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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (November 5, 2018) is 1998 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFC-TBD' is mentioned on line 249, but not defined -- Obsolete informational reference (is this intentional?): RFC 5661 (Obsoleted by RFC 8881) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network File System Version 4 C. Lever, Ed. 3 Internet-Draft Oracle 4 Updates: 7530 (if approved) D. Noveck 5 Intended status: Standards Track NetApp 6 Expires: May 9, 2019 November 5, 2018 8 NFS version 4.0 Trunking Update 9 draft-ietf-nfsv4-mv0-trunking-update-02 11 Abstract 13 The file system location-related attribute in NFS version 4.0, 14 fs_locations, informs clients about alternate locations of file 15 systems. An NFS version 4.0 client can use this information to 16 handle migration and replication of server filesystems. This 17 document describes how an NFS version 4.0 client can additionally use 18 this information to discover an NFS version 4.0 server's trunking 19 capabilities. This document updates RFC 7530. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on May 9, 2019. 38 Copyright Notice 40 Copyright (c) 2018 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 57 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 4. Document Organization . . . . . . . . . . . . . . . . . . . . 6 59 5. Changes Within Section 8 of [RFC7530] . . . . . . . . . . . . 7 60 5.1. Updated Section 8.1 of [RFC7530], entitled 61 "Location Attributes" . . . . . . . . . . . . . . . . . . 7 62 5.2. Updates to Section 8.4 of [RFC7530], entitled 63 "Uses of Location Information" . . . . . . . . . . . . . 9 64 5.2.1. Updated Introduction to Section 8.4 of [RFC7530], 65 entitled "Uses of Location Information" . . . . . . . 9 66 5.2.2. New Sub-section of Section 8.4 of [RFC7530], 67 to be entitled "Trunking Discovery and Detection" . . 10 68 5.2.3. New Sub-section of Section 8.4 of [RFC7530], 69 to be entitled "Location Attributes and Connection 70 Type Selection" . . . . . . . . . . . . . . . . . . . 11 71 5.2.4. Updated Section 8.4.1 of [RFC7530], entitled 72 "File System Replication and Trunking" . . . . . . . 11 73 5.2.5. Updated Section 8.4.2 of [RFC7530], entitled 74 "File System Migration" . . . . . . . . . . . . . . . 12 75 5.2.6. New Sub-section of Section 8.4 of [RFC7530], 76 to be entitled "Interaction of Trunking, Migration, 77 and Replication" . . . . . . . . . . . . . . . . . . 12 78 5.3. Updated Section 8.5 of [RFC7530], entitled 79 "Location Entries and Server Identity Update" . . . . . . 14 80 6. Updates to [RFC7530] Outside Section Eight . . . . . . . . . 14 81 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 82 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 83 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 84 9.1. Normative References . . . . . . . . . . . . . . . . . . 17 85 9.2. Informative References . . . . . . . . . . . . . . . . . 17 86 Appendix A. Section Classification . . . . . . . . . . . . . . . 18 87 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 18 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 90 1. Introduction 92 The NFS version 4.0 specification [RFC7530] defines a migration 93 feature which enables the transfer of a file system from one server 94 to another without disruption of client activity. There were a 95 number of issues with the original definition of this feature, now 96 resolved with the publication of [RFC7931]. 98 After a migration event, a client must determine whether state 99 recovery is necessary. To do this, it needs to determine whether the 100 source and destination server addresses represent the same server 101 instance, if the client has already established a lease on the 102 destination server for other file systems, and if the destination 103 server instance has lock state for the migrated file system. 105 As part of addressing this need, [RFC7931] introduces trunking into 106 NFS version 4.0 along with a trunking detection mechanism. This 107 enables a client to determine whether two distinct network addresses 108 are connected to the same NFS version 4.0 server instance. 109 Nevertheless, the use of the concept of server-trunkability is the 110 same in both protocol versions. 112 File system migration, replication, and referrals are distinct 113 protocol features. However, it is not appropriate to treat each of 114 these features in isolation. For example, client migration recovery 115 processing needs to deal with the possibility of multiple server 116 addresses in a returned fs_locations attribute. In addition, the 117 contents of the fs_locations attribute, which provides both trunking- 118 related and replication information, may change over repeated 119 retrievals, requiring an integrated description of how clients are to 120 deal with such changes. The issues discussed in the current document 121 relate to the interpretation of the fs_locations attribute and to the 122 proper client and server handling of changes in fs_locations 123 attribute values. 