idnits 2.17.1 draft-ietf-nfsv4-rfc5667bis-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to contain a disclaimer for pre-RFC5378 work, but was first submitted on or after 10 November 2008. The disclaimer is usually necessary only for documents that revise or obsolete older RFCs, and that take significant amounts of text from those RFCs. If you can contact all authors of the source material and they are willing to grant the BCP78 rights to the IETF Trust, you can and should remove the disclaimer. Otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (April 4, 2017) is 2579 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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5661 (Obsoleted by RFC 8881) == Outdated reference: A later version (-11) exists of draft-ietf-nfsv4-versioning-09 -- Obsolete informational reference (is this intentional?): RFC 5666 (Obsoleted by RFC 8166) -- Obsolete informational reference (is this intentional?): RFC 5667 (Obsoleted by RFC 8267) Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 3 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 Obsoletes: 5667 (if approved) April 4, 2017 5 Intended status: Standards Track 6 Expires: October 6, 2017 8 Network File System (NFS) Upper Layer Binding To RPC-Over-RDMA Version 9 One 10 draft-ietf-nfsv4-rfc5667bis-08 12 Abstract 14 This document specifies Upper Layer Bindings of Network File System 15 (NFS) protocol versions to RPC-over-RDMA Version One, enabling the 16 use of Direct Data Placement. This document obsoletes RFC 5667. 18 Requirements Language 20 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 21 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 22 document are to be interpreted as described in [RFC2119]. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on October 6, 2017. 41 Copyright Notice 43 Copyright (c) 2017 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 This document may contain material from IETF Documents or IETF 57 Contributions published or made publicly available before November 58 10, 2008. The person(s) controlling the copyright in some of this 59 material may not have granted the IETF Trust the right to allow 60 modifications of such material outside the IETF Standards Process. 61 Without obtaining an adequate license from the person(s) controlling 62 the copyright in such materials, this document may not be modified 63 outside the IETF Standards Process, and derivative works of it may 64 not be created outside the IETF Standards Process, except to format 65 it for publication as an RFC or to translate it into languages other 66 than English. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 2. Reply Size Estimation . . . . . . . . . . . . . . . . . . . . 3 72 2.1. Short Reply Chunk Retry . . . . . . . . . . . . . . . . . 4 73 3. Upper Layer Binding for NFS Versions 2 and 3 . . . . . . . . 5 74 3.1. Reply Size Estimation . . . . . . . . . . . . . . . . . . 5 75 3.2. RPC Binding Considerations . . . . . . . . . . . . . . . 5 76 4. Upper Layer Bindings for NFS Version 2 and 3 Auxiliary 77 Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 6 78 4.1. MOUNT, NLM, and NSM Protocols . . . . . . . . . . . . . . 6 79 4.2. NFSACL Protocol . . . . . . . . . . . . . . . . . . . . . 6 80 5. Upper Layer Binding For NFS Version 4 . . . . . . . . . . . . 7 81 5.1. DDP-Eligibility . . . . . . . . . . . . . . . . . . . . . 7 82 5.2. Reply Size Estimation . . . . . . . . . . . . . . . . . . 7 83 5.3. RPC Binding Considerations . . . . . . . . . . . . . . . 8 84 5.4. NFS COMPOUND Requests . . . . . . . . . . . . . . . . . . 8 85 5.5. NFS Callback Requests . . . . . . . . . . . . . . . . . . 10 86 5.6. Session-Related Considerations . . . . . . . . . . . . . 11 87 5.7. Transport Considerations . . . . . . . . . . . . . . . . 12 88 6. Extending NFS Upper Layer Bindings . . . . . . . . . . . . . 13 89 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 90 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 91 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 92 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 93 9.2. Informative References . . . . . . . . . . . . . . . . . 15 94 Appendix A. Changes Since RFC 5667 . . . . . . . . . . . . . . . 