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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) == Outdated reference: A later version (-34) exists of draft-dreibholz-rserpool-asap-hropt-08 == Outdated reference: A later version (-31) exists of draft-dreibholz-rserpool-enrp-takeover-05 == Outdated reference: A later version (-32) exists of draft-ietf-tsvwg-sctpsocket-30 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Dreibholz 3 Internet-Draft University of Duisburg-Essen 4 Intended status: Experimental X. Zhou 5 Expires: January 4, 2012 Hainan University 6 July 03, 2011 8 Definition of a Delay Measurement Infrastructure and Delay-Sensitive 9 Least-Used Policy for Reliable Server Pooling 10 draft-dreibholz-rserpool-delay-08.txt 12 Abstract 14 This document contains the definition of a delay measurement 15 infrastructure and a delay-sensitive Least-Used policy for Reliable 16 Server Pooling. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on January 4, 2012. 35 Copyright Notice 37 Copyright (c) 2011 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 This document may contain material from IETF Documents or IETF 51 Contributions published or made publicly available before November 52 10, 2008. The person(s) controlling the copyright in some of this 53 material may not have granted the IETF Trust the right to allow 54 modifications of such material outside the IETF Standards Process. 55 Without obtaining an adequate license from the person(s) controlling 56 the copyright in such materials, this document may not be modified 57 outside the IETF Standards Process, and derivative works of it may 58 not be created outside the IETF Standards Process, except to format 59 it for publication as an RFC or to translate it into languages other 60 than English. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 67 1.3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. Delay-Measurement Infrastructure . . . . . . . . . . . . . . . 3 69 2.1. Quantification of Distance . . . . . . . . . . . . . . . . 3 70 2.2. Distance Measurement Environment . . . . . . . . . . . . . 4 71 3. Distance-Sensitive Least-Used Policy . . . . . . . . . . . . . 4 72 3.1. Description . . . . . . . . . . . . . . . . . . . . . . . . 5 73 3.2. ENRP Server Considerations . . . . . . . . . . . . . . . . 5 74 3.3. Pool User Considerations . . . . . . . . . . . . . . . . . 5 75 3.4. Pool Member Selection Policy Parameter . . . . . . . . . . 5 76 4. Reference Implementation . . . . . . . . . . . . . . . . . . . 6 77 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 79 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 80 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 81 7.2. Informative References . . . . . . . . . . . . . . . . . . 7 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 84 1. Introduction 86 Reliable Server Pooling defines protocols for providing highly 87 available services. PEs of a pool may be distributed over a large 88 geographical area, in order to provide redundancy in case of 89 localized disasters. But the current pool policies defined in 90 [RFC5356] do not incorporate the fact of distances (i.e. delay) 91 between PU and PE. This leads to a low performance for delay- 92 sensitive applications. 94 1.1. Scope 96 This draft defines a delay measurement infrastructure for ENRP 97 servers to add delay information into the handlespace. Furthermore, 98 a delay-sensitive Least-Used policy is defined. Performance 99 evaluations can be found in [KiVS2007]. 101 1.2. Terminology 103 The terms are commonly identified in related work and can be found in 104 the Aggregate Server Access Protocol and Endpoint Handlespace 105 Redundancy Protocol Common Parameters document [RFC5354]. 107 1.3. Conventions 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 111 document are to be interpreted as described in [RFC2119]. 113 2. Delay-Measurement Infrastructure 115 This section describes the necessary delay measurement infrastructure 116 for the policy later defined in Section 3. It has to be provided as 117 part of the ENRP servers. 