125 Therefore the goals of this document are: 127 o To provide NFS version 4.0 with a means of trunking discovery, 128 compatible with the means of trunking detection introduced by 129 [RFC7931]. 131 o To describe how NFS version 4.0 clients are to handle the presence 132 of multiple network addresses associated to the same server, when 133 recovering from a replication and migration event. 135 o To describe how NFS version 4.0 clients are to handle changes in 136 the contents of returned fs_locations attributes, including those 137 that indicate changes in the responding NFS version 4.0 server's 138 trunking configuration. 140 The current document pursues these goals by presenting a set of 141 updates to [RFC7530] as summarized in Sections 5 and 6 below. 143 2. Requirements Language 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 147 document are to be interpreted as described in BCP 14 [RFC2119] 148 [RFC8174] when, and only when, they appear in all capitals, as shown 149 here. 151 3. Terminology 153 Most of the terms related to handling the fs_locations attribute are 154 appropriately defined in Section 5.1 below. However, there are a few 155 terms used outside that context that are explained in this section. 157 Trunking refers to a situation in which a client uses multiple 158 network addresses communicate with the same server. Trunking was 159 first introduced to NFSv4.0 by [RFC7931]. Regarding network 160 addresses and the handling of trunking we use the following 161 terminology: 163 o Each NFSv4 server is assumed to have a set of IP addresses to 164 which NFSv4 requests may be sent by clients. These are referred 165 to as the server's network addresses. Access to a specific server 166 network address might involve the use of multiple network ports, 167 since the ports to be used for particular types of connections 168 might be required to be different. 170 o Clients may establish connections to NFSv4 servers via one of 171 several connection types, supporting the NFSv4 protocol layered on 172 top of an RPC stream transport, as described in [RFC5531], or on 173 top of RPC-over-RDMA, as described in [RFC8166]. The combination 174 of a server network address and a particular connection type is 175 referred to as a "server endpoint". 177 o Each network address, when combined with a pathname providing the 178 location of a file system root directory relative to the 179 associated server root file handle, defines a file system network 180 access path. 182 o Two network addresses connected to the same server are said to be 183 server-trunkable. Unlike the case of NFSv4.1 (which introduced 184 the concept of trunking to NFS version 4), NFSv4.0 only recgnizes 185 a single type of trunking relationship between addresses. NFSv4.1 186 distinguishes two (see [RFC5661]). Despite this difference, two 187 addresses connected to the same NFSv4.0 server would normally be 188 connected to the same server if NFSv4.1 were used. 190 Particularly important is the distinction between trunking detection 191 and trunking discovery. The definitions we present are applicable to 192 all minor versions of NFSv4, but we put particular emphasis on how 193 these terms apply to NFS version 4.0. 195 o Trunking detection refers to ways of confirming that two unique 196 network addresses are associated with the same NFSv4 server 197 instance. The means available to make this determination depends 198 on the protocol version and, in some cases, on the client 199 implementation. 201 In the case of NFS version 4.0, the means to be used are described 202 in [RFC7931] and require use of the Uniform Client String approach 203 to be effective. This is in contrast to later minor versions for 204 which the means of trunking detection are described by [RFC5661]. 206 o Trunking discovery is a process by which an NFSv4 client, 207 accessing one server network address, can obtain other addresses 208 that might be associated with the same server instance. Typically 209 a client builds on a trunking detection facility by providing one 210 or more methods by which candidate addresses are made available to 211 the client, who then uses trunking detection to appropriately 212 filter them. 214 Trunking discovery is not discussed in [RFC7530] and no 215 description of it is provided in [RFC7931]. 217 Discussion of the term "replica" is complicated for a number of 218 reasons. Even though the term is used in explaining the issues in 219 [RFC7530] that need to be addressed in this document, a full 220 explanation of this term requires explanation of related terms 221 connected to the fs_locations attribute, which is provided in 222 Section 5.1 of the current document. 