idnits 2.17.1 draft-ietf-cdni-problem-statement-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 25, 2012) is 4294 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-10) exists of draft-ietf-cdni-use-cases-08 -- Obsolete informational reference (is this intentional?): RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Obsolete informational reference (is this intentional?): RFC 3466 (Obsoleted by RFC 7336) -- Obsolete informational reference (is this intentional?): RFC 3570 (Obsoleted by RFC 6770) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group B. Niven-Jenkins 3 Internet-Draft Velocix (Alcatel-Lucent) 4 Intended status: Informational F. Le Faucheur 5 Expires: December 27, 2012 Cisco 6 N. Bitar 7 Verizon 8 June 25, 2012 10 Content Distribution Network Interconnection (CDNI) Problem Statement 11 draft-ietf-cdni-problem-statement-08 13 Abstract 15 Content Delivery Networks (CDNs) provide numerous benefits: reduced 16 delivery cost for cacheable content, improved quality of experience 17 for End Users and increased robustness of delivery. For these 18 reasons they are frequently used for large-scale content delivery. 19 As a result, existing CDN Providers are scaling up their 20 infrastructure and many Network Service Providers (NSPs) are 21 deploying their own CDNs. It is generally desirable that a given 22 content item can be delivered to an End User regardless of that End 23 User's location or attachment network. This is the motivation for 24 interconnecting standalone CDNs so they can interoperate as an open 25 content delivery infrastructure for the end-to-end delivery of 26 content from Content Service Providers (CSPs) to End Users. However, 27 no standards or open specifications currently exist to facilitate 28 such CDN interconnection. 30 The goal of this document is to outline the problem area of CDN 31 interconnection for the IETF CDNI (CDN Interconnection) working 32 group. 34 Status of this Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on December 27, 2012. 50 Copyright Notice 52 Copyright (c) 2012 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 69 1.2. CDN Background . . . . . . . . . . . . . . . . . . . . . . 10 70 2. CDN Interconnection Use Cases . . . . . . . . . . . . . . . . 11 71 3. CDN Interconnection Model & Problem Area for IETF . . . . . . 12 72 4. Scoping the CDNI Problem . . . . . . . . . . . . . . . . . . . 16 73 4.1. CDNI Request Routing Interface . . . . . . . . . . . . . . 17 74 4.2. CDNI Metadata Interface . . . . . . . . . . . . . . . . . 17 75 4.3. CDNI Logging Interface . . . . . . . . . . . . . . . . . . 18 76 4.4. CDNI Control Interface . . . . . . . . . . . . . . . . . . 18 77 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 78 6. Security Considerations . . . . . . . . . . . . . . . . . . . 18 79 6.1. Security of the CDNI Control interface . . . . . . . . . . 19 80 6.2. Security of the CDNI Request Routing Interface . . . . . . 19 81 6.3. Security of the CDNI Metadata interface . . . . . . . . . 20 82 6.4. Security of the CDNI Logging interface . . . . . . . . . . 20 83 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 84 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 85 8.1. Normative References . . . . . . . . . . . . . . . . . . . 20 86 8.2. Informative References . . . . . . . . . . . . . . . . . . 20 87 Appendix A. Design considerations for realizing the CDNI 88 Interfaces . . . . . . . . . . . . . . . . . . . . . 23 89 A.1. CDNI Request Routing Interface . . . . . . . . . . . . . . 23 90 A.2. CDNI Metadata Interface . . . . . . . . . . . . . . . . . 25 91 A.3. CDNI Logging Interface . . . . . . . . . . . . . . . . . . 26 92 A.4. CDNI Control Interface . . . . . . . . . . . . . . . . . . 27 93 Appendix B. Additional Material . . . . . . . . . . . . . . . . . 27 94 B.1. Non-Goals for IETF . . . . . . . . . . . . . . . . . . . . 28 95 B.2. Relationship to relevant IETF Working Groups & IRTF 96 Reserach Groups . . . . . . . . . . . . . . . . . . . . . 29 97 B.2.1. ALTO WG . . . . . . . . . . . . . . . . . . . . . . . 29 98 B.2.2. DECADE WG . . . . . . . . . . . . . . . . . . . . . . 30 99 B.2.3. PPSP WG . . . . . . . . . . . . . . . . . . . . . . . 31 100 B.2.4. IRTF P2P Research Group . . . . . . . . . . . . . . . 31 101 Appendix C. Additional Material . . . . . . . . . . . . . . . . . 32 102 C.1. Related standardization activites . . . . . . . . . . . . 32 103 C.1.1. IETF CDI Working Group (Concluded) . . . . . . . . . . 33 104 C.1.2. 3GPP . . . . . . . . . . . . . . . . . . . . . . . . . 33 105 C.1.3. ISO MPEG . . . . . . . . . . . . . . . . . . . . . . . 34 106 C.1.4. ATIS IIF . . . . . . . . . . . . . . . . . . . . . . . 35 107 C.1.5. CableLabs . . . . . . . . . . . . . . . . . . . . . . 35 108 C.1.6. ETSI MCD . . . . . . . . . . . . . . . . . . . . . . . 35 109 C.1.7. ETSI TISPAN . . . . . . . . . . . . . . . . . . . . . 35 110 C.1.8. ITU-T . . . . . . . . . . . . . . . . . . . . . . . . 36 111 C.1.9. Open IPTV Forum (OIPF) . . . . . . . . . . . . . . . . 36 112 C.1.10. TV-Anytime Forum . . . . . . . . . . . . . . . . . . . 36 113 C.1.11. SNIA . . . . . . . . . . . . . . . . . . . . . . . . . 37 114 C.1.12. Summary of existing standardization work . . . . . . . 37 115 C.2. Related Research Projects . . . . . . . . . . . . . . . . 39 116 C.2.1. OCEAN . . . . . . . . . . . . . . . . . . . . . . . . 39 117 C.2.2. Eurescom P1955 . . . . . . . . . . . . . . . . . . . . 39 118 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40 120 1. Introduction 122 The volume of video and multimedia content delivered over the 123 Internet is rapidly increasing and expected to continue doing so in 124 the future. In the face of this growth, Content Delivery Networks 125 (CDNs) provide numerous benefits: reduced delivery cost for cacheable 126 content, improved quality of experience for End Users (EUs) and 127 increased robustness of delivery. For these reasons CDNs are 128 frequently used for large-scale content delivery. As a result, 129 existing CDN Providers are scaling up their infrastructure and many 130 Network Service Providers (NSPs) are deploying their own CDNs. 132 It is generally desirable that a given content item can be delivered 133 to an EU regardless of that EU's location or the network they are 134 attached to. However, a given CDN in charge of delivering a given 135 content may not have a footprint that expands close enough to the 136 EU's current location or attachment network, or may not have the 137 necessary resources, to realize the user experience and cost benefit 138 that a more distributed CDN infrastructure would allow. This is the 139 motivation for interconnecting standalone CDNs so that their 140 collective CDN footprint and resources can be leveraged for the end- 141 to-end delivery of content from Content Service Providers (CSPs) to 142 EUs. As an example, a CSP could contract with an "authoritative" CDN 143 Provider for the delivery of content and that authoritative CDN 144 Provider could contract with one or more downstream CDN Provider(s) 145 to distribute and deliver some or all of the content on behalf of the 146 authoritative CDN Provider. 148 A typical end to end content delivery scenario would then involve the 149 following business arrangements: 151 o A business arrangement between the EU and his CSP, authorizing 152 access by the EU to content items controlled by the CSP. 153 o A business arrangement between the CSP and an "authoritative" CDN 154 Provider where the CSP authorizes the CDN Provider to perform the 155 content delivery on behalf of the CSP. 156 o A business arrangement between the authoritative CDN Provider and 157 another (or other) CDN(s) where the authoritative CDN may delegate 158 the actual serving of some of the content delivery requests to the 159 other CDN(s). A particular case, is where this other CDN Provider 160 happens to also be the Network Service Provider providing network 161 access to the EU, in which case there is also a separate and 162 independent business relationship between the EU and the NSP for 163 the corresponding network access. 165 The formation and details of any business relationships between a CSP 166 and a CDN Provider as well as between one CDN Provider and another 167 CDN Provider are out of scope of this document. However, this 168 document concerns itself with the fact that no standards or open 169 specifications currently exist to facilitate such CDN interconnection 170 from a technical perspective. 172 One possible flow for performing an end to end content delivery 173 across a CDN Interconnect is described below: 175 o The initial request from an EU's User Agent is first received by 176 the authoritative (upstream) CDN, which is the CDN with a business 177 arrangement with the CSP. 178 o The authoritative (upstream) CDN may serve the request itself, or 179 it may elect to use CDN Interconnect to redirect the request to a 180 downstream CDN that is in a better position to do so (e.g. a 181 downstream CDN that is "closer" to the EU). 182 o The EU's User Agent will "follow" the redirect returned by the 183 authoritative CDN and request the content from the downstream CDN. 184 If required the downstream CDN will acquire the requested content 185 from the authoritative (upstream) CDN, and if necessary the 186 authoritative CDN will acquire the requested content from the 187 Content Service Provider. 189 The goal of this document is to outline the problem area of CDN 190 interconnection. Section 2 discusses the use cases for CDN 191 interconnection. Section 3 presents the CDNI model and problem area 192 being considered by the IETF. Section 4 describes each CDNI 193 interface individually and highlights example candidate protocols 194 that could be considered for reuse or leveraging to implement the 195 CDNI interfaces. Appendix B.2 describes the relationships between 196 the CDNI problem space and other relevant IETF Working Groups and 197 IRTF Reserach Groups. 199 1.1. Terminology 201 This document uses the following terms: 203 Content: Any form of digital data. One important form of Content 204 with additional constraints on distribution and delivery is 205 continuous media (i.e. where there is a timing relationship between 206 source and sink). 208 Metadata: Metadata in general is data about data. 210 Content Metadata: This is metadata about Content. Content Metadata 211 comprises: 213 1. Metadata that is relevant to the distribution of the content (and 214 therefore relevant to a CDN involved in the delivery of that 215 content). We refer to this type of metadata as "Content 216 Distribution Metadata". See also the definition of Content 217 Distribution Metadata. 218 2. Metadata that is associated with the actual Content or content 219 representation, and not directly relevant to the distribution of 220 that Content. For example, such metadata may include information 221 pertaining to the Content's genre, cast, rating, etc as well as 222 information pertaining to the Content representation's 223 resolution, aspect ratio, etc. 225 Content Distribution Metadata: The subset of Content Metadata that is 226 relevant to the distribution of the content. This is the metadata 227 required by a CDN in order to enable and control content distribution 228 and delivery by the CDN. In a CDN Interconnection environment, some 229 of the Content Distribution Metadata may have an intra-CDN scope (and 230 therefore need not be communicated between CDNs), while some of the 231 Content Distribution Metadata may have an inter-CDN scope (and 232 therefore needs to be communicated between CDNs). 