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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Q. Xie 3 Internet-Draft Motorola 4 Expires: August 30, 2003 R. Stewart 5 Cisco 6 M. Stillman 7 Nokia 8 March 1, 2003 10 Endpoint Name Resolution Protocol (ENRP) 11 draft-ietf-rserpool-enrp-05.txt 13 Status of this Memo 15 This document is an Internet-Draft and is in full conformance with 16 all provisions of Section 10 of RFC2026. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that other 20 groups may also distribute working documents as Internet-Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at http:// 28 www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on August 30, 2003. 35 Copyright Notice 37 Copyright (C) The Internet Society (2003). All Rights Reserved. 39 Abstract 41 Endpoint Name Resolution Protocol (ENRP) is designed to work in 42 conjunction with the Aggregate Server Access Protocol (ASAP) to 43 accomplish the functionality of the Reliable Server Pooling 44 (Rserpool) requirements and architecture. Within the operational 45 scope of Rserpool, ENRP defines the procedures and message formats of 46 a distributed, fault-tolerant registry service for storing, 47 bookkeeping, retrieving, and distributing pool operation and 48 membership information. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4 53 1.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . 4 54 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 6 55 3. ENRP Message Definitions . . . . . . . . . . . . . . . . . 7 56 3.1 PEER_PRESENCE message . . . . . . . . . . . . . . . . . . 7 57 3.2 PEER_NAME_TABLE_REQUEST message . . . . . . . . . . . . . 8 58 3.3 PEER_NAME_TABLE_RESPONSE message . . . . . . . . . . . . . 9 59 3.4 PEER_NAME_UPDATE message . . . . . . . . . . . . . . . . . 11 60 3.5 PEER_LIST_REQUEST message . . . . . . . . . . . . . . . . 12 61 3.6 PEER_LIST_RESPONSE message . . . . . . . . . . . . . . . . 13 62 3.7 PEER_INIT_TAKEOVER message . . . . . . . . . . . . . . . . 14 63 3.8 PEER_INIT_TAKEOVER_ACK message . . . . . . . . . . . . . . 15 64 3.9 PEER_TAKEOVER_SERVER message . . . . . . . . . . . . . . . 15 65 3.10 PEER_OWNERSHIP_CHANGE message . . . . . . . . . . . . . . 16 66 3.11 PEER_ERROR message . . . . . . . . . . . . . . . . . . . . 18 67 4. ENRP Operation Procedures . . . . . . . . . . . . . . . . 19 68 4.1 Methods for Communicating amongst ENRP Servers . . . . . . 19 69 4.2 ENRP Server Initialization . . . . . . . . . . . . . . . . 20 70 4.2.1 Generate a Server Identifier . . . . . . . . . . . . . . . 21 71 4.2.2 Acquire Peer Server List . . . . . . . . . . . . . . . . . 21 72 4.2.3 Download ENRP Namespace Data from Mentor Peer . . . . . . 23 73 4.3 Handle PE Registration . . . . . . . . . . . . . . . . . . 25 74 4.3.1 Rules on PE Re-registration . . . . . . . . . . . . . . . 26 75 4.4 Handle PE De-registration . . . . . . . . . . . . . . . . 27 76 4.5 Pool Handle Translation . . . . . . . . . . . . . . . . . 28 77 4.6 Server Namespace Update . . . . . . . . . . . . . . . . . 28 78 4.6.1 Announcing Addition or Update of PE . . . . . . . . . . . 29 79 4.6.2 Announcing Removal of PE . . . . . . . . . . . . . . . . . 29 80 4.7 Detecting and Removing Unreachable PE . . . . . . . . . . 30 81 4.8 Helping PE and PU to Discover Home ENRP Server . . . . . . 31 82 4.9 Maintaining Peer List and Monitoring Peer Status . . . . . 31 83 4.9.1 Discovering New Peer . . . . . . . . . . . . . . . . . . . 31 84 4.9.2 Server Sending Heartbeat . . . . . . . . . . . . . . . . . 32 85 4.9.3 Detecting Peer Server Failure . . . . . . . . . . . . . . 32 86 4.10 Taking-over a Failed Peer Server . . . . . . . . . . . . . 32 87 4.10.1 Initiate Server Take-over Arbitration . . . . . . . . . . 32 88 4.10.2 Take-over Target Peer Server . . . . . . . . . . . . . . . 33 89 4.11 Namespace Data Auditing and Re-synchronization . . . . . . 34 90 4.11.1 Auditing Prodecures . . . . . . . . . . . . . . . . . . . 34 91 4.11.2 Re-synchronization Prodecures . . . . . . . . . . . . . . 34 92 4.12 Handling Unrecognized Message or Unrecognized Parameter . 35 93 5. Variables and Time Constants . . . . . . . . . . . . . . . 36 94 5.1 Variables . . . . . . . . . . . . . . . . . . . . . . . . 36 95 5.2 Timer Constants . . . . . . . . . . . . . . . . . . . . . 36 96 6. Security Considerations . . . . . . . . . . . . . . . . . 37 97 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 38 98 Normative References . . . . . . . . . . . . . . . . . . . 39 99 Informative References . . . . . . . . . . . . . . . . . . 40 100 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 40 101 Intellectual Property and Copyright Statements . . . . . . 41 103 1. Introduction 105 ENRP is designed to work in conjunction with ASAP [1] to accomplish 106 the functionality of Rserpool as defined by its requirements [2] and 107 architecture [3]. 109 Within the operation scope of Rserpool, ENRP defines the procedures 110 and message formats of a distributed fault-tolerant registry service 111 for storing, bookkeeping, retrieving, and distributing pool operation 112 and membership information. 114 Whenever appropriate, in the rest of this document we will refer to 115 this Rserpool registry service as ENRP namespace, or simply 116 namespace. 118 1.1 Definitions 120 This document uses the following terms: 122 Operation scope: See [3]; 124 Pool (or server pool): See [3]; 126 Pool handle (or pool name): See [3]; 128 Pool element (PE): See [3]; 130 Pool user (PU): See [3]; 132 Pool element handle: See [3]; 134 ENRP namespace (or namespace): See [3]; 136 ENRP namespace server (or ENRP server): See [3]; 138 ENRP client channel: The communication channel through which a PE 139 requests for ENRP namespace service. The ENRP client channel is 140 usually defined by the transport address of the home ENRP server 141 and a well known port number; 143 ENRP server channel: Defined by a well known multicast IP address and 144 a well known port number. All ENRP servers in an operation scope 145 can send multicast messages to other servers through this channel. 146 PEs are also allowed to multicast on this channel occasionally; 148 Home ENRP server: The ENRP server to which a PE or PU currently 149 belongs. A PE MUST only have one home ENRP server at any given 150 time and both the PE and its home ENRP server MUST keep track of 151 this master/slave relationship between them. A PU SHOULD select 152 one of the available ENRP servers as its home ENRP server, but the 153 ENRP server does not need to know, nor does it need to keep track 154 of this relationship. 156 2. Conventions 158 The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, 159 SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when 160 they appear in this document, are to be interpreted as described in 161 [5]. 163 3. ENRP Message Definitions 165 In this section, we defines the format of all ENRP messages. These 166 are messages sent and received amongst ENRP servers in an operation 167 scope. Messages sent and received between a PE/PU and an ENRP server 168 are part of ASAP and are defined in [1]. A common format, defined in 169 [10], is used for all ENRP and ASAP messages. 171 Most ENRP messages contains a combination of fixed fields and TLV 172 parameters. The TLV parameters are also defined in [10]. 174 All messages, as well as their fields/parameters described below, 175 MUST be transmitted in network byte order (a.k.a. Big Endian, i.e., 176 the most significant byte first). 178 For ENRP, the following message types are defined: 180 Type Message Name 181 ----- ------------------------- 182 0x0 - (reserved by IETF) 183 0x1 - PEER_PRESENCE 184 0x2 - PEER_NAME_TABLE_REQUEST 185 0x3 - PEER_NAME_TABLE_RESPONSE 186 0x4 - PEER_NAME_UPDATE 187 0x5 - PEER_LIST_REQUEST 188 0x6 - PEER_LIST_RESPONSE 189 0x7 - PEER_INIT_TAKEOVER 190 0x8 - PEER_INIT_TAKEOVER_ACK 191 0x9 - PEER_TAKEOVER_SERVER 192 0xa - PEER_OWNERSHIP_CHANGE 193 0xb - PEER_ERROR 194 0xc-0xFF - (reserved by IETF) 196 3.1 PEER_PRESENCE message 198 This ENRP message is used to announce (periodically) the presence of 199 an ENRP server, or to probe the status of a peer ENRP sever. 