CDNI H. Liu Internet-Draft Yale University Intended status: Informational Oct 22, 2011 Expires: April 24, 2012 A Cost Perspective on Using Multiple CDNs draft-liu-cdni-cost-00 Abstract This document describes several potential price and charge issues in CDN interconnection. It discusses some optional charge models when CDNs are interconnected and presents a need from Content Service Providers (CSP) or CDNs to optimize their cost locally and guarantee their performance. It finally shows how can CDNI frameworks and protocols support price, charge and policy information exchanging. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 24, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Liu Expires April 24, 2012 [Page 1] Internet-Draft CDNI Cost Oct 2011 (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 BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Content Customer (CC) . . . . . . . . . . . . . . . . . 3 1.1.2. Content Service Provider (CSP) . . . . . . . . . . . . 3 1.1.3. Upstream CDN (U-CDN) . . . . . . . . . . . . . . . . . 3 1.1.4. Downstream CDN (D-CDN) . . . . . . . . . . . . . . . . 3 1.1.5. Relay CDN (R-CDN) . . . . . . . . . . . . . . . . . . . 3 2. Charge Models in CDNI . . . . . . . . . . . . . . . . . . . . . 3 2.1. CDNI Network . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Recursive Charge Model . . . . . . . . . . . . . . . . . . 4 2.3. Interative Charge Model . . . . . . . . . . . . . . . . . . 5 3. Local Optimization . . . . . . . . . . . . . . . . . . . . . . 5 4. Protocol Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Liu Expires April 24, 2012 [Page 2] Internet-Draft CDNI Cost Oct 2011 1. Introduction The cost optimization perspective so far has not been considered in inter-connecting multiple Content Delivery Networks (CDNs). Specifically, a Content Service Provider (CSP) with multiple CDNs may consider cost or conduct cost optimization, in addition to performance, when deciding how to direct a request when it has multiple candidate CDNs. This draft discussses some potential charge/price models in CDNI and shows that CSPs and CDNs can optimize their benefit locally, based on charge and performance information. It also shows how to integrate the model into CDNI's protocol and architecture design. 1.1. Concepts 1.1.1. Content Customer (CC) A content customer downloads and consume content from Internet. 1.1.2. Content Service Provider (CSP) A content service provider leverages CDNs to delivery their content to content customers over Internet. 1.1.3. Upstream CDN (U-CDN) Upstream CDNs are directly connected with CSPs. CSPs have commercial contract with upstream CDNs and can upload content objects into them. Upstream CDNs charge their CSPs according to the storage, number of requests and traffic usage. 1.1.4. Downstream CDN (D-CDN) Downstream CDNs serve content customers directly. The content requests will be finally redirected to downstream CDNs. 1.1.5. Relay CDN (R-CDN) If a CDN is on the path of content delivery, but is neither an upstream CDN nor a downstream CDN, it is a relay CDN. 2. Charge Models in CDNI Liu Expires April 24, 2012 [Page 3] Internet-Draft CDNI Cost Oct 2011 2.1. CDNI Network Figure 1 shows a simple case when CDNs are interconnected. CSP rents two upstream CDNs, U-CDN-1 and U-CDN-2. To delivery content to CC-2, CSP-1 can choose either U-CDN-1 or U-CDN-2 to carry the task. Typically, the costs and performances of U-CDN-1 and U-CDN-2 are different. CSP needs the price and performance information for the decision. Next we present two potential and simple charge models in CDNI. +-------+ | CSP-1 |----------------------- +-------+ | | | ,---------. ,---------. ,-' `-. ,-' `-. ( U-CDN-1 ) ( U-CDN-2 ) `-. ,-' `-. ,-' `---------' `---------' | / ,---------. / ,-' `-. / ( R-CDN-1 ) / `-. ,-' / / `---------' \ / / \ / ,---------. ,---------. / ,-' `-. ,-' `-. ( D-CDN-1 ) ( D-CDN-2 ) `-. ,-' `-. ,-' `---------' `---------' | | +-------+ +-------+ | CC-1 | | CC-2 | +-------+ +-------+ A Simple Case of CDN Interconnection Figure 1 2.2. Recursive Charge Model In this model, CSP-1 does not know about how U-CDN-1 and U-CDN-2 will handle the content delivery tasks. It only redirects the requests from CCs to U-CDN-1 or U-CDN-2, and the upstreaming CDNs will response or redirect the requests. For CSP-1, it only knows about the price and the performance to select U-CDN-1 or U-CDN-2. U-CDN-1 Liu Expires April 24, 2012 [Page 4] Internet-Draft CDNI Cost Oct 2011 will make contracts with R-CDN-1 and so does U-CDN-2 with D-CDN-2. 2.3. Interative Charge Model In this model, CSP-1 has the knowledge about the details of the content delivery paths. Interatively, U-CDN-1 tells CSP-1 about the price to R-CDN-1, R-CDN-1 tells CSP-1 about the prices of D-CDN-1 and D-CDN-2. When CSP-1 knows about all the options to delivery the content, it can choose an optimal one which can maximize its benefits. 3. Local Optimization With the price and performance information provided by CDNs, CSPs can locally perform an optimization. If its target is to minimize its CDN cost, it needs to consider the storage and traffic costs of all the options. It can smartly put populary content into CDNs whose traffic prices are cheaper and put cold content into CDNs whose storage prices are cheaper. If its targets is to get best delivery performance, it can choose the best delivery path according to the performance feedback information. 4. Protocol Considerations Given that CDN charge or price infomation is various with time and essential to CPs and CDNs, it is best to be considered in CDNI protocol design. The messages carrying this information can be exchanged among CPs and CDNs. The CDN performance information can be sent by CDNs themselves or CCs to CSPs. To select a U-CDN or a content delivery path, a CSP can leverage the request redirection mechanism. 5. Security Considerations This document does not contain any security considerations. 6. IANA Considerations This document does not have any IANA considerations. 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Liu Expires April 24, 2012 [Page 5] Internet-Draft CDNI Cost Oct 2011 Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Hongqiang Liu Yale University Email: hongqiang.liu@yale.edu Liu Expires April 24, 2012 [Page 6]