224 The term is also used in previous documents about NFSv4.0 (i.e., 225 [RFC7530] and [RFC7931]) with a meaning different from that in the 226 current document. In these documents each replica is identified by a 227 single network access path. However, in the current document a set 228 of network access paths which have server-trunkable network addresses 229 and the same root-relative file system pathname are considered to be 230 a single replica with multiple network access paths. Although 231 [RFC7931] enables an NFSv4.0 client to determine whether two network 232 addresses were server-trunkable, it never described these as 233 connected to a single replica, leaving in effect the approach 234 established in [RFC7530]. 236 4. Document Organization 238 The sections of the current document are divided into four types 239 based on how they relate to the eventual updating of the NFS verion 240 4.0 specification. Once this update is published, NFS version 4.0 241 will be specified by multiple documents that need to be read 242 together, until such time as a consolidated replacement specification 243 is produced. 245 o The base specification [RFC7530]. 247 o The migration-related update [RFC7931]. 249 o This document [RFC-TBD]. 251 The section types are as follows. See Appendix A for a 252 classification of each section of the current document. 254 o An explanatory section does not contain any material that is meant 255 to update the specification of NFS version 4.0. Such sections may 256 contain explanation about why and how changes are to be done, but 257 do not include any text that is to update [RFC7530] or appear in 258 an eventual consolidated document. 260 o A replacement section contains text that is to replace and thus 261 supersede text within [RFC7530] and then appear in an eventual 262 consolidated document. The titles of replacement sections 263 indicate what section of [RFC7530] is to be replaced. 265 o An additional section contains text which, although not replacing 266 anything in [RFC7530], will be part of the specification of NFS 267 version 4.0 and will be expected to be part of an eventual 268 consolidated document. The titles of additional sections provide 269 an indication of where in an updated [RFC7530], the new section 270 would appear. 272 o An editing section contains some text that replaces text within 273 [RFC7530], although the entire section will not consist of such 274 text and will include other text as well. Such sections make 275 relatively minor adjustments in the existing NFS version 4.0 276 specification which are expected to be reflected in an eventual 277 consolidated document. Generally such replacement text appears as 278 a quotation, possibly taking the form of an indented set of 279 paragraphs. 281 5. Changes Within Section 8 of [RFC7530] 283 Most of the updates to [RFC7530] to provide support for trunking 284 using the fs_locations attribute apply to Section 8 of that document, 285 entitled "Multi-Server Namespace". 287 o Section 5.1 replaces Section 8.1 of [RFC7530], entitled "Location 288 Attributes". This section has been reorganized and extended to 289 explicitly allow the use of fs_locations to provide trunking- 290 related information that appropriately interacts with the 291 migration, replication and referral features of fs_locations. 292 Terminology used to describe the interactions is added. 294 o Section 5.2 updates Section 8.4 of [RFC7530], entitled "Uses of 295 Location Information". This section comprises the bulk of the 296 updates. Each paragraph of Section 8.4 and its sub-sections has 297 been reviewed to clarify the provision of trunking-related 298 information using the fs_locations attribute. 300 * Section 5.2.1 replaces the introductory material within 301 Section 8.4 of [RFC7530]. 303 * Section 5.2.2 is to be added as a new sub-section of 304 Section 8.4 before the updated Section 8.4.1 of [RFC7530]. 306 * Section 5.2.3 is to be added as a new sub-section of 307 Section 8.4 before the updated Section 8.4.1 of [RFC7530]. 309 * Section 5.2.4 replaces Section 8.4.1 of [RFC7530], entitled 310 "File System Replication". 312 * Section 5.2.5 replaces Section 8.4.2 of [RFC7530], entitled 313 "File System Migration". 315 * Section 5.2.6 is to be added as a new sub-section of 316 Section 8.4 before Section 8.4.3 of [RFC7530]. 318 o Section 5.3 replaces Section 8.5 of [RFC7530], entitled "Location 319 Entries and Server Identity". The last paragraph of the existing 320 section has been removed. 322 5.1. Updated Section 8.1 of [RFC7530], entitled "Location Attributes" 324 The fs_locations attribute (described as "RECOMMENDED" in [RFC7530]) 325 allows specification of file system locations where the data 326 corresponding to a given file system may be accessed. This attribute 327 represents such file system instances as a server address target (as 328 either a DNS host name representing one or more network addresses, or 329 a single literal network address) together with the path of that file 330 system within the associated single-server namespace. Individual 331 fs_locations entries can express trunkable addresses, locations of 332 file system replicas on other servers, migration targets, or pure 333 referrals. 