201 0 1 2 3 202 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 1 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 204 | Type = 0x1 |0|0|0|0|0|0|0|R| Message Length = 0xC | 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 | Sender Server's ID | 207 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 208 | Receiver Server's ID | 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 : Server Information Param (optional) : 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 R (reply_required) flag: 1 bit 215 Set to '1' if the sender requires a response to this message, 216 otherwise set to '0'. 218 Sender Server's ID: 32 bit (unsiged integer) 220 This is the ID of the ENRP server which sends the message. 222 Receiver Server's ID: 32 bit (unsiged integer) 224 This is the ID of the ENRP server to which the message is 225 intended. If the message is not intended to an individual 226 server (e.g., the message is multicasted to a group of 227 servers), this field MUST be set with all 0's. 229 Server Information Parameter: 231 If present, contains the server information of the sender of 232 this message (Server Information Parameter is defined in [10]). 233 This parameter is optional. However, if this message is sent in 234 response to a received "reply required" PEER_PRESENCE from a 235 peer, the sender then MUST include its server information. 237 Note, at startup an ENRP server MUST pick a randomly generated, 238 non-zero 32-bit unsigned integer as its ID and MUST use this same ID 239 for its entire life. 241 3.2 PEER_NAME_TABLE_REQUEST message 243 An ENRP server sends this message to one of its peers to request a 244 copy of the namespace data. This message is normally used during 245 server initialization or namespace re-synchronization. 247 0 1 2 3 248 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 1 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Type = 0x2 |0|0|0|0|0|0|0|W| Message Length = 0xC | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Sender Server's ID | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | Receiver Server's ID | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 W (oWn-children-only) flag: 1 bit 259 Set to '1' if the sender of this message is only requesting 260 information about the PEs owned by the message receiver. 261 Otherwise, set to '0'. 263 Sender Server's ID: 265 See Section 3.1. 267 Receiver Server's ID: 269 See Section 3.1. 271 3.3 PEER_NAME_TABLE_RESPONSE message 272 0 1 2 3 273 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 1 274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 275 | Type = 0x3 |0|0|0|0|0|0|R|M| Message Length | 276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 277 | Sender Server's ID | 278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 279 | Receiver Server's ID | 280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 281 : : 282 : Pool entry #1 (see below) : 283 : : 284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 285 : : 286 : ... : 287 : : 288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 289 : : 290 : Pool entry #n (see below) : 291 : : 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 R (Reject) flag: 1 bit 296 MUST be set to '1' if the sender of this message is rejecting a 297 namespace request. In such a case, this message MUST be sent 298 with no pool entries included. 300 M (More_to_send) flag: 1 bit 302 Set to '1' if the sender has more pool entries to sent in 303 subsequent PEER_NAME_TABLE_RESPONSE messages, otherwise, set to 304 '0'. 306 Message Length: 16 bits (unsigned integer) 308 Indicates the entire length of the message in number of octets. 310 Note, the value in Message Length field will NOT cover any 311 padding at the end of this message. 313 Sender Server's ID: 315 See Section 3.1. 317 Receiver Server's ID: 319 See Section 3.1. 321 Pool entry #1-#n: 323 If R flag is '0', at least one pool entry SHOULD be present in 324 the message. Each pool entry MUST start with a pool handle 325 parameter as defined in section 3.1.7, followed by one or more 326 pool element parameters, i.e.: 328 +---------------------------+ 329 : Pool handle : 330 +---------------------------+ 331 : PE #1 : 332 +---------------------------+ 333 : PE #2 : 334 +---------------------------+ 335 : ... : 336 +---------------------------+ 337 : PE #n : 338 +---------------------------+ 340 3.4 PEER_NAME_UPDATE message 342 0 1 2 3 343 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 1 344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 | Type = 0x4 |0|0|0|0|0|0|0|0| Message Length | 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 | Update Action | (reserved) | 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 349 | Sender Server's ID | 350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 351 | Receiver Server's ID | 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 : Pool handle : 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 : Pool Element : 356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 358 Message Length: 16 bits (unsigned integer) 360 Indicates the entire length of the message in number of octets. 362 Note, the value in Message Length field will NOT cover any 363 padding at the end of this message. 365 Update Action: 16 bits (unsigned integer) 367 This field indicates what act is requested to the specified PE. 368 It MUST take one of the following values: 370 0x0 - ADD_PE: add or update the specified PE in the ENRP 371 namespace 373 0x1 - DEL_PE: delete the specified PE from the ENRP namespace. 375 Other values are reserved by IETF and MUST not be used. 377 Reserved: 16 bits 379 MUST be set to 0's by sender and ignored by the receiver. 381 Sender Server's ID: 383 See Section 3.1. 385 Receiver Server's ID: 387 See Section 3.1. 389 Pool handle: 391 Specifies to which the PE belongs. 393 Pool Element: 395 Specifies the PE. 397 3.5 PEER_LIST_REQUEST message 399 This ENRP message is used to request a copy of the current known ENRP 400 peer server list. This message is normally sent from a newly started 401 ENRP server to an existing ENRP server as part of the initialization 402 process of the new server. 404 0 1 2 3 405 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 1 406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 407 | Type = 0x5 |0|0|0|0|0|0|0|0| Message Length = 0xC | 408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 409 | Sender Server's ID | 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Receiver Server's ID | 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 Sender Server's ID: 416 See Section 3.1. 418 Receiver Server's ID: 420 See Section 3.1. 422 3.6 PEER_LIST_RESPONSE message 424 This message is used to respond a PEER_LIST_REQUEST. 426 0 1 2 3 427 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 1 428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 429 | Type = 0x6 |0|0|0|0|0|0|0|R| Message Length | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | Sender Server's ID | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | Receiver Server's ID | 434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 435 : Server Info Param of Peer #1 : 436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 : ... : 438 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 439 : Server Info Param of Peer #n : 440 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 R (Reject) flag: 1 bit 444 MUST be set to '1' if the sender of this message is rejecting a 445 peer list request. In such a case, this message MUST be sent 446 with no peer server ID included. 448 Message Length: 16 bits (unsigned integer) 450 Indicates the entire length of the message in number of octets. 452 Note, the value in Message Length field will NOT cover any 453 padding at the end of this message. 455 Sender Server's ID: 457 See Section 3.1. 459 Receiver Server's ID: 461 See Section 3.1. 463 Server Information Parameter of Peer #1-#n: 465 Each contains a Server Information Parameter of a peer known to 466 the sender. The Server Information Parameter is defined in 467 [10]. 469 3.7 PEER_INIT_TAKEOVER message 471 This message is used by an ENRP server (the takeover initiator) to 472 declare its intention of taking over a specific peer ENRP server. 