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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Dreibholz 3 Internet-Draft Simula Research Laboratory 4 Intended status: Experimental X. Zhou 5 Expires: February 7, 2018 Hainan University 6 August 06, 2017 8 Definition of a Delay Measurement Infrastructure and Delay-Sensitive 9 Least-Used Policy for Reliable Server Pooling 10 draft-dreibholz-rserpool-delay-20.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 February 7, 2018. 35 Copyright Notice 37 Copyright (c) 2017 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 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.3. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Delay-Measurement Infrastructure . . . . . . . . . . . . . . 3 57 2.1. Quantification of Distance . . . . . . . . . . . . . . . 3 58 2.2. Distance Measurement Environment . . . . . . . . . . . . 3 59 3. Distance-Sensitive Least-Used Policy . . . . . . . . . . . . 4 60 3.1. Description . . . . . . . . . . . . . . . . . . . . . . . 4 61 3.2. ENRP Server Considerations . . . . . . . . . . . . . . . 4 62 3.3. Pool User Considerations . . . . . . . . . . . . . . . . 4 63 3.4. Pool Member Selection Policy Parameter . . . . . . . . . 5 64 4. Reference Implementation . . . . . . . . . . . . . . . . . . 5 65 5. Testbed Platform . . . . . . . . . . . . . . . . . . . . . . 6 66 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 67 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 68 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 70 8.2. Informative References . . . . . . . . . . . . . . . . . 7 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 73 1. Introduction 75 Reliable Server Pooling defines protocols for providing highly 76 available services. PEs of a pool may be distributed over a large 77 geographical area, in order to provide redundancy in case of 78 localized disasters. But the current pool policies defined in 79 [RFC5356] do not incorporate the fact of distances (i.e. delay) 80 between PU and PE. This leads to a low performance for delay- 81 sensitive applications. 83 1.1. Scope 85 This draft defines a delay measurement infrastructure for ENRP 86 servers to add delay information into the handlespace. Furthermore, 87 a delay-sensitive Least-Used policy is defined. Performance 88 evaluations can be found in [KiVS2007]. 90 1.2. Terminology 92 The terms are commonly identified in related work and can be found in 93 the Aggregate Server Access Protocol and Endpoint Handlespace 94 Redundancy Protocol Common Parameters document [RFC5354]. 96 1.3. Conventions 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 100 document are to be interpreted as described in [RFC2119]. 102 2. Delay-Measurement Infrastructure 104 This section describes the necessary delay measurement infrastructure 105 for the policy later defined in Section 3. It has to be provided as 106 part of the ENRP servers. 108 2.1. Quantification of Distance 110 Measuring delay for SCTP associations is easy: the SCTP protocol 111 [RFC4960] already calculates a smoothed round-trip time (RTT) for the 112 primary path. This RTT only has to be queried via the standard SCTP 113 API as defined in [RFC6458]. By default, the calculated RTT has a 114 small restriction: a SCTP endpoint waits up to 200ms before 115 acknowledging a packet, in order to piggyback the acknowledgement 116 chunk with payload data. In this case, the RTT would include this 117 latency. By using the option SCTP_DELAYED_SACK (see [RFC6458]), the 118 maximum delay before acknowledging a packet can be set to 0ms (i.e. 119 "acknowledge as soon as possible"). After that, the RTT 120 approximately consists of the network latency only. Then, using the 121 RTT, the end-to-end delay between two associated components is 122 approximately 0.5*RTT. 124 In real networks, there may be negligible delay differences: for 125 example, the delay between a PU and PE #1 is 5ms and the latency 126 between the PU and PE #2 is 6ms. From the service user's 127 perspective, such minor delay differences may be ignored and are 128 furthermore unavoidable in Internet scenarios. Therefore, the 129 distance parameter between two components A and B is defined as 130 follows: 132 Distance = DistanceStep * round( (0.5*RTT) / DistanceStep ) 134 That is, the distance parameter is defined as the nearest integer 135 multiple of the constant DistanceStep for the measured delay (i.e. 136 0.5*RTT). 