335 We introduce the following terminology: 337 o Trunking is a situation in which multiple network addresses are 338 connected to the same NFS server. Network addresses connected to 339 the same NFS server instance are said to be server-trunkable. 341 o Trunking detection refers to ways of confirming that two distinct 342 network addresses are connected to the same NFSv4 server instance. 344 o Trunking discovery is a process by which a client using one 345 network address can obtain other candidate addresses that are 346 server-trunkable with it. 348 Regarding terminology relating to GETATTR attributes used in trunking 349 discovery and other multi-server namespace features: 351 o Location attributes include only the fs_locations GETATTR 352 attribute. 354 o Location entries (fs_location4, defined in [RFC7530] 355 Section 2.2.6) are the individual file system locations in the 356 fs_locations attribute (defined in [RFC7530] Section 2.2.7). A 357 file system location entry designates a set of network addresses 358 to which clients may establish connections. The entry may 359 designate multiple such addresses because the server host name may 360 map to multiple network addresses, and because multiple connection 361 types may be used to communicate with each specified network 362 address. All such addresses MUST provide a way of connecting to a 363 single server. 365 o File system location elements are derived from file system 366 location entries. If a file system location entry specifies a 367 network address, there is only a single corresponding location 368 element. When a file system location entry contains a host name, 369 the host name is resolved by the client, producing one file system 370 location element for each of the resulting network addresses. 372 o All file system location elements consist of a file system 373 location address, which is the network address of an interface to 374 a server, and an fs_name, which is the location of the file system 375 within the server's pseudo-fs. 377 o If the server has no pseudo-fs and only a single exported file 378 system at the root filehandle, the fs_name may be empty. 380 5.2. Updates to Section 8.4 of [RFC7530], entitled "Uses of Location 381 Information" 383 The subsections below provide replacement sections for existing 384 sections within Section 8.4 of [RFC7530] or new sub-sections to be 385 added to that section. 387 5.2.1. Updated Introduction to Section 8.4 of [RFC7530], entitled "Uses 388 of Location Information" 390 Together with the possibility of absent file systems, the file system 391 location-bearing attribute fs_locations provides a number of 392 important facilities that enable reliable, manageable, and scalable 393 data access. 395 When a file system is present on the queried server, this attribute 396 can provide a set of locations that clients may use to access the 397 file system. In the event that server failure, communications 398 problems, or other difficulties make continued access to the file 399 system impossible or otherwise impractical, the returned information 400 provides alternate locations that enable continued access to the file 401 system. Provision of such alternative file system locations is 402 referred to as "replication". 404 When alternative file system locations are provided, they may 405 represent distinct physical copies of the same file system data or 406 separate NFS server instances that provide access to the same 407 physical file system. Another possible use of the provision of 408 multiple file system location entries is trunking, wherein the file 409 system location entries do not in fact represent different servers 410 but rather are distinct network paths to the same server. 412 A client may use file system location elements simultaneously to 413 provide higher-performance access to the target file system. The 414 client utilizes trunking detection and/or discovery, further 415 described in Section 5.2.2 of the current document, to determine a 416 set of network paths that are server-trunkable with the one currently 417 being used to access the file system. 419 When a file system is present and subsequently becomes absent, 420 clients can be given the opportunity to have continued access to 421 their data at an alternative file system location. Transfer of the 422 file system contents to the new file system location is referred to 423 as "migration". The client's responsibilities in dealing with this 424 transition depend on the specific nature of the new access path as 425 well as how and whether data was in fact migrated. See Sections 426 5.2.5 and 5.2.6 of the current document for details. 428 The fs_locations attribute can designate one or more remote file 429 system locations in place of an absent file system. This is known as 430 a "referral". A particularly important case is that of a "pure 431 referral", in which the absent file system has never been present on 432 the NFS server. Such a referral is a means by which a file system 433 located on one server can redirect clients to file systems located on 434 other servers, thus enabling the creation of a multi-server 435 namespace. 