474 0 1 2 3 475 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 1 476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 | Type = 0x7 |0|0|0|0|0|0|0|0| Message Length | 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 479 | Sender Server's ID | 480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 | Receiver Server's ID | 482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 | Target Server's ID | 484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 486 Sender Server's ID: 488 See Section 3.1. 490 Receiver Server's ID: 492 See Section 3.1. 494 Target Server's ID: 496 Contains the 32-bit server ID of the peer ENRP that is the 497 target of this takeover attempt. 499 3.8 PEER_INIT_TAKEOVER_ACK message 501 This message is used to acknowledge the takeover initiator that the 502 sender of this message received the PEER_INIT_TAKEOVER message and 503 that it does not object to the takeover. 505 0 1 2 3 506 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 1 507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 | Type = 0x8 |0|0|0|0|0|0|0|0| Message Length | 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | Sender Server's ID | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 | Receiver Server's ID | 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 514 | Target Server's ID | 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 Sender Server's ID: 519 See Section 3.1. 521 Receiver Server's ID: 523 See Section 3.1. 525 Target Server's ID: 527 Contains the 32-bit server ID of the peer ENRP that is the 528 target of this takeover attempt. 530 3.9 PEER_TAKEOVER_SERVER message 532 This message is used by the takeover initiator to declare that a 533 takeover is underway. 535 0 1 2 3 536 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 1 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | Type = 0x9 |0|0|0|0|0|0|0|0| Message Length | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | Sender Server's ID | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 542 | Receiver Server's ID | 543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 | Target Server's ID | 545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 547 Sender Server's ID: 549 See Section 3.1. 551 Receiver Server's ID: 553 See Section 3.1. 555 Target Server's ID: 557 Contains the 32-bit server ID of the peer ENRP that is the 558 target of this takeover operation. 560 3.10 PEER_OWNERSHIP_CHANGE message 562 This message is used by the ENRP server, normally after a successful 563 takeover, to declare that it is now the new home ENRP server of the 564 listed PEs in the listed pools. 566 0 1 2 3 567 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 1 568 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 569 | Type = 0xa |0|0|0|0|0|0|0|0| Message Length | 570 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 571 | Sender Server's ID | 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 | Receiver Server's ID | 574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 : Pool handle #1 : 576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 : PE Identifier Param #1 of pool #1 : 578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 579 : ... : 580 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 : PE Identifier Param #k of pool #1 : 582 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 583 : : 584 : ... : 585 : : 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 : Pool handle #M : 588 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 : PE Identifier Param #1 of pool #M : 590 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 : ... : 592 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 : PE Identifier Param #n of pool #M : 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 Sender Server's ID: 598 See Section 3.1. 600 Receiver Server's ID: 602 See Section 3.1. 604 Pool handles and PE Identifier parameters: 606 Each listed pool handle is followed by a list of PE Identifier 607 parameters, indicating that the sender of this message is 608 taking ownership of the listed PEs in the pool. 610 3.11 PEER_ERROR message 612 This message is used by an ENRP server to report an operation error 613 to one of its peers. 615 0 1 2 3 616 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 1 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 | Type = 0xb |0|0|0|0|0|0|0|0| Message Length | 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 | Sender Server's ID | 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 | Receiver Server's ID | 623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 : Operation Error Parameter : 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 627 Sender Server's ID: 629 See Section 3.1. 631 Receiver Server's ID: 633 See Section 3.1. 635 Operation Error Parameter: 637 This parameter, defined in [10], indicates the type of error(s) 638 being reported. 640 4. ENRP Operation Procedures 642 In this section, we discuss the operation procedures defined by ENRP. 643 An ENRP server MUST following these procedures when sending, 644 receiving, or processing ENRP messages. 646 Many of the Rserpool events call for both server-to-server and PU/ 647 PE-to-server message exchanges. Only the message exchanges and 648 activities between an ENRP server and its peer(s) are considered 649 within the ENRP scope and are defined in this document. 651 Procedures for exchanging messages between a PE/PU and ENRP servers 652 are defined in [1]. 654 4.1 Methods for Communicating amongst ENRP Servers 656 Within an Rserpool operation scope, ENRP servers need to communicate 657 with each other in order to exchange information such as the pool 658 membership changes, namespace data synchronization, etc. 660 Two types of communications are used amongst ENRP servers: 662 o point-to-point message exchange from one ENPR server to a specific 663 peer server, and 665 o announcements from one server to all its peer servers in the 666 operation scope. 668 Point-to-point communication is always carried out over an SCTP 669 associaiton between the sending server and the receiving server. 671 Announcements are communicated out with one of the following two 672 approaches: 674 1. The sending server sends the announcement message to a well-known 675 RSERPOOL IP multicast channel that its peer servers subscribe to. 677 Note: Because IP multicast is not reliable, this approach does 678 not gaurrantee that all the peers will receive the announcement 679 message. Moreover, since IP multicast is not secure, this 680 approach cannot provide any security to the communication. 682 2. The sending server sends multiple copies of the announcement, one 683 to each of its peer servers, over a set of point-to-point SCTP 684 associations between the sending server and the peers. 686 This approach gaurrantees the reliabe receiption of the message. 687 When needed, data security can be achieved by using IP security 688 mechanisms such as IPsec [9] or TLS [8]. 690 In order to maximize inter-operability of ENRP servers, the following 691 rules MUST be followed: 693 1. At the startup time, a new ENRP server SHOULD make a decision on 694 whether it will enable IP multicast for ENRP announcements. This 695 decision should be based on factors such as the availability of 696 IP multicast and the security requirements from the user of 697 Rserpool. 699 2. If an ENRP server disables multicast, it then: 701 A. MUST NOT subscribe to the well-known server multicast 702 channel, i.e., it only receives peer announcements over SCTP 703 associations, and 705 B. MUST transmit all its out-going announcements over 706 point-to-point SCTP associations with its peers. 708 3. If an ENRP server enables itself to use multicast, it then: 710 A. MUST subcribe to the well-known server multicast channel to 711 ready itself for receiving peers' multicast announcements, 713 B. MUST also be prepared to receive peer announcements over 714 point-to-point SCTP associations from peers. 716 C. MUST track internally which peers are multicast-enabled and 717 which are not. Note: A peer is always assumed to be 718 multicast-disabled until/unless an ENRP message of any type 719 is received from that peer over the well-known server 720 multicast channel. 