf-alto-unified-props-new] to 322 encode properties of ANEs; and (3) an extension to the cost map and 323 endpoint cost resource to provide path vectors and properties of ANEs 324 in a single response. 326 4.1. New Cost Type to Encode Path Vectors 328 Existing cost types defined in [RFC7285] allow only scalar cost 329 values. However, the "path vector" abstraction requires to convey 330 vector format information. To achieve this requirement, this 331 document defines a new cost mode to enable the cost value to carry an 332 array of elements, and a new cost metric to take names of ANEs as 333 elements in the array. We call such an array of ANEs a path vector. 334 In this way, the cost map and endpoint cost service can convey the 335 path vector to represent the routing information. Detailed 336 information and specifications are given in Section 5.1 and 337 Section 5.2. 339 4.2. New ALTO Entity Domain to Provide ANE Properties 341 The path vector can only represent the route between the source and 342 the destination. Although the application can find the shared ANEs 343 among different paths, it is not enough for most use cases, which 344 requires the bandwidth or delay information of the ANEs. So this 345 document adopts the property map defined in 346 [I-D.ietf-alto-unified-props-new] to provide the general properties 347 of ANEs. The document registers a new entity domain called "ane" to 348 represent the ANE. The address of the ANE entity is just the ANE 349 name used by the path vector. By requesting the property map of 350 entities in the "ane" domain, the client can retrieve the properties 351 of ANEs in path vectors. 353 4.3. Extended Cost Map/Endpoint Cost Service for Compound Resources 355 Providing the path vector information and the ANE properties by 356 separated resources have several known benefits: (1) can be better 357 compatible with the base ALTO protocol; (2) can make different 358 property map resources reuse the same cost map or endpoint cost 359 resource. However, it conducts two issues: 361 o Efficiency: The separated resources will require the ALTO client 362 to invoke multiple requests/responses to collect all needed 363 information. It increases the communication overhead. 365 o Consistency: The path vectors and properties of ANEs are 366 correlated. So querying them one by one may conduct consistency 367 issue. Once the path vector changes during the client requests 368 the ANE properties, the ANE properties may be inconsistent with 369 the previous path vector. 371 To solve these issues, this document introduces an extension to cost 372 map and endpoint cost service, which allows the ALTO server to attach 373 a property map in the data entry of a cost map or an endpoint cost 374 service response. 376 These issues may exist in all general cases for querying separated 377 ALTO information resources. But solving this general problem is not 378 in the scope of this document. 380 5. Cost Type 382 This document extends the cost types defined in Section 6.1 of 383 [RFC7285] by introducing a new cost mode "array" and a new cost 384 metric "ane-path". In the rest content, this document uses "path- 385 vector" to indicate the combination cost type of the cost mode 386 "array" and the cost metric "ane-path". 388 5.1. Cost Mode: array 390 This document extends the CostMode defined in Section 10.5 of 391 [RFC7285] with a new cost mode: "array". This cost mode indicates 392 that every cost value in a cost map represents an array rather than a 393 simple value. The values are arrays of JSONValue. The specific type 394 of each element in the array depends on the cost metric. 396 5.2. Cost Metric: ane-path 398 This document specifies a new cost metric: "ane-path". This cost 399 metric indicates that the cost value is a list of ANEs which the path 400 from a source to a destination goes across. The values are arrays of 401 ANE names which are defined in Section 6.2. 403 The cost metric "ane-path" SHOULD NOT be used when the cost mode is 404 not "array" unless it is explicitly specified by a future extension. 