CDNI J. Seedorf Internet-Draft NEC Intended status: Informational Y. Yang Expires: September 6, 2015 Yale J. Peterson Neustar March 5, 2015 CDNI Footprint and Capabilities Advertisement using ALTO draft-seedorf-cdni-request-routing-alto-08 Abstract Network Service Providers (NSPs) are currently considering to deploy Content Delivery Networks (CDNs) within their networks. As a consequence of this development, there is a need for interconnecting these local CDNs. The necessary interfaces for inter-connecting CDNs are currently being defined in the Content Delivery Networks Interconnection (CDNI) WG. This document focuses on the CDNI Footprint & Capabilities Advertisement interface (FCI). Specifically, this document specifies a new Application Layer Traffic Optimization (ALTO) service to facilitate Footprint & Capabilities Advertisement in a CDNI context. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 6, 2015. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. Seedorf, et al. Expires September 6, 2015 [Page 1] Internet-Draft CDNI FCI using ALTO March 2015 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. ALTO within CDNI Request Routing . . . . . . . . . . . . . . 3 3. Assumptions and High-Level Design Considerations . . . . . . 4 3.1. General Assumptions and Considerations . . . . . . . . . 4 3.2. Semantics for Footprint/Capabilities Advertisment . . . . 5 3.3. Advantages of using ALTO as the CDNI FCI protocol . . . . 7 3.4. Selection of a Downstream CDN with ALTO . . . . . . . . . 7 4. CDNI FCI ALTO Service . . . . . . . . . . . . . . . . . . . . 8 4.1. Server Response Encoding . . . . . . . . . . . . . . . . 8 4.1.1. CDNI FCI Map . . . . . . . . . . . . . . . . . . . . 8 4.1.2. Meta Information . . . . . . . . . . . . . . . . . . 8 4.1.3. Data Information . . . . . . . . . . . . . . . . . . 8 4.2. Protocol Errors . . . . . . . . . . . . . . . . . . . . . 9 4.3. Example . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Useful ALTO extensions for CDNI Request Routing . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 1. Introduction Many Network Service Providers (NSPs) are currently considering or have already started to deploy Content Delivery Networks (CDNs) within their networks. As a consequence of this development, there is a need for interconnecting these local CDNs. Content Delivery Networks Interconnection (CDNI) has the goal of standardizing protocols to enable such interconnection of CDNs [RFC6707]. The CDNI problem statement [RFC6707] envisions four interfaces to be standardized within the IETF for CDN interconnection: o CDNI Request Routing Interface Seedorf, et al. Expires September 6, 2015 [Page 2] Internet-Draft CDNI FCI using ALTO March 2015 o CDNI Metadata Interface o CDNI Logging Interface o CDNI Control Interface This document focuses solely on the CDNI Request Routing Interface, which can be further divided into two interfaces (see [RFC6707] for a detailed description): the CDNI Request Routing Redirection interface (RI), and the CDNI Footprint & Capabilities Advertisement interface (FCI). This document specifies a new Application Layer Traffic Optimization (ALTO) [RFC7285] service called 'CDNI Footprint & Capabilities Advertisement Service'. This service is used to transport CDNI FCI JSON objects, which are defined in a separate document [I-D.ma-cdni-capabilities]. An abstraction for managing individual CDNI capabilities in an opaque manner is defined as 'FCIBase' object in [I-D.ietf-cdni-footprint-capabilities-semantics]. Throughout this document, we use the terminology for CDNI defined in [RFC6707]. 2. ALTO within CDNI Request Routing The main purpose of the CDNI Request Routing Interface is described in [RFC6707] as follows: "The CDNI Request Routing interface enables a Request Routing function in an Upstream CDN to query a Request Routing function in a Downstream CDN to determine if the Downstream CDN is able (and willing) to accept the delegated Content Request. It also allows the Downstream CDN to control what should be returned to the User Agent in the redirection message by the upstream Request Routing function." On a high level, the scope of the CDNI Request Routing Interface therefore contains two main tasks: o A) Determining if the downstream CDN is willing to accept a delegated content request o B) Redirecting the content request coming from an upstream CDN to the proper entry point or entity in the downstream CDN More precisely, in [RFC7336] the request routing interface is broadly divided into two functionalities: o 1) the asynchronous advertisement of footprint and capabilities by a dCDN that allows a uCDN to decide whether to redirect particular user requests to that dCDN (the CDNI FCI) o 2) the synchronous operation of actually redirecting a user request (the CDNI RI) Seedorf, et al. Expires September 6, 2015 [Page 3] Internet-Draft CDNI FCI