722 D. when sending out an announcement, MUST send a copy to the 723 well-known server multicast channel AND a copy to each of the 724 peers that are marked as multicast-disabled over a 725 point-to-point SCTP association. 727 4.2 ENRP Server Initialization 729 This section describes the steps a new ENRP server needs to take in 730 order to join the other existing ENRP servers, or to initiate the 731 namespace service if it is the first ENRP server started in the 732 operation scope. 734 4.2.1 Generate a Server Identifier 736 A new ENRP server MUST generate a non-zero, 32-bit server Id that is 737 as unique as possible in the operation scope and this server Id MUST 738 remain unchanged for the lifetime of the server. Normally, a good 739 32-bit random number will be good enough as the server Id ([11] 740 provides some information on randomness guidelines). 742 4.2.2 Acquire Peer Server List 744 At startup, the ENRP server (initiating server) will first attempt to 745 learn all existing peer ENRP servers in the same operation scope, or 746 to determine that it is along in the scope. 748 The initiating server uses an existing peer server to bootstrap 749 itself into service. We call this peer server the mentor server. 751 4.2.2.1 Find the mentor server 753 If the initiating server is told about an existing peer server 754 through some administrative means (such as DNS query, configuration 755 database, startup scripts, etc), the initiating server SHOULD then 756 use this peer server as its mentor server and SHOULD skip the 757 remaining steps in this subsection. 759 If multiple existing peer servers are specified, the initiating 760 server SHOULD pick one of them as its mentor peer server, keep the 761 others as its backup menter peers, and skip the remaining steps in 762 this subsection. 764 If no existing peer server is specified to the initiating server AND 765 if multicast is available in the operation scope, the following 766 mentor peer discovery procedures SHOULD be followed: 768 1. The initiating server SHOULD first join the well-known ENRP 769 server multicast channel. 771 2. Then the initiating server SHOULD send a PEER_PRESENCE message, 772 with the 'Reply_required' flag set, over the multicast channel. 773 Upon the reception of this PEER_PRESENCE message, a peer server 774 MUST send a PEER_PRESENCE, without the 'Reply_required' flag, 775 back to the initiating server. 777 3. When the first response to its original PEER_PRESENCE arrives, 778 the initiating server SHOULD take the sender of this received 779 response as its mentor peer server. This completes the discovery 780 of the mentor peer server. 782 If responses are also received from other peers (a likely event 783 when multiple peers exist in the operation scope at the time the 784 new server started), the initiating server SHOULD keep a list of 785 those responded as its backup mentor peers (see below). 787 4. If no response to its PEER_PRESENCE message are received after 788 TIMEOUT-SERVER-HUNT seconds, the initiating server SHOULD repeat 789 steps 2) and 3) for up to MAX-TIME-SERVER-HUNT times. After that, 790 if there is still no response, the initiating server MUST assume 791 that it is alone in the operation scope. 793 5. If the initiating server determined that it is alone in the 794 scope, it MUST skip the procedures in Section 4.2.2.2 and Section 795 4.2.3 and MUST consider its initialization completed and start 796 offering ENRP services. 798 Note, if multicast is not available (or not allowed for reasons such 799 as security concerns) in the operation scope, at least one peer 800 server MUST be specified to the initiating server through 801 administrative means, unless the initiation server is the first 802 server to start in the operation scope. 804 Note, if the administratively specified menter peer(s) fails, the 805 initiating server SHOULD use the auto-discover procedure defined in 806 steps 1-5 above. 808 4.2.2.2 Request complete server list from mentor peer 810 Once the initiating server finds its mentor peer server (by either 811 discovery or administrative means), the initiating server MUST send a 812 PEER_LIST_REQUEST message to the mentor peer server to request a copy 813 of the complete server list maintained by the mentor peer (see 814 Section 4.9 for maintaining server list). 816 Upon the reception of this request, the mentor peer server SHOULD 817 reply with a PEER_LIST_RESPONSE message and include in the message 818 body all existing ENRP servers known by the mentor peer. 820 Upon the reception of the PEER_LIST_RESPONSE message from the mentor 821 peer, the initiating server MUST use the server information carried 822 in the message to initialize its own peer list. 824 However, if the mentor itself is in the process of startup and not 825 ready to provide a peer server list (for example, the mentor peer is 826 waiting for a response to its own PEER_LIST_REQUEST to another 827 server), it MUST rejest the request by the initiating server and 828 respond with a PEER_LIST_RESPONSE message with the R flag set to '1', 829 and with no server information included in the response. 831 In the case where its PEER_LIST_REQUEST is rejected by the mentor 832 peer, the initiating server SHOULD either wait for a few seconds and 833 re-send the PEER_LIST_REQUEST to the mentor server, or if there is a 834 backup mentor peer available, select another mentor peer server and 835 send the PEER_LIST_REQUEST to the new mentor server. 837 4.2.3 Download ENRP Namespace Data from Mentor Peer 839 After a peer list download is completed, the initiating server MUST 840 request a copy of the current namespace data from its mentor peer 841 server, by taking the following steps: 843 1. The initiating server MUST first send a PEER_NAME_TABLE_REQUEST 844 message to the mentor peer, with W flag set to '0', indicating 845 that the entire namespace is requested. 847 2. Upon the reception of this message, the mentor peer MUST start a 848 download session in which a copy of the current namespace data 849 maintained by the mentor peer is sent to the initiating server in 850 one or more PEER_NAME_TABLE_RESPONSE messages. 852 If more than one PEER_NAME_TABLE_RESPONSE message are used during 853 the download, the mentor peer MUST use the M flag in each 854 PEER_NAME_TABLE_RESPONSE message to indicate whether this message 855 is the last one for the download session. In particular, the 856 mentor peer MUST set the M flag to '1' in the outbound 857 PEER_NAME_TABLE_RESPONSE if there is more data to be transferred 858 and MUST keep track of the progress of the current download 859 session. The mentor peer MUST set the M flag to '0' in the last 860 PEER_NAME_TABLE_RESPONSE for the download session and close the 861 download session (i.e., removing any internal record of the 862 session) after sending out the last message. 864 3. During the downloading, every time the initiating server receives 865 a PEER_NAME_TABLE_RESPONSE message, it MUST transfer the data 866 entries carried in the message into its local namespace database, 867 and then check whether or not this message is the last one for 868 the download session. 870 If the M flag is set to '1' in the just processed 871 PEER_NAME_TABLE_RESPONSE message, the initiating server MUST send 872 another PEER_NAME_TABLE_REQUEST message to the mentor peer to 873 request for the next PEER_NAME_TABLE_RESPONSE message. 875 4. When unpacking the data entries from a PEER_NAME_TABLE_RESPONSE 876 message into its local namespace database, the initiating server 877 MUST handle each pool entry carried in the message using the 878 following rules: 880 A. If the pool does not exist in the local namespace, the 881 initiating server MUST creates the pool in the local 882 namespace and add the PE(s) in the pool entry to the pool. 884 When creating the pool, the initiation server MUST set the 885 overall member selection policy type of the pool to the 886 policy type indicated in the first PE. 888 B. If the pool already exists in the local namespace, but the 889 PE(s) in the pool entry is not currently a member of the 890 pool, the initiating server MUST add the PE(s) to the pool. 892 C. If the pool already exists in the local namespace AND the 893 PE(s) in the Pool entry is already a member of the pool, the 894 initiating server server SHOULD replace the attributes of the 895 existing PE(s) with the new information. 