437 Because client support for the fs_locations attribute is OPTIONAL, a 438 server may (but is not required to) take action to hide migration and 439 referral events from such clients by acting as a proxy, for example. 441 5.2.2. New Sub-section of Section 8.4 of [RFC7530], to be entitled 442 "Trunking Discovery and Detection" 444 Trunking is a situation in which multiple distinct network addresses 445 are associated with the same NFS server instance. As a matter of 446 convenience, we say that two network addresses connected to the same 447 NFS server instance are server-trunkable. Section 5.4 of [RFC7931] 448 explains why NFSv4 clients need to be aware of NFS server identity to 449 manage lease and lock state effectively when multiple connections to 450 the same server exist. 452 Trunking detection refers to a way for an NFSv4 client to confirm 453 that two independently acquired network addresses are connected to 454 the same NFSv4 server. Section 5.8 of [RFC7931] describes an 455 OPTIONAL means by which it can be determined if two network addresses 456 correspond to the same NFSv4.0 server instance. Without trunking 457 detection, an NFSv4.0 client has no other way to confirm that two 458 network addresses are server-trunkable. 460 In the particular context of NFS version 4.0, trunking detection 461 requires that the client support the Uniform Client ID String 462 approach (UCS), described in Section 5.6 of [RFC7931]. Any NFSv4.0 463 client that supports migration or trunking detection needs to present 464 a Uniform Client ID String to all NFSv4.0 servers. If it does not do 465 so, it will be unable to perform trunking detection. 467 Trunking discovery is the process by which an NFSv4 client using a 468 host name or one of an NFSv4 server's network addresses can obtain 469 other candidate network addresses that are trunkable with it; i.e., a 470 set of addresses that might be connected to the same NFSv4 server 471 instance. An NFSv4.0 client can discover server-trunkable network 472 addresses in a number of ways: 474 o An NFS server's host name is provided either at mount time or in a 475 returned file system location entry. A DNS query of this host 476 name can return more than one network address. The returned 477 network addresses are candidates for trunking. 479 o Location entries returned in an fs_locations attribute can specify 480 network addresses. These network addresses are candidates for 481 trunking. 483 When there is a means of trunking detection available, an NFSv4.0 484 client can confirm that a set of network addresses correspond to the 485 same NFSv4.0 server instance and thus any of them can be used to 486 access that server. 488 5.2.3. New Sub-section of Section 8.4 of [RFC7530], to be entitled 489 "Location Attributes and Connection Type Selection" 491 Because of the need to support multiple connections, clients face the 492 issue of determining the proper connection type to use when 493 establishing a connection to a server network address. The 494 fs_locations attribute provides no information to support connection 495 type selection. As a result, clients supporting multiple connection 496 types need to attempt to establish a connection on various connection 497 types until the one preferred by the client is successfully 498 established. 500 5.2.4. Updated Section 8.4.1 of [RFC7530], entitled "File System 501 Replication and Trunking" 503 On first access to a file system, the client should obtain the value 504 of the set of alternative file system locations by interrogating the 505 fs_locations attribute. Trunking discovery and/or detection can then 506 be applied to the file system location entries to separate the 507 candidate server-trunkable addresses from the replica addresses that 508 provide alternative locations of the file system. Server-trunkable 509 addresses may be used simultaneously to provide higher performance 510 through the exploitation of multiple paths between client and target 511 file system. 513 In the event that server failures, communications problems, or other 514 difficulties make continued access to the current file system 515 impossible or otherwise impractical, the client can use the 516 alternative file system locations as a way to maintain continued 517 access to the file system. See Section 5.2.6 of the current document 518 for more detail. 520 5.2.5. Updated Section 8.4.2 of [RFC7530], entitled "File System 521 Migration" 523 When a file system is present and becomes absent, clients can be 524 given the opportunity to have continued access to their data at an 525 alternative file system location specified by the fs_locations 526 attribute. Typically, a client will be accessing the file system in 527 question, get an NFS4ERR_MOVED error, and then use the fs_locations 528 attribute to determine the new location of the data. See 529 Section 5.2.6 of the current document for more detail. 