138 2.2. Distance Measurement Environment 140 In order to define a distance-aware policy, it is first necessary to 141 define a basic rule: PEs and PUs choose "nearby" ENRP servers. Since 142 the operation scope of RSerPool is restricted to a single 143 organization, this condition can be met easily by appropriately 144 locating ENRP servers. 146 o A Home ENRP server can measure the delay of the ASAP associations 147 to its PE. As part of its ENRP updates to other ENRP servers, it 148 can report this measured delay together with the PE information. 150 o A non-Home-ENRP server receiving such an update simply adds the 151 delay of the ENRP association with the Home ENRP server to the 152 PE's reported delay. 154 Now, each ENRP server can approximate the distance to every PE in the 155 operation scope using the equation in Section 2.1. 157 Note, that delay changes are propagated to all ENRP servers upon PE 158 re-registrations, i.e. the delay information (and the approximated 159 distance) dynamically adapts to the state of the network. 161 3. Distance-Sensitive Least-Used Policy 163 In this section, a distance-sensitive Least Used policy is defined, 164 based on the delay-measurement infrastructure introduced in 165 Section 2. 167 3.1. Description 169 The Least Used with Distance Penalty Factor (LU-DPF) policy uses load 170 information provided by the pool elements to select the lowest-loaded 171 pool elements within the pool. If there are multiple elements having 172 lowest load, the nearest PE should be chosen. 174 3.2. ENRP Server Considerations 176 The ENRP server SHOULD select at most the requested number of pool 177 elements. Their load values SHOULD be the lowest possible ones 178 within the pool and their distances also SHOULD be lowest. Each 179 element MUST NOT be reported more than once to the pool user. If 180 there is a choice of equal-loaded and equal-distanced pool elements, 181 round robin selection SHOULD be made among these elements. The 182 returned list of pool elements MUST be sorted by load value in 183 ascending order (1st key) and distance in ascending order (2nd key). 185 3.3. Pool User Considerations 187 The pool user should try to use the pool elements returned from the 188 list in the order returned by the ENRP server. A subsequent call for 189 handle resolution may result in the same list. Therefore, it is 190 RECOMMENDED for a pool user to request multiple entries in order to 191 have a sufficient amount of feasible backup entries available. 193 3.4. Pool Member Selection Policy Parameter 195 0 1 2 3 196 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 1 197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 198 | Parameter Type = 0x6 | Length = 0x14 | 199 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 | Policy Type = 0x40000010 | 201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 | Load | 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 204 | Load DPF | 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 | Distance | 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 o Load: Current load of the pool element. 211 o Load DPF: The LoadDPF setting of the PE. 213 o Distance: The approximated distance in milliseconds. 215 * Between PE and Home ENRP server: The distance SHOULD be set to 216 0. 218 * Between Non-Home ENRP server and Home ENRP server: The delay 219 measured on the ASAP association between Home ENRP server and 220 PE. 222 * Between ENRP server and PU: The sums of the measured delays on 223 the ASAP association and the ENRP association to the Home ENRP 224 server. 226 4. Reference Implementation 228 The RSerPool reference implementation RSPLIB can be found at 229 [RSerPool-Website]. It supports the functionalities defined by 230 [RFC5351], [RFC5352], [RFC5353], [RFC5354] and [RFC5356] as well as 231 the options [I-D.dreibholz-rserpool-asap-hropt], 232 [I-D.dreibholz-rserpool-enrp-takeover] and of course the option 233 defined by this document. An introduction to this implementation is 234 provided in [Dre2006]. 