using ALTO March 2015 Application Layer Traffic Optimization (ALTO) [RFC7285] is an approach for guiding the resource provider selection process in distributed applications that can choose among several candidate resources providers to retrieve a given resource. By conveying network layer (topology) information, an ALTO server can provide important information to "guide" the resource provider selection process in distributed applications. Usually, it is assumed that an ALTO server conveys information these applications cannot measure themselves [RFC5693]. Originally, ALTO was motivated by the huge amount of cross-ISP traffic generated by P2P applications [RFC5693]. Recently, however, ALTO is also being considered for improving the request routing in CDNs [I-D.jenkins-alto-cdn-use-cases]. In this context, it has also been proposed to use ALTO for selecting an entry-point in a downstream NSP's network (see section 3.4 "CDN delivering Over-The- Top of a NSP's network" in [I-D.jenkins-alto-cdn-use-cases]). Also, the CDNI problem statement explicitly mentions ALTO as a candidate protocol for "algorithms for selection of CDN or Surrogate by Request-Routing systems" [RFC6707]. 3. Assumptions and High-Level Design Considerations In this section we list some assumptions and design issues to be considered when using ALTO for the CDNI Footprint and Capabilities Advertisement interface. 3.1. General Assumptions and Considerations Below we list some general assumptions and considerations: o As explicitly being out-of-scope for CDNI [RFC6707], it is assumed that ingestion of content or acquiring content across CDNs is not part of request routing as considered within CDNI standardization work. The focus of using ALTO (as considered in this document) is hence on request routing only, assuming that the content (desired by the end user) is available in the downstream CDN (or can be aquired by the downstream CDN by some means). o Federation Model: "Footprint and Capabilities Advertisement" and in general CDN request routing depends on the federation model among the CDN providers. Designing a suitable solution thus depends on whether a solution is needed for different settings, where CDNs consist of both NSP CDNs (serving individual ASes) and general, traditional CDNs (such as Akamai). We assume that CDNI is not designed for a setting where only NSP CDNs each serve a single AS only. Seedorf, et al. Expires September 6, 2015 [Page 4] Internet-Draft CDNI FCI using ALTO March 2015 o In this document, it is assumed that the upstream CDN (uCDN) makes the decision on selecting a downstream CDN, based on information that each downstream CDN has made available to the upstream CDN. Further, we assume that in principle more than one dCDN may be suitable for a given end-user request (i.e. different dCDNs may claim "overlapping" footprints). The uCDN hence potentially has to select among several candidate downstream CDNs for a given end user request. o It is not clear what kind(s) of business, contract, and operational relationships two peering CDNs may form. For the Internet, we see provider-customer and peering as two main relations; providers may use different charging models (e.g., 95-percentile, total volume) and may provide different SLAs. Given such unknown characteristics of CDN peering business agreements, we should design the protocol to support as much diverse potential business and operational models as possible. 3.2. Semantics for Footprint/Capabilities Advertisment The CDNI document on "Footprint and Capabilities Semantics" [I-D.ietf-cdni-footprint-capabilities-semantics] defines the semantics for the CDNI FCI. It thus provides guidance on what Footprint and Capabilities mean in a CDNI context and how a protocol solution should in principle look like. Here we briefly summarize the key points of the semantics of Footprint and Capabilities (for a detailed discussion, the reader is referred to [I-D.ietf-cdni-footprint-capabilities-semantics]): o Often, footprint and capabilities are tied together and cannot be interpreted independently from each other. In such cases, i.e. where capabilities must be expressed on a per footprint basis, it may be beneficial to combine footprint and capabilities advertisement. o Given that a large part of Footprint and Capabilities Advertisement will actually happen in contractual agreements, the semantics of CDNI Footprint and Capabilities advertisement refer to answering the following question: what exactly still needs to be advertised by the CDNI FCI? For instance, updates about temporal failures of part of a footprint can be useful information to convey via the CDNI request routing interface. Such information would provide updates on information previously agreed in contracts between the participating CDNs. In other words, the CDNI FCI is a means for a dCDN to provide changes/updates regarding