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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 I2RS working group J. Haas 3 Internet-Draft Juniper 4 Intended status: Informational S. Hares 5 Expires: April 30, 2017 Huawei 6 October 27, 2016 8 I2RS Ephemeral State Requirements 9 draft-ietf-i2rs-ephemeral-state-21.txt 11 Abstract 13 The I2RS (interface to the routing system) Architecture document 14 (RFC7921) abstractly describes a number of requirements for ephemeral 15 state (in terms of capabilities and behaviors) which any protocol 16 suite attempting to meet the needs of I2RS has to provide. This 17 document describes, in detail, requirements for ephemeral state for 18 those implementing the I2RS protocol. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on April 30, 2017. 37 Copyright Notice 39 Copyright (c) 2016 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 56 2. Review of Requirements from I2RS architecture document . . . 3 57 3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 4 58 3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 4 59 3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 5 60 3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 5 61 3.4. Ephemeral Configuration overlapping Local Configuration . 5 62 4. YANG Features for Ephemeral State . . . . . . . . . . . . . . 6 63 5. NETCONF Features for Ephemeral State . . . . . . . . . . . . 6 64 6. RESTCONF Features for Ephemeral State . . . . . . . . . . . . 6 65 7. Requirements regarding Supporting Multi-Head Control via 66 client Priority . . . . . . . . . . . . . . . . . . . . . . . 6 67 8. Multiple Message Transactions . . . . . . . . . . . . . . . . 8 68 9. Pub/Sub Requirements Expanded for Ephemeral State . . . . . . 8 69 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 70 11. Security Considerations . . . . . . . . . . . . . . . . . . . 9 71 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 72 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 73 13.1. Normative References: . . . . . . . . . . . . . . . . . 10 74 13.2. Informative References . . . . . . . . . . . . . . . . . 11 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 77 1. Introduction 79 The Interface to the Routing System (I2RS) Working Group is chartered 80 with providing architecture and mechanisms to inject into and 81 retrieve information from the routing system. The I2RS Architecture 82 document [RFC7921] abstractly documents a number of requirements for 83 implementing the I2RS requirements. Section 2 reviews key 84 requirements related to ephemeral state. [RFC7921] defines ephemeral 85 state as "state which does not survive the reboot of a routing device 86 or the reboot of the software handling the I2RS software on a routing 87 device" (see section 1.1 of [RFC7921]). 89 The I2RS Working Group has chosen to use the YANG data modeling 90 language [RFC7950] as the basis to implement its mechanisms. 92 Additionally, the I2RS Working group has chosen to re-use two 93 existing protocols, NETCONF [RFC6241] and its similar but lighter- 94 weight relative RESTCONF [I-D.ietf-netconf-restconf], as the 95 protocols for carrying I2