897 5. When the last PEER_NAME_TABLE_RESPONSE message is received from 898 the mentor peer and unpacked into the local namespace, the 899 initialization process is completed and the initiating server 900 SHOULD start to provide ENRP services. 902 Under certain circumstances, the mentor peer itself may not be able 903 to provide a namespace download to the initiating server. For 904 example, the mentor peer is in the middle of initializing its own 905 namespace database, or it has currently too many download sessions 906 open to other servers. 908 In such a case, the mentor peer MUST rejest the request by the 909 initiating server and respond with a PEER_NAME_TABLE_RESPONSE message 910 with the R flag set to '1', and with no pool entries included in the 911 response. 913 In the case where its PEER_NAME_TABLE_REQUEST is rejected by the 914 mentor peer, the initiating server SHOULD either wait for a few 915 seconds and re-send the PEER_NAME_TABLE_REQUEST to the mentor server, 916 or if there is a backup mentor peer available, select another mentor 917 peer server and send the PEER_NAME_TABLE_REQUEST to the new mentor 918 server. 920 A started namespace download session may get interrupted for some 921 reason. To cope with this, the initiating server SHOULD start a timer 922 everytime it finishes sending a PEER_NAME_TABLE_REQUEST to its mentor 923 peer. If this timer expires without receiving a response from the 924 mentor peer, the initiating server SHOULD abort the current download 925 session and re-start a new namespace download with a backup mentor 926 peer, if one is available. 928 Similarly, after sending out a PEER_NAME_TABLE_RESPONSE, if the 929 mentor peer has still more data to send, it SHOULD start a session 930 timer. If this timer expires without receiving another request from 931 the initiating server, the mentor peer SHOULD abort the session, 932 cleaning out any resource and record of the session. 934 4.3 Handle PE Registration 936 To register itself with the namespace, a PE sends a REGISTRATION 937 message to its home ENRP server. The format of REGISTRATION message 938 and rules of sending it are defined in [1]. 940 In the REGISTRATION message, the PE indicates the name of the pool it 941 wishes to join in a pool handle parameter, and its complete transport 942 information and any load control information in a PE parameter. 944 The ENRP server handles the REGISTRATION message according to the 945 following rules: 947 1. If the named pool does not exist in the namespace, the ENRP 948 server MUST creates a new pool with that name in the namespace 949 and add the PE to the pool as its first PE; 951 When a new pool is created, the overall member selection policy 952 of the pool MUST be set to the policy type indicated by the first 953 PE. 955 2. If the named pool already exists in the namespace, but the 956 requesting PE is not currently a member of the pool, the ENRP 957 server will add the PE as a new member to the pool; 959 After adding the PE to the pool, the server MUST check if the 960 policy type indicated by the PE is the same as the overall policy 961 type of the pool. If different, the ENRP server MUST attempt to 962 override the PE's policy and make it the same as the overall 963 policy. 965 A. If no additional policy-related information are required to 966 perform the override (e.g., overriding Least-used with 967 Round-robin does not require additional policy-related 968 information), the ENRP server MUST replace the PE's policy 969 type with the overall policy type. 971 B. If additional policy information is required (e.g., 972 overriding Round-robin with Least-load will require the 973 knowledge of the load factor of the PE), the ENRP server MUST 974 reject the regirstration with an error code "Pooling policy 975 inconsistent". 977 3. If the named pool already exists in the namespace AND the 978 requesting PE is already a member of the pool, the ENRP server 979 SHOULD consider this as a re-registration case. The ENRP Server 980 SHOULD replace the attributes of the existing PE with the 981 information carried in the received REGISTRATION message. 983 4. After accepting the registration, the ENRP server MUST assgin 984 itself the owner of this PE. If this is a re-registration, the 985 ENRP server MUST take over ownership of this PE regardless of 986 whether the PE was previously owned by the server or by a peer of 987 it. 989 5. The ENRP server may reject the registration due to reasons such 990 as invalid values, lack of resource, authentication failure, etc. 992 In all above cases, the ENRP server MUST reply to the requesting PE 993 with a REGISTRATION_RESPONSE message. If the registration is 994 rejected, the ENRP server MUST indicate the rejection by including 995 the proper Operation Error parameter in the REGISTRATION_RESPONSE 996 message. 998 If the registration is granted with a polcy override (see Step 2a 999 above), in the REGISTRATION_RESPONSE message the ENRP server SHOULD 1000 also send back the registrant PE the new policy, in a Member 1001 Selection Policy Parameter, so as to inform the PE that a policy 1002 override is performed. 1004 If the registration is granted (i.e., one of cases 1-3 above), the 1005 ENRP server MUST assign itself to be the home ENRP server of the PE, 1006 i.e., to "own" the PE. 1008 Implementation note: for better performance, the ENRP server may 1009 find it both efficient and convenient to internally maintain two 1010 separate PE lists or tables - one is for the PEs that are "owned" 1011 by the ENRP server and the other for all the PEs owned by its 1012 peer(s). 1014 Moreover, if the registration is granted, the ENRP server MUST take 1015 the namespace update action as described in Section 4.6 to inform its 1016 peers about the change just made. If the registration is denied, no 1017 message will be sent to its peers. 1019 4.3.1 Rules on PE Re-registration 1021 A PE may re-register itself to the namespace with a new set of 1022 attributtes in order to, for example, extend its registration life, 1023 change its load factor value, etc. 1025 A PE may modify its load factor value at any time via 1026 re-registration. Based on the number of PEs in the pool and the 1027 pool's overall policy type, this operation allows the PE to 1028 dynamically control its share of inbound messages received by the 1029 pool (also see Section ???? in [1] for more on load control). 1031 Moreover, when re-registering, the PE MUST NOT change its policy 1032 type. The server MUST reject the re-registration if the PE attempt to 1033 change its policy type. In the rejection, the server SHOULD attach an 1034 error code "Pooling Policy Inconsistent". 1036 Regardless whether it is the current owner of the PE, if the 1037 re-registration is granted to the PE, the ENRP server MUST assign 1038 itself to be the new home ENRP server of the PE. 1040 Moreover, if the re-registration is granted, the ENRP server MUST 1041 take the namespace update action as described in Section 4.6 to 1042 inform its peers about the change just made. If the re-registration 1043 is denied, no message will be sent to its peers. 1045 4.4 Handle PE De-registration 1047 To remove itself from a pool, a PE sends a DEREGISTRATION message to 1048 its home ENRP server. The complete format of DEREGISTRATION message 1049 and rules of sending it are defined in [1]. 1051 In the DEREGISTRATION message the PE indicates the name of the pool 1052 it belongs to in a pool handle parameter and provides its PE 1053 identifer. 1055 Upon receiving the message, the ENRP server SHALL remove the PE from 1056 its namespace. Moreover, if the PE is the last one of the named pool, 1057 the ENRP server will remove the pool from the namespace as well. 1059 If the ENRP server fails to find any record of the PE in its 1060 namespace, it SHOULD consider the de-registration granted and 1061 completed. 