531 Such migration can help provide load balancing or general resource 532 reallocation. The protocol does not specify how the file system will 533 be moved between servers. It is anticipated that a number of 534 different server-to-server transfer mechanisms might be used, with 535 the choice left to the server implementer. The NFSv4 protocol 536 specifies the method used to communicate the migration event between 537 client and server. 539 When an alternative file system location is designated as the target 540 for migration, it must designate the same data. Where file systems 541 are writable, a change made on the original file system must be 542 visible on all migration targets. Where a file system is not 543 writable but represents a read-only copy (possibly periodically 544 updated) of a writable file system, similar requirements apply to the 545 propagation of updates. Any change visible in the original file 546 system must already be effected on all migration targets, to avoid 547 any possibility that a client, in effecting a transition to the 548 migration target, will see any reversion in file system state. 550 5.2.6. New Sub-section of Section 8.4 of [RFC7530], to be entitled 551 "Interaction of Trunking, Migration, and Replication" 553 When the set of network addresses designated by a file system 554 location attribute changes, NFS4ERR_MOVED might or might not result. 555 In some of the cases in which NFS4ERR_MOVED is returned migration has 556 occurred, while in others there is a shift in the network addresses 557 used to access a particular file system with no migration. 559 1. When the list of network addresses is a superset of that 560 previously in effect, there is no need for migration or any other 561 sort of client adjustment. Nevertheless, the client is free to 562 use an additional address in the replacement list if that address 563 provides another path to the same server. Or, the client may 564 treat that address as it does a replica, to be used if current 565 server addresses become unavailable. 567 2. When the list of network addresses is a subset of that previously 568 in effect, immediate action is not needed if an address missing 569 in the replacement list is not currently in use by the client. 570 The client should avoid using that address in the future, whether 571 the address is for a replica or an additional path to the server 572 being used. 574 3. When an address being removed is one of a number of paths to the 575 current server, the client may continue to use it until 576 NFS4ERR_MOVED is received. This is not considered a migration 577 event unless the last available path to the server has become 578 unusable. 580 When migration does occur, multiple addresses may be in use on the 581 server previous to migration and multiple addresses may be available 582 for use on the destination server. 584 With regard to the server in use, it may be that return of 585 NFS4ERR_MOVED indicates that a particular network address is no 586 longer to be used, without implying that migration of the file system 587 to a different server is needed. Clients should not conclude that 588 migration has occurred until confirming that all network addresses 589 known to be associated with that server are not usable. 591 It should be noted that the need to defer this determination is not 592 absolute. If a client is not aware of all network addresses for any 593 reason, it may conclude that migration has occurred when it has not 594 and treat a switch to a different server address as if it were a 595 migration event. This is harmless since the use of the same server 596 via a new address will appear as a successful instance of Transparent 597 State Migration. 599 Although significant harm cannot arise from this misapprehension, it 600 can give rise to disconcerting situations. For example, if a lock 601 has been revoked during the address shift, it will appear to the 602 client as if the lock has been lost during migration, normally 603 calling for it to be recoverable via an fs-specific grace period 604 associated with the migration event. 606 With regard to the destination server, it is desirable for the client 607 to be aware of all valid network addresses that can be used to access 608 the destination server. However, there is no need for this to be 609 done immediately. Implementations can process the additional file 610 system location elements in parallel with normal use of the first 611 valid file system location entry found to access the destination. 613 Because a file system location attribute may include entries relating 614 to the current server, the migration destination, and possible 615 replicas to use, scanning for available network addresses could 616 potentially be a long process. To keep this process as short as 617 possible, Servers are REQUIRED to place file system location entries 618 that represent addresses usable with the current server or a 619 migration target before those associated with replicas. A client can 620 then cease scanning for trunkable file system location entries once 621 it encounters a file system location element whose fs_name differs 622 from the current fs_name, or whose address is not server-trunkable 623 with the one it is currently using. 