119 2.1. Quantification of Distance 121 Measuring delay for SCTP associations is easy: the SCTP protocol 122 [RFC4960] already calculates a smoothed round-trip time (RTT) for the 123 primary path. This RTT only has to be queried via the standard SCTP 124 API as defined in [I-D.ietf-tsvwg-sctpsocket]. By default, the 125 calculated RTT has a small restriction: a SCTP endpoint waits up to 126 200ms before acknowledging a packet, in order to piggyback the 127 acknowledgement chunk with payload data. In this case, the RTT would 128 include this latency. Using the option SCTP_DELAYED_ACK_TIME (see 129 [I-D.ietf-tsvwg-sctpsocket]), the maximum delay before acknowledging 130 a packet can be set to 0ms (i.e. "acknowledge as soon as possible"). 132 After that, the RTT approximately consists of the network latency 133 only. Then, using the RTT, the end-to-end delay between two 134 associated components is approximately 0.5*RTT. 136 In real networks, there may be negligible delay differences: for 137 example, the delay between a PU and PE #1 is 5ms and the latency 138 between the PU and PE #2 is 6ms. From the service user's 139 perspective, such minor delay differences may be ignored and are 140 furthermore unavoidable in Internet scenarios. Therefore, the 141 distance parameter between two components A and B is defined as 142 follows: 144 Distance = DistanceStep * round( (0.5*RTT) / DistanceStep ) 146 That is, the distance parameter is defined as the nearest integer 147 multiple of the constant DistanceStep for the measured delay (i.e. 148 0.5*RTT). 150 2.2. Distance Measurement Environment 152 In order to define a distance-aware policy, it is first necessary to 153 define a basic rule: PEs and PUs choose "nearby" ENRP servers. Since 154 the operation scope of RSerPool is restricted to a single 155 organization, this condition can be met easily by appropriately 156 locating ENRP servers. 158 o A Home ENRP server can measure the delay of the ASAP associations 159 to its PE. As part of its ENRP updates to other ENRP servers, it 160 can report this measured delay together with the PE information. 162 o A non-Home-ENRP server receiving such an update simply adds the 163 delay of the ENRP association with the Home ENRP server to the 164 PE's reported delay. 166 Now, each ENRP server can approximate the distance to every PE in the 167 operation scope using the equation in Section 2.1. 169 Note, that delay changes are propagated to all ENRP servers upon PE 170 re-registrations, i.e. the delay information (and the approximated 171 distance) dynamically adapts to the state of the network. 173 3. Distance-Sensitive Least-Used Policy 175 In this section, a distance-sensitive Least Used policy is defined, 176 based on the delay-measurement infrastructure introduced in 177 Section 2. 179 3.1. Description 181 The Least Used with Distance Penalty Factor (LU-DPF) policy uses load 182 information provided by the pool elements to select the lowest-loaded 183 pool elements within the pool. If there are multiple elements having 184 lowest load, the nearest PE should be chosen. 186 3.2. ENRP Server Considerations 188 The ENRP server SHOULD select at most the requested number of pool 189 elements. Their load values SHOULD be the lowest possible ones 190 within the pool and their distances also SHOULD be lowest. Each 191 element MUST NOT be reported more than once to the pool user. If 192 there is a choice of equal-loaded and equal-distanced pool elements, 193 round robin selection SHOULD be made among these elements. The 194 returned list of pool elements MUST be sorted by load value in 195 ascending order (1st key) and distance in ascending order (2nd key). 197 3.3. Pool User Considerations 199 The pool user should try to use the pool elements returned from the 200 list in the order returned by the ENRP server. A subsequent call for 201 handle resolution may result in the same list. Therefore, it is 202 RECOMMENDED for a pool user to request multiple entries in order to 203 have a sufficient amount of feasible backup entries available. 205 3.4. Pool Member Selection Policy Parameter 207 0 1 2 3 208 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | Parameter Type = 0x6 | Length = 0x14 | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | Policy Type = 0x40000010 | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | Load | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 | Load DPF | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 | Distance | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 221 o Load: Current load of the pool element. 223 o Load DPF: The LoadDPF setting of the PE. 225 o Distance: The approximated distance in milliseconds. 