234 CDNI Metadata: Content Distribution Metadata with inter-CDN scope. 235 For example, CDNI Metadata may include geo-blocking information (i.e. 236 information defining geographical areas where the content is to be 237 made available or blocked), availability windows (i.e. information 238 defining time windows during which the content is to be made 239 available or blocked) and access control mechanisms to be enforced 240 (e.g. URI signature validation). CDNI Metadata may also include 241 information about desired distribution policy (e.g. prepositioned vs 242 dynamic acquisition) and about where/how a CDN can acquire the 243 content. CDNI Metadata may also include content management 244 information (e.g. request for deletion of Content from Surrogates) 245 across interconnected CDNs. 247 Dynamic content acquisition: Dynamic content acquisition is where a 248 CDN acquires content from the content source in response to an End 249 User requesting that content from the CDN. In the context of CDN 250 Interconnection, dynamic acquisition means that a downstream CDN 251 acquires the content from content sources (including upstream CDNs) 252 at some point in time after a request for that content is delegated 253 to the downstream CDN by an Upstream CDN (and that specific content 254 is not yet available in the downstream CDN). 256 Dynamic CDNI metadata acquisition: In the context of CDN 257 Interconnection, dynamic CDNI metadata acquisition means that a 258 downstream CDN acquires CDNI metadata for content from the upstream 259 CDN at some point in time after a request for that content is 260 delegated to the downstream CDN by an Upstream CDN (and that specific 261 CDNI metadata is not yet available in the downstream CDN). See also 262 the definitions for downstream CDN and upstream CDN. 264 Pre-positioned content acquisition: Content Pre-positioning is where 265 a CDN acquires content from the content source prior to, or 266 independently of, any End User requesting that content from the CDN. 267 In the context of CDN interconnection the Upstream CDN instructs the 268 Downstream CDN to acquire the content from content sources (including 269 upstream CDNs) in advance of or independent of any End User 270 requesting it. 272 Pre-positioned CDNI Metadata acquisition: In the context of CDN 273 Interconnection, CDNI Metadata pre-positioning is where the 274 Downstream CDN acquires CDNI metadata for content prior to or 275 independent of any End User requesting that content from the 276 Downstream CDN. 278 End User (EU): The 'real' user of the system, typically a human but 279 maybe some combination of hardware and/or software emulating a human 280 (e.g. for automated quality monitoring etc.) 282 User Agent (UA): Software (or a combination of hardware and software) 283 through which the End User interacts with a Content Service. The 284 User Agent will communicate with a Content Service for the selection 285 of content and one or more CDNs for the delivery of the Content. 286 Such communication is not restricted to HTTP and may be via a variety 287 of protocols. Examples of User Agents (non-exhaustive) are: 288 Browsers, Set Top Boxes (STBs), dedicated content applications (e.g. 289 media players), etc. 291 Network Service Provider (NSP): Provides network-based connectivity/ 292 services to End Users. 294 Content Service Provider (CSP): Provides a Content Service to End 295 Users (which they access via a User Agent). A CSP may own the 296 Content made available as part of the Content Service, or may license 297 content rights from another party. 299 Content Service: The service offered by a Content Service Provider. 300 The Content Service encompasses the complete service which may be 301 wider than just providing access to items of Content, e.g. the 302 Content Service also includes any middleware, key distribution, 303 program guide, etc. which may not require any direct interaction with 304 the CDN, or CDNs, involved in the distribution and delivery of the 305 content. 307 Content Distribution Network (CDN) / Content Delivery Network (CDN): 308 Network infrastructure in which the network elements cooperate at 309 layers 4 through layer 7 for more effective delivery of Content to 310 User Agents. Typically a CDN consists of a Request Routing system, a 311 Distribution System (that includes a set of Surrogates), a Logging 312 System and a CDN control system. 314 CDN Provider: The service provider who operates a CDN and offers a 315 service of content delivery, typically used by a Content Service 316 Provider or another CDN Provider. Note that a given entity may 317 operate in more than one role. For example, a company may 318 simultaneously operate as a Content Service Provider, a Network 319 Service Provider and a CDN Provider. 321 CDN Interconnection (CDNI): A relationship between a pair of CDNs 322 that enables one CDN to provide content delivery services on behalf 323 of another CDN. A CDN Interconnection may be wholly or partially 324 realized through a set of interfaces over which a pair of CDNs 325 communicate with each other in order to achieve the delivery of 326 content to User Agents by Surrogates in one CDN (the downstream CDN) 327 on behalf of another CDN (the upstream CDN). 329 Authoritative CDN: A CDN which has a direct relationship with a CSP 330 for the distribution & delivery of that CSP's content by the 331 authoritative CDN or by downstream CDNs of the authoritative CDN. 333 Upstream CDN: For a given End User request, the CDN (within a pair of 334 directly interconnected CDNs) that redirects the request to the other 335 CDN. 337 Downstream CDN: For a given End User request, the CDN (within a pair 338 of directly interconnected CDNs) to which the request is redirected 339 by the other CDN (the Upstream CDN). Note that in the case of 340 successive redirections (e.g. CDN1-->CDN2-->CDN3) a given CDN (e.g. 341 CDN2) may act as the Downstream CDN for a redirection (e.g. 342 CDN1-->CDN2) and as the Upstream CDN for the subsequent redirection 343 of the same request (e.g. CDN2-->CDN3). 345 Over-the-top (OTT): A service, e.g. content delivery using a CDN, 346 operated by a different operator than the NSP to which the users of 347 that service are attached. 349 Surrogate: A device/function (often called a cache) that interacts 350 with other elements of the CDN for the control and distribution of 351 Content within the CDN and interacts with User Agents for the 352 delivery of the Content. Typically, surrogates will cache requested 353 content so that it can deliver the same content to a number of User 354 Agents (and their End Users) avoiding the need for those requests to 355 transit multiple times through the network core (i.e from the content 356 origin to the surrogate). 358 Request Routing System: The function within a CDN responsible for 359 receiving a content request from a User Agent, obtaining and 360 maintaining necessary information about a set of candidate surrogates 361 or candidate CDNs, and for selecting and redirecting the user to the 362 appropriate surrogate or CDN. To enable CDN Interconnection, the 363 Request Routing System must also be capable of handling User Agent 364 content requests passed to it by another CDN. 366 Distribution System: The function within a CDN responsible for 367 distributing Content Distribution Metadata as well as the Content 368 itself inside the CDN (e.g. down to the surrogates). 370 Delivery: The function within CDN surrogates responsible for 371 delivering a piece of content to the User Agent. For example, 372 delivery may be based on HTTP progressive download or HTTP adaptive 373 streaming. 375 Logging System: The function within a CDN responsible for collecting 376 the measurement and recording of distribution and delivery 377 activities. The information recorded by the logging system may be 378 used for various purposes including charging (e.g. of the CSP), 379 analytics and monitoring. 381 Control System: The function within a CDN responsible for 382 bootstrapping and controlling the other components of the CDN as well 383 as for handling interactions with external systems (e.g. handling 384 delivery service creation/update/removal requests, or specific 385 service provisioning requests). 387 Quality of Experience (QoE): As defined in Section 2.4 of [RFC6390] 389 1.2. CDN Background 391 Readers are assumed to be familiar with the architecture, features 392 and operation of CDNs. For readers less familiar with the operation 393 of CDNs, the following resources may be useful: 395 o RFC 3040 [RFC3040] describes many of the component technologies 396 that are used in the construction of a CDN. 397 o Taxonomy [TAXONOMY] compares the architecture of a number of CDNs. 398 o RFC 3466 [RFC3466] and RFC 3570 [RFC3570] are the output of the 399 IETF Content Delivery Internetworking (CDI) working group which 400 was closed in 2003. 402 Note: Some of the terms used in this document are similar to terms 403 used the above referenced documents. When reading this document 404 terms should be interpreted as having the definitions provided in 405 Section 1.1. 407 2. CDN Interconnection Use Cases 409 An increasing number of NSPs are deploying CDNs in order to deal 410 cost-effectively with the growing usage of on-demand video services 411 and other content delivery applications. 413 CDNs allow caching of content closer to the edge of a network so that 414 a given item of content can be delivered by a CDN Surrogate (i.e. a 415 cache) to multiple User Agents (and their End Users) without 416 transiting multiple times through the network core (i.e from the 417 content origin to the surrogate). This contributes to bandwidth cost 418 reductions for the NSP and to improved quality of experience for the 419 End Users. CDNs also enable replication of popular content across 420 many surrogates, which enables content to be served to large numbers 421 of User Agents concurrently. This also helps dealing with situations 422 such as flash crowds and denial of service attacks. 424 The CDNs deployed by NSPs are not just restricted to the delivery of 425 content to support the Network Service Provider's own 'walled garden' 426 services, such as IP delivery of television services to Set Top 427 Boxes, but are also used for delivery of content to other devices 428 including PCs, tablets, mobile phones etc. 430 Some service providers operate over multiple geographies and federate 431 multiple affiliate NSPs. These NSPs typically operate independent 432 CDNs. As they evolve their services (e.g. for seamless support of 433 content services to nomadic users across affiliate NSPs) there is a 434 need for interconnection of these CDNs, that represents a first use 435 case for CDNI. However there are no open specifications, nor common 436 best practices, defining how to achieve such CDN interconnection. 