16 95 Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 17 96 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 98 1. Introduction 100 The RPC-over-RDMA Version One transport may employ direct data 101 placement to convey data payloads associated with RPC transactions 102 [I-D.ietf-nfsv4-rfc5666bis]. To enable successful interoperation, 103 RPC client and server implementations using RPC-over-RDMA Version One 104 must agree which XDR data items and RPC procedures are eligible to 105 use direct data placement (DDP). 107 An Upper Layer Binding specifies this agreement for one RPC Program. 108 Other operational details, such as RPC binding assignments, pairing 109 Write chunks with result data items, and reply size estimation, are 110 also specified by this Binding. 112 This document contains material required of Upper Layer Bindings, as 113 specified in [I-D.ietf-nfsv4-rfc5666bis], for the following NFS 114 protocol versions: 116 o NFS Version 2 [RFC1094] 118 o NFS Version 3 [RFC1813] 120 o NFS Version 4.0 [RFC7530] 122 o NFS Version 4.1 [RFC5661] 124 o NFS Version 4.2 [RFC7862] 126 Upper Layer Bindings are also provided for auxiliary protocols used 127 with NFS versions 2 and 3. 129 This document assumes the reader is already familiar with concepts 130 and terminology defined in [I-D.ietf-nfsv4-rfc5666bis] and the 131 documents it references. 133 2. Reply Size Estimation 135 During the construction of each RPC Call message, a requester is 136 responsible for allocating appropriate resources for receiving the 137 corresponding Reply message. If the requester expects the RPC Reply 138 message will be larger than its inline threshold, it provides Write 139 and/or Reply chunks wherein the responder can place results and the 140 reply's Payload stream. 142 A reply resource overrun occurs if the RPC Reply Payload stream does 143 not fit into the provided Reply chunk, or no Reply chunk was provided 144 and the Payload stream does not fit inline. This prevents the 145 responder from returning the Upper Layer reply to the requester. 147 Therefore reliable reply size estimation is necessary to ensure 148 successful interoperation. 150 In most cases, the NFS protocol's XDR definition provides enough 151 information to enable an NFS client to predict the maximum size of 152 the expected Reply message. If there are variable-size data items in 153 the result, the maximum size of the RPC Reply message can be 154 estimated as follows: 156 o The client requests only a specific portion of an object (for 157 example, using the "count" and "offset" fields in an NFS READ). 159 o The client limits the number of results (e.g. using the "count" 160 field of an NFS READDIR request). 162 o The client has already cached the size of the whole object it is 163 about to request (say, via a previous NFS GETATTR request). 165 o The client and server have negotiated a maximum size for all calls 166 and responses (using a CREATE_SESSION operation, for instance). 168 2.1. Short Reply Chunk Retry 170 In a few cases, either the size of one or more returned data items or 171 the number of returned data items cannot be known in advance of 172 forming an RPC Call. 174 If an NFS server finds that the NFS client provided inadequate 175 receive resources to return the whole reply, it returns an RPC level 176 error or a transport error, such as ERR_CHUNK. 178 In response to these errors, an NFS client can choose to: 180 o Terminate the RPC transaction immediately with an error, or 182 o Allocate a larger Reply chunk and send the same request as a new 183 RPC transaction (to avoid hitting in a Duplicate Reply Cache). 184 The NFS client should avoid retrying the request indefinitely 185 because a responder may return ERR_CHUNK for a variety of reasons. 187 Subsequent sections of this document discuss exactly which operations 188 might have ultimate difficulty with Reply size estimation. These 189 operations are eligible for "short Reply chunk retry." Unless 190 explicitly mentioned as applicable, short Reply chunk retry should 191 not be used. 193 NFS server implementations can avoid connection loss by first 194 confirming that target RDMA segments are large enough to receive 195 results before initiating explicit RDMA operations. 