DECADE P. Zhang Internet-Draft Mar 5, 2012 Intended status: Informational Expires: September 6, 2012 Comparison of DECADE with CDNi draft-zhang-decade-cdni-comparison-00 Abstract This document gives a brief comparison of DECADE and CDNi, two working groups on content delivery. CDNi aims at overcoming the limited resource and footprints of a single CDN by interconnecting multiple CDNs. While DECADE is mainly concerned with reducing the last-mile bandwidth bottleneck and inter-domain traffics with in- network storage. This in-network storage can also be utilized by Content Service Providers (CSPs) as a CDN, whose footprints be across multiple Internet Service Providers (CSPs). In this sense, DECADE can also be a possible approach to overcome the limited footprints of a single CDN. This document attempts to gain some understanding on the relationship of these two solutions. 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, 2012. Copyright Notice Copyright (c) 2012 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 (http://trustee.ietf.org/license-info) in effect on the date of Zhang Expires September 6, 2012 [Page 1] Internet-Draft DECADE vs. CDNi Mar 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Content Service Provider (CSP) . . . . . . . . . . . . 3 1.1.2. DECADE server . . . . . . . . . . . . . . . . . . . . . 3 1.1.3. DECADE portal . . . . . . . . . . . . . . . . . . . . . 3 2. DECADE as a CDN across mutliple ISPs . . . . . . . . . . . . . 4 3. Comparison of DECADE with CDNi . . . . . . . . . . . . . . . . 5 3.1. Deployment complexity and cost . . . . . . . . . . . . . . 6 3.2. Support of individual users . . . . . . . . . . . . . . . . 6 3.3. Support of P2P mode . . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 6. Normative References . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Zhang Expires September 6, 2012 [Page 2] Internet-Draft DECADE vs. CDNi Mar 2012 1. Introduction Content Delivery Networks (CDNs) are widely utilized to deliver videos, voices, and other content generated by Content Service Providers (CSPs) to end users. However, a single CDN is mostly constrained in geographical coverage and resource volume, and the CDNi working group is aimed at interconnecting standalone CDNs so that their geographic coverage and resources can be aggregated. On the other hand, DECADE working group is aimed at introducing in- network storage to alleviate last-mile bandwidth bottleneck, as well as reduce inter-domain traffics. Seemingly the goals of DECADE and CDNi are orthogonal, but actually the in-network storage of DECADE can be leveraged by CSPs to deliver their content in a similar way as using a CDN. For example, after an ISP have deployed DECADE servers its network, a CSP can send their content to the DECADE Portal provided by the ISP, which will distribute the content to DECADE servers in multiple locations. When a content request the content from CSP, it is directed to the DECADE portal, which then select a DECADE server that is optimal for them. In this way, DECADE provides a similar service like CDN in a single ISP. In the next section, we will show how DECADE can be used as a CDN across multiple ISPs. To this end, we are interested in comparing DECADE with CDNi as another possible approach to overcome the geographical coverage limitation of standalone CDNs. 1.1. Concepts 1.1.1. Content Service Provider (CSP) A content service provider leverages CDNs to delivery their content to content customers over Internet. 1.1.2. DECADE server A DECADE server is implemented with DECADE protocols, management mechanism and storage strategies. It is an important element to provide DECADE services. In a DECADE server, we have a number of Data Lockers each of which is a virtual account and private STORAGE space for applications. 1.1.3. DECADE portal A DECADE portal offers CSPs a portal site for file upload. It also uses ALTO service to direct end users to an optimal DECADE Server to download files. Zhang Expires September 6, 2012 [Page 3] Internet-Draft DECADE vs. CDNi Mar 2012 2. DECADE as a CDN across mutliple ISPs The DECADE integration example document illustrates how to construct a file distribution platform based on the DECADE+ALTO architecture. In that document, DECADE is deployed in a single ISP, and CSPs can use DECADE as a distribution platform or CDN in within this ISP. In the following, we illustrate how this example can be extended to the multiple-ISP scenarios, in which DECADE servers owned by multiple ISPs can be leveraged to deliver content for CSPs. For simplicity of illustration, let us take two ISPs for example. A CSP register at ISP-1 and upload the file to the DECADE portal of ISP-1, which then distributes the file to multiple DECADE servers. A client in ISP-2 requests the file from the CSP, and is redirected to the DECADE portal in ISP-1, which recognizes that the request is from a client in ISP-2. Then, it redirects the request to the optimal DECADE server (DECADE server B) at ISP-2 using information provided by ALTO service. If server B has the file cached in its memory, then it sends