438 CSPs have a desire to be able to get (some of) their content to very 439 large numbers of End Users, who are often distributed across a number 440 of geographies, while maintaining a high quality of experience, all 441 without having to maintain direct business relationships with many 442 different CDN Providers (or having to extend their own CDN to a large 443 number of locations). Some NSPs are considering interconnecting 444 their respective CDNs (as well as possibly over-the-top CDNs) so that 445 this collective infrastructure can address the requirements of CSPs 446 in a cost effective manner. This represents a second use case for 447 CDNI. In particular, this would enable the CSPs to benefit from on- 448 net delivery (i.e. within the Network Service Provider's own network/ 449 CDN footprint) whenever possible and off-net delivery otherwise, 450 without requiring the CSPs to maintain direct business relationships 451 with all the CDNs involved in the delivery. Again, CDN Providers 452 (NSPs or over-the-top CDN operators) are faced with a lack of open 453 specifications and best practices. 455 NSPs have often deployed CDNs as specialized cost-reduction projects 456 within the context of a particular service or environment. Some NSPs 457 operate separate CDNs for separate services. For example, there may 458 be a CDN for managed IPTV service delivery, a CDN for web-TV delivery 459 and a CDN for video delivery to Mobile terminals. As NSPs integrate 460 their service portfolio, there is a need for interconnecting these 461 CDNs, representing a third use case for CDNI. Again, NSPs face the 462 problem of lack of open interfaces for CDN interconnection. 464 For operational reasons (e.g. disaster, flash crowd) or commercial 465 reasons, an over-the-top CDN may elect to make use of another CDN 466 (e.g. an NSP CDN with on-net Surrogates for a given footprint) for 467 serving a subset of the user requests (e.g. requests from users 468 attached to that NSP), which results in a fourth use case for CDNI 469 because CDN Providers (over-the-top CDN Providers or NSPs) are faced 470 with a lack of open specifications and best practices. 472 Use cases for CDN Interconnection are further discussed in 473 [I-D.ietf-cdni-use-cases]. 475 3. CDN Interconnection Model & Problem Area for IETF 477 This section discusses the problem area for the IETF work on CDN 478 Interconnection. 480 Interconnecting CDNs involves interactions among multiple different 481 functions and components that form each CDN. Only some of those 482 require standardization. 484 Some NSPs have started to perform experiments to explore whether 485 their CDN use cases can already be addressed with existing CDN 486 implementations. One set of such experiments is documented in 487 [I-D.bertrand-cdni-experiments]. The conclusions of those 488 experiments are that while some basic limited CDN Interconnection 489 functionality can be achieved with existing CDN technology, the 490 current lack of any standardized CDNI interfaces with the necessary 491 level of functionality such as those discussed in this document is 492 preventing the deployment of CDN Interconnection. 494 Listed below are the four interfaces required to interconnect a pair 495 of CDNs and that constitute the problem space of CDN Interconnection 496 along with the required functionality of each interface for which 497 standards do not currently exist. As part of the development of the 498 CDNI interfaces it will also be necessary to agree on common 499 mechanisms for how to identify and name the data objects that are to 500 be interchanged between interconnected CDNs. 502 The use of the term "interface" is meant to encompass the protocol 503 over which CDNI data representations (e.g. CDNI Metadata objects) 504 are exchanged as well as the specification of the data 505 representations themselves (i.e. what properties/fields each object 506 contains, its structure, etc.). 508 o CDNI Control interface: This interface allows the "CDNI Control" 509 system in interconnected CDNs to communicate. This interface may 510 support the following: 511 * Allow bootstrapping of the other CDNI interfaces (e.g. 512 interface address/URL discovery and establishment of security 513 associations). 514 * Allow configuration of the other CDNI interfaces (e.g. 515 Upstream CDN specifies information to be reported through the 516 CDNI Logging interface). 517 * Allow the downstream CDN to communicate static (or fairly 518 static) information about its delivery capabilities and 519 policies. 520 * Allow bootstrapping of the interface between CDNs for content 521 acquisition (even if that interface itself is outside the scope 522 of the CDNI work). 523 * Allow an upstream CDN to initiate or request specific actions 524 to be undertaken in the downstream CDN. For example, to allow 525 an upstream CDN to initiate content or CDNI Metadata 526 acquisition (pre-positioning) or to request the invalidation or 527 purging of content files and/or CDNI Metadata in a downstream 528 CDN. 529 o CDNI Request Routing interface: This interface allows the Request 530 Routing systems in interconnected CDNs to communicate to ensure 531 that an End User request can be (re)directed from an upstream CDN 532 to a surrogate in the downstream CDN, in particular where 533 selection responsibilities may be split across CDNs (for example 534 the upstream CDN may be responsible for selecting the downstream 535 CDN while the downstream CDN may be responsible for selecting the 536 actual surrogate within that downstream CDN). In particular, the 537 functions of the CDN Request Routing interface may be divided as 538 follows: 539 * A CDNI Request Routing Redirection interface which allows the 540 upstream CDN to query the downstream CDN at request routing 541 time before redirecting the request to the downstream CDN. 542 * A CDNI Footprint & Capabilities advertisement interface which 543 allows the downstream CDN to provide to the upstream CDN 544 (static or dynamic) information (e.g. resources, footprint, 545 load) to facilitate selection of the downstream CDN by the 546 upstream CDN request routing system when processing subsequent 547 content requests from User Agents. 549 o CDNI Metadata distribution interface: This interface allows the 550 Distribution system in interconnected CDNs to communicate to 551 ensure CDNI Metadata can be exchanged across CDNs. See 552 Section 1.1 for definition and examples of CDNI Metadata. 553 o CDNI Logging interface: This interface allows the Logging system 554 in interconnected CDNs to communicate the relevant activity logs 555 in order to allow log consuming applications to operate in a 556 multi-CDN environments. For example, an upstream CDN may collect 557 delivery logs from a downstream CDN in order to perform 558 consolidated charging of the CSP or for settlement purposes across 559 CDNs. Similarly, an upstream CDN may collect delivery logs from a 560 downstream CDN in order to provide consolidated reporting and 561 monitoring to the CSP. 563 Note that the actual grouping of functionalities under these four 564 interfaces is considered tentative at this stage and may be changed 565 after further study (e.g. some subset of functionality be moved from 566 one interface into another). 568 The above list covers a significant potential problem space, in part 569 because in order to interconnect two CDNs there are several 'touch 570 points' that require standardization. However, it is expected that 571 the CDNI interfaces need not be defined from scratch and instead can 572 very significantly reuse or leverage existing protocols; this is 573 discussed further in Section 4. 575 The interfaces that form the CDNI problem area are illustrated in 576 Figure 1. 578 -------- 579 / \ 580 | CSP | 581 \ / 582 -------- 583 * 584 * 585 * /\ 586 * / \ 587 ---------------------- |CDNI| ---------------------- 588 / Upstream CDN \ | | / Downstream CDN \ 589 | +-------------+ | Control Interface| +-------------+ | 590 |******* Control |<======|====|========>| Control *******| 591 |* +------*----*-+ | | | | +-*----*------+ *| 592 |* * * | | | | * * *| 593 |* +------*------+ | Logging Interface| +------*------+ *| 594 |* ***** Logging |<======|====|========>| Logging ***** *| 595 |* * +-*-----------+ | | | | +-----------*-+ * *| 596 |* * * * | Request Routing | * * * *| 597 .....*...+-*---------*-+ | Interface | +-*---------*-+...*.*... 598 . |* * *** Req-Routing |<======|====|========>| Req-Routing *** * *| . 599 . |* * * +-------------+.| | | | +-------------+ * * *| . 600 . |* * * . CDNI Metadata | * * *| . 601 . |* * * +-------------+ |. Interface | +-------------+ * * *| . 602 . |* * * | Distribution|<==.===|====|========>| Distribution| * * *| . 603 . |* * * | | | . \ / | | | * * *| . 604 . |* * * |+---------+ | | . \/ | | +---------+| * * *| . 605 . |* * ***| +---------+| | ....Request......+---------+ |*** * *| . 606 . |* *****+-|Surrogate|************************|Surrogate|-+***** *| . 607 . |******* +---------+| | Acquisition | |+----------+ *******| . 608 . | +-------------+ | | +-------*-----+ | . 609 . \ / \ * / . 610 . ---------------------- ---------*------------ . 611 . * . 612 . * Delivery . 613 . * . 614 . +--*---+ . 615 ...............Request.............................| User |..Request.. 616 | Agent| 617 +------+ 619 <==> interfaces inside the scope of CDNI 620 **** interfaces outside the scope of CDNI 621 .... interfaces outside the scope of CDNI 623 Figure 1: A Model for the CDNI Problem Area 625 As illustrated in Figure 1, the acquisition of content between 626 interconnected CDNs is out of scope for CDNI, which deserves some 627 additional explanation. The consequence of such a decision is that 628 the CDNI problem space described in this document is focussed on only 629 defining the control plane for CDNI; and the CDNI data plane (i.e. 630 the acquisition & distribution of the actual content objects) is out 631 of scope. The rationale for such a decision is that CDNs today 632 typically already use standardized protocols such as HTTP, FTP, 633 rsync, etc. to acquire content from their CSP customers and it is 634 expected that the same protocols could be used for acquisition 635 between interconnected CDNs. Therefore the problem of content 636 acquisition is considered already solved and all that is required 637 from specifications developed by the CDNI working group is to 638 describe within the CDNI Metadata the parameters to use to retrieve 639 the content for example the IP address/hostname to connect to, what 640 protocol to use to retrieve the content, etc. 642 4. Scoping the CDNI Problem 644 This section outlines how the scope of work addressing the CDNI 645 problem space can be constrained through reuse or leveraging of 646 existing protocols to implement the CDNI interfaces. This discussion 647 is not intended to pre-empt any working group decision as to the most 648 appropriate protocols, technologies and solutions to select to 649 realize the CDNI interfaces but is intended as an illustration of the 650 fact that the CDNI interfaces need not be created in a vacuum and 651 that reuse or leverage of existing protocols is likely possible. 