197 3. Upper Layer Binding for NFS Versions 2 and 3 199 The Upper Layer Binding specification in this section applies to NFS 200 Version 2 [RFC1094] and NFS Version 3 [RFC1813]. For brevity, in 201 this document a "Legacy NFS client" refers to an NFS client using the 202 NFS version 2 or NFS version 3 RPC Programs (100003) to communicate 203 with an NFS server. Likewise, a "Legacy NFS server" is an NFS server 204 communicating with clients using NFS version 2 or NFS version 3. 206 The following XDR data items in NFS versions 2 and 3 are DDP- 207 eligible: 209 o The opaque file data argument in the NFS WRITE procedure 211 o The pathname argument in the NFS SYMLINK procedure 213 o The opaque file data result in the NFS READ procedure 215 o The pathname result in the NFS READLINK procedure 217 All other argument or result data items in NFS versions 2 and 3 are 218 not DDP-eligible. 220 A transport error does not give an indication of whether the server 221 has processed the arguments of the RPC Call, or whether the server 222 has accessed or modified client memory associated with that RPC. 224 3.1. Reply Size Estimation 226 A Legacy NFS client determines the maximum reply size for each 227 operation using the criteria outlined in Section 2. There are no 228 operations in NFS version 2 or 3 that benefit from short Reply chunk 229 retry. 231 3.2. RPC Binding Considerations 233 Legacy NFS servers traditionally listen for clients on UDP and TCP 234 port 2049. Additionally, they register these ports with a local 235 portmapper [RFC1833] service. 237 A Legacy NFS server supporting RPC-over-RDMA Version One on such a 238 network and registering itself with the RPC portmapper MAY choose an 239 arbitrary port, or MAY use the alternative well-known port number for 240 its RPC-over-RDMA service (see Section 8). The chosen port MAY be 241 registered with the RPC portmapper under the netids assigned in 242 [I-D.ietf-nfsv4-rfc5666bis]. 244 4. Upper Layer Bindings for NFS Version 2 and 3 Auxiliary Protocols 246 NFS versions 2 and 3 are typically deployed with several other 247 protocols, sometimes referred to as "NFS auxiliary protocols." These 248 are distinct RPC Programs that define procedures which are not part 249 of the NFS version 2 or version 3 RPC Programs. The Upper Layer 250 Bindings in this section apply to: 252 o Versions 2 and 3 of the MOUNT protocol [RFC1813] 254 o Versions 1, 3, and 4 of the NLM protocol [RFC1813] 256 o Version 1 of the NSM protocol, described in Chapter 11 of [XNFS] 258 o Version 1 of the NFSACL protocol, which does not have a public 259 definition. NFSACL is treated in this document as a de facto 260 standard, as there are several interoperating implementations. 262 4.1. MOUNT, NLM, and NSM Protocols 264 Historically, NFS/RDMA implementations have chosen to convey the 265 MOUNT, NLM, and NSM protocols via TCP. To enable interoperation of 266 these protocols when NFS/RDMA is in use, a legacy NFS server MUST 267 provide TCP-based MOUNT, NLM, and NSM services. 269 4.2. NFSACL Protocol 271 Legacy clients and servers that support the NFSACL RPC Program 272 typically convey NFSACL procedures on the same connection as NFS RPC 273 Programs. This obviates the need for separate rpcbind queries to 274 discover server support for this RPC Program. 276 ACLs are typically small, but even large ACLs must be encoded and 277 decoded to some degree. Thus no data item in this Upper Layer 278 Protocol is DDP-eligible. 280 For procedures whose replies do not include an ACL object, the size 281 of a reply is determined directly from the NFSACL RPC Program's XDR 282 definition. 284 There is no protocol-specified size limit for NFS version 3 ACLs, and 285 there is no mechanism in either the NFSACL or NFS RPC Programs for a 286 Legacy client to ascertain the largest ACL a Legacy server can 287 return. Legacy client implementations should choose a maximum size 288 for ACLs based on their own internal limits. 290 Because an NFSACL client cannot know in advance how large a returned 291 ACL will be, it can use short Reply chunk retry when an NFSACL GETACL 292 operation encounters a transport error. 