405 If an ALTO client send queries with the cost metric "ane-path" and a 406 non "array" cost mode, the ALTO server SHOULD return an error with 407 the error code "E_INVALID_FIELD_VALUE"; If an ALTO server declares 408 the support of a cost type with the cost metric "ane-path" and a non 409 "array" cost mode, the ALTO client SHOULD assume such a cost type is 410 invalid and ignore it. 412 5.3. Path Vector Cost Type Semantics 414 The new cost type follows the convention of the cost types in the 415 base ALTO protocol. Table 1 lists some of the current defined cost 416 types and their semantics. 418 +------------+--------------+---------------------------------------+ 419 | Cost Mode | Cost Metric | Semantics | 420 +------------+--------------+---------------------------------------+ 421 | numerical | routingcost | a number representing the routing | 422 | | | cost | 423 | numerical | hopcount | a number representing the hop count | 424 | ordinal | routingcost | a ranking representing the routing | 425 | | | cost | 426 | ordinal | hopcount | a ranking representing the hop count | 427 | array | ane-path | a list representing the ane path | 428 +------------+--------------+---------------------------------------+ 430 Table 1: Cost Types and Their Semantics 432 The "routingcost" and "hopcount" can encoded in "numerical" or 433 "ordinal", however, the cost metric "ane-path" can only be applied to 434 the cost mode "array" defined in this document to convey path vector 435 information. The cost metric "ane-path" can not be used in 436 "numerical" or "ordinal" unless it is defined in future extensions. 437 If the ALTO server declares that it support cost type with cost 438 metric being "ane-path" and cost mode not being "array", the ALTO 439 client SHOULD ignore them. 441 6. ANE Domain 443 This document specifies a new ALTO entity domain called "ane" in 444 addition to the ones in [I-D.ietf-alto-unified-props-new]. The ANE 445 domain associates property values with the ANEs in a network. The 446 entity in ANE domain is often used in the path vector by cost maps or 447 endpoint cost resources. Accordingly, the ANE domain always depends 448 on a cost map or an endpoint cost map. 450 6.1. Domain Name 452 ane 454 6.2. Domain-Specific Entity Addresses 456 The entity address of ane domain is encoded as a JSON string. The 457 string MUST be no more than 64 characters, and it MUST NOT contain 458 characters other than US-ASCII alphanumeric characters 459 (U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ("-", 460 U+002D), the colon (":", U+003A), the at sign ("@", code point 461 U+0040), the low line ("_", U+005F), or the "." separator (U+002E). 462 The "." separator is reserved for future use and MUST NOT be used 463 unless specifically indicated in this document, or an extension 464 document. 466 To simplify the description, we use "ANE name" to indicate the 467 address of an entity in ANE domain in this document. 469 The ANE name is usually unrelated to the physical device information. 470 It is usually generated by the ALTO server on demand and used to 471 distinguish from other ANEs in its dependent cost map or endpoint 472 cost map. 474 6.3. Hierarchy and Inheritance 476 There is no hierarchy or inheritance for properties associated with 477 ANEs. 479 7. Protocol Extensions for Path Vector Compound Query 481 To make the ALTO client query the path vectors and properties of ANEs 482 efficiently and consistently, this document extends the Filtered Cost 483 Map and Endpoint Cost Service. 485 7.1. Filtered Cost Map Extensions 487 This document extends Filtered Cost Map, as defined in Section 11.3.2 488 of [RFC7285], by adding new input parameters and capabilities, and by 489 augmenting the property map into the data entry of the response. 