653 The four CDNI interfaces (CDNI Control interface, CDNI Request 654 Routing interface, CDNI Metadata interface, CDNI Logging interface) 655 described in Section 3 within the CDNI problem area are all control 656 plane interfaces operating at the application layer (Layer 7 in the 657 OSI network model). Firstly, since it is not expected that these 658 interfaces would exhibit unique session, transport or network 659 requirements as compared to the many other existing applications in 660 the Internet, it is expected that the CDNI interfaces will be defined 661 on top of existing session, transport and network protocols. 663 Secondly, although a new application protocol could be designed 664 specifically for CDNI our analysis below shows that this is 665 unnecessary and it is recommended that existing application protocols 666 be reused or leveraged (HTTP [RFC2616], Atom Publishing Protocol 667 [RFC5023], XMPP [RFC6120], for example) to realize the CDNI 668 interfaces. 670 4.1. CDNI Request Routing Interface 672 The CDNI Request Routing interface enables a Request Routing function 673 in an upstream CDN to query a Request Routing function in a 674 downstream CDN to determine if the downstream CDN is able (and 675 willing) to accept the delegated content request. It also allows the 676 downstream CDN to control what should be returned to the User Agent 677 in the redirection message by the upstream Request Routing function . 679 The CDNI Request Routing interface is therefore a fairly 680 straightforward request/response interface and could be implemented 681 over any number of request/response protocols. For example, it may 682 be implemented as a WebService using one of the common WebServices 683 methodologies (XML-RPC, HTTP query to a known URI, etc.). This 684 removes the need for the CDNI working group to define a new protocol 685 for the request/response element of the CDNI Request Routing 686 interface. 688 Additionally, as discussed in Section 3, the CDNI Request Routing 689 interface is also expected to enable a downstream CDN to provide to 690 the upstream CDN (static or dynamic) information (e.g. resources, 691 footprint, load) to facilitate selection of the downstream CDN by the 692 upstream CDN request routing system when processing subsequent 693 content requests from User Agents. It is expected that such 694 functionality of the CDNI request Routing could be specified by the 695 CDNI working group with significant leveraging of existing IETF 696 protocols supporting the dynamic distribution of reachability 697 information (for example by leveraging existing routing protocols) or 698 supporting application level queries for topological information (for 699 example by leveraging ALTO [RFC5693]). 701 4.2. CDNI Metadata Interface 703 The CDNI Metadata interface enables the Distribution System in a 704 downstream CDN to request CDNI Metadata from an upstream CDN so that 705 the downstream CDN can properly process and respond to redirection 706 requests received over the CDNI Request Routing interface and Content 707 Requests received directly from User Agents. 709 The CDNI Metadata interface is therefore similar to the CDNI Request 710 Routing interface because it is a request/response interface with the 711 potential addition that CDNI Metadata search may have more complex 712 semantics than a straightforward Request Routing redirection request. 713 Therefore, like the CDNI Request Routing interface, the CDNI Metadata 714 interface may be implemented as a WebService using one of the common 715 WebServices methodologies (XML-RPC, HTTP query to a known URI, etc.) 716 or possibly using other existing protocols such as XMPP [RFC6120]. 717 This removes the need for the CDNI working group to define a new 718 protocol for the request/response element of the CDNI Metadata 719 interface. 721 4.3. CDNI Logging Interface 723 The CDNI Logging interface enables details of content distribution 724 and delivery activities to be exchanged between interconnected CDNs. 725 For example the exchange of log records related to the delivery of 726 content, similar to the log records recorded in a web server's access 727 log. 729 Several protocols already exist that could potentially be used to 730 exchange CDNI logs between interconnected CDNs including SNMP, 731 syslog, ftp (and secure variants), HTTP POST, etc. 733 4.4. CDNI Control Interface 735 The CDNI Control interface allows the Control System in 736 interconnected CDNs to communicate. The exact inter-CDN control 737 functionality required to be supported by the CDNI Control interface 738 is less well defined than the other three CDNI interfaces at this 739 time. 741 It is expected that for the Control interface, as for the other CDNI 742 Interfaces, existing protocols can be reused or leveraged. 744 5. IANA Considerations 746 This document makes no request of IANA. 748 Note to RFC Editor: this section may be removed on publication as an 749 RFC. 751 6. Security Considerations 753 Distribution of content by a CDN comes with a range of security 754 considerations such as how to enforce control of access to the 755 content by end users in line with the CSP policy, or how to trust the 756 logging information generated by the CDN for the purposes of charging 757 the CSP. These security aspects are already dealt with by CDN 758 Providers and CSPs today in the context of standalone CDNs. However, 759 interconnection of CDNs introduces a new set of security 760 considerations by extending the trust model to a chain of trust (i.e. 761 the CSP "trusts" a CDN that "trusts" another CDN). The mechanisms 762 used to mitigate these risks in multi-CDN environments may be similar 763 to those used in the single CDN case, but their suitability in this 764 more complex environment must be validated. 766 The interconnection of CDNs may also introduce additional privacy 767 considerations on top of those that apply to the single CDN case. In 768 a multi-CDN environment, the different CDNs may reside in different 769 legal regimes that require differing privacy requirements to be 770 enforced. Such privacy requirements may impact the granularity of 771 information that can be exchanged across the CDNI interfaces. For 772 example the Logging System in a downstream CDN may need to apply some 773 degree of anonymization, obfuscation or even the complete removal of 774 some fields before exchanging log records containing details of End 775 User deliveries with an upstream CDN. 777 Maintaining the security of the content itself, its associated 778 metadata (including delivery policies) and the CDNs distributing and 779 delivering it, are critical requirements for both CDN Providers and 780 CSPs and the CDN Interconnection interfaces must provide sufficient 781 mechanisms to maintain the security of the overall system of 782 interconnected CDNs as well as the information (content, metadata, 783 logs, etc) distributed and delivered through any set of 784 interconnected CDNs. 786 6.1. Security of the CDNI Control interface 788 Information exchanged between interconnected CDNs over this interface 789 is of a sensitive nature. A pair of CDNs use this interface to allow 790 bootstrapping of all the other CDNI interfaces possibly including 791 establishment of the mechanisms for securing these interfaces. 792 Therefore, corruption of that interface may result in corruption of 793 all other interfaces. Using this interface, an upstream CDN may pre- 794 position or delete content or metadata in a downstream CDN and a 795 downstream CDN may provide administrative information to an upstream 796 CDN, etc. All of these operations require that the peer CDNs are 797 appropriately authenticated and that the confidentiality and 798 integrity of information flowing between them can be ensured. 800 6.2. Security of the CDNI Request Routing Interface 802 Appropriate levels of authentication and confidentiality must be used 803 in this interface because it allows an upstream CDN to query the 804 downstream CDN in order to redirect requests, and conversely, allows 805 the downstream CDN to influence the upstream CDN's Request Routing 806 function. 808 In the absence of appropriate security on this interface, a rogue 809 upstream CDN could inundate downstream CDNs with bogus requests, or 810 have the downstream CDN send the rogue upstream CDN private 811 information. Also, a rogue downstream CDN could influence the 812 upstream CDN so the upstream CDN redirects requests to the rogue dCDN 813 or another dCDN in order to, for example, attract additional delivery 814 revenue. 816 6.3. Security of the CDNI Metadata interface 818 This interface allows a downstream CDN to request CDNI metadata from 819 an upstream CDN, and therefore the upstream CDN must ensure that the 820 former is appropriately authenticated before sending the data. 821 Conversely, a downstream CDN must authenticate an upstream CDN before 822 requesting metadata to insulate itself from poisoning by rogue 823 upstream CDNs. The confidentiality and integrity of the information 824 exchanged between the peers must be protected. 826 6.4. Security of the CDNI Logging interface 828 Logging data consists of potentially sensitive information (which end 829 user accessed which media resource, IP addresses of end users, 830 potential names and subscriber account information, etc.). 831 Confidentiality of this information must be protected as log records 832 are moved between CDNs. This information may also be sensitive from 833 the viewpoint that it can be the basis for charging across CDNs. 834 Therefore, appropriate levels of protection are needed against 835 corruption, duplication and loss of this information. 837 7. Acknowledgements 839 The authors would like to thank Andre Beck, Gilles Bertrand, Mark 840 Carlson, Bruce Davie, David Ferguson, Yiu Lee, Kent Leung, Will Li, 841 Kevin Ma, Julien Maisonneuve, Guy Meador, Larry Peterson, Emile 842 Stephan, Oskar van Deventer, Mahesh Viveganandhan and Richard Woundy 843 for their review comments and contributions to the text. 845 8. References 847 8.1. Normative References 849 8.2. Informative References 851 [3GP-DASH] 852 "Transparent end-to-end Packet-switched Streaming Service 853 (PSS); Progressive Download and Dynamic Adaptive Streaming 854 over HTTP (3GP-DASH) 855 http://www.3gpp.org/ftp/Specs/html-info/26247.htm". 857 [ALTO-Charter] 858 "IETF ALTO WG Charter 859 (http://datatracker.ietf.org/wg/alto/charter/)". 861 [ATIS] "ATIS (http://www.atis.org/)". 863 [ATIS-COD] 864 "ATIS IIF: IPTV Content on Demand Service, January 2011 (h 865 ttp://www.atis.org/iif/_Com/Docs/Task_Forces/ARCH/ 866 ATIS-0800042.pdf)". 868 [CDI-Charter] 869 "IETF CDI WG Charter 870 (http://www.ietf.org/wg/concluded/cdi)". 872 [CableLabs] 873 "CableLabs (http://www.cablelabs.com/about/)". 875 [CableLabs-Metadata] 876 "CableLabs VoD Metadata Project Primer 877 (http://www.cablelabs.com/projects/metadata/primer/)". 