294 5. Upper Layer Binding For NFS Version 4 296 The Upper Layer Binding specification in this section applies to RPC 297 Programs defined in NFS Version 4.0 [RFC7530], NFS Version 4.1 298 [RFC5661], and NFS Version 4.2 [RFC7862]. 300 5.1. DDP-Eligibility 302 Only the following XDR data items in the COMPOUND procedure of all 303 NFS version 4 minor versions are DDP-eligible: 305 o The opaque data field in the WRITE4args structure 307 o The linkdata field of the NF4LNK arm in the createtype4 union 309 o The opaque data field in the READ4resok structure 311 o The linkdata field in the READLINK4resok structure 313 5.2. Reply Size Estimation 315 Within NFS version 4, there are certain variable-length result data 316 items whose maximum size cannot be estimated by clients reliably 317 because there is no protocol-specified size limit on these arrays. 318 These include: 320 o The attrlist4 field 322 o Fields containing ACLs such as fattr4_acl, fattr4_dacl, 323 fattr4_sacl 325 o Fields in the fs_locations4 and fs_locations_info4 data structures 327 o Fields opaque to the NFS version 4 protocol which pertain to pNFS 328 layout metadata, such as loc_body, loh_body, da_addr_body, 329 lou_body, lrf_body, fattr_layout_types and fs_layout_types, 331 5.2.1. Reply Size Estimation for Minor Version 0 333 The NFS version 4.0 protocol itself does not impose any bound on the 334 size of NFS calls or responses. 336 Some of the data items enumerated in Section 5.2 (in particular, the 337 items related to ACLs and fs_locations) make it difficult to predict 338 the maximum size of NFS version 4.0 replies that interrogate 339 variable-length fattr4 attributes. Client implementations might rely 340 on their own internal architectural limits to constrain the reply 341 size, but such limits are not always guaranteed to be reliable. 343 When an especially large fattr4 result is expected, a Reply chunk 344 might be required. An NFS version 4.0 client can use short Reply 345 chunk retry when an NFS COMPOUND containing a GETATTR operation 346 encounters a transport error. 348 The use of NFS COMPOUND operations raises the possibility of requests 349 that combine a non-idempotent operation (e.g. RENAME) with a GETATTR 350 operation that requests one or more variable-length results. This 351 combination should be avoided by ensuring that any GETATTR operation 352 that requests a result of unpredictable length is sent in an NFS 353 COMPOUND by itself. 355 5.2.2. Reply Size Estimation for Minor Version 1 and Newer 357 In NFS version 4.1 and newer minor versions, the csa_fore_chan_attrs 358 argument of the CREATE_SESSION operation contains a 359 ca_maxresponsesize field. The value in this field can be taken as 360 the absolute maximum size of replies generated by an NFS version 4.1 361 server. 363 This value can be used in cases where it is not possible to estimate 364 a reply size upper bound precisely. In practice, objects such as 365 ACLs, named attributes, layout bodies, and security labels are much 366 smaller than this maximum. 368 5.3. RPC Binding Considerations 370 NFS version 4 servers are required to listen on TCP port 2049, and 371 they are not required to register with an rpcbind service [RFC7530]. 373 Therefore, an NFS version 4 server supporting RPC-over-RDMA Version 374 One MUST use the alternative well-known port number for its RPC-over- 375 RDMA service (see Section 8). Clients SHOULD connect to this well- 376 known port without consulting the RPC portmapper (as for NFS version 377 4 on TCP transports). 379 5.4. NFS COMPOUND Requests 381 5.4.1. Multiple DDP-eligible Data Items 383 An NFS version 4 COMPOUND procedure can contain more than one 384 operation that carries a DDP-eligible data item. An NFS version 4 385 client provides XDR Position values in each Read chunk to 386 disambiguate which chunk is associated with which argument data item. 387 However NFS version 4 server and client implementations must agree in 388 advance on how to pair Write chunks with returned result data items. 390 In the following list, a "READ operation" refers to any NFS Version 4 391 operation which has a DDP-eligible result data item. The mechanism 392 specified in Section 4.3.2 of [I-D.ietf-nfsv4-rfc5666bis]) is applied 393 to this class of operations: 395 o If an NFS version 4 client wishes all DDP-eligible items in an NFS 396 reply to be conveyed inline, it leaves the Write list empty. 