625 5.3. Updated Section 8.5 of [RFC7530], entitled "Location Entries and 626 Server Identity Update" 628 As mentioned above, a single file system location entry may have a 629 server address target in the form of a DNS host name that resolves to 630 multiple network addresses, while multiple file system location 631 entries may have their own server address targets that reference the 632 same server. 634 When server-trunkable addresses for a server exist, the client may 635 assume that for each file system in the namespace of a given server 636 network address, there exist file systems at corresponding namespace 637 locations for each of the other server network addresses. It may do 638 this even in the absence of explicit listing in fs_locations. Such 639 corresponding file system locations can be used as alternative 640 locations, just as those explicitly specified via the fs_locations 641 attribute. 643 6. Updates to [RFC7530] Outside Section Eight 645 Since the existing description of NFS4ERR_MOVED in Section 13.1.2.4 646 of [RFC7530] does not take proper account of trunking, it needs to be 647 modified by replacing the first two sentences of the description with 648 the following material: 650 The file system that contains the current filehandle object cannot 651 be accessed using the current network address. It may be 652 accessible using other network addresses connected to the same 653 server, it may have been relocated to another server, or it may 654 never have been present. 656 7. Security Considerations 658 The Security Considerations section of [RFC7530] needs the additions 659 below to properly address some aspects of trunking discovery, 660 referral, migration, and replication. 662 The possibility that requests to determine the set of network 663 addresses corresponding to a given server might be interfered with 664 or have their responses corrupted needs to be taken into account. 666 o When DNS is used to convert NFS server host names to network 667 addresses and DNSSEC [RFC4033] is not available, the validity 668 of the network addresses returned cannot be relied upon. 669 However, when the client uses RPCSEC_GSS [RFC7861] to access 670 NFS servers, it is possible for mutual authentication to detect 671 invalid server addresses. Other forms of transport layer 672 security (e.g., [RFC8446]) can also offer strong authentication 673 of NFS servers. 675 o Fetching file system location information SHOULD be performed 676 using RPCSEC_GSS with integrity protection, as previously 677 explained in the Security Considerations section of [RFC7530]. 678 Making a request of this sort without using strong integrity 679 protection permits corruption during transit of returned file 680 system location information. The client implementer needs to 681 recognize that using such information to access an NFS server 682 without use of RPCSEC_GSS (e.g., by using AUTH_SYS as defined 683 in [RFC5531]) can result in the client interacting with an 684 unverified network address that is posing as an NFSv4 server. 686 o Despite the fact that it is a REQUIREMENT of [RFC7530] that 687 "implementations" provide "support" for the use of RPCSEC_GSS, 688 it cannot be assumed that use of RPCSEC_GSS is always possible 689 between any particular client-server pair. 691 o Returning only network addresses to a client that has no 692 trusted DNS resolution service can hamper its ability to use 693 RPCSEC_GSS. 695 Therefore an NFSv4 server SHOULD present file system location 696 entries that correspond to file systems on other servers using 697 only host names. This enables the client to interrogate the 698 fs_locations on the destination server to obtain trunking 699 information (as well as replica information) using RPCSEC_GSS with 700 integrity, validating the host name provided while assuring that 701 the response has not been corrupted. 703 When RPCSEC_GSS is not available on an NFS server, returned file 704 system location information is subject to corruption during 705 transit and cannot be relied upon. In the case of a client being 706 directed to another server after NFS4ERR_MOVED, this could vitiate 707 the authentication provided by the use of RPCSEC_GSS on the 708 destination. Even when RPCSEC_GSS authentication is available on 709 the destination, this server might validly represent itself as the 710 server to which the client was erroneously directed. Without a 711 way to decide wether the server is a valid one, the client can 712 only determine, using RPCSEC_GSS, that the server corresponds to 713 the host name provided, with no basis for trusting that server. 714 The client should not use such unverified file system location 715 entries as a basis for migration, even though RPCSEC_GSS might be 716 available on the destination server. 