491 The "media type", "HTTP method", and "uses" specifications (described 492 in Sections 11.3.2.1, 11.3.2.2, and 11.3.2.5 of [RFC7285], 493 respectively) remain the same. 495 7.1.1. Capabilities 497 The Filtered Cost Map capabilities are extended with two new members: 499 o dependent-property-map 501 o allow-compound-response 503 The capability "dependent-property-map" indicates which property map 504 this resource depends on, and the capability "allow-compound- 505 response" indicates whether the ALTO server supports the resource to 506 compound the property map with its own response data. With these two 507 additional members, the FilteredCostMapCapabilities object in 508 Section 11.3.2.4 of [RFC7285] is extended as follows: 510 object { 511 [ResourceID dependent-property-map;] 512 [JSONBool allow-compound-response;] 513 } PVFCMCapabilities : FilteredCostMapCapabilities; 515 dependent-property-map: This field MUST be specified when the "cost- 516 type-names" includes a cost type name indicating a "ane-path" 517 metric. Its value MUST be a resource id indicating a property map 518 including "ane" domain. If not, the ALTO client SHOULD consider 519 this resource is invalid. 521 allow-compound-response: If present, the true value means the ALTO 522 client can request the resource to augment its dependent property 523 map into the response automatically; the false value means the 524 ALTO client cannot request the compound response. If omitted, the 525 default value is false; 527 To be noticed that the capability "cost-constraints" is unexpected 528 for the "array" cost mode. The syntax and semantics of constraint 529 tests on the "array" cost mode depends on the implementation and can 530 be defined in the future documents. But it is not in the scope of 531 this document. 533 7.1.2. Accept Input Parameters 535 The ReqFilteredCostMap object in Section 11.3.2.3 of [RFC7285] is 536 extended as follows: 538 object { 539 [PropertyName compound-properties<1..*>;] 540 } ReqPVFilteredCostMap : ReqFilteredCostMap; 542 compound-properties: If the capability "allow-compound-response" is 543 false, the ALTO client MUST NOT specify this field, and the ALTO 544 server MUST reject the request and return "E_INVALID_FILED_VALUE" 545 error when it receives a request including this field. If this 546 field is specified and accepted, the ALTO server MUST augment the 547 dependent property map with the properties in this field into the 548 response automatically. 550 7.1.3. Response 552 If the ALTO client specifies the "cost-type" input parameter with 553 "ane-path" metric, the "dependent-vtags" field in the "meta" field of 554 the response MUST include the version tag of its dependent property 555 map following its dependent network map. 557 If the ALTO client specifies the "compound-properties" input 558 parameter which is accepted by the ALTO server, the response MUST 559 include a "property-map" field following the "cost-map" field, and 560 its value MUST be a PropertyMapData object. This PropertyMapData 561 object MUST be equivalent to the result when query the dependent 562 property map resource using the following request: the "entities" 563 field includes all the ANE names appearing in the cost values of the 564 "cost-map" field, the "properties" field has the same value as the 565 "compound-properties" field does. The properties shown in the 566 "compound-properties" input parameter but are not supported by the 567 dependent property map SHOULD be omitted from the response. 569 7.2. Endpoint Cost Service Extensions 571 This document extends the Endpoint Cost Service, as defined in 572 Section 11.5.1 of [RFC7285], by adding new input parameters and 573 capabilities and by augmenting the property map into the data entry 574 of the response. 576 The media type, HTTP method, and "uses" specifications (described in 577 Sections 11.5.1.1, 11.5.1.2, and 11.5.1.5 of [RFC7285], respectively) 578 are unchanged. 580 7.2.1. Capabilities 582 The extensions to the Endpoint Cost Service capabilities are 583 identical to the extensions to the Filtered Cost Map (see 584 Section 7.1.1). 586 7.2.2. Accept Input Parameters 588 The ReqEndpointCostMap object in Section 11.5.1.3 of [RFC7285] is 589 extended as follows: 591 object { 592 [PropertyName compound-properties<1..