398 o The first chunk in the Write list MUST be used by the first READ 399 operation in an NFS version 4 COMPOUND procedure. The next Write 400 chunk is used by the next READ operation, and so on. 402 o If an NFS version 4 client has provided a matching non-empty Write 403 chunk, then the corresponding READ operation MUST return its DDP- 404 eligible data item using that chunk. 406 o If an NFS version 4 client has provided an empty matching Write 407 chunk, then the corresponding READ operation MUST return all of 408 its result data items inline. 410 o If a READ operation returns a union arm which does not contain a 411 DDP-eligible result, and the NFS version 4 client has provided a 412 matching non-empty Write chunk, an NFS version 4 server MUST 413 return an empty Write chunk in that Write list position. 415 o If there are more READ operations than Write chunks, then 416 remaining NFS Read operations in an NFS version 4 COMPOUND that 417 have no matching Write chunk MUST return their results inline. 419 5.4.2. NFS Version 4 COMPOUND Example 421 The following example shows a Write list with three Write chunks, A, 422 B, and C. The NFS version 4 server consumes the provided Write 423 chunks by writing the results of the designated operations in the 424 compound request (READ and READLINK) back to each chunk. 426 Write list: 428 A --> B --> C 430 NFS version 4 COMPOUND request: 432 PUTFH LOOKUP READ PUTFH LOOKUP READLINK PUTFH LOOKUP READ 433 | | | 434 v v v 435 A B C 437 If the NFS version 4 client does not want to have the READLINK result 438 returned via RDMA, it provides an empty Write chunk for buffer B to 439 indicate that the READLINK result must be returned inline. 441 5.5. NFS Callback Requests 443 The NFS version 4 family of protocols support server-initiated 444 callbacks to notify NFS version 4 clients of events such as recalled 445 delegations. 447 5.5.1. NFS Version 4.0 Callback 449 NFS version 4.0 implementations typically employ a separate TCP 450 connection to handle callback operations, even when the forward 451 channel uses an RPC-over-RDMA Version One transport. 453 No operation in the NFS version 4.0 callback RPC Program conveys a 454 significant data payload. Therefore, no XDR data items in this RPC 455 Program is DDP-eligible. 457 A CB_RECALL reply is small and fixed in size. The CB_GETATTR reply 458 contains a variable-length fattr4 data item. See Section 5.2.1 for a 459 discussion of reply size prediction for this data item. 461 An NFS version 4.0 client advertises netids and ad hoc port addresses 462 for contacting its NFS version 4.0 callback service using the 463 SETCLIENTID operation. 465 5.5.2. NFS Version 4.1 Callback 467 In NFS version 4.1 and newer minor versions, callback operations may 468 appear on the same connection as is used for NFS version 4 forward 469 channel client requests. NFS version 4 clients and servers MUST use 470 the approach described in [I-D.ietf-nfsv4-rpcrdma-bidirection] when 471 backchannel operations are conveyed on RPC-over-RDMA Version One 472 transports. 474 The csa_back_chan_attrs argument of the CREATE_SESSION operation 475 contains a ca_maxresponsesize field. The value in this field can be 476 taken as the absolute maximum size of backchannel replies generated 477 by a replying NFS version 4 client. 479 There are no DDP-eligible data items in callback procedures defined 480 in NFS version 4.1 or NFS version 4.2. However, some callback 481 operations, such as messages that convey device ID information, can 482 be large, in which case a Long Call or Reply might be required. 484 When an NFS version 4.1 client can support Long Calls in its 485 backchannel, it reports a backchannel ca_maxrequestsize that is 486 larger than the connection's inline thresholds. Otherwise an NFS 487 version 4 server MUST use only Short messages to convey backchannel 488 operations. 490 5.6. Session-Related Considerations 492 The presence of an NFS session (defined in [RFC5661]) has no effect 493 on the operation of RPC-over-RDMA Version One. None of the 494 operations introduced to support NFS sessions (e.g. the SEQUENCE 495 operation) contain DDP-eligible data items. There is no need to 496 match the number of session slots with the number of available RPC- 497 over-RDMA credits. 