236 5. Testbed Platform 238 A large-scale and realistic Internet testbed platform with support 239 for the multi-homing feature of the underlying SCTP protocol is 240 NorNet. A description of NorNet is provided in [PAMS2013-NorNet], 241 some further information can be found on the project website 242 [NorNet-Website]. 244 6. Security Considerations 246 Security considerations for RSerPool systems are described by 247 [RFC5355]. 249 7. IANA Considerations 251 This document does not require additional IANA actions beyond those 252 already identified in the ENRP and ASAP protocol specifications. 254 8. References 256 8.1. Normative References 258 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 259 Requirement Levels", BCP 14, RFC 2119, 260 DOI 10.17487/RFC2119, March 1997, 261 . 263 [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", 264 RFC 4960, DOI 10.17487/RFC4960, September 2007, 265 . 267 [RFC5351] Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An 268 Overview of Reliable Server Pooling Protocols", RFC 5351, 269 DOI 10.17487/RFC5351, September 2008, 270 . 272 [RFC5352] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, 273 "Aggregate Server Access Protocol (ASAP)", RFC 5352, 274 DOI 10.17487/RFC5352, September 2008, 275 . 277 [RFC5353] Xie, Q., Stewart, R., Stillman, M., Tuexen, M., and A. 278 Silverton, "Endpoint Handlespace Redundancy Protocol 279 (ENRP)", RFC 5353, DOI 10.17487/RFC5353, September 2008, 280 . 282 [RFC5354] Stewart, R., Xie, Q., Stillman, M., and M. Tuexen, 283 "Aggregate Server Access Protocol (ASAP) and Endpoint 284 Handlespace Redundancy Protocol (ENRP) Parameters", 285 RFC 5354, DOI 10.17487/RFC5354, September 2008, 286 . 288 [RFC5355] Stillman, M., Ed., Gopal, R., Guttman, E., Sengodan, S., 289 and M. Holdrege, "Threats Introduced by Reliable Server 290 Pooling (RSerPool) and Requirements for Security in 291 Response to Threats", RFC 5355, DOI 10.17487/RFC5355, 292 September 2008, . 294 [RFC5356] Dreibholz, T. and M. Tuexen, "Reliable Server Pooling 295 Policies", RFC 5356, DOI 10.17487/RFC5356, September 2008, 296 . 298 [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. 299 Yasevich, "Sockets API Extensions for the Stream Control 300 Transmission Protocol (SCTP)", RFC 6458, 301 DOI 10.17487/RFC6458, December 2011, 302 . 304 [I-D.dreibholz-rserpool-asap-hropt] 305 Dreibholz, T., "Handle Resolution Option for ASAP", draft- 306 dreibholz-rserpool-asap-hropt-20 (work in progress), 307 January 2017. 309 [I-D.dreibholz-rserpool-enrp-takeover] 310 Dreibholz, T. and X. Zhou, "Takeover Suggestion Flag for 311 the ENRP Handle Update Message", draft-dreibholz-rserpool- 312 enrp-takeover-17 (work in progress), January 2017. 314 8.2. Informative References 316 [Dre2006] Dreibholz, T., "Reliable Server Pooling - Evaluation, 317 Optimization and Extension of a Novel IETF Architecture", 318 March 2007, . 322 [KiVS2007] 323 Dreibholz, T. and E. Rathgeb, "On Improving the 324 Performance of Reliable Server Pooling Systems for 325 Distance-Sensitive Distributed Applications", Proceedings 326 of the 15. ITG/GI Fachtagung Kommunikation in Verteilten 327 Systemen (KiVS) Pages 39-50, ISBN 978-3-540-69962-0, 328 DOI 10.1007/978-3-540-69962-0_4, February 2007, 329 . 332 [PAMS2013-NorNet] 333 Dreibholz, T. and E. Gran, "Design and Implementation of 334 the NorNet Core Research Testbed for Multi-Homed Systems", 335 Proceedings of the 3nd International Workshop on Protocols 336 and Applications with Multi-Homing Support (PAMS) Pages 337 1094-1100, ISBN 978-0-7695-4952-1, 338 DOI 10.1109/WAINA.2013.71, March 2013, 339 . 343 [RSerPool-Website] 344 Dreibholz, T., "Thomas Dreibholz's RSerPool Page", 345 Online: http://www.iem.uni-due.de/~dreibh/rserpool/, 2016, 346 . 348 [NorNet-Website] 349 Dreibholz, T., "NorNet - A Real-World, Large-Scale Multi- 350 Homing Testbed", Online: https://www.nntb.no/, 2017, 351 . 353 Authors' Addresses 355 Thomas Dreibholz 356 Simula Research Laboratory, Network Systems Group 357 Martin Linges vei 17 358 1364 Fornebu, Akershus 359 Norway 361 Phone: +47-6782-8200 362 Fax: +47-6782-8201 363 Email: dreibh@simula.no 364 URI: http://www.iem.uni-due.de/~dreibh/ 365 Xing Zhou 366 Hainan University, College of Information Science and Technology 367 Renmin Avenue 58 368 570228 Haikou, Hainan 369 China 371 Phone: +86-898-66279141 372 Email: zhouxing@hainu.edu.cn 373 URI: http://www.hainu.edu.cn/stm/xinxi/2011330/10409758.shtml