1063 The ENRP server may reject the de-registration request for various 1064 reasons, such as invalid parameters, authentication failure, etc. 1066 In response, the ENRP server MUST send a DEREGISTRATION_RESPONSE 1067 message to the PE. If the de-registration is rejected, the ENRP 1068 server MUST indicate the rejection by including the proper Operation 1069 Error parameter. 1071 It should be noted that de-registration does not stop the PE from 1072 sending or receiving application messages. 1074 Once the de-registration request is granted AND the PE removed from 1075 its local copy of the namespace, the ENRP server MUST take the 1076 namespace update action described in Section 4.6 to inform its peers 1077 about the change just made. Otherwise, NO message SHALL be send to 1078 its peers. 1080 4.5 Pool Handle Translation 1082 A PU uses the pool handle translation service of an ENRP server to 1083 resolve a pool handle to a list of accessible transport addresses of 1084 the member PEs of the pool. 1086 This requires the PU to send a NAME_RESOLUTION message to its home 1087 ENRP server and in the NAME_RESOLUTION message specify the pool 1088 handle to be translated in a Pool Handle parameter. Complete 1089 defintion of the NAME_RESOLUTION message and the rules of sending it 1090 are defined in [1]. 1092 An ENRP server SHOULD be prepared to receive NAME_RESOLUTION requests 1093 from PUs either over an SCTP associaiton on the well-know SCTP port, 1094 or over a TCP connection on the well-know TCP port. 1096 Upon reception of the NAME_RESOLUTION message, the ENRP server MUST 1097 first look up the pool handle in its namespace. If the pool exits, 1098 the home ENRP server MUST compose and send back a 1099 NAME_RESOLUTION_RESPONSE message to the requesting PU. 1101 In the response message, the ENRP server MUST list all the PEs 1102 currently registered in this pool, in a list of PE parameters. The 1103 ENRP server MUST also include a pool member selection policy 1104 parameter to indicate the overall member selection policy for the 1105 pool, if the current pool member selection policy is not round-robin 1106 (if the overall policy is round-Robin, this parameter MAY be 1107 omitted?). 1109 If the named pool does not exist in the namespace, the ENRP server 1110 MUST respond with a NAME_UNKNOWN message. 1112 The complete format of NAME_RESOLUTION_RESPONSE and NAME_UNKNOWN 1113 messages and the rules of receiving them are defined in [1]. 1115 4.6 Server Namespace Update 1117 This includes a set of update operations used by an ENRP server to 1118 inform its peers when its local namespace is modified, e.g., addition 1119 of a new PE, removal of an existing PE, change of pool or PE 1120 properties. 1122 4.6.1 Announcing Addition or Update of PE 1124 When a new PE is granted registration to the namespace or an existing 1125 PE is granted a re-registration, the home ENRP server uses this 1126 procedure to inform all its peers. 1128 This is an ENRP announcement and is sent to all the peer of the home 1129 ENRP server. See Section 4.1 on how annoucements are sent. 1131 An ENRP server MUST announce this update to all its peers in a 1132 PEER_NAME_UPDATE message with the Update Action field set to ADD_PE, 1133 indicating the addition of a new PE or the modification of an 1134 existing PE. The complete new information of the PE and the pool its 1135 belongs to MUST be indicated in the message with a PE parameter and a 1136 Pool Handle parameter, respectively. 1138 The home ENRP server SHOULD fill in its server Id in the Sender 1139 Server's ID field and leave the Receiver Server's ID blank (i.e., all 1140 0's). 1142 When a peer receives this PEER_NAME_UPDATE message, it MUST take the 1143 following actions: 1145 1. If the named pool indicated by the pool handle does not exist in 1146 its local copy of the namespace, the peer MUST create the named 1147 pool in its local namespace and add the PE to the pool as the 1148 first PE. It MUST then copy in all other attributes of the PE 1149 carried in the message. 1151 When the new pool is created, the overall member selection policy 1152 of the pool MUST be set to the policy type indicated by the PE. 1154 2. If the named pool already exists in the peer's local copy of the 1155 namespace AND the PE does not exist, the peer MUST add the PE to 1156 the pool as a new PE and copy in all attributes of the PE carried 1157 in the message. 1159 3. If the named pool exists AND the PE is already a member of the 1160 pool, the peer MUST replace the attributes of the PE with the new 1161 information carried in the message. 1163 4.6.2 Announcing Removal of PE 1165 When an existing PE is granted de-registration or is removed from its 1166 namespace for some other reasons (e.g., purging an unreachable PE, 1167 see Section 4.7), the ENRP server MUST uses this procedure to inform 1168 all its peers about the change just made. 1170 This is an ENRP announcement and is sent to all the peer of the home 1171 ENRP server. See Section 4.1 on how annoucements are sent. 1173 An ENRP server MUST announce the PE removal to all its peers in a 1174 PEER_NAME_UPDATE message with the Update Action field set to DEL_PE, 1175 indicating the removal of an existing PE. The complete information of 1176 the PE and the pool its belongs to MUST be indicated in the message 1177 with a PE parameter and a Pool Handle parameter, respectively. 1179 [editor's note: only the pool handle and the PE's id are needed, it 1180 should reduce the size of the message] 1182 The sending server MUST fill in its server ID in the Sender Server's 1183 ID field and leave the Receiver Server's ID blank (i.e., set to all 1184 0's). 1186 When a peer receives this PEER_NAME_UPDATE message, it MUST first 1187 find pool and the PE in its own namespace, and then remove the PE 1188 from its local namespace. If the removed PE is the last one in the 1189 pool, the peer MUST also delete the pool from its local namespace. 1191 If the peer fails to find the PE or the pool in its namespace, it 1192 SHOULD take no further actions. 1194 4.7 Detecting and Removing Unreachable PE 1196 Whenever a PU finds a PE unreachable (e.g., via an SCTP SEND.FAILURE 1197 Notification, see section 10.2 of [7]), the PU SHOULD send an 1198 ENDPOINT_UNREACHABLE message to its home ENRP server. The message 1199 SHOULD contain the pool handle and the PE Id of the unreachable PE. 1201 Upon the reception of an ENDPOINT_UNREACHABLE message, a server MUST 1202 immediately send a point-to-point ENDPOINT_KEEP_ALIVE message to the 1203 PE in question. If this ENDPOINT_KEEP_ALIVE fails (e.g., it results 1204 in an SCTP SEND.FAILURE notification), the ENRP server MUST consider 1205 the PE as truly unreachable and MUST remove the PE from its namespace 1206 and take actions described in Section 4.6.2. 1208 If the ENDPOINT_UNREACHABLE message is transmitted successfully to 1209 the PE, the ENRP server MUST retain the PE in its namespace. 1210 Moreover, the server SHOULD keep a counter to record how many 1211 ENDPOINT_UNREACHABLE messages it has received reporting reachability 1212 problem relating to this PE. If the counter exceeds the protocol 1213 threshold MAX-BAD-PE-REPORT, the ENRP server SHOULD remove the PE 1214 from its namespace and take actions described in Section 4.6.2. 1216 Optionally, an ENRP server may also periodically send point-to-point 1217 ENDPOINT_KEEP_ALIVE messages to each of the PEs owned by the ENRP 1218 server in order to check their reachability status. If the send of 1219 ENDPOINT_KEEP_ALIVE to a PE fails, the ENRP server MUST consider the 1220 PE as unreachable and MUST remove the PE from its namespace and take 1221 actions described in Section 4.6.2. Note, if an ENRP server owns a 1222 large number of PEs, the implementation should pay attention not to 1223 flood the network with bursts of ENDPOINT_KEEP_ALIVE messages. 1224 Instead, the implementation should try to smooth out the 1225 ENDPOINT_KEEP_ALIVE message traffic over time. 1227 The complete definition and rules of sending ENDPOINT_UNREACHABLE and 1228 receiving ENDPOINT_KEEP_ALIVE messages are described in [1]. 