*>;] 593 } ReqPVEndpointCostMap : ReqEndpointCostMap; 595 The "compound-properties" has the same interpretation as defined in 596 Section 7.1.2 598 7.2.3. Response 600 If the ALTO client specifies the "cost-type" input parameter with 601 "ane-path" metric, the response MUST include the "meta" field with 602 the "dependent-vtags" in it, and the "dependent-vtags" field MUST 603 include the version tag of its dependent property map. 605 If the ALTO client specifies the "compound-properties" input 606 parameter which is accepted by the ALTO server, the response MUST 607 include a "property-map" field following the "endpoint-cost-map" 608 field, and its value MUST be a PropertyMapData object. This 609 PropertyMapData object MUST be equivalent to the result when query 610 the dependent property map resource using the following request: the 611 "entities" field includes all the ANE names appearing in the cost 612 values of the "endpoint-cost-map" field, the "properties" field has 613 the same value as the "compound-properties" field does. The 614 properties shown in the "compound-properties" input parameter but are 615 not supported by the dependent property map SHOULD be omitted from 616 the response. 618 8. Examples 620 This section lists some examples of path vector queries and the 621 corresponding responses. 623 8.1. Workflow 625 This section gives a typical workflow of how an ALTO client query 626 path vectors using the extension. 628 1. Send a GET request for the whole Information Resource Directory. 630 2. Look for the resource of the (Filtered) Cost Map/Endpoint Cost 631 Service which supports the "ane-path" cost metric and get the 632 resource ID of the dependent property map. 634 3. Check whether the capabilities of the property map includes the 635 desired "prop-types". 637 4. Check whether the (Filtered) Cost Map/Endpoint Cost Service 638 allows the compound response. 640 1. If allowed, the ALTO client can send a request including the 641 desired ANE properties to the ALTO server and receive a 642 compound response with the cost map/endpoint cost map and the 643 property map. 645 2. If not allowed, the ALTO client sends a query for the cost 646 map/endpoint cost map first. After receiving the response, 647 the ALTO client interprets all the ANE names appearing in the 648 response and sends another query for the property map on 649 those ANE names. 651 8.2. Information Resource Directory Example 653 Here is an example of an Information Resource Directory. In this 654 example, filtered cost map "cost-map-pv" doesn't support the multi- 655 cost extension but support the path-vector extension, "endpoint- 656 multicost-map" supports both multi-cost extension and path-vector 657 extension. Filtered Property Map "propmap-availbw-delay" supports 658 properties "availbw" and "delay". 660 { 661 "meta": { 662 "cost-types": { 663 "path-vector": { 664 "cost-mode": "array", 665 "cost-metric": "ane-path" 666 }, 667 "num-routingcost": { 668 "cost-mode": "numerical", 669 "cost-metric": "routingcost" 670 }, 671 "num-hopcount": { 672 "cost-mode": "numerical", 673 "cost-metric": "hopcount" 674 } 675 } 677 }, 678 "resources": { 679 "my-default-networkmap": { 680 "uri" : "http://alto.example.com/networkmap", 681 "media-type" : "application/alto-networkmap+json" 682 }, 683 "my-default-cost-map": { 684 "uri": "http://alto.example.com/costmap/pv", 685 "media-type": "application/alto-costmap+json", 686 "accepts": "application/alto-costmapfilter+json", 687 "capabilities": { 688 "cost-type-names": [ "num-hopcount", 689 "num-routingcost" ] 690 }, 691 "uses": [ "my-default-networkmap" ] 692 }, 693 "cost-map-pv": { 694 "uri": "http://alto.example.com/costmap/pv", 695 "media-type": "application/alto-costmap+json", 696 "accepts": "application/alto-costmapfilter+json", 697 "capabilities": { 698 "cost-type-names": [ "path-vector" ], 699 "dependent-property-map": "propmap-availbw-delay" 700 }, 701 "uses": [ "my-default-networkmap" ] 702 }, 703 "endpoint-cost-pv": { 704 "uri": "http://alto.exmaple.com/endpointcost/pv", 705 "media-type": "application/alto-endpointcost+json", 706 "accepts": "application/alto-endpointcostparams+json", 707 "capabilities": { 708 "cost-type-names": [ "path-vector" ], 709 "dependent-property-map": "propmap-availbw-delay", 710 "allow-compound-response": true 711 } 712 }, 713 "invalid-cost-map" : { 714 "uri": "http://alto.example.com/costmap/invalid", 715 "media-type": "application/alto-costmap+json", 716 "accepts": "application/alto-costmapfilter+json", 717 "capabilities": { 718 "cost-type-names": [ "path-vector" ], 719 "allow-compound-response": true 720 }, 721 "uses": [ "my-default-networkmap" ] 722 }, 723 "propmap-availbw-delay": { 724 "uri": "http://alto.exmaple.com/propmap/ane-prop", 725 "media-type": "application/alto-propmap+json", 726 "accepts": "application/alto-propmapparams+json", 727 "capabilities": { 728 "domain-types": [ "ane" ], 729 "prop-types": [ "availbw", "delay" ] 730 }, 731 "uses": [ "cost-map-pv", "endpoint-cost-pv" ] 732 } 733 } 734 } 736 8.3. Example # 1 738 Query filtered cost map to get the path vectors. 