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While DECADE is mainly concerned with reducing the 16 last-mile bandwidth bottleneck and inter-domain traffics with in- 17 network storage. This in-network storage can also be utilized by 18 Content Service Providers (CSPs) as a CDN, whose footprints be across 19 multiple Internet Service Providers (CSPs). In this sense, DECADE 20 can also be a possible approach to overcome the limited footprints of 21 a single CDN. This document attempts to gain some understanding on 22 the relationship of these two solutions. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on September 6, 2012. 41 Copyright Notice 43 Copyright (c) 2012 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 1.1. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.1.1. Content Service Provider (CSP) . . . . . . . . . . . . 3 61 1.1.2. DECADE server . . . . . . . . . . . . . . . . . . . . . 3 62 1.1.3. DECADE portal . . . . . . . . . . . . . . . . . . . . . 3 63 2. DECADE as a CDN across mutliple ISPs . . . . . . . . . . . . . 4 64 3. Comparison of DECADE with CDNi . . . . . . . . . . . . . . . . 5 65 3.1. Deployment complexity and cost . . . . . . . . . . . . . . 6 66 3.2. Support of individual users . . . . . . . . . . . . . . . . 6 67 3.3. Support of P2P mode . . . . . . . . . . . . . . . . . . . . 6 68 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 69 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 70 6. Normative References . . . . . . . . . . . . . . . . . . . . . 7 71 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 73 1. Introduction 75 Content Delivery Networks (CDNs) are widely utilized to deliver 76 videos, voices, and other content generated by Content Service 77 Providers (CSPs) to end users. However, a single CDN is mostly 78 constrained in geographical coverage and resource volume, and the 79 CDNi working group is aimed at interconnecting standalone CDNs so 80 that their geographic coverage and resources can be aggregated. 82 On the other hand, DECADE working group is aimed at introducing in- 83 network storage to alleviate last-mile bandwidth bottleneck, as well 84 as reduce inter-domain traffics. Seemingly the goals of DECADE and 85 CDNi are orthogonal, but actually the in-network storage of DECADE 86 can be leveraged by CSPs to deliver their content in a similar way as 87 using a CDN. For example, after an ISP have deployed DECADE servers 88 its network, a CSP can send their content to the DECADE Portal 89 provided by the ISP, which will distribute the content to DECADE 90 servers in multiple locations. When a content request the content 91 from CSP, it is directed to the DECADE portal, which then select a 92 DECADE server that is optimal for them. In this way, DECADE provides 93 a similar service like CDN in a single ISP. In the next section, we 94 will show how DECADE can be used as a CDN across multiple ISPs. 96 To this end, we are interested in comparing DECADE with CDNi as 97 another possible approach to overcome the geographical coverage 98 limitation of standalone CDNs. 100 1.1. Concepts 102 1.1.1. Content Service Provider (CSP) 104 A content service provider leverages CDNs to delivery their content 105 to content customers over Internet. 107 1.1.2. DECADE server 109 A DECADE server is implemented with DECADE protocols, management 110 mechanism and storage strategies. It is an important element to 111 provide DECADE services. In a DECADE server, we have a number of 112 Data Lockers each of which is a virtual account and private STORAGE 113 space for applications. 115 1.1.3. DECADE portal 117 A DECADE portal offers CSPs a portal site for file upload. It also 118 uses ALTO service to direct end users to an optimal DECADE Server to 119 download files. 121 2. DECADE as a CDN across mutliple ISPs 123 The DECADE integration example document illustrates how to construct 124 a file distribution platform based on the DECADE+ALTO architecture. 125 In that document, DECADE is deployed in a single ISP, and CSPs can 126 use DECADE as a distribution platform or CDN in within this ISP. In 127 the following, we illustrate how this example can be extended to the 128 multiple-ISP scenarios, in which DECADE servers owned by multiple 129 ISPs can be leveraged to deliver content for CSPs. 131 For simplicity of illustration, let us take two ISPs for example. A 132 CSP register at ISP-1 and upload the file to the DECADE portal of 133 ISP-1, which then distributes the file to multiple DECADE servers. A 134 client in ISP-2 requests the file from the CSP, and is redirected to 135 the DECADE portal in ISP-1, which recognizes that the request is from 136 a client in ISP-2. Then, it redirects the request to the optimal 137 DECADE server (DECADE server B) at ISP-2 using information provided 138 by ALTO service. If server B has the file cached in its memory, then 139 it sends the file directly to the user. Otherwise, server B will 140 send a request to the DECADE portal of ISP-1. Recognizing this 141 request is from a DECADE server, it is redirected to the optimal 142 server DECADE server A in ISP-1. Then A sends the file to B, which 143 will cache the file and send it to the client that requested the 144 file. 146 The detailed communication diagram is as follow, and we omit the 147 interaction of DECADE-1 portal with ALTO servers for limited space. 