499 However, there are a few new cases where an RPC transaction can fail. 500 For example, a requester might receive, in response to an RPC 501 request, an RDMA_ERROR message with an rdma_err value of ERR_CHUNK, 502 or an RDMA_MSG containing an RPC_GARBAGEARGS reply. These situations 503 are no different from existing RPC errors which an NFS session 504 implementation is already prepared to handle for other transports. 505 And as with other transports during such a failure, there might be no 506 SEQUENCE result available to the requester to distinguish whether 507 failure occurred before or after the requested operations were 508 executed on the responder. 510 When a transport error occurs (e.g. RDMA_ERROR), the requester 511 proceeds as usual to match the incoming XID value to a waiting RPC 512 Call. The RPC transaction is terminated, and the result status is 513 reported to the Upper Layer Protocol. The requester's session 514 implementation then determines the session ID and slot for the failed 515 request, and performs slot recovery to make that slot usable again. 516 If this is not done, that slot could be rendered permanently 517 unavailable. 519 5.7. Transport Considerations 521 5.7.1. Congestion Avoidance 523 Section 3.1 of [RFC7530] states: 525 Where an NFSv4 implementation supports operation over the IP 526 network protocol, the supported transport layer between NFS and IP 527 MUST be an IETF standardized transport protocol that is specified 528 to avoid network congestion; such transports include TCP and the 529 Stream Control Transmission Protocol (SCTP). 531 Section 2.9.1 of [RFC5661] also states: 533 Even if NFSv4.1 is used over a non-IP network protocol, it is 534 RECOMMENDED that the transport support congestion control. 536 It is permissible for a connectionless transport to be used under 537 NFSv4.1; however, reliable and in-order delivery of data combined 538 with congestion control by the connectionless transport is 539 REQUIRED. As a consequence, UDP by itself MUST NOT be used as an 540 NFSv4.1 transport. 542 RPC-over-RDMA Version One is constructed on a platform of RDMA 543 Reliable Connections [I-D.ietf-nfsv4-rfc5666bis] [RFC5041]. RDMA 544 Reliable Connections are reliable, connection-oriented transports 545 that guarantee in-order delivery, meeting all above requirements for 546 NFS version 4 transports. 548 5.7.2. Retransmission and Keep-alive 550 NFS version 4 client implementations often rely on a transport-layer 551 keep-alive mechanism to detect when an NFS version 4 server has 552 become unresponsive. When an NFS server is no longer responsive, 553 client-side keep-alive terminates the connection, which in turn 554 triggers reconnection and RPC retransmission. 556 Some RDMA transports (such as Reliable Connections on InfiniBand) 557 have no keep-alive mechanism. Without a disconnect or new RPC 558 traffic, such connections can remain alive long after an NFS server 559 has become unresponsive. Once an NFS client has consumed all 560 available RPC-over-RDMA credits on that transport connection, it will 561 forever await a reply before sending another RPC request. 563 NFS version 4 clients SHOULD reserve one RPC-over-RDMA credit to use 564 for periodic server or connection health assessment. This credit can 565 be used to drive an RPC request on an otherwise idle connection, 566 triggering either a quick affirmative server response or immediate 567 connection termination. 569 In addition to network partition and request loss scenarios, RPC- 570 over-RDMA transport connections can be terminated when a Transport 571 header is malformed, Reply messages are larger than receive 572 resources, or when too many RPC-over-RDMA messages are sent at once. 573 In such cases: 575 o If there is a transport error indicated (ie, RDMA_ERROR) before 576 the disconnect or instead of a disconnect, the requester MUST 577 respond to that error as prescribed by the specification of the 578 RPC transport. Then the NFS version 4 rules for handling 579 retransmission apply. 