740 POST /costmap/pv HTTP/1.1 741 Host: alto.example.com 742 Accept: application/alto-costmap+json, 743 application/alto-error+json 744 Content-Length: [TBD] 745 Content-Type: application/alto-costmapfilter+json 747 { 748 "cost-type": { 749 "cost-mode": "array", 750 "cost-metric": "ane-path" 751 }, 752 "pids": { 753 "srcs": [ "PID1" ], 754 "dsts": [ "PID2", "PID3" ] 755 } 756 } 757 HTTP/1.1 200 OK 758 Content-Length: [TBD] 759 Content-Type: application/alto-costmap+json 761 { 762 "meta": { 763 "dependent-vtags": [ 764 { 765 "resource-id": "my-default-networkmap", 766 "tag": "75ed013b3cb58f896e839582504f622838ce670f" 767 } 768 ], 769 "cost-type": { 770 "cost-mode": "array", 771 "cost-metric": "ane-path" 772 } 773 }, 774 "cost-map": { 775 "PID1": { 776 "PID2": [ "ane:L001", "ane:L003" ], 777 "PID3": [ "ane:L001", "ane:L004" ] 778 } 779 } 780 } 782 Then query the properties of ANEs in path vectors. 784 POST /propmap/ane-prop HTTP/1.1 785 Host: alto.example.com 786 Accept: application/alto-propmap+json, 787 application/alto-error+json 788 Content-Length: [TBD] 789 Content-Type: application/alto-propmapparams+json 791 { 792 "entities": [ "ane:L001", "ane:L003", "ane:L004" ], 793 "properties": [ "delay" ] 794 } 795 HTTP/1.1 200 OK 796 Content-Length: [TBD] 797 Content-Type: application/alto-propmap+json 799 { 800 "meta": { 801 "dependent-vtags": [ 802 { 803 "resource-id": "cost-map-pv", 804 "tag": "a7d57e120ab63124e3c9a82f7a54bc120fc96216" 805 } 806 ] 807 }, 808 "property-map": { 809 "ane:L001": { "delay": 46}, 810 "ane:L003": { "delay": 50}, 811 "ane:L004": { "delay": 70} 812 } 813 } 815 8.4. Example # 2 817 POST /endpointcost/pv HTTP/1.1 818 Host: alto.example.com 819 Accept: application/alto-endpointcost+json, 820 application/alto-error+json 821 Content-Length: [TBD] 822 Content-Type: application/alto-endpointcostparams+json 824 { 825 "multi-cost-types": [ 826 { 827 "cost-mode": "array", 828 "cost-metric": "ane-path" 829 }, 830 { 831 "cost-mode": "numerical", 832 "cost-metric": "routingcost" 833 } 834 ], 835 "endpoints": { 836 "srcs": [ "ipv4:192.0.2.2" ], 837 "dsts": [ "ipv4:192.0.2.89", 838 "ipv4:203.0.113.45", 839 "ipv6:2001:db8::10" ] 840 } 841 } 842 HTTP/1.1 200 OK 843 Content-Length: [TBD] 844 Content-Type: application/alto-endpointcost+json 846 { 847 "meta": { 848 "cost-type": [ 849 {"cost-mode": "array", "cost-metric": "ane-path"} 850 ] 851 }, 852 "endpoint-cost-map": { 853 "ipv4:192.0.2.2": { 854 "ipv4:192.0.2.89": [ "ane:L001", "ane:L003", 855 "ane:L004" ], 856 "ipv4:203.0.113.45": [ "ane:L001", "ane:L004", 857 "ane:L005" ], 858 "ipv6:2001:db8::10": [ "ane:L001", "ane:L005", 859 "ane:L007" ] 860 } 861 } 862 } 864 POST /endpointcost/pv HTTP/1.1 865 Host: alto.example.com 866 Accept: application/alto-endpointcost+json, 867 application/alto-error+json 868 Content-Length: [TBD] 869 Content-Type: application/alto-endpointcostparams+json 871 { 872 "entities": [ "ane:L001", "ane:L003", "ane:L004", 873 "ane:L005", "ane:L007" ], 874 "properties": [ "availbw" ] 875 } 876 HTTP/1.1 200 OK 877 Content-Length: [TBD] 878 Content-Type: application/alto-propmap+json 880 { 881 "meta": { 882 "dependent-vtags": [ 883 { 884 "resource-id": "endpoint-cost-pv", 885 "tag": "12c0889c3c0892bb67df561ed16d93f5d1fa75cf" 886 } 887 ] 888 }, 889 "property-map": { 890 "ane:L001": { "availbw": 50 }, 891 "ane:L003": { "availbw": 48 }, 892 "ane:L004": { "availbw": 55 }, 893 "ane:L005": { "availbw": 60 }, 894 "ane:L007": { "availbw": 35 } 895 } 896 } 898 8.5. Example #3 899 POST /endpointcost/pv HTTP/1.1 900 Host: alto.example.com 901 Accept: application/alto-endpointcost+json, 902 application/alto-error+json 903 Content-Length: [TBD] 904 Content-Type: application/alto-endpointcostparams+json 906 { 907 "multi-cost-types": [ 908 { 909 "cost-mode": "array", 910 "cost-metric": "ane-path" 