879 [DECADE-Charter] 880 "IETF DECADE WG Charter 881 (http://datatracker.ietf.org/wg/decade/charter/)". 883 [I-D.bertrand-cdni-experiments] 884 Faucheur, F. and L. Peterson, "Content Distribution 885 Network Interconnection (CDNI) Experiments", 886 draft-bertrand-cdni-experiments-02 (work in progress), 887 February 2012. 889 [I-D.ietf-cdni-use-cases] 890 Bertrand, G., Emile, S., Burbridge, T., Eardley, P., Ma, 891 K., and G. Watson, "Use Cases for Content Delivery Network 892 Interconnection", draft-ietf-cdni-use-cases-08 (work in 893 progress), June 2012. 895 [I-D.jenkins-alto-cdn-use-cases] 896 Niven-Jenkins, B., Watson, G., Bitar, N., Medved, J., and 897 S. Previdi, "Use Cases for ALTO within CDNs", 898 draft-jenkins-alto-cdn-use-cases-03 (work in progress), 899 June 2012. 901 [MPEG-DASH] 902 "Information technology - MPEG systems technologies - Part 903 6: Dynamic adaptive streaming over HTTP (DASH), (DIS 904 version), February 2011 905 http://mpeg.chiariglione.org/ 906 working_documents.htm#MPEG-B". 908 [OIPF-Overview] 909 "OIPF Release 2 Specification Volume 1 - Overview", 910 September 2010. 912 [P2PRG-CDNI] 913 Davie, B. and F. Le Faucheur, "Interconnecting CDNs aka 914 "Peering Peer-to-Peer" 915 (http://www.ietf.org/proceedings/77/slides/P2PRG-2.pdf)", 916 March 2010. 918 [PPSP-Charter] 919 "IETF PPSP WG Charter 920 (http://datatracker.ietf.org/wg/ppsp/charter/)". 922 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 923 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 924 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 926 [RFC3040] Cooper, I., Melve, I., and G. Tomlinson, "Internet Web 927 Replication and Caching Taxonomy", RFC 3040, January 2001. 929 [RFC3466] Day, M., Cain, B., Tomlinson, G., and P. Rzewski, "A Model 930 for Content Internetworking (CDI)", RFC 3466, 931 February 2003. 933 [RFC3568] Barbir, A., Cain, B., Nair, R., and O. Spatscheck, "Known 934 Content Network (CN) Request-Routing Mechanisms", 935 RFC 3568, July 2003. 937 [RFC3570] Rzewski, P., Day, M., and D. Gilletti, "Content 938 Internetworking (CDI) Scenarios", RFC 3570, July 2003. 940 [RFC5023] Gregorio, J. and B. de hOra, "The Atom Publishing 941 Protocol", RFC 5023, October 2007. 943 [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic 944 Optimization (ALTO) Problem Statement", RFC 5693, 945 October 2009. 947 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 948 Protocol (XMPP): Core", RFC 6120, March 2011. 950 [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New 951 Performance Metric Development", BCP 170, RFC 6390, 952 October 2011. 954 [SNIA-CDMI] 955 "SNIA CDMI (http://www.snia.org/tech_activities/standards/ 956 curr_standards/cdmi)". 958 [TAXONOMY] 959 Pathan, A., "A Taxonomy and Survey of Content Delivery 960 Networks 961 (http://www.gridbus.org/reports/CDN-Taxonomy.pdf)", 2007. 963 [Y.1910] "ITU-T Recomendation Y.1910 "IPTV functional 964 architecture"", September 2008. 966 [Y.2019] "ITU-T Recomendation Y.2019 "Content delivery functional 967 architecture in NGN"", September 2010. 969 Appendix A. Design considerations for realizing the CDNI Interfaces 971 This section expands on how CDNI interfaces can reuse and leverage 972 existing protocols before describing each CDNI interface individually 973 and highlighting example candidate protocols that could be considered 974 for reuse or leveraging to implement the CDNI interfaces. 976 A.1. CDNI Request Routing Interface 978 The CDNI Request Routing interface enables a Request Routing function 979 in an upstream CDN to query a Request Routing function in a 980 downstream CDN to determine if the downstream CDN is able (and 981 willing) to accept the delegated content request and to allow the 982 downstream CDN to control what the upstream Request Routing function 983 should return to the User Agent in the redirection message. 985 Therefore, the CDNI Request Routing interface needs to offer a 986 mechanism for an upstream CDN to issue a "Redirection Request" to a 987 downstream CDN. The Request Routing interface needs to be able to 988 support scenarios where the initial User Agent request to the 989 upstream CDN is received over DNS as well as over a content specific 990 application protocol (e.g. HTTP, RTSP, RTMP, etc.). 992 Therefore a Redirection Request is expected to contain information 993 such as: 995 o The protocol (e.g. DNS, HTTP) over which the upstream CDN 996 received the initial User Agent request. 997 o Additional details of the User Agent request that are required to 998 perform effective Request Routing by the Downstream CDN. For DNS 999 this would typically be the IP address of the DNS resolver making 1000 the request on behalf of the User Agent. For requests received 1001 over content specific application protocols the Redirection 1002 Request could contain significantly more information related to 1003 the original User Agent request but at a minimum is expected to 1004 include the User Agent's IP address, the equivalent of the HTTP 1005 Host header and the equivalent of the HTTP abs_path defined in 1006 [RFC2616]. 1008 It should be noted that, the CDNI architecture needs to consider that 1009 a downstream CDN may receive requests from User Agents without first 1010 receiving a Redirection Request from an upstream CDN for the 1011 corresponding User Agent request, for example because: 1013 o User Agents (or DNS resolvers) may cache DNS or application 1014 responses from Request Routers. 1015 o Responses to Redirection Requests over the Request Routing 1016 interface may be cacheable. 1017 o Some CDNs may rely on simple coarse policies, e.g. CDN B agrees 1018 to always serve CDN A's delegated redirection requests, in which 1019 case the necessary redirection details are exchanged out of band 1020 (of the CDNI interfaces), e.g. configured. 1022 On receiving a Redirection Request, the downstream CDN will use the 1023 information provided in the request to determine if it is able (and 1024 willing) to accept the delegated content request and needs to return 1025 the result of its decision to the upstream CDN. 1027 Thus, a Redirection Response from the downstream CDN is expected to 1028 contain information such as: 1030 o Status code indicating acceptance or rejection (possibly with 1031 accompanying reasons). 1032 o Information to allow redirection by the Upstream CDN. In the case 1033 of DNS-based request routing, this is expected to include the 1034 equivalent of a DNS record(s) (e.g. a CNAME) that the upstream CDN 1035 should return to the requesting DNS resolver. In the case of 1036 application based request routing, this is expected to include the 1037 information necessary to construct the application specific 1038 redirection response(s) to return to the requesting User Agent. 1039 For HTTP requests from User Agents this could include a URI that 1040 the upstream CDN could return in a HTTP 3xx response. 1042 The CDNI Request Routing interface is therefore a fairly 1043 straightforward request/response interface and could be implemented 1044 over any number of request/response protocols. For example, it may 1045 be implemented as a WebService using one of the common WebServices 1046 methodologies (XML-RPC, HTTP query to a known URI, etc.). This 1047 removes the need for the CDNI working group to define a new protocol 1048 for the request/response element of the CDNI Request Routing 1049 interface. Thus, the CDNI working group would be left only with the 1050 task of specifying: 1052 o The recommended request/response protocol to use along with any 1053 additional semantics and procedures that are specific to the CDNI 1054 Request Routing interface (e.g. handling of malformed requests/ 1055 responses). 1056 o The syntax (i.e representation/encoding) of the redirection 1057 requests and responses. 1058 o The semantics (i.e. meaning and expected contents) of the 1059 redirection requests and responses. 1061 Additionally, as discussed in Section 3, the CDNI Request Routing 1062 interface is also expected to enable a downstream CDN to provide to 1063 the upstream CDN (static or dynamic) information (e.g. resources, 1064 footprint, load) to facilitate selection of the downstream CDN by the 1065 upstream CDN request routing system when processing subsequent 1066 content requests from User Agents. It is expected that such 1067 functionality of the CDNI request Routing could be specified by the 1068 CDNI working group with significant leveraging of existing IETF 1069 protocols supporting the dynamic distribution of reachability 1070 information (for example by leveraging existing routing protocols) or 1071 supporting application level queries for topological information (for 1072 example by leveraging ALTO). 1074 A.2. CDNI Metadata Interface 1076 The CDNI Metadata interface enables the Distribution System in a 1077 downstream CDN to obtain CDNI Metadata from an upstream CDN so that 1078 the downstream CDN can properly process and respond to: 1080 o Redirection Requests received over the CDNI Request Routing 1081 interface. 1082 o Content Requests received directly from User Agents. 1084 The CDNI Metadata interface needs to offer a mechanism for an 1085 Upstream CDN to: 1087 o Distribute/update/remove CDNI Metadata to a Downstream CDN. 1089 and/or to allow a downstream CDN to: 1091 o Make direct requests for CDNI Metadata objects 1092 o Make recursive requests for CDNI metadata, for example to enable a 1093 downstream CDN to walk down a tree of objects with inter-object 1094 relationships. 1096 The CDNI Metadata interface is therefore similar to the CDNI Request 1097 Routing interface because it is a request/response interface with the 1098 potential addition that CDNI Metadata search may have more complex 1099 semantics than a straightforward Request Routing redirection request. 1100 Therefore, like the CDNI Request Routing interface, the CDNI Metadata 1101 interface may be implemented as a WebService using one of the common 1102 WebServices methodologies (XML-RPC, HTTP query to a known URI, etc.) 1103 or possibly using other existing protocols such as XMPP [RFC6120]. 1104 This removes the need for the CDNI working group to define a new 1105 protocol for the request/response element of the CDNI Metadata 1106 interface. 1108 Thus, the CDNI working group would be left only with the task of 1109 specifying: 1111 o The recommended request/response protocol to use along with any 1112 additional semantics that are specific to the CDNI Metadata 1113 interface (e.g. handling of malformed requests/responses). 1114 o The syntax (i.e representation/encoding) of the CDNI Metadata 1115 objects that will be exchanged over the interface. 1116 o The semantics (i.e. meaning and expected contents) of the 1117 individual properties of a Metadata object. 1118 o How the relationships between different CDNI Metadata objects are 1119 represented. 1121 A.3. CDNI Logging Interface 1123 The CDNI Logging interface enables details of content distribution 1124 and delivery activities to be exchanged between interconnected CDNs, 1125 such as log records related to the delivery of content (similar to 1126 the log records recorded in a web server's access log). 1128 Within CDNs today, log records are used for a variety of purposes. 