581 o If there is a transport disconnect and the responder has provided 582 no other response for a request, then only the NFS version 4 rules 583 for handling retransmission apply. 585 6. Extending NFS Upper Layer Bindings 587 RPC Programs such as NFS are required to have an Upper Layer Binding 588 specification to interoperate on RPC-over-RDMA Version One transports 589 [I-D.ietf-nfsv4-rfc5666bis]. Via standards action, the Upper Layer 590 Binding specified in this document can be extended to cover versions 591 of the NFS version 4 protocol specified after NFS version 4 minor 592 version 2, or separately published extensions to an existing NFS 593 version 4 minor version, as described in [I-D.ietf-nfsv4-versioning]. 595 7. Security Considerations 597 RPC-over-RDMA Version One supports all RPC security models, including 598 RPCSEC_GSS security and transport-level security [RFC2203]. The 599 choice of what Direct Data Placement mechanism to convey RPC argument 600 and results does not affect this, since it changes only the method of 601 data transfer. Specifically, the requirements of 602 [I-D.ietf-nfsv4-rfc5666bis] ensure that this choice does not 603 introduce new vulnerabilities. 605 Because this document defines only the binding of the NFS protocols 606 atop [I-D.ietf-nfsv4-rfc5666bis], all relevant security 607 considerations are therefore to be described at that layer. 609 8. IANA Considerations 611 The use of direct data placement in NFS introduces a need for an 612 additional port number assignment for networks that share traditional 613 UDP and TCP port spaces with RDMA services. The iWARP protocol is 614 such an example [RFC5041] [RFC5040]. 616 For this purpose, a set of transport protocol port number assignments 617 is specified by this document. IANA has assigned the following ports 618 for NFS/RDMA in the IANA port registry, according to the guidelines 619 described in [RFC6335]. 621 nfsrdma 20049/tcp Network File System (NFS) over RDMA 622 nfsrdma 20049/udp Network File System (NFS) over RDMA 623 nfsrdma 20049/sctp Network File System (NFS) over RDMA 625 This document should be listed as the reference for the nfsrdma port 626 assignments. This document does not alter these assignments. 628 9. References 630 9.1. Normative References 632 [I-D.ietf-nfsv4-rfc5666bis] 633 Lever, C., Simpson, W., and T. Talpey, "Remote Direct 634 Memory Access Transport for Remote Procedure Call, Version 635 One", draft-ietf-nfsv4-rfc5666bis-11 (work in progress), 636 March 2017. 638 [I-D.ietf-nfsv4-rpcrdma-bidirection] 639 Lever, C., "Bi-directional Remote Procedure Call On RPC- 640 over-RDMA Transports", draft-ietf-nfsv4-rpcrdma- 641 bidirection-08 (work in progress), March 2017. 643 [RFC1833] Srinivasan, R., "Binding Protocols for ONC RPC Version 2", 644 RFC 1833, DOI 10.17487/RFC1833, August 1995, 645 . 647 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 648 Requirement Levels", BCP 14, RFC 2119, 649 DOI 10.17487/RFC2119, March 1997, 650 . 652 [RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol 653 Specification", RFC 2203, DOI 10.17487/RFC2203, September 654 1997, . 656 [RFC5661] Shepler, S., Ed., Eisler, M., Ed., and D. Noveck, Ed., 657 "Network File System (NFS) Version 4 Minor Version 1 658 Protocol", RFC 5661, DOI 10.17487/RFC5661, January 2010, 659 . 661 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 662 Cheshire, "Internet Assigned Numbers Authority (IANA) 663 Procedures for the Management of the Service Name and 664 Transport Protocol Port Number Registry", BCP 165, 665 RFC 6335, DOI 10.17487/RFC6335, August 2011, 666 . 668 [RFC7530] Haynes, T., Ed. and D. Noveck, Ed., "Network File System 669 (NFS) Version 4 Protocol", RFC 7530, DOI 10.17487/RFC7530, 670 March 2015, . 672 [RFC7862] Haynes, T., "Network File System (NFS) Version 4 Minor 673 Version 2 Protocol", RFC 7862, DOI 10.17487/RFC7862, 674 November 2016, . 676 9.2. Informative References 678 [I-D.ietf-nfsv4-versioning] 679 Noveck, D., "Rules for NFSv4 Extensions and Minor 680 Versions", draft-ietf-nfsv4-versioning-09 (work in 681 progress), December 2016. 683 [RFC1094] Nowicki, B., "NFS: Network File System Protocol 684 specification", RFC 1094, DOI 10.17487/RFC1094, March 685 1989, . 