911 }, 912 { 913 "cost-mode": "numerical", 914 "cost-metric": "routingcost" 915 } 916 ], 917 "endpoints": { 918 "srcs": [ "ipv4:192.0.2.2" ], 919 "dsts": [ "ipv4:192.0.2.89", 920 "ipv4:203.0.113.45", 921 "ipv6:2001:db8::10" ] 922 }, 923 "properties": [ "delay", "availbw" ] 924 } 925 HTTP/1.1 200 OK 926 Content-Length: [TBD] 927 Content-Type: application/alto-endpointcost+json 929 { 930 "meta": { 931 "dependent-vtags": [ 932 { 933 "resource-id": "propmap-availbw-delay", 934 "tag": "bb6bb72eafe8f9bdc4f335c7ed3b10822a391cef" 935 } 936 ], 937 "cost-type": [ 938 {"cost-mode": "array", "cost-metric": "ane-path"} 939 ] 940 }, 941 "endpoint-cost-map": { 942 "ipv4:192.0.2.2": { 943 "ipv4:192.0.2.89": [ "ane:L001", "ane:L003", 944 "ane:L004" ], 945 "ipv4:203.0.113.45": [ "ane:L001", "ane:L004", 946 "ane:L005" ], 947 "ipv6:2001:db8::10": [ "ane:L001", "ane:L005", 948 "ane:L007" ] 949 } 950 }, 951 "property-map": { 952 "ane:L001": { "availbw": 50, "delay": 46 }, 953 "ane:L003": { "availbw": 48, "delay": 50 }, 954 "ane:L004": { "availbw": 55, "delay": 70 }, 955 "ane:L005": { "availbw": 60, "delay": 100 }, 956 "ane:L007": { "availbw": 35, "delay": 100 } 957 } 958 } 960 9. Compatibility 962 9.1. Compatibility with Legacy ALTO Clients/Servers 964 The path vector extension on Filtered Cost Map and Endpoint Cost 965 Service is backward compatible with the base ALTO protocol: 967 o If the ALTO server provides extended capabilities "dependent- 968 property-map" and "allow-compound-response" for Filtered Cost Map 969 or Endpoint Cost Service, but the client only supports the base 970 ALTO protocol, then the client will ignore those capabilities 971 without conducting any incompatibility. 973 o If the client sends a request with the input parameter 974 "properties", but the server only supports the base ALTO protocol, 975 the server will ignore this field. 977 9.2. Compatibility with Multi-Cost Extension 979 This document does not specify how to integrate the "array" cost mode 980 and the "ane-path" cost metric with the multi-cost extension 981 [RFC8189]. Although there is no reason why somebody has to compound 982 the path vectors with other cost types in a single query, there is no 983 compatible issue doing it without constraint tests. 985 As Section 7.1.1 mentions, the syntax and semantics of whether 986 "constraints" or "or-constraints" field for the "array" cost mode is 987 not specified in this document. So if an ALTO server provides a 988 resource with the "array" cost mode and the capability "cost- 989 constraints" or "testable-cost-types-names", the ALTO client MAY 990 ignore the capability "cost-constraints" or "testable-cost-types- 991 names" unless the implementation or future docuements specify the 992 behavior. 994 9.3. Compatibility with Incremental Update 996 As this document still follows the basic request/response protocol 997 with JSON encoding, it is surely compatible with the incremental 998 update service as defined by [I-D.ietf-alto-incr-update-sse]. But 999 the following details are to be noticed: 1001 o When using the compound response, updates on both cost map and 1002 property map SHOULD be notified. 1004 o When not using the compound response, because the cost map is in 1005 the "uses" attribute of the property map, once the path vectors in 1006 the cost map change, the ALTO server MUST send the updates of the 1007 cost map before the updates of the property map. 1009 10. General Discussions 1011 10.1. Provide Calendar for Property Map 1013 Fetching the historical network information is useful for many 1014 traffic optimization problem. [I-D.ietf-alto-cost-calendar] already 1015 proposes an ALTO extension called Cost Calendar which provides the 1016 historical cost values using Filtered Cost Map and Endpoint Cost 1017 Service. However, the calendar for only path costs is not enough. 1019 For example, as the properties of ANEs (e.g., available bandwidth and 1020 link delay) are usually the real-time network states, they change 1021 frequently in the real network. It is very helpful to get the 1022 historical value of these properties. Applications may predicate the 1023 network status using these information to better optimize their 1024 performance. 