a footprint and/or capabilities it has prior agreed to serve in a contract with a uCDN. Seedorf, et al. Expires September 6, 2015 [Page 5] Internet-Draft CDNI FCI using ALTO March 2015 o It seems clear that "coverage/reachability" types of footprint must be supported within CDNI. The following such types of footprint are mandatory and must be supported by the CDNI FCI: * List of ISO Country Codes * List of AS numbers * Set of IP-prefixes A 'set of IP-prefixes' must be able to contain full IP addresses, i.e., a /32 for IPv4 and a /128 for IPv6, and also IP prefixes with an arbitrary prefix length. There must also be support for multiple IP address versions, i.e., IPv4 and IPv6, in such a footprint. o For all of these mandatory-to-implement footprint types, footprints can be viewed as constraints for delegating requests to a dCDN: A dCDN footprint advertisement tells the uCDN the limitations for delegating a request to the dCDN. For IP prefixes or ASN(s), the footprint signals to the uCDN that it should consider the dCDN a candidate only if the IP address of the request routing source falls within the prefix set (or ASN, respectively). The CDNI specifications do not define how a given uCDN determines what address ranges are in a particular ASN. Similarly, for country codes a uCDN should only consider the dCDN a candidate if it covers the country of the request routing source. The CDNI specifications do not define how a given uCDN determines the country of the request routing source. Multiple footprint constraints are additive, i.e. the advertisement of different types of footprint narrows the dCDN candidacy cumulatively. o The following capabilities seem useful as 'base' capabilities, i.e. ones that are needed in any case and therefore constitute mandatory capabilities to be supported by the CDNI FCI: * Delivery Protocol (e.g., HTTP vs. RTMP) * Acquisition Protocol (for aquiring content from a uCDN) * Redirection Mode (e.g., DNS Redirection vs. HTTP Redirection as discussed in [RFC7336]) * Capabilities related to CDNI Logging (e.g., supported logging mechanisms) Seedorf, et al. Expires September 6, 2015 [Page 6] Internet-Draft CDNI FCI using ALTO March 2015 * Capabilities related to CDNI Metadata (e.g., authorization algorithms or support for proprietary vendor metadata) 3.3. Advantages of using ALTO as the CDNI FCI protocol The following reasons make ALTO a suitable candidate protocol for downstream CDN selection as part of CDNI request routing and in particular for an FCI protocol: o CDN request routing is done at the application layer. ALTO is a protocol specifically designed to improve application layer traffic (and application layer connections among hosts on the Internet) by providing additonal information to applications that these applications could not easily retrieve themselves. For CDNI, this is exactly the case: a uCDN wants to improve application layer CDN request routing by using dedicated information (provided by a dCDN) that the uCDN could not easily obtain otherwise. o The semantics of an ALTO network map are an exact match for the needed information to convey a footprint by a downstream CDN, in particular if such a footprint is being expressed by IP-prefix ranges. o Security: ALTO maps can be signed and hence provide inherent integrity protection (see Section 6) o RESTful-Design: The ALTO protocol has undergone extensive revisions in order to provide a RESTful design regarding the client-server interaction specified by the protocol. A CDNI FCI interface based on ALTO would inherit this RESTful design. o Error-handling: The ALTO protocol has undergone extensive revisions in order to provide sophisticated error-handling, inparticular regarding unexpected cases. A CDNI FCI interface based on ALTO would inherit this thought-through and mature error- handling. o Filtered network map: The ALTO Map Filtering Service (see [RFC7285] for details) would allow a uCDN to query only for parts of an ALTO map. 3.4. Selection of a Downstream CDN with ALTO Under the considerations stated in Section 3, ALTO can help the upstream CDN provider to select a proper downstream CDN provider for a given end user request as follows: Each downstream CDN provider Seedorf, et al. Expires September 6, 2015 [Page 7] Internet-Draft CDNI FCI using ALTO March 2015 hosts an ALTO server which provides ALTO services which convey CDNI FCI information to an ALTO client at the upstream CDN provider. 