1129 Specifically CDNs use logs to generate Call Data Records (CDRs) for 1130 passing to billing and payment systems and to real-time (and near 1131 real-time) analytics systems. Such applications place requirements 1132 on the CDNI Logging interface to support guaranteed and timely 1133 delivery of log messages between interconnected CDNs. It may also be 1134 necessary to be able to prove the integrity of received log messages. 1136 Several protocols already exist that could potentially be used to 1137 exchange CDNI logs between interconnected CDNs including SNMP Traps, 1138 syslog, ftp, HTTP POST, etc. although it is likely that some of the 1139 candidate protocols may not be well suited to meet all the 1140 requirements of CDNI. For example SNMP traps pose scalability 1141 concerns and SNMP does not support guaranteed delivery of Traps and 1142 therefore could result in log records being lost and the consequent 1143 CDRs and billing records for that content delivery not being produced 1144 as well as that content delivery being invisible to any analytics 1145 platforms. 1147 Although it is not necessary to define a new protocol for exchanging 1148 logs across the CDNI Logging interface, the CDNI working group would 1149 still need to specify: 1151 o The recommended protocol to use. 1152 o A default set of log fields and their syntax & semantics. Today 1153 there is no standard set of common log fields across different 1154 content delivery protocols and in some cases there is not even a 1155 standard set of log field names and values for different 1156 implementations of the same delivery protocol. 1157 o A default set of conditions that trigger log records to be 1158 generated. 1160 A.4. CDNI Control Interface 1162 The CDNI Control interface allows the Control System in 1163 interconnected CDNs to communicate. The exact inter-CDN control 1164 functionality required to be supported by the CDNI Control interface 1165 is less well defined than the other three CDNI interfaces at this 1166 time. 1168 However, as discussed in Section 3, the CDNI Control interface may be 1169 required to support functionality similar to the following: 1170 o Allow an upstream CDN and downstream CDN to establish, update or 1171 terminate their CDNI interconnection. 1172 o Allow bootstrapping of the other CDNI interfaces (e.g. protocol 1173 address discovery and establishment of security associations). 1174 o Allow configuration of the other CDNI interfaces (e.g. Upstream 1175 CDN specifies information to be reported through the CDNI Logging 1176 interface). 1177 o Allow the downstream CDN to communicate static information about 1178 its delivery capabilities, resources and policies. 1179 o Allow bootstrapping of the interface between CDNs for content 1180 acquisition (even if that interface itself is outside the scope of 1181 the CDNI work). 1182 It is expected that for the Control interface also, existing 1183 protocols can be reused or leveraged. Those will be considered once 1184 the requirements for the Control interface have been refined. 1186 Appendix B. Additional Material 1188 This section records related information that was produced as part of 1189 defining the CDNI problem statement. 1191 B.1. Non-Goals for IETF 1193 Listed below are aspects of content delivery that the authors propose 1194 be kept outside of the scope of the CDNI working group: 1195 o The interface between Content Service Provider and the 1196 Authoritative CDN (i.e. the upstream CDN contracted by the CSP for 1197 delivery by this CDN or by its downstream CDNs). 1198 o The delivery interface between the delivering CDN surrogate and 1199 the User Agent, such as streaming protocols. 1200 o The request interface between the User Agent and the request- 1201 routing system of a given CDN. Existing IETF protocols (e.g. 1202 HTTP, RTSP, DNS) are commonly used by User Agents to request 1203 content from a CDN and by CDN request routing systems to redirect 1204 the User Agent requests. The CDNI working group need not define 1205 new protocols for this purpose. Note however, that the CDNI 1206 control plane interface may indirectly affect some of the 1207 information exchanged through the request interface (e.g. URI). 1208 o The content acquisition interface between CDNs (i.e. the data 1209 plane interface for actual delivery of a piece of content from one 1210 CDN to the other). This is expected to use existing protocols 1211 such as HTTP or protocols defined in other forums for content 1212 acquisition between an origin server and a CDN (e.g. HTTP-based 1213 C2 reference point of ATIS IIF CoD). The CDN Interconnection 1214 problem space described in this document may therefore only 1215 concern itself with the agreement/negotiation aspects of which 1216 content acquisition protocol is to be used between two 1217 interconnected CDNs in view of facilitating interoperability. 1218 o End User/User Agent Authentication. End User/User Agent 1219 authentication and authorization are the responsibility of the 1220 Content Service Provider. 1221 o Content preparation, including encoding and transcoding. The CDNI 1222 architecture aims at allowing distribution across interconnected 1223 CDNs of content treated as opaque objects. Interpretation and 1224 processing of the objects, as well as optimized delivery of these 1225 objects by the surrogate to the End User are outside the scope of 1226 CDNI. 1227 o Digital Rights Management (DRM). DRM is an end-to-end issue 1228 between a content protection system and the User Agent. 1229 o Applications consuming CDNI logs (e.g. charging, analytics, 1230 reporting,...). 1231 o Internal CDN interfaces & protocols (i.e. interfaces & protocols 1232 within one CDN). 1233 o Scalability of individual CDNs. While scalability of the CDNI 1234 interfaces/approach is in scope, how an individual CDN scales is 1235 out of scope. 1236 o Actual algorithms for selection of CDNs or Surrogates by Request 1237 Routing systems (however, some specific parameters required as 1238 input to these algorithms may be in scope when they need to be 1239 communicated across CDNs). 1240 o Surrogate algorithms. For example caching algorithms and content 1241 acquisition methods are outside the scope of the CDNI work. 1242 Content management (e.g. Content Deletion) as it relates to CDNI 1243 content management policies, is in scope but the internal 1244 algorithms used by a cache to determine when to no longer cache an 1245 item of Content (in the absence of any specific metadata to the 1246 contrary) is out of scope. 1247 o Element management interfaces. 1248 o Commercial, business and legal aspects related to the 1249 interconnections of CDNs. 1251 B.2. Relationship to relevant IETF Working Groups & IRTF Reserach 1252 Groups 1254 B.2.1. ALTO WG 1256 As stated in the ALTO Working Group charter [ALTO-Charter]: 1258 "The Working Group will design and specify an Application-Layer 1259 Traffic Optimization (ALTO) service that will provide applications 1260 with information to perform better-than-random initial peer 1261 selection. ALTO services may take different approaches at balancing 1262 factors such as maximum bandwidth, minimum cross-domain traffic, 1263 lowest cost to the user, etc. The working group will consider the 1264 needs of BitTorrent, tracker-less P2P, and other applications, such 1265 as content delivery networks (CDN) and mirror selection." 1267 In particular, the ALTO service can be used by a CDN Request Routing 1268 system to improve its selection of a CDN surrogate to serve a 1269 particular User Agent request (or to serve a request from another 1270 surrogate). [I-D.jenkins-alto-cdn-use-cases] describes a number of 1271 use cases for a CDN to be able to obtain network topology and cost 1272 information from an ALTO server(s) and discusses how CDN Request 1273 Routing could be used as an integration point of ALTO into CDNs. It 1274 is possible that the ALTO service could be used in the same manner in 1275 a multi-CDN environment based on CDN Interconnection. For example, 1276 an upstream CDN may take advantage of the ALTO service in its 1277 decision for selecting a downstream CDN to which a user request 1278 should be delegated. 1280 However, the current work of ALTO is complementary to and does not 1281 overlap with the work described in this document because the 1282 integration between ALTO and a CDN is an internal decision for a 1283 specific CDN and is therefore out of scope for the CDNI working 1284 group. One area for further study is whether additional information 1285 should be provided by an ALTO service to facilitate CDNI CDN 1286 selection. 1288 B.2.2. DECADE WG 1290 The DECADE Working Group [DECADE-Charter] is addressing the problem 1291 of reducing traffic on the last-mile uplink, as well as backbone and 1292 transit links caused by P2P streaming and file sharing applications. 1293 It addresses the problem by enabling an application endpoint to make 1294 content available from an in-network storage service and by enabling 1295 other application endpoints to retrieve the content from there. 1297 Exchanging data through the in-network storage service in this 1298 manner, instead of through direct communication, provides significant 1299 gain where: 1301 o The network capacity/bandwidth from in-network storage service to 1302 application endpoint significantly exceeds the capacity/bandwidth 1303 from application endpoint to application endpoint (e.g. because of 1304 an end-user uplink bottleneck); and 1305 o Where the content is to be accessed by multiple instances of 1306 application endpoints (e.g. as is typically the case for P2P 1307 applications). 1309 While, as is the case for any other data distribution application, 1310 the DECADE architecture and mechanisms could potentially be used for 1311 exchange of CDNI control plane information via an in-network-storage 1312 service (as opposed to directly between the entities terminating the 1313 CDNI interfaces in the neighbor CDNs), we observe that: 1315 o CDNI would operate as a "Content Distribution Application" from 1316 the DECADE viewpoint (i.e. would operate on top of DECADE). 1317 o There does not seem to be obvious benefits in integrating the 1318 DECADE control plane responsible for signaling information 1319 relating to control of the in-network storage service itself, and 1320 the CDNI control plane responsible for application-specific CDNI 1321 interactions (such as exchange of CDNI metadata, CDNI request 1322 redirection, transfer of CDNI logging information). 1323 o There would typically be limited benefits in making use of a 1324 DECADE in-network storage service because the CDNI interfaces are 1325 expected to be terminated by a very small number of CDNI clients 1326 (if not one) in each CDN, and the CDNI clients are expected to 1327 benefit from high bandwidth/capacity when communicating directly 1328 to each other (at least as high as if they were communicating via 1329 an in-network storage server). 