1026 So the coming requirement may be a general calendar service for the 1027 ALTO information resources. 1029 10.2. Constraint Tests for General Cost Types 1031 The constraint test is a simple approach to query the data. It 1032 allows users to filter the query result by specifying some boolean 1033 tests. This approach is already used in the ALTO protocol. 1034 [RFC7285] and [RFC8189] allow ALTO clients to specify the 1035 "constraints" and "or-constraints" tests to better filter the result. 1037 However, the current defined syntax is too simple and can only be 1038 used to test the scalar cost value. For more complex cost types, 1039 like the "array" mode defined in this document, it does not work 1040 well. It will be helpful to propose more general constraint tests to 1041 better perform the query. 1043 In practice, it is too complex to customize a language for the 1044 general-purpose boolean tests, and can be a duplicated work. So it 1045 may be a good idea to integrate some already defined and widely used 1046 query languages (or their subset) to solve this problem. The 1047 candidates can be XQuery and JSONiq. 1049 10.3. General Compound Resources Query 1051 As the last paragraph of Section 4.3 mentions, querying multiple ALTO 1052 information resources continuously is a general requirement. And the 1053 coming issues like inefficiency and inconsistency are also general. 1054 There is no standard solving these issues yet. So we need some 1055 approach to make the ALTO client request the compound ALTO 1056 information resources in a single query. 1058 11. Security Considerations 1060 11.1. Privacy Concerns 1062 We can identify multiple potential security issues. A main security 1063 issue is network privacy, as the path vector information may reveal 1064 more network internal structures than the more abstract single-node 1065 abstraction. The network should consider protection mechanisms to 1066 reduce information exposure, in particular, in settings where the 1067 network and the application do not belong to the same trust domain. 1068 On the other hand, in a setting of the same trust domain, a key 1069 benefit of the path-vector abstraction is reduced information 1070 transfer from the network to the application. 1072 Beyond the privacy issues, the computation of the path vector is 1073 unlikely to be cacheable, in that the results will depend on the 1074 particular requests (e.g., where the flows are distributed). Hence, 1075 this service may become an entry point for denial of service attacks 1076 on the availability of an ALTO server. Hence, authenticity and 1077 authorization of this ALTO service may need to be better protected. 1079 11.2. Resource Consumption on ALTO Servers 1081 The dependent Property Map of path vectors is dynamically enriched 1082 when the (Filtered) Cost Map/Endpoint Cost Service is queried of the 1083 path-vector information. The properties of the abstract network 1084 elements can consume a large amount of resources when cached. So, a 1085 time-to-live is needed to remove outdated entries in the Abstract 1086 Network Element Property Map. 1088 12. IANA Considerations 1090 12.1. ALTO Cost Mode Registry 1092 This document specifies a new cost mode "array". However, the base 1093 ALTO protocol does not have a Cost Mode Registry where new cost mode 1094 can be registered. This new cost mode will be registered once the 1095 registry is defined either in a revised version of [RFC7285] or in 1096 another future extension. 1098 12.2. ALTO Cost Metric Registry 1100 A new cost metric needs to be registered in the "ALTO Cost Metric 1101 Registry", listed in Table 2. 1103 +-------------+---------------------+ 1104 | Identifier | Intended Semantics | 1105 +-------------+---------------------+ 1106 | ane-path | See Section 5.2 | 1107 +-------------+---------------------+ 1109 Table 2: ALTO Cost Metrics 1111 12.3. ALTO Domain Registry 1113 As proposed in Section 9.2 of [I-D.ietf-alto-unified-props-new], 1114 "ALTO Domain Registry" is requested. Besides, a new domain is to be 1115 registered, listed in Table 3. 