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Song 3 Internet-Draft Huawei 4 Intended status: Standards Track Y. Zhang 5 Expires: March 7, 2013 China Mobile 6 Y. Sun 7 ICT/CAS 8 Sep 3, 2012 10 A SLR (Service Level Requirements) based footprint for CDNI 11 draft-song-cdni-slr-based-footprint-02 13 Abstract 15 Footprint advertisement is a very important step for CDN 16 interconnection and generates a lot of discussion. Actually, each 17 CDN can serve the whole world if its surrogates are publicly 18 reachable by IP addresses. But if a CDN does that, it can not 19 satisfy the requirements from the applications. So CDNs deliver 20 contents for applications, and the basic requirements should be from 21 the applications. One CDN can serve different applications well with 22 different footprint. But there is rare discussion on service level 23 requirements based footprint. This document is used to generate the 24 discussion on this aspect. 26 Status of this Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on March 7, 2013. 43 Copyright Notice 45 Copyright (c) 2012 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 2. Why SLR Based Footprint . . . . . . . . . . . . . . . . . . . . 3 62 3. What are the Parameters for SLR . . . . . . . . . . . . . . . . 4 63 3.1. Average Response Time . . . . . . . . . . . . . . . . . . . 4 64 3.2. Throughput . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3.3. Startup Delay . . . . . . . . . . . . . . . . . . . . . . . 4 66 3.4. Average downloading rate . . . . . . . . . . . . . . . . . 5 67 3.5. Hit Ratio . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 3.6. Capability . . . . . . . . . . . . . . . . . . . . . . . . 5 69 3.7. Up-time . . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 3.8. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 5 71 4. Dynamic Mapping for Footprint . . . . . . . . . . . . . . . . . 5 72 5. Message Flows . . . . . . . . . . . . . . . . . . . . . . . . . 6 73 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 74 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 75 8. Normative References . . . . . . . . . . . . . . . . . . . . . 6 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 78 1. Terminology 80 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 81 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 82 document are to be interpreted as described in [RFC2119]. 84 2. Why SLR Based Footprint 86 Each CDN's footprint can be worldwide, if its surrogates' IP 87 addresses are publicly reachable. However, not every CDN can serve 88 the applications for worldwide distribution because it can not 89 satisfy the serverice level required by those applications. So what 90 an application basically needs is a CDN to satisfy its service level, 91 and distribute the contents to certain areas. If a CDN or together 92 with its downstream CDNs, cannot meet the SLR (service level 93 requirements) in an area from an application, then we can say this 94 upstream CDN is not competent for this content distribution task. 95 This document specifies how the parameters of SLR impact a CDN's 96 footprint. There is other draft [I-D.he-cdni-cap-info-advertising] 97 mentioned capability advertisement, please note that capability 98 advertisement is also very important and footprint is impacted by 99 capability of a CDN. We consider capability as one service 100 requirement factor from applications. While each CDN serve many 101 tasks concurrently, the dynamic resources that it can allocate is 102 also variable at different time. 104 The physical deployment area of a CDN might be small, but it can have 105 larger footprint area where it can satisfy an application's SLR. The 106 footprint area might be even larger than a CDN that has larger 107 physical deployment area. Choosing SLR as the basis for footprint 108 can avoid some CDN magnifying its service level and service area on 109 purpose, and also make some other "small" but powerful CDN be treated 110 with justness. 112 We think that applications should participate in the CDN 113 interconnection process implicitly, i.e. its requirements for service 114 level should be transmitted between upstream and downstream CDNs 115 (message protection is required due to the privacy). A downstream 116 CDN should notify its capability information to its upstream CDN as 117 well when notifying its footprint that satisfies certain SLR, which 118 will allow a upstream CDN to choose multiple downstream CDN to 119 fullfill a task even in a same area. 121 From the application's perspective, a file downloading application 122 may not care about when the user receive the first bit, but more care 123 about the average downloading rate. While a streaming application 124 may have a different opinion. So for a same CDN, it can serve the 125 file downloading application well with one wider footprint and serve 126 streaming application well with another smaller footprint. 128 In general, service level is the main driver for the definition of 129 footprint, and applications do not care about the locations where a 130 CDN's surrogates are deployed while it can satisfy its service 131 requirements. And topologically, ALTO [I-D.ietf-alto-protocol] is 132 used for the appropriate surrogate selection after the footprints are 133 defined. And ALTO network map information can also be used for the 134 footprint description to upstream CDN . 