718 When a file system location attribute is fetched upon connecting 719 with an NFSv4 server, it SHOULD, as stated above, be done using 720 RPCSEC_GSS with integrity protection. 722 When file system location information cannot be protected in 723 transit, the client can subject it to additional filtering to 724 prevent the client from being inappropriately directed. For 725 example, if a range of network addresses can be determined that 726 assure that the servers and clients using AUTH_SYS are subject to 727 appropriate constraints (such as physical network isolation and 728 the use of administrative controls within the operating systems), 729 then network adresses in this range can be used with others 730 discarded or restricted in their use of AUTH_SYS. 732 When neither integrity protection nor filtering is possible, it is 733 best for the client to ignore trunking and replica information or 734 simply not fetch the file system location information for these 735 purposes. 737 To summarize considerations regarding the use of RPCSEC_GSS in 738 fetching file system location information, consider the following 739 possibilities for requests to interrogate location information, 740 with interrogation approaches on the referring and destination 741 servers arrived at separately: 743 o The use of RPCSEC_GSS with integrity protection is RECOMMENDED 744 in all cases, since the absence of integrity protection exposes 745 the client to the possibility of the results being modified in 746 transit. 748 o The use of requests issued without RPCSEC_GSS (e.g., using 749 AUTH_SYS), while undesirable, might be unavoidable in some 750 cases. Where the use of returned file system location 751 information cannot be avoided, it should be subject to 752 filtering to eliminate untrusted network addresses. The 753 specifics will vary depending on the degree of network 754 isolation and whether the request is to the referring or 755 destination servers. 757 8. IANA Considerations 759 This document does not require actions by IANA. 761 9. References 763 9.1. Normative References 765 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 766 Requirement Levels", BCP 14, RFC 2119, 767 DOI 10.17487/RFC2119, March 1997, 768 . 770 [RFC5531] Thurlow, R., "RPC: Remote Procedure Call Protocol 771 Specification Version 2", RFC 5531, DOI 10.17487/RFC5531, 772 May 2009, . 774 [RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System 775 (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530, 776 March 2015, . 778 [RFC7931] Noveck, D., Ed., Shivam, P., Lever, C., and B. Baker, 779 "NFSv4.0 Migration: Specification Update", RFC 7931, 780 DOI 10.17487/RFC7931, July 2016, 781 . 783 [RFC8166] Lever, C., Ed., Simpson, W., and T. Talpey, "Remote Direct 784 Memory Access Transport for Remote Procedure Call Version 785 1", RFC 8166, DOI 10.17487/RFC8166, June 2017, 786 . 788 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 789 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 790 May 2017, . 792 9.2. Informative References 794 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 795 Rose, "DNS Security Introduction and Requirements", 796 RFC 4033, DOI 10.17487/RFC4033, March 2005, 797 . 799 [RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed., 800 "Network File System (NFS) Version 4 Minor Version 1 801 Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010, 802 . 804 [RFC7861] Adamson, A. and N. Williams, "Remote Procedure Call (RPC) 805 Security Version 3", RFC 7861, DOI 10.17487/RFC7861, 806 November 2016, . 808 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 809 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 810 . 812 Appendix A. Section Classification 814 All sections of this document are considered explanatory with the 815 following exceptions. 817 o Sections 5.1 and 5.2.1 are replacement sections. 819 o Section 5.2.2 is an additional section. 821 o Sections 5.2.4 and 5.2.5 are replacement sections. 823 o Section 5.2.6 is an additional section. 825 o Section 5.3 is a replacement section. 827 o Section 6 is an editing section. 829 o Section 7 is an additional section. 831 Acknowledgments 833 The authors wish to thank Andy Adamson, who wrote the original 834 version of this document. All the innovation in this document is the 835 result of Andy's work, while mistakes are best ascribed to the 836 current authors. 838 The editor wishes to thank Greg Marsden for his support of this work, 839 and Robert Thurlow for review and suggestions. 841 Special thanks go to Transport Area Director Spencer Dawkins, NFSV4 842 Working Group Chairs Spencer Shepler and Brian Pawlowski, and NFSV4 843 Working Group Secretary Thomas Haynes for their ongoing support. 845 Authors' Addresses 846 Charles Lever (editor) 847 Oracle Corporation 848 1015 Granger Avenue 849 Ann Arbor, MI 48104 850 United States of America 852 Phone: +1 248 816 6463 853 Email: chuck.lever@oracle.com 855 David Noveck 856 NetApp 857 1601 Trapelo Road 858 Waltham, MA 02451 859 United States of America 861 Phone: +1 781 572 8038 862 Email: davenoveck@gmail.com