the file directly to the user. Otherwise, server B will send a request to the DECADE portal of ISP-1. Recognizing this request is from a DECADE server, it is redirected to the optimal server DECADE server A in ISP-1. Then A sends the file to B, which will cache the file and send it to the client that requested the file. The detailed communication diagram is as follow, and we omit the interaction of DECADE-1 portal with ALTO servers for limited space. Zhang Expires September 6, 2012 [Page 4] Internet-Draft DECADE vs. CDNi Mar 2012 _________ ____________ __________ __________ __________ | | |Publisher's | | DECADE-1 | | DECADE | | DECADE | | Client | | Portal | | Portal | | Server A | | Server B | |_________| |____________| |__________| |__________| |__________| | | | | | |Download Req | | | | |------------->| | | | | URLs&Tokens | | | | |<-------------| | | | | | | | | | Download Require(Tokens) | | | |------------------------------>| | | | | | | | | addree of the optimal server | | | | in ISP-2 | | | |<------------------------------| | | | | | | | | | Get Data (Tokens) | | |------------------------------------------------------------>| | | | | | | | | Download Require(Tokens) | | | |<----------------------------| | | | | | | | | addree of the optimal | | | | server in ISP-1 | | | |---------------------------->| | | | | Get Data | | | | | (Tokens) | | | | |<--------------| | | | | Send Data | | | | |-------------->| | | Send Data | | | |<------------------------------------------------------------| An example of distribution platform of DECADE across two ISPs Figure 1 3. Comparison of DECADE with CDNi In this section, we take DECADE as another possible solution to the limited coverage problem of standalone CDNs, and try to compare it to the CDNi solution. Zhang Expires September 6, 2012 [Page 5] Internet-Draft DECADE vs. CDNi Mar 2012 Before comparisons, we should note the similarity and relation between DECADE and CDNi. First, note that these two solutions can both benefit from using ALTO as a service to make decisions. In DECADE, ALTO helps DECADE portal to decide which is the best server for a specific end users; In CDNi, a CDN can use ALTO to decide to which CDN it should redirect a client's requests. Secondly, as outlined in the requirement document of CDNi, DECADE can be used by CDNi for control message exchanges, acquisition of content objects between different CDNs, and for content delivery within a given CDN. But the benefits of using DECADE in CDNi are rather limited. 3.1. Deployment complexity and cost Since DECADE provides a open standard for in-network storage architecture, ISPs can easily deploy their own DECADE servers in their networks. Moreover, it is more likely that ISP can deploy their storage servers more widely and closer to end users in their networks than third-party CDN providers can. When multiple ISPs have deployed their DECADE storage systems, a CSP can just subscribe the DECADE service provided by one ISP, and can distribute its content to DECADE servers across these multiple ISPs, as shown in the example in the last section. The possible requirement may be there should be a charging model so that ISPs can charge each other on the DECADE storage consumption incurred by delivering content generated by CSPs in other ISPs. Since ISPs have already initiated contracts with each other, this model can be built just like traffic charging model. Moreover, no request routing interface is needed by DECADE. The downside is that ISPs should deploy DECADE servers, and for ISPs that have no DECADE service, their users can be outside of coverage. While using CDNi, existing CDNs can be leveraged without the need to deploy new servers. This implies a lower deployment cost. 3.2. Support of individual users Apart from providing service to large CSPs, DECADE can also provide services to personal users. For example, a user can register at a nearby DECADE server deployed by the ISP she subscribes to. Using this DECADE server, it is possible for her to stream videos or voices to her friends, despite the uplink link bandwidth constraint. On the other hand, most CDNs are CSP oriented and not practical for individual end users. This will also be true for CDNi, which is a interconnection of CDNs. 3.3. Support of P2P mode Since DECADE service can be open to end users, CSPs can also distribute their content using P2P. Under this mode, end users will upload and download chunks of a file to and from the DECADE server Zhang Expires September 6, 2012 [Page 6] Internet-Draft DECADE vs. CDNi Mar 2012 they are connected to. By using P2P, CSPs can reduce the cost of employing DECADE services provided by ISPs. But it is more likely that CSPs still use DECADE services to distribute content, but can use P2P simultaneously to reduce cost. 4. Security Considerations This document does not contain any security considerations. 5. IANA Considerations This document does not have any IANA considerations. 6. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Author's Address Peng Zhang Email: pzhang.thu@gmail.com Zhang Expires September 6, 2012 [Page 7]