136 3. What are the Parameters for SLR 138 The general principal for service level requirements is fast, 139 scalable, secure and reliable. But it needs detailed measurement 140 metrics for it. Here we put the capability requirements as one 141 parameter for SLR, as one upstream CDN can choose multiple downstream 142 CDNs to satisfy an customer application's requirements. It does not 143 matter that much if with one footprint, one downstream CDN can 144 satisfy the performance requirements but not capability requirements. 145 This section lists the possible parameters for SLR. 147 We consider the parameters that are not high dynamic. Those 148 parameters that are dynamic at a very brief time frame, but 149 statistically rather static at a reasonable time frame (like one 150 month) can be considered for footprint determination. 152 However, this document is not going to define the specifics for the 153 measurement methods. 155 3.1. Average Response Time 157 This value is to refelct the average response time in normal network 158 condition. This value impacts the footprint a lot. 160 3.2. Throughput 162 This parameter will also impact the footprint. If a CDN's available 163 throughput is very big then it can serve more than its deployment 164 area. 166 3.3. Startup Delay 168 This parameter is a very important metric for the streaming media 169 delivery. As a TCP connection throughput close to MTU/RTT. Long 170 distance transport maybe mean smaller MTU and longer RTT, as well as 171 more packet lost rate, which will result in a low rate data 172 transport, and in consequence long startup delay. 174 3.4. Average downloading rate 176 Application usually needs the CDN to gurantee a certain downloading 177 rate for a certain service. More discussion is needed on this 178 parameter and how it impacts footprint. 180 3.5. Hit Ratio 182 This parameter is about the content availability. High hit ratio 183 means more local service and low burden on original servers. This 184 parameter is more related to the CDN's optimization policies than to 185 the footprint. 187 3.6. Capability 189 For the capability, we consider the processing power of the CDN and 190 its features that can support certain kinds of applications. 192 3.7. Up-time 194 Uptime is a measure of the time a machine has been up without any 195 downtime. For a CDN system, it usually needs to guarantee a 100% up- 196 time for system (not for each host). 198 3.8. Discussion 200 Not all parameters required for a certain service level are listed. 201 More discussion is needed. Some parameters might impact a CDN's 202 footprint, and some will not. Should all of them or just a portion 203 that affect the footprint be conveyed in the same way among CDNs? 205 4. Dynamic Mapping for Footprint 207 Each CDN participate in the CDN interconnection network should 208 maintain a map between the SLR parameters and its footprint. There 209 are choices to exchange the map information. 211 (1) An application's SLR is directly sent from upstream CDN to the 212 downstream CDN. So that downstream CDN can report its footprint to 213 upstream CDN accordingly. The downstream CDN should guarantee it 214 satisfies the SLR for users in its reported footprint. Although this 215 method requires message exchange for each application, but it is 216 simple to implement. 218 (2) Each CDN report its mapping between SLR parameters and footprint 219 to upstream CDN. And the upstream CDN will make the final decision 220 on the downstream CDN's footprint according to a specific 221 application's SLR. This method reduces the messge exchanges but the 222 map itself might be very complicated, due to various combination of 223 these parameter values exist. 225 5. Message Flows 227 TBD. 229 6. Security Considerations 231 These security issues are open for discussion: 233 (1) Applications might take its service level requrements as a 234 confidential? Although it can be a confidential to users, but it can 235 be protected without leaking to any third party that is not involved 236 in the CDN interconnection? 238 (2) CDNs might take its footprint according to SLR as confidential? 240 (3) Footprint cheating. A CDN may cheat with its footprint. If the 241 behavior is disovered, the application cannot get the service level 242 in that announced footprint, punishment policies should be applied to 243 the CDN provider. 245 7. IANA Considerations 247 There is no IANA consideration for this document. 249 8. Normative References 251 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 252 Requirement Levels", BCP 14, RFC 2119, March 1997. 254 [I-D.he-cdni-cap-info-advertising] 255 He, X., Dawkins, S., Chen, G., Zhang, Y., and W. Ni, 256 "Capability Information Advertising for CDN 257 Interconnection", draft-he-cdni-cap-info-advertising-01 258 (work in progress), March 2012. 260 [I-D.seedorf-cdni-request-routing-alto] 261 Seedorf, J., "CDNI Request Routing with ALTO", 262 draft-seedorf-cdni-request-routing-alto-02 (work in 263 progress), July 2012. 265 [I-D.ietf-alto-protocol] 266 Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol", 267 draft-ietf-alto-protocol-12 (work in progress), July 2012. 269 Authors' Addresses 271 Haibin Song 272 Huawei 274 Email: haibin.song@huawei.com 276 Yunfei Zhang 277 China Mobile 279 Email: zhangyunfei@chinamobile.com 281 Yi Sun 282 ICT/CAS 284 Email: sunyi@ict.ac.cn