4. CDNI FCI ALTO Service The ALTO protocol is based on an ALTO Information Service Framework which consists of several services, where all ALTO services are 'provided through a common transport protocol, messaging structure and encoding, and transaction model' [RFC7285]. The ALTO protocol specification [RFC7285] defines several such services, e.g. the ALTO map service. This document defines a new ALTO Service called 'CDNI Footprint & Capabilities Advertisement Service' which conveys JSON objects of media type 'application/alto-fcimap+json'. This media type and JSON object format is defined in [I-D.ma-cdni-capabilities]; this document specifies how to transport such JSON objects via the ALTO protocol with the ALTO 'CDNI Footprint & Capabilities Advertisement Service'. An abstraction for managing individual CDNI capabilities in an opaque manner is defined as 'FCIBase' object in [I-D.ietf-cdni-footprint-capabilities-semantics]. 4.1. Server Response Encoding 4.1.1. CDNI FCI Map The media type of the CDNI FCI Map is 'application/alto-cdni- fcimap+json'. The HTTP Method, Accept Input Parameters, Capabilities, Uses, and Response of the CDNI FCI Map are specified in [I-D.ma-cdni-capabilities]. 4.1.2. Meta Information The 'meta' field of a FCIMapData response MUST include 'vtag', which is an ALTO Version Tag of the retrieved FCIMapData according to [RFC7285] (Section 10.3.). It thus contains a 'resource-id' attribute, and a 'tag' is an identifier string. 4.1.3. Data Information The data component of a CDNI FCI Map resource is named 'fcimap' which is a JSON object of type FCIMapData. This JSON object of type FCIMapData is derived from ResponseEntityBase as specified in the ALTO protocol [RFC7285] (Section 8.4.) and specified in [I-D.ma-cdni-capabilities]. Seedorf, et al. Expires September 6, 2015 [Page 8] Internet-Draft CDNI FCI using ALTO March 2015 4.2. Protocol Errors Protocol errors are handled as specified in the ALTO protocol [RFC7285] (Section 8.5.). 4.3. Example The following example shows an CDNI FCI Map as in [I-D.ma-cdni-capabilities], however with meta-information as defined in Section 4.1.2 of this document. Seedorf, et al. Expires September 6, 2015 [Page 9] Internet-Draft CDNI FCI using ALTO March 2015 GET /fcimap HTTP/1.1 Host: alto.example.com Accept: application/alto-fcimap+json,application/alto-error+json HTTP/1.1 200 OK Content-Length: 439 Content-Type: application/alto-fcimap+json { "meta" : { "vtag": { "resource-id": "my-default-fcimap", "tag": "da65eca2eb7a10ce8b059740b0b2e3f8eb1d4785" } }, "fcimap": [ { "name": "delivery_protocol", "values": [ "HTTP", "RTSP", "MMS" ] }, { "name": "delivery_protocol", "values": [ "RTMP", "HTTPS" ], "footprint": [ { "type": "IPv4CIDR", "values": [ "10.1.0.0/16", "10.10.10.0/24" ] } ] } ] } 5. Useful ALTO extensions for CDNI Request Routing It is envisioned that yet-to-be-defined ALTO extensions will be standardized that make the ALTO protocol more suitable and useful for applications other than the originally considered P2P use case [I-D.marocco-alto-next]. Some of these extensions to the ALTO protocol would be useful for ALTO to be used as a protocol within CDNI request routing, and in particular within the "Footprint and Seedorf, et al. Expires September 6, 2015 [Page 10] Internet-Draft CDNI FCI using ALTO March 2015 Capabilities Advertisment" part of the CDNI request routing interface. The following proposed extensions to ALTO would be beneficial to facilitate CDNI request routing with ALTO as outlined in Section 3.4: o Server-initiated Notifications and Incremental Updates: In case the footprint or the capabilities of a downstream CDN change abruptly (i.e. unexpectedly from the perspective of an upstream CDN), server initiated notifications would enable a dCDN to directly inform an upstream CDN about such changes. Consider the case where - due to failure - part of the footprint of the dCDN is not functioning, i.e. the CDN cannot serve content to such clients with reasonable QoS. Without server-initiated notifications, the uCDN might still use a very recent network and cost map from dCDN, and therefore redirect request to dCDN which it cannot serve. Similarly, the possibility for incremental updates would enable efficient conveyance of the aforementioned (or similar) status changes by the dCDN to the uCDN. A proposal for server-initiated ALTO updates can be found in [I-D.marocco-alto-ws]. A discussion of incremental ALTO updates can be found in [I-D.schwan-alto-incr-updates]. o Content Availability on Hosts: A dCDN might want to express CDN capabilties in terms of certain content types (e.g. codecs/ formats, or content from certain content providers). A new endpoint property for ALTO that would be able to express such "content availability" would enable a dCDN to make available such information to an upstream CDN. This would enable a uCDN to determine if a given dCDN actually has the capabilities for a given request with respect to the type of content requested. o Resource Availability on Hosts or Links: The capabilities on links (e.g. maximum bandwidth) or caches (e.g. average load) might be useful information for an upstream CDN for optimized dowmstream CDN selection. For instance, if a uCDN receives a streaming request for content with a certain bitrate, it needs to know if it is