1331 The DECADE in-network storage architecture and mechanisms may 1332 theoretically be used for the acquisition of the content objects 1333 themselves between interconnected CDNs. It is not expected that this 1334 would have obvious benefits in typical situations where a content 1335 object is acquired only once from an Upstream CDN to a Downstream CDN 1336 (and then distributed as needed inside the Downstream CDN). But it 1337 might have benefits in some particular situations. Since the 1338 acquisition protocol between CDNs is outside the scope of the CDNI 1339 work, this question is left for further study. 1341 The DECADE in-network storage architecture and mechanisms may 1342 potentially also be used within a given CDN for the distribution of 1343 the content objects themselves among surrogates of that CDN. Since 1344 the CDNI work does not concern itself with operation within a CDN, 1345 this question is left for further study. 1347 Therefore, the work of DECADE may be complementary to but does not 1348 overlap with the CDNI work described in this document. 1350 B.2.3. PPSP WG 1352 As stated in the PPSP Working Group charter [PPSP-Charter]: 1354 "The Peer-to-Peer Streaming Protocol (PPSP) working group develops 1355 two signaling and control protocols for a peer-to-peer (P2P) 1356 streaming system for transmitting live and time-shifted media content 1357 with near real-time delivery requirements." and "The PPSP working 1358 group designs a protocol for signaling and control between trackers 1359 and peers (the PPSP "tracker protocol") and a signaling and control 1360 protocol for communication among the peers (the PPSP "peer 1361 protocol"). The two protocols enable peers to receive streaming data 1362 within the time constraints required by specific content items." 1364 Therefore PPSP is concerned with the distribution of the streamed 1365 content itself along with the necessary signaling and control 1366 required to distribute the content. As such, it could potentially be 1367 used for the acquisition of streamed content across interconnected 1368 CDNs. But since the acquisition protocol is outside the scope of the 1369 work proposed for CDNI, we leave this for further study. Also, 1370 because of its streaming nature, PPSP is not seen as applicable to 1371 the distribution and control of the CDNI control plane and CDNI data 1372 representations. 1374 Therefore, the work of PPSP may be complementary to but does not 1375 overlap with the work described in this document for CDNI. 1377 B.2.4. IRTF P2P Research Group 1379 Some information on CDN interconnection motivations and technical 1380 issues were presented in the P2P RG at IETF 77. The presentation can 1381 be found in [P2PRG-CDNI]. 1383 Appendix C. Additional Material 1385 Note to RFC Editor: This appendix is to be removed on publication as 1386 an RFC. 1388 C.1. Related standardization activites 1390 There are a number of other standards bodies and industry forums that 1391 are working in areas related to CDNs, and in some cases related to 1392 CDNI. This section outlines any potential overlap with the work of 1393 the CDNI working group and any component that could potentially be 1394 reused to realize the CDNI interfaces. 1396 A number of standards bodies have produced specifications related to 1397 CDNs, for example: 1399 o ETSI TISPAN (Telecommunications and Internet converged Services 1400 and Protocols for Advanced Networking) has a series of 1401 specifications focusing on CDNs. 1402 o The Open IPTV Forum (OIPF) and ATIS IPTV Interoperability Forum 1403 (IIF) specify the architecture and the protocols of an IPTV 1404 solution. Although OIPF and ATIS specifications include the 1405 interaction with a CDN, the CDN specifications are coupled with 1406 their IPTV specifications and do not cover interconnection of 1407 CDNs. 1408 o ATIS Cloud Services Forum (CSF) has started investigating 1409 interconnection of CDNs. The ATIS CSF focuses on defining use 1410 cases and requirements for such CDN interconnection, which are 1411 expected to be considered as input into the work of the CDNI 1412 working group. At the time of writing this document, ATIS CSF is 1413 not specifying the corresponding protocols or interfaces and is 1414 expected to leverage the work of the IETF CDNI working group for 1415 those. 1416 o CableLabs, SNIA and ITU have developed (or are working on) 1417 definitions for content related metadata and specifications for 1418 its distribution. However, they do not include metadata specific 1419 to the distribution of content within a CDN or between 1420 interconnected CDNs. 1421 o IETF CDI working group (now concluded) touched on the same problem 1422 space as the present document. However, in accordance with its 1423 initial charter, the CDI working group did not define any 1424 protocols or interfaces to actually enable CDN Interconnection and 1425 at that time (2003) there was not enough industry interest and 1426 real life requirements to justify rechartering the working group 1427 to conduct the corresponding protocol work. 1429 Although some of the specifications describe multi-CDN cooperation or 1430 include reference points for interconnecting CDNs, none of them 1431 specify in sufficient detail all the CDNI interfaces and CDNI 1432 Metadata representations required to enable even a base level of CDN 1433 Interconnection functionality to be implemented. 1435 C.1.1. IETF CDI Working Group (Concluded) 1437 The Content Distribution Internetworking (CDI) Working Group was 1438 formed in the IETF following a BoF in December 2000 and closed in mid 1439 2003. 1441 For convenience, here is an extract from the CDI working group 1442 charter [CDI-Charter]: 1444 " 1446 o The goal of this working group is to define protocols to allow the 1447 interoperation of separately-administered content networks. 1448 o A content network is an architecture of network elements, arranged 1449 for efficient delivery of digital content. Such content includes, 1450 but is not limited to, web pages and images delivered via HTTP, 1451 and streaming or continuous media which are controlled by RTSP. 1452 o The working group will first define requirements for three modes 1453 of content internetworking: interoperation of request-routing 1454 systems, interoperation of distribution systems, and 1455 interoperation of accounting systems. These requirements are 1456 intended to lead to a follow-on effort to define protocols for 1457 interoperation of these systems. 1458 o In its initial form, the working group is not chartered to deliver 1459 those protocols [...] 1461 " 1463 Thus, the CDI working group touched on the same problem space as the 1464 present document. 1466 The CDI working group published 3 Informational RFCs: 1468 o RFC 3466 [RFC3466] - "A Model for Content Internetworking (CDI)". 1469 o RFC 3568 [RFC3568] - "Known Content Network (CN) Request-Routing 1470 Mechanisms". 1471 o RFC 3570 [RFC3570] - "Content Internetworking (CDI) Scenarios". 1473 C.1.2. 3GPP 1475 3GPP was the first organization that released a specification related 1476 to adaptive streaming over HTTP. 3GPP Release 9 specification on 1477 adaptive HTTP streaming was published in March 2010, and there have 1478 been some bug fixes on this specification since the publication. In 1479 addition, 3GPP has produced an extended version for Release 10, which 1480 was published in 2011. This release will include a number of 1481 clarifications, improvements and new features. 1483 [3GP-DASH] is defined as a general framework independent of the data 1484 encapsulation format. It has support for fast initial startup and 1485 seeking, adaptive bitrate switching, re-use of HTTP origin and cache 1486 servers, re-use of existing media playout engines, on-demand, live 1487 and time-shifted delivery. It specifies syntax and semantics of 1488 Media Presentation Description (MPD), format of segments and delivery 1489 protocol for segments. It does not specify content provisioning, 1490 client behavior or transport of MPD. 1492 The content retrieved by a client using [3GP-DASH] adaptive streaming 1493 could be obtained from a CDN but this is not discussed or specified 1494 in the 3GPP specifications as it is transparent to [3GP-DASH] 1495 operations. Similarly, it is expected that [3GP-DASH] can be used 1496 transparently from the CDNs as a delivery protocol (between the 1497 delivering CDN surrogate and the User Agent) in a CDN Interconnection 1498 environment. [3GP-DASH] could also be a candidate for content 1499 acquisition between CDNs in a CDN Interconnection environment. 1501 C.1.3. ISO MPEG 1503 Within ISO MPEG, the Dynamic Adaptive Streaming over HTTP (DASH) ad- 1504 hoc group adopted the 3GPP Release 9 [3GP-DASH] specification as a 1505 starting point and has made some improvements and extensions. 1506 Similar to 3GPP SA4, the MPEG DASH ad-hoc group has been working on 1507 standardizing the manifest file and the delivery format. 1508 Additionally, the MPEG DASH ad-hoc group has also been working on the 1509 use of MPEG-2 Transport Streams as a media format, conversion from/to 1510 existing file formats, common encryption, and so on. The MPEG DASH 1511 specification could also be a candidate for delivery to the User 1512 Agent and for content acquisition between CDNs in a CDN 1513 Interconnection environment. The Draft International Standard (DIS) 1514 version [MPEG-DASH] is currently publicly available since early 1515 February 2011. 1517 In the 95th MPEG meeting in January 2011, the DASH ad-hoc group 1518 decided to start a new evaluation experiment called "CDN-EE". The 1519 goals are to understand the requirements for MPEG DASH to better 1520 support CDN-based delivery, and to provide a guidelines document for 1521 CDN operators to better support MPEG DASH streaming services. The 1522 ongoing work is still very preliminary and does not currently target 1523 looking into CDN Interconnection use cases. 1525 C.1.4. ATIS IIF 1527 ATIS ([ATIS]) IIF is the IPTV Interoperability Forum (within ATIS) 1528 that develops requirements, standards, and specifications for IPTV. 1530 ATIS IIF is developing the "IPTV Content on Demand (CoD) Service" 1531 specification. This includes use of a CDN (referred to in ATIS IIF 1532 CoD as the "Content Distribution and Delivery Functions") for support 1533 of a Content on Demand (CoD) Service as part of a broader IPTV 1534 service. However, this only covers the case of a managed IPTV 1535 service (in particular where the CDN is administered by the service 1536 provider) and does not cover the use, or interconnection, of multiple 1537 CDNs. 1539 C.1.5. CableLabs 1541 "Founded in 1988 by cable operating companies, Cable Television 1542 Laboratories, Inc. (CableLabs) is a non-profit research and 1543 development consortium that is dedicated to pursuing new cable 1544 telecommunications technologies and to helping its cable operator 1545 members integrate those technical advancements into their business 1546 objectives." [CableLabs] 1548 CableLabs has defined specifications for CoD Content Metadata as part 1549 of its VOD Metadata project. 