227 * Between PE and Home ENRP server: The distance SHOULD be set to 228 0. 230 * Between Non-Home ENRP server and Home ENRP server: The delay 231 measured on the ASAP association between Home ENRP server and 232 PE. 234 * Between ENRP server and PU: The sums of the measured delays on 235 the ASAP association and the ENRP association to the Home ENRP 236 server. 238 4. Reference Implementation 240 The RSerPool reference implementation RSPLIB can be found at 241 [RSerPoolPage]. It supports the functionalities defined by 242 [RFC5351], [RFC5352], [RFC5353], [RFC5354] and [RFC5356] as well as 243 the options [I-D.dreibholz-rserpool-asap-hropt], 244 [I-D.dreibholz-rserpool-enrp-takeover] and of course the option 245 defined by this document. An introduction to this implementation is 246 provided in [Dre2006]. 248 5. Security Considerations 250 Security considerations for RSerPool systems are described by 251 [RFC5355]. 253 6. IANA Considerations 255 This document does not require additional IANA actions beyond those 256 already identified in the ENRP and ASAP protocol specifications. 258 7. References 260 7.1. Normative References 262 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 263 Requirement Levels", BCP 14, RFC 2119, March 1997. 265 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", 266 RFC 4960, September 2007. 268 [RFC5351] Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An 269 Overview of Reliable Server Pooling Protocols", RFC 5351, 270 September 2008. 272 [RFC5352] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, 273 "Aggregate Server Access Protocol (ASAP)", RFC 5352, 274 September 2008. 276 [RFC5353] Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A. 277 Silverton, "Endpoint Handlespace Redundancy Protocol 278 (ENRP)", RFC 5353, September 2008. 280 [RFC5354] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, 281 "Aggregate Server Access Protocol (ASAP) and Endpoint 282 Handlespace Redundancy Protocol (ENRP) Parameters", 283 RFC 5354, September 2008. 285 [RFC5355] Stillman, M., Gopal, R., Guttman, E., Sengodan, S., and M. 286 Holdrege, "Threats Introduced by Reliable Server Pooling 287 (RSerPool) and Requirements for Security in Response to 288 Threats", RFC 5355, September 2008. 290 [RFC5356] Dreibholz, T. and M. Tuexen, "Reliable Server Pooling 291 Policies", RFC 5356, September 2008. 293 [I-D.dreibholz-rserpool-asap-hropt] 294 Dreibholz, T., "Handle Resolution Option for ASAP", 295 draft-dreibholz-rserpool-asap-hropt-08 (work in progress), 296 January 2011. 298 [I-D.dreibholz-rserpool-enrp-takeover] 299 Dreibholz, T. and X. Zhou, "Takeover Suggestion Flag for 300 the ENRP Handle Update Message", 301 draft-dreibholz-rserpool-enrp-takeover-05 (work in 302 progress), January 2011. 304 [I-D.ietf-tsvwg-sctpsocket] 305 Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 306 Yasevich, "Sockets API Extensions for Stream Control 307 Transmission Protocol (SCTP)", 308 draft-ietf-tsvwg-sctpsocket-30 (work in progress), 309 June 2011. 311 7.2. Informative References 313 [Dre2006] Dreibholz, T., "Reliable Server Pooling -- Evaluation, 314 Optimization and Extension of a Novel IETF Architecture", 315 Ph.D. Thesis University of Duisburg-Essen, Faculty of 316 Economics, Institute for Computer Science and Business 317 Information Systems, URL: http:// 318 duepublico.uni-duisburg-essen.de/servlets/DerivateServlet/ 319 Derivate-16326/Dre2006-final.pdf, March 2007. 321 [KiVS2007] 322 Dreibholz, T. and E. Rathgeb, "On Improving the 323 Performance of Reliable Server Pooling Systems for 324 Distance-Sensitive Distributed Applications", 325 Proceedings of the 15. ITG/GI Fachtagung Kommunikation in 326 Verteilten Systemen, February 2007. 328 [RSerPoolPage] 329 Dreibholz, T., "Thomas Dreibholz's RSerPool Page", 330 URL: http://tdrwww.iem.uni-due.de.de/dreibholz/rserpool/. 332 Authors' Addresses 334 Thomas Dreibholz 335 University of Duisburg-Essen, Institute for Experimental Mathematics 336 Ellernstrasse 29 337 45326 Essen, Nordrhein-Westfalen 338 Germany 340 Phone: +49-201-1837637 341 Fax: +49-201-1837673 342 Email: dreibh@iem.uni-due.de 343 URI: http://www.iem.uni-due.de/~dreibh/ 345 Xing Zhou 346 Hainan University, College of Information Science and Technology 347 Renmin Avenue 58 348 570228 Haikou, Hainan 349 China 351 Phone: +86-898-66279141 352 Email: zhouxing@hainu.edu.cn