likely that a dCDN can fulfill such stringent application-level requirements (i.e. can be expected to have enough consistent bandwidth) before it redirects the request. In general, if ALTO could convey such information via new endpoint properties, it would enable more sophisticated means for downstream CDN selection with ALTO. Seedorf, et al. Expires September 6, 2015 [Page 11] Internet-Draft CDNI FCI using ALTO March 2015 6. Security Considerations One important security consideration is the proper authentication of advertisement information provided by a downstream CDN. The ALTO protocol provides a specification for a signature of ALTO information (see 8.2.2. of [RFC7285]. ALTO thus provides a proper means for protecting the integrity of FCI information. More Security Considerations will be discussed in a future version of this document. 7. Acknowledgements The authors would like to thank Kevin Ma, Daryl Malas, and Matt Caulfield for their timely reviews and invaluable comments. Jan Seedorf is partially supported by the GreenICN project (GreenICN: Architecture and Applications of Green Information Centric Networking), a research project supported jointly by the European Commission under its 7th Framework Program (contract no. 608518) and the National Institute of Information and Communications Technology (NICT) in Japan (contract no. 167). The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the GreenICN project, the European Commission, or NICT. 8. References 8.1. Normative References [RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic Optimization (ALTO) Problem Statement", RFC 5693, October 2009. [RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content Distribution Network Interconnection (CDNI) Problem Statement", RFC 6707, September 2012. [RFC6770] Bertrand, G., Stephan, E., Burbridge, T., Eardley, P., Ma, K., and G. Watson, "Use Cases for Content Delivery Network Interconnection", RFC 6770, November 2012. [RFC7285] Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", RFC 7285, September 2014. Seedorf, et al. Expires September 6, 2015 [Page 12] Internet-Draft CDNI FCI using ALTO March 2015 [RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, "Framework for Content Distribution Network Interconnection (CDNI)", RFC 7336, August 2014. [RFC7337] Leung, K. and Y. Lee, "Content Distribution Network Interconnection (CDNI) Requirements", RFC 7337, August 2014. 8.2. Informative References [I-D.peterson-CDNI-strawman] Peterson, L. and J. Hartman, "Content Distribution Network Interconnection (CDNI) Problem Statement", draft-peterson- CDNI-strawman-01 (work in progress), May 2011. [I-D.marocco-alto-next] Marocco, E. and V. Gurbani, "Extending the Application- Layer Traffic Optimization (ALTO) Protocol", draft- marocco-alto-next-00 (work in progress), January 2012. [I-D.marocco-alto-ws] Marocco, E. and J. Seedorf, "WebSocket-based server-to- client notifications for the Application-Layer Traffic Optimization (ALTO) Protocol", draft-marocco-alto-ws-02 (work in progress), February 2014. [I-D.schwan-alto-incr-updates] Schwan, N. and B. Roome, "ALTO Incremental Updates", draft-schwan-alto-incr-updates-02 (work in progress), July 2012. [I-D.jenkins-alto-cdn-use-cases] Niven-Jenkins, B., Watson, G., Bitar, N., Medved, J., and S. Previdi, "Use Cases for ALTO within CDNs", draft- jenkins-alto-cdn-use-cases-03 (work in progress), June 2012. [I-D.ma-cdni-capabilities] Ma, K. and J. Seedorf, "CDNI Footprint & Capabilities Advertisement Interface", draft-ma-cdni-capabilities-06 (work in progress), June 2014. [I-D.liu-cdni-cost] Liu, H., "A Cost Perspective on Using Multiple CDNs", draft-liu-cdni-cost-00 (work in progress), October 2011. Seedorf, et al. Expires September 6, 2015 [Page 13] Internet-Draft CDNI FCI using ALTO March 2015 [I-D.ietf-cdni-metadata] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma, "CDN Interconnection Metadata", draft-ietf-cdni- metadata-09 (work in progress), March 2015. [I-D.ietf-cdni-logging] Faucheur, F., Bertrand, G., Oprescu, I., and R. Peterkofsky, "CDNI Logging Interface", draft-ietf-cdni- logging-15 (work in progress), February 2015. [I-D.ietf-cdni-footprint-capabilities-semantics] Seedorf, J., Peterson, J., Previdi, S., Brandenburg, R., and K. Ma, "CDNI Request Routing: Footprint and Capabilities Semantics", draft-ietf-cdni-footprint- capabilities-semantics-05 (work in progress), March 2015. Authors' Addresses Jan Seedorf NEC Laboratories Europe, NEC Europe Ltd. Kurfuersten-Anlage 36 Heidelberg 69115 Germany Phone: +49 (0) 6221 4342 221 Email: jan.seedorf@neclab.eu URI: http://www.neclab.eu Y.R. Yang Yale University 51 Prospect Street New Haven 06511 USA Email: yry@cs.yale.edu URI: http://www.cs.yale.edu/~yry/ Jon Peterson NeuStar 1800 Sutter St Suite 570 Concord CA 94520 USA Email: jon.peterson@neustar.biz Seedorf, et al. Expires September 6, 2015 [Page 14]