149 _________ ____________ __________ __________ __________ 150 | | |Publisher's | | DECADE-1 | | DECADE | | DECADE | 151 | Client | | Portal | | Portal | | Server A | | Server B | 152 |_________| |____________| |__________| |__________| |__________| 153 | | | | | 154 |Download Req | | | | 155 |------------->| | | | 156 | URLs&Tokens | | | | 157 |<-------------| | | | 158 | | | | | 159 | Download Require(Tokens) | | | 160 |------------------------------>| | | 161 | | | | | 162 | addree of the optimal server | | | 163 | in ISP-2 | | | 164 |<------------------------------| | | 165 | | | | | 166 | | Get Data (Tokens) | | 167 |------------------------------------------------------------>| 168 | | | | | 169 | | | Download Require(Tokens) | 170 | | |<----------------------------| 171 | | | | | 172 | | | addree of the optimal | 173 | | | server in ISP-1 | 174 | | |---------------------------->| 175 | | | | Get Data | 176 | | | | (Tokens) | 177 | | | |<--------------| 178 | | | | Send Data | 179 | | | |-------------->| 180 | | Send Data | | | 181 |<------------------------------------------------------------| 183 An example of distribution platform of DECADE across two ISPs 185 Figure 1 187 3. Comparison of DECADE with CDNi 189 In this section, we take DECADE as another possible solution to the 190 limited coverage problem of standalone CDNs, and try to compare it to 191 the CDNi solution. 193 Before comparisons, we should note the similarity and relation 194 between DECADE and CDNi. First, note that these two solutions can 195 both benefit from using ALTO as a service to make decisions. In 196 DECADE, ALTO helps DECADE portal to decide which is the best server 197 for a specific end users; In CDNi, a CDN can use ALTO to decide to 198 which CDN it should redirect a client's requests. Secondly, as 199 outlined in the requirement document of CDNi, DECADE can be used by 200 CDNi for control message exchanges, acquisition of content objects 201 between different CDNs, and for content delivery within a given CDN. 202 But the benefits of using DECADE in CDNi are rather limited. 204 3.1. Deployment complexity and cost 206 Since DECADE provides a open standard for in-network storage 207 architecture, ISPs can easily deploy their own DECADE servers in 208 their networks. Moreover, it is more likely that ISP can deploy 209 their storage servers more widely and closer to end users in their 210 networks than third-party CDN providers can. When multiple ISPs have 211 deployed their DECADE storage systems, a CSP can just subscribe the 212 DECADE service provided by one ISP, and can distribute its content to 213 DECADE servers across these multiple ISPs, as shown in the example in 214 the last section. The possible requirement may be there should be a 215 charging model so that ISPs can charge each other on the DECADE 216 storage consumption incurred by delivering content generated by CSPs 217 in other ISPs. Since ISPs have already initiated contracts with each 218 other, this model can be built just like traffic charging model. 219 Moreover, no request routing interface is needed by DECADE. The 220 downside is that ISPs should deploy DECADE servers, and for ISPs that 221 have no DECADE service, their users can be outside of coverage. 222 While using CDNi, existing CDNs can be leveraged without the need to 223 deploy new servers. This implies a lower deployment cost. 225 3.2. Support of individual users 227 Apart from providing service to large CSPs, DECADE can also provide 228 services to personal users. For example, a user can register at a 229 nearby DECADE server deployed by the ISP she subscribes to. Using 230 this DECADE server, it is possible for her to stream videos or voices 231 to her friends, despite the uplink link bandwidth constraint. On the 232 other hand, most CDNs are CSP oriented and not practical for 233 individual end users. This will also be true for CDNi, which is a 234 interconnection of CDNs. 236 3.3. Support of P2P mode 238 Since DECADE service can be open to end users, CSPs can also 239 distribute their content using P2P. Under this mode, end users will 240 upload and download chunks of a file to and from the DECADE server 241 they are connected to. By using P2P, CSPs can reduce the cost of 242 employing DECADE services provided by ISPs. But it is more likely 243 that CSPs still use DECADE services to distribute content, but can 244 use P2P simultaneously to reduce cost. 246 4. Security Considerations 248 This document does not contain any security considerations. 250 5. IANA Considerations 252 This document does not have any IANA considerations. 254 6. Normative References 256 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 257 Requirement Levels", BCP 14, RFC 2119, March 1997. 259 Author's Address 261 Peng Zhang 263 Email: pzhang.thu@gmail.com