1230 4.8 Helping PE and PU to Discover Home ENRP Server 1232 At its startup time, or whenever its current home ENRP server is not 1233 providing services, a PE or PU will attempt to find a new home 1234 server. For this reason, the PE or PU will need to maintain a list of 1235 currently available ENRP servers in its scope. 1237 To help the PE or PU maintaining this list, an ENRP server, if it is 1238 enabled for multicast, SHOULD periodically send out a SERVER_ANNOUNE 1239 message every SERVER-ANNOUNCE-CYCLE seconds to the well-known ASAP 1240 multicast channel. And in the SERVER_ANNOUNE message the ENRP server 1241 SHOULD include all the transport addresses available for ASAP 1242 communications. If the ENRP server only supports SCTP for ASAP 1243 communications, the transport information MAY be omitted in the 1244 SERVER_ANNOUNCE message. 1246 For the complete procedure of this, see Section 3.6?? in [1]. 1248 4.9 Maintaining Peer List and Monitoring Peer Status 1250 An ENRP server MUST keep an internal record on the status of each of 1251 its known peers. This record is referred to as the server's "peer 1252 list" 1254 4.9.1 Discovering New Peer 1256 If a message of any type is received from a previously unknown peer, 1257 the ENRP server MUST consider this peer a new peer in the operation 1258 scope and add it to the peer list. 1260 The ENRP server MUST send a PEER_PRESENCE message with the 1261 Reply-required flag set to '1' to the source address found in the 1262 arrived message. This will force the new peer to reply with its own 1263 PEER_PRESENCE containing its full server information (see Section 1264 3.1). 1266 [editor's note: should we ask for a peer list from the new peer? 1267 this may help mending two splitted networks.] 1269 4.9.2 Server Sending Heartbeat 1271 Every PEER-HEARTBEAT-CYCLE seconds, an ENRP server MUST announce its 1272 continued presence to all its peer with a PEER_PRESENCE message. In 1273 the PEER_PRESENCE message, the ENRP server MUST set the 1274 'Replay_required' flag to '0', indicating that no response is 1275 required. 1277 The arrival of this periodic PEER_PRESENCE message will cause all its 1278 peers to update their internal variable "Peer-last-heared" for the 1279 sending server (see Section 4.9.3 for more details). 1281 4.9.3 Detecting Peer Server Failure 1283 An ENRP server MUST keep an interanl variable "Peer-last-heared" for 1284 each of its known peers and the value of this variable MUST be 1285 updated to the current local time everytime a message of any type 1286 (point-to-point or announcement) is received from the cooresponding 1287 peer. 1289 If a peer has not been heard for more than MAX-TIME-LAST-HEARD 1290 seconds, the ENRP server MUST immediately send a point-to-point 1291 PEER_PRESENCE with 'Reply_request' flag set to '1' to that peer. 1293 If the send fails or the peer does not reply after 1294 MAX-TIME-NO-RESPONSE seconds, the ENRP server MUST consider the peer 1295 server dead and SHOULD initiate the takeover procedure defined in 1296 Section 4.10. 1298 4.10 Taking-over a Failed Peer Server 1300 In the following descriptions, We call the ENRP server that detects 1301 the failed peer server and initiates the take-over the "initiating 1302 server" and the failed peer server the "target server." 1304 4.10.1 Initiate Server Take-over Arbitration 1306 The initiating server SHOULD fisrt start a take-over arbitration 1307 process by announcing a PEER_INIT_TAKEOVER message to all its peer 1308 servers. See Section 4.1 on how annoucements are sent. In the 1309 message, the initiating server MUST fill in the Sender Server's ID 1310 and Target Server's ID. 1312 After announcing the PEER_INIT_TAKEOVER message, the initiating 1313 server SHOULD wait for a PEER_INIT_TAKEOVER_ACK message from _each_ 1314 of its known peers, except of the target server. [editor's note: how 1315 long should it wait?] 1317 Each of the peer servers that receives the PEER_INIT_TAKEOVER message 1318 from the initiating server SHOULD take the following actions: 1320 1. If the peer server finds that itself is the target server 1321 indicated in the PEER_INIT_TAKEOVER message, it MUST immediately 1322 announce a PEER_PRESENCE message to all its peer ENRP servers in 1323 an attempt to stop this take-over process. This indicates a false 1324 failure detection case by the initiating server. 1326 2. If the peer server finds that itself has already started its own 1327 take-over arbitration process on the same target server, it MUST 1328 perform the following arbitration: 1330 A. if the peer's server ID is smaller in value than the Sender 1331 Server's ID in the arrived PEER_INIT_TAKEOVER message, the 1332 peer server SHOULD immediately abort its own take-over 1333 attempt. Moreover, the peer SHOULD mark the target server as 1334 "not active" on its internal peer list so that its status 1335 will no longer be monitored by the peer, and reply the 1336 initiating server with a PEER_INIT_TAKEOVER_ACK message. 1338 B. Otherwise, the peer MUST ignore the PEER_INIT_TAKEOVER 1339 message and take no action. 1341 3. If the peer finds that it is neither the target server nor is in 1342 its own take-over process, the peer SHOULD: a) mark the target 1343 server as "not active" on its internal peer list so that its 1344 status will no longer be monitored by this peer, and b) reply to 1345 the initiating server with a PEER_INIT_TAKEOVER_ACK message. 1347 Once the initiating server has received PEER_INIT_TAKEOVER_ACK 1348 message from _all_ of its currently known peers (except for the 1349 target server), it SHOULD consider that it has won the arbitration 1350 and SHOULD proceed to complete the take-over, following the steps 1351 described in Section 4.10.2. 1353 However, if it receives a PEER_PRESENCE from the target server at any 1354 point in the arbitration process, the initiating server SHOULD 1355 immediately abort the take-over process and mark the status of the 1356 target server as "active". 1358 4.10.2 Take-over Target Peer Server 1360 The initiating ENRP server SHOULD first send, via an announcement, a 1361 PEER_TAKEOVER_SERVER message to inform all its active peers that the 1362 take-over is enforced. The target server's ID MUST be filled in the 1363 message. The initiating server SHOULD then remove the target server 1364 from its internal peer list. 1366 [editor's note: peers should remove the target server from their list 1367 upon receiving this message. Do we really need this message? we can 1368 consolidate this with the ownership_change msg.] 1370 Then it SHOULD examine its local copy of the namespace and claim 1371 ownership of each of the PEs originally owned by the target server, 1372 by following these steps: 1374 1. mark itself as the home ENRP server of each of the PEs originally 1375 owned by the target server; 1377 2. send a point-to-point ENDPOINT_KEEP_ALIVE message to each of the 1378 PEs. This will trigger the PE to adopt the initiating sever as 1379 its new home ENRP server; 1381 3. after claiming the ownership of all the PEs originally owned by 1382 the target server, announce the ownership changes of all the 1383 affected PEs in a PEER_OWNERSHIP_CHANGE message to all the 1384 currently known peers. Note, if the list of affected PEs is long, 1385 the sender MAY announce the ownership changes in multiple 1386 PEER_OWNERSHIP_CHANGE messages. 1388 When a peer receives the PEER_OWNERSHIP_CHANGE message from the 1389 initiating server, it SHOULD find each of the reported PEs in its 1390 local copy of the namespace and update the PE's home ENRP server to 1391 be the sender of the message (i.e., the initiating server). 1393 4.11 Namespace Data Auditing and Re-synchronization 1395 Message losses or certain temporary breaks in network connectivity 1396 may result in data inconsistency in the local namespace copy of some 1397 of the ENRP servers in an operation scope. Therefore, each ENRP 1398 server in the operation scope SHOULD periodically verify that its 1399 local copy of namespace data is still in sync with that of its peers. 1401 This section defines the auditing and re-synchronization procedures 1402 for an ENRP server to maintain its namespace data consistency. 