687 [RFC1813] Callaghan, B., Pawlowski, B., and P. Staubach, "NFS 688 Version 3 Protocol Specification", RFC 1813, 689 DOI 10.17487/RFC1813, June 1995, 690 . 692 [RFC5040] Recio, R., Metzler, B., Culley, P., Hilland, J., and D. 693 Garcia, "A Remote Direct Memory Access Protocol 694 Specification", RFC 5040, DOI 10.17487/RFC5040, October 695 2007, . 697 [RFC5041] Shah, H., Pinkerton, J., Recio, R., and P. Culley, "Direct 698 Data Placement over Reliable Transports", RFC 5041, 699 DOI 10.17487/RFC5041, October 2007, 700 . 702 [RFC5666] Talpey, T. and B. Callaghan, "Remote Direct Memory Access 703 Transport for Remote Procedure Call", RFC 5666, 704 DOI 10.17487/RFC5666, January 2010, 705 . 707 [RFC5667] Talpey, T. and B. Callaghan, "Network File System (NFS) 708 Direct Data Placement", RFC 5667, DOI 10.17487/RFC5667, 709 January 2010, . 711 [XNFS] The Open Group, "Protocols for Interworking: XNFS, Version 712 3W", February 1998. 714 Appendix A. Changes Since RFC 5667 716 Corrections and updates made necessary by new language in 717 [I-D.ietf-nfsv4-rfc5666bis] have been introduced. For example, 718 references to deprecated features of RPC-over-RDMA Version One, such 719 as RDMA_MSGP, and the use of the Read list for handling RPC replies, 720 have been removed. The term "mapping" has been replaced with the 721 term "binding" or "Upper Layer Binding" throughout the document. 722 Material that duplicates what is in [I-D.ietf-nfsv4-rfc5666bis] has 723 been deleted. 725 Material required by [I-D.ietf-nfsv4-rfc5666bis] for Upper Layer 726 Bindings that was not present in [RFC5667] has been added. A 727 complete discussion of reply size estimation has been introduced for 728 all protocols covered by the Upper Layer Bindings in this document. 730 Technical corrections have been made. For example, the mention of 731 12KB and 36KB inline thresholds have been removed. The reference to 732 a non-existant NFS version 4 SYMLINK operation has been replaced. 734 The discussion of NFS version 4 COMPOUND handling has been completed. 735 Some changes were made to the algorithm for matching DDP-eligible 736 results to Write chunks. 738 Requirements to ignore extra Read or Write chunks have been removed 739 from the NFS version 2 and 3 Upper Layer Binding, as they conflict 740 with [I-D.ietf-nfsv4-rfc5666bis]. 742 A section discussing NFS version 4 retransmission and connection loss 743 has been added. 745 The following additional improvements have been made, relative to 746 [RFC5667]: 748 o An explicit discussion of NFS version 4.0 and NFS version 4.1 749 backchannel operation has replaced the previous treatment of 750 callback operations. 752 o A binding for NFS version 4.2 has been added. 754 o A section suggesting a mechanism for periodically assessing 755 connection health has been introduced. 757 o Ambiguous or erroneous uses of RFC2119 terms have been corrected. 759 o References to obsolete RFCs have been updated. 761 o An IANA Considerations Section has been added, which specifies the 762 port assignments for NFS/RDMA. This replaces the example 763 assignment that appeared in [RFC5666]. 765 o Code excerpts have been removed, and figures have been modernized. 767 Appendix B. Acknowledgments 769 The author gratefully acknowledges the work of Brent Callaghan and 770 Tom Talpey on the original NFS Direct Data Placement specification 771 [RFC5667]. The author also wishes to thank Bill Baker and Greg 772 Marsden for their support of this work. 774 Dave Noveck provided excellent review, constructive suggestions, and 775 consistent navigational guidance throughout the process of drafting 776 this document. Dave also contributed the text of Section 5.6 and 777 Section 6, and insisted on precise discussion of reply size 778 estimation. 780 Thanks to Karen Deitke for her sharp observations about idempotency, 781 and the clarity of the discussion of NFS COMPOUNDs and NFS sessions. 783 Special thanks go to Transport Area Director Spencer Dawkins, nfsv4 784 Working Group Chair Spencer Shepler, and nfsv4 Working Group 785 Secretary Thomas Haynes for their support. 787 Author's Address 788 Charles Lever (editor) 789 Oracle Corporation 790 1015 Granger Avenue 791 Ann Arbor, MI 48104 792 USA 794 Phone: +1 248 816 6463 795 Email: chuck.lever@oracle.com