1551 C.1.6. ETSI MCD 1553 ETSI MCD (Media Content Distribution) is the ETSI technical committee 1554 "in charge of guiding and coordinating standardization work aiming at 1555 the successful overall development of multimedia systems (television 1556 and communication) responding to the present and future market 1557 requests on media content distribution". 1559 MCD created a specific work item on interconnection of heterogeneous 1560 CDNs ("CDN Interconnection, use cases and requirements") in March 1561 2010. MCD very recently created a working group to progress this 1562 work item. However, no protocol level work has yet started in MCD 1563 for CDN Interconnection. 1565 C.1.7. ETSI TISPAN 1567 ETSI TISPAN has published two sets of IPTV specifications, one of 1568 which is based on IMS. In addition, TISPAN has published a CDN 1569 architecture supporting delivery of various content services such as 1570 time-shifted TV and VoD to TISPAN devices (UEs) or regular PCs. The 1571 use cases allow for hierarchically and geographically distributed CDN 1572 scenarios, along with multi-CDN cooperation. As a result, the 1573 architecture contains reference points to support interconnection of 1574 other TISPAN CDNs. The protocol definition phase for the 1575 corresponding CDN architecture was kicked-off at the end of 2010 as 1576 is still in progress. In line with its long history of leveraging 1577 IETF protocols, ETSI could potentially leverage CDNI interfaces 1578 developed in the IETF for their related protocol level work on 1579 interconnections of CDNs. 1581 C.1.8. ITU-T 1583 SG13 is developing standards related to the support of IPTV services 1584 (i.e.. multimedia services such as television/VoD/audio/text/ 1585 graphics/data delivered over IP-based managed networks). 1587 ITU-T Recommendation Y.1910 [Y.1910] provides the description of the 1588 IPTV functional architecture. This architecture includes functions 1589 and interfaces for the distribution and delivery of content. This 1590 architecture is aligned with the ATIS IIF architecture. 1592 Based upon ITU-T Rec. Y.1910, ITU-T Rec. Y.2019 [Y.2019] describes in 1593 more detail the content delivery functional architecture. This 1594 architecture allows CDN Interconnection: some interfaces (such as D3, 1595 D4) at the control level allow relationships between different CDNs, 1596 in the same domain or in different domains. Generic procedures are 1597 described, but the choice of the protocols is open. 1599 C.1.9. Open IPTV Forum (OIPF) 1601 The Open IPTV Forum has developed an end-to-end solution to allow any 1602 OIPF terminal to access enriched and personalized IPTV services 1603 either in a managed or a non-managed network[OIPF-Overview]. Some 1604 OIPF services (such as Network PVR) may be hosted in a CDN. 1606 To that end, the Open IPTV Forum specification is made of 5 parts: 1608 o Media Formats including HTTP Adaptive Streaming 1609 o Content Metadata 1610 o Protocols 1611 o Terminal (Declarative or Procedural Application Environment) 1612 o Authentication, Content Protection and Service Protection 1614 C.1.10. TV-Anytime Forum 1616 Version 1 of the TV-Anytime Forum specifications were published as 1617 ETSI TS 102 822-1 through ETSI TS 102 822-7 "Broadcast and On-line 1618 Services: Search, select, and rightful use of content on personal 1619 storage systems ("TV-Anytime")". It includes the specification of 1620 content metadata in XML schemas (ETSI TS 102 822-3) which define 1621 technical parameters for the description of CoD and Live contents. 1622 The specification is referenced by DVB and OIPF. 1624 The TV-anytime Forum was closed in 2005. 1626 C.1.11. SNIA 1628 The Storage Networking Industry Association (SNIA) is an association 1629 of producers and consumers of storage networking products whose goal 1630 is to further storage networking technology and applications. 1632 SNIA has published the Cloud Data Management Interface (CDMI) 1633 standard ([SNIA-CDMI]). 1635 "The Cloud Data Management Interface defines the functional interface 1636 that applications will use to create, retrieve, update and delete 1637 data elements from the Cloud. As part of this interface the client 1638 will be able to discover the capabilities of the cloud storage 1639 offering and use this interface to manage containers and the data 1640 that is placed in them. In addition, metadata can be set on 1641 containers and their contained data elements through this interface." 1643 C.1.12. Summary of existing standardization work 1645 The following sections will summarize the existing work of the 1646 standard bodies listed earlier against the CDNI problem space. 1647 Appendix C.1.12.1 summarizes existing interfaces that could be 1648 leveraged for content acquisition between CDNs and Appendix C.1.12.2 1649 summarizes existing metadata specifications that may be applicable to 1650 CDNI. To date we are not aware of any standardization activities in 1651 the areas of the remaining CDNI interfaces (CDNI Request Routing, 1652 CDNI Control and CDNI Logging). 1654 C.1.12.1. Content Acquisition across CDNs and Delivery to End User 1655 (Data plane) 1657 A number of standards bodies have completed work in the areas of 1658 content acquisition interface between a CSP and a CDN, as well as as 1659 on the delivery interface between the surrogate and the User Agent. 1660 Some of this work is summarized below. 1662 TISPAN, OIPF and ATIS have specified IPTV and/or Content on Demand 1663 (CoD) services, including the data plane aspects (typically different 1664 flavors of RTP/RTCP and HTTP) to obtain content and deliver it to 1665 User Agents. For example, : 1666 o The OIPF data plane includes both RTP and HTTP flavors (HTTP 1667 progressive download, HTTP Adaptive streaming [3GP-DASH]). 1669 o The ATIS IIF specification "IPTV Content on Demand (CoD) Service" 1670 [ATIS-COD] defines a reference point (C2) and the corresponding 1671 HTTP-based data plane protocol for content acquisition between an 1672 authoritative origin server and the CDN. 1673 While these protocols have not been explicitly specified for content 1674 acquisition across CDNs, they are suitable (in addition to others 1675 such as standard HTTP) for content acquisition between CDNs in a CDN 1676 Interconnection environment. Therefore for the purpose of the CDNI 1677 working group there are already multiple existing data plane 1678 protocols that can be used for content acquisition across CDNs. 1680 Similarly, there are multiple existing standards (e.g. the OIPF data 1681 plane mentioned above, HTTP adaptive streaming [3GP-DASH]) or public 1682 specifications (e.g. vendor specific HTTP Adaptive streaming 1683 specifications) so that content delivery can be considered already 1684 solved (or at least sufficiently addressed in other forums). 1686 Thus, specification of the content acquisition interface between CDNs 1687 and the delivery interface between the surrogate and the User Agent 1688 are out of scope for the CDNI working group. The CDNI working group 1689 may only concern itself with the negotiation/selection aspects of the 1690 acquisition protocol to be used in a CDN interonnect scenario. 1692 C.1.12.2. CDNI Metadata 1694 CableLabs, ITU, OIPF and TV-Anytime have work items dedicated to the 1695 specification of content metadata: 1697 o CableLabs has defined specifications for CoD Content Metadata as 1698 part of its VOD Metadata project. "The VOD Metadata project is a 1699 cable television industry and cross-industry-wide effort to 1700 specify the metadata and interfaces for distribution of video-on- 1701 demand (VOD) material from multiple content providers to cable 1702 operators." [CableLabs-Metadata]. However, while the CableLabs 1703 work specifies an interface between a content provider and a 1704 service provider running a CDN, it does not include an interface 1705 that could be used between CDNs. 1706 o ITU Study Group 16 has started work on a number of draft 1707 Recommendations (H.IPTV-CPMD, H.IPTV-CPMD, HSTP.IPTV-CMA, 1708 HSTP.IPTV-UMCI) specifying metadata for content distribution in 1709 IPTV services. 1710 o An Open IPTV Terminal receives the technical description of the 1711 content distribution from the OIPF IPTV platform before receiving 1712 any content. The Content distribution metadata is sent in the 1713 format of a TV-Anytime XSD including tags to describes the 1714 location and program type (on demand or Live) as well as 1715 describing the time availability of the on demand and live 1716 content. 1718 However the specifications outlined above do not include metadata 1719 specific to the distribution of content within a CDN or between 1720 interconnected CDNs, for example geo-blocking information, 1721 availability windows, access control mechanisms to be enforced by the 1722 surrogate, how to map an incoming content request to a file on the 1723 origin server or acquire it from the upstream CDN etc. 1725 The CDMI standard ([SNIA-CDMI]) from SNIA defines metadata that can 1726 be associated with data that is stored by a cloud storage provider. 1727 While the metadata currently defined do not match the needs of CDN 1728 Interconnection, it is worth considering CDMI as one of the existing 1729 pieces of work that may potentially be leveraged for the CDNI 1730 Metadata interface (e.g by extending the CDMI metadata to address 1731 more specific CDNI needs). 1733 C.2. Related Research Projects 1735 C.2.1. OCEAN 1737 OCEAN (http://www.ict-ocean.eu/) is an EU funded research project 1738 that started in February 2010 for 3 years. Some of its objectives 1739 are relevant to CDNI. It aims, among other things, at designing a 1740 new architectural framework for audiovisual content delivery over the 1741 Internet, defining public interfaces between its major building 1742 blocks in order to foster multi-vendor solutions and interconnection 1743 between Content Networks (the term "Content Networks" corresponds 1744 here to the definition introduced in [RFC3466], which encompasses 1745 CDNs). 1747 OCEAN has not yet published any open specifications, nor common best 1748 practices, defining how to achieve such CDN interconnection. 1750 C.2.2. Eurescom P1955 1752 Eurescom P1955 was a 2010 research project involving a four European 1753 Network operators, which studied the interests and feasibility of 1754 interconnecting CDNs by firstly elaborating the main service models 1755 around CDN interconnection, as well as analyzing an adequate CDN 1756 interconnection technical architecture and framework, and finally by 1757 providing recommendations for telcos to implement CDN 1758 interconnection. The Eurescom P1955 project ended in July 2010. 1760 The authors are not aware of material discussing CDN interconnection 1761 protocols or interfaces made publicly available as a deliverable of 1762 this project. 1764 Authors' Addresses 1766 Ben Niven-Jenkins 1767 Velocix (Alcatel-Lucent) 1768 326 Cambridge Science Park 1769 Milton Road, Cambridge CB4 0WG 1770 UK 1772 Email: ben@velocix.com 1774 Francois Le Faucheur 1775 Cisco Systems 1776 Greenside, 400 Avenue de Roumanille 1777 Sophia Antipolis 06410 1778 France 1780 Phone: +33 4 97 23 26 19 1781 Email: flefauch@cisco.com 1783 Nabil Bitar 1784 Verizon 1785 40 Sylvan Road 1786 Waltham, MA 02145 1787 USA 1789 Email: nabil.bitar@verizon.com