1117 +-------------+--------------------------+--------------------------+ 1118 | Identifier | Entity Address Encoding | Hierarchy & Inheritance | 1119 +-------------+--------------------------+--------------------------+ 1120 | ane | See Section 6.2 | None | 1121 +-------------+--------------------------+--------------------------+ 1123 Table 3: ALTO Domain 1125 12.4. ALTO Network Element Property Type Registry 1127 The "ALTO Abstract Network Element Property Type Registry" is 1128 required by the ALTO Domain "ane", listed in Table 4. 1130 +-------------+--------------------------+ 1131 | Identifier | Intended Semantics | 1132 +-------------+--------------------------+ 1133 | availbw | The available bandwidth | 1134 | delay | The transmission delay | 1135 +-------------+--------------------------+ 1137 Table 4: ALTO Abstract Network Element Property Types 1139 13. Acknowledgments 1141 The authors would like to thank discussions with Randriamasy Sabine, 1142 Andreas Voellmy, Erran Li, Haibin Son, Haizhou Du, Jiayuan Hu, Qiao 1143 Xiang, Tianyuan Liu, Xiao Shi, Xin Wang, and Yan Luo. 1145 14. References 1147 14.1. Normative References 1149 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1150 Requirement Levels", BCP 14, RFC 2119, 1151 DOI 10.17487/RFC2119, March 1997, 1152 . 1154 14.2. Informative References 1156 [I-D.amante-i2rs-topology-use-cases] 1157 Medved, J., Previdi, S., Lopez, V., and S. Amante, 1158 "Topology API Use Cases", draft-amante-i2rs-topology-use- 1159 cases-01 (work in progress), October 2013. 1161 [I-D.bernstein-alto-topo] 1162 Bernstein, G., Yang, Y., and Y. Lee, "ALTO Topology 1163 Service: Uses Cases, Requirements, and Framework", draft- 1164 bernstein-alto-topo-00 (work in progress), October 2013. 1166 [I-D.ietf-alto-cost-calendar] 1167 Randriamasy, S., Yang, Y., Wu, Q., Lingli, D., and N. 1168 Schwan, "ALTO Cost Calendar", draft-ietf-alto-cost- 1169 calendar-01 (work in progress), February 2017. 1171 [I-D.ietf-alto-incr-update-sse] 1172 Roome, W. and Y. Yang, "ALTO Incremental Updates Using 1173 Server-Sent Events (SSE)", draft-ietf-alto-incr-update- 1174 sse-08 (work in progress), January 2018. 1176 [I-D.ietf-alto-unified-props-new] 1177 Roome, W., Chen, S., xinwang2014@hotmail.com, x., Yang, 1178 Y., and J. Zhang, "Extensible Property Maps for the ALTO 1179 Protocol", draft-ietf-alto-unified-props-new-01 (work in 1180 progress), December 2017. 1182 [I-D.lee-alto-app-net-info-exchange] 1183 Lee, Y., Dhody, D., Wu, Q., Bernstein, G., and T. Choi, 1184 "ALTO Extensions to Support Application and Network 1185 Resource Information Exchange for High Bandwidth 1186 Applications in TE networks", draft-lee-alto-app-net-info- 1187 exchange-04 (work in progress), October 2013. 1189 [I-D.yang-alto-topology] 1190 Bernstein, G., Lee, Y., Roome, W., Scharf, M., and Y. 1191 Yang, "ALTO Topology Extensions: Node-Link Graphs", draft- 1192 yang-alto-topology-06 (work in progress), March 2015. 1194 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., 1195 Previdi, S., Roome, W., Shalunov, S., and R. Woundy, 1196 "Application-Layer Traffic Optimization (ALTO) Protocol", 1197 RFC 7285, DOI 10.17487/RFC7285, September 2014, 1198 . 1200 [RFC8189] Randriamasy, S., Roome, W., and N. Schwan, "Multi-Cost 1201 Application-Layer Traffic Optimization (ALTO)", RFC 8189, 1202 DOI 10.17487/RFC8189, October 2017, 1203 . 1205 Authors' Addresses 1207 Greg Bernstein 1208 Grotto Networking 1209 Fremont, CA 1210 USA 1212 Email: gregb@grotto-networking.com 1213 Shiwei Dawn Chen 1214 Tongji University 1215 4800 Caoan Road 1216 Shanghai 201804 1217 China 1219 Email: dawn_chen_f@hotmail.com 1221 Kai Gao 1222 Tsinghua University 1223 Beijing Beijing 1224 China 1226 Email: gaok12@mails.tsinghua.edu.cn 1228 Young Lee 1229 Huawei 1230 TX 1231 USA 1233 Email: leeyoung@huawei.com 1235 Wendy Roome 1236 Nokia/Bell Labs (Retired) 1237 124 Burlington Rd 1238 Murray Hill, NJ 07974 1239 USA 1241 Phone: +1-908-464-6975 1242 Email: wendy@wdroome.com 1244 Michael Scharf 1245 Nokia 1246 Germany 1248 Email: michael.scharf@nokia.com 1249 Y. Richard Yang 1250 Yale University 1251 51 Prospect St 1252 New Haven CT 1253 USA 1255 Email: yry@cs.yale.edu 1257 Jingxuan Jensen Zhang 1258 Tongji University 1259 4800 Caoan Road 1260 Shanghai 201804 1261 China 1263 Email: jingxuan.n.zhang@gmail.com