1404 4.11.1 Auditing Prodecures 1406 [TBD] 1408 4.11.2 Re-synchronization Prodecures 1409 Once an ENRP server determines that there is inconsistancy between 1410 its local namespace data and a peer's namespace data with regarding 1411 to the PEs owned by that peer, it SHOULD perform the following steps 1412 to re-synchronize the data: 1414 1. The ENRP server SHOULD first "mark" every PE it knows about that 1415 is owned by the peer in its local namespace database; 1417 2. The ENRP server SHOULD then send a PEER_NAME_TABLE_REQUEST 1418 message with W flag set to '1' to the peer to request a complete 1419 list of PEs owned by the peer; 1421 3. Upon reception of the PEER_NAME_TABLE_REQUEST message with W flag 1422 set to '1', the peer server SHOULD immediately respond with a 1423 PEER_NAME_TABLE_RESPONSE message listing all PEs currently owned 1424 by the peer. 1426 4. Upon reception of the PEER_NAME_TABLE_RESPONSE message, the ENRP 1427 server SHOULD transfer the PE entries carried in the message into 1428 its local namespace database. If an PE entry being transferred 1429 already exists in its local database, the ENRP server MUST 1430 replace the entry with the copy found in the message and remove 1431 the "mark" from the entry. 1433 5. After transferring all the PE entries from the received 1434 PEER_NAME_TABLE_RESPONSE message into its local database, the 1435 ENRP server SHOULD check whether there are still PE entries that 1436 remain "marked" in its local namespace. If so, the ENRP server 1437 SHOULD silently remove those "marked" entries. 1439 Note, similar to what is described in Section 4.2.3, the peer may 1440 reject the PEER_NAME_TABLE_REQUEST or use more than one 1441 PEER_NAME_TABLE_RESPONSE message to respond. 1443 4.12 Handling Unrecognized Message or Unrecognized Parameter 1445 When an ENRP server receives an ENRP message with an unknown message 1446 type or a message of known type that contains an unknow parameter, it 1447 SHOULD handle the unknow message or the unknown parameter according 1448 to the unrecognized message and parameter handling rules defined in 1449 Sections 3 and 4 in [10]. 1451 According to the rules, if an error report to the message sender is 1452 needed, the ENRP server that discovered the error SHOULD send back an 1453 ENRP_ERROR message with proper error cause code. 1455 5. Variables and Time Constants 1457 5.1 Variables 1459 Peer-last-heared - the local time that a peer server was last heard 1460 (via receiving either a multicast or point-to-point message from 1461 the peer). 1463 5.2 Timer Constants 1465 MAX-TIME-SERVER-HUNT - the maximal number of attempts a sender will 1466 make to contact an ENRP server (Default=3 times). 1468 TIMEOUT-SERVER-HUNT - pre-set threshold for how long a sender will 1469 wait for a response from an ENRP server (Default=5 secends). 1471 PEER-HEARTBEAT-CYCLE - the period for an ENRP server to announce a 1472 heartheat message to all its known peers. (Default=30 secs.) 1474 SERVER-ANNOUNCE-CYCLE - the period for an ENRP server to announce a 1475 SERVER_ANNOUNCE message to all PEs and PUs. (Default=5 secs.) 1477 MAX-TIME-LAST-HEARD - pre-set threshold for how long an ENRP server 1478 will wait before considering a silent peer server potentially 1479 dead. (Default=61 secs.) 1481 MAX-TIME-NO-RESPONSE - pre-set threshold for how long a message 1482 sender will wait for a response after sending out a message. 1483 (Default=5 secs.) 1485 MAX-BAD-PE-REPORT - the maximal number of unreachability reports on a 1486 PE that an ENRP server will allow before purging this PE from the 1487 namespace. (Default=3) 1489 6. Security Considerations 1491 Due to varying requirements and multiple use cases of Rserpool, we 1492 point out two basic security protocols, IPsec and TLS. We 1493 specifically do not discuss whether one security protocol would be 1494 preferred over the other. This choice will be made by designers and 1495 network architects based on system requirements. 1497 For networks that demand IPsec security, implementations MUST support 1498 [9] which describes IPsec-SCTP. IPsec is two layers below RSerPool. 1499 Therefore, if IPsec is used for securing Rserpool, no changes or 1500 special considerations need to be made to Rserpool to secure the 1501 protocol. 1503 For networks that cannot or do not wish to use IPsec and prefer 1504 instead TLS, implementations MUST support TLS with SCTP as described 1505 in [8] or TLS over TCP as described in [6]. When using TLS/SCTP we 1506 must ensure that RSerPool does not use any features of SCTP that are 1507 not available to an TLS/SCTP user. This is not a difficult technical 1508 problem, but simply a requirement. When describing an API of the 1509 RSerPool lower layer we have also to take into account the 1510 differences between TLS and SCTP. This is also not difficult, but it 1511 is in contrast to the IPsec solution which is transparently layered 1512 below Rserpool. 1514 Support for security is required for the ENRP server and the PEs. 1515 Security support for the Rserpool end user is optional. Note that 1516 the end user implementation contains a piece of the Rserpool protocol 1517 -- namely ASAP -- whereby the pool handle is passed for name 1518 resolution to the ENRP server and IP address(es) are returned. 1520 The argument for optional end user security is as follows: If the 1521 user doesn't require security protection for example, against 1522 eavesdropping for the request for pool handle resolution and 1523 response, then they are free to make that choice. However, if the 1524 end user does require security, they are guaranteed to get it due to 1525 the requirement for security support for the ENRP server. It is also 1526 possible for the ENRP server to reject an unsecured request from the 1527 user due to its security policy in the case that it requires 1528 enforcement of strong security. But this will be determined by the 1529 security requirements of the individual network design. 1531 7. Acknowledgements 1533 The authors wish to thank John Loughney, Lyndon Ong, and many others 1534 for their invaluable comments. 1536 Normative References 1538 [1] Stewart, R., Xie, Q., Stillman, M. and M. Tuexen, "Aggregate 1539 Server Access Protocol (ASAP)", draft-ietf-rserpool-asap-05 1540 (work in progress), October 2002. 1542 [2] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney, 1543 J. and M. Stillman, "Requirements for Reliable Server Pooling", 1544 RFC 3237, January 2002. 1546 [3] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney, 1547 J. and M. Stillman, "Architecture for Reliable Server Pooling", 1548 draft-ietf-rserpool-arch-03 (work in progress), July 2002. 1550 [4] Bradner, S., "The Internet Standards Process -- Revision 3", 1551 BCP 9, RFC 2026, October 1996. 1553 [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement 1554 Levels", BCP 14, RFC 2119, March 1997. 1556 [6] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 1557 2246, January 1999. 1559 [7] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, 1560 H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, 1561 "Stream Control Transmission Protocol", RFC 2960, October 2000. 1563 [8] Jungmaier, A., Rescorla, E. and M. Tuexen, "TLS over SCTP", 1564 draft-ietf-tsvwg-tls-over-sctp-00 (work in progress), November 1565 2001. 1567 [9] Bellovin, S., Ioannidis, J., Keromytis, A. and R. Stewart, "On 1568 the Use of SCTP with IPsec", draft-ietf-ipsec-sctp-03 (work in 1569 progress), February 2002. 1571 [10] Stewart, R. and Q. Xie, "Aggregate Server Access Protocol 1572 (ASAP) and Endpoint Name Resolution (ENRP) common parameters 1573 document", draft-ietf-rserpool-common-param-00 (work in 1574 progress), July 2002. 1576 Informative References 1578 [11] Eastlake, D., Crocker, S. and J. Schiller, "Randomness 1579 Recommendations for Security", RFC 1750, December 1994. 1581 Authors' Addresses 1583 Qiaobing Xie 1584 Motorola, Inc. 1585 1501 W. Shure Drive, 2-F9 1586 Arlington Heights, IL 60004 1587 US 1589 Phone: +1-847-632-3028 1590 EMail: qxie1@email.mot.com 1592 Randall R. Stewart 1593 Cisco 1594 24 Burning Bush Trail 1595 Crystal Lake, IL 60012 1596 US 1598 Phone: +1-815-477-2127 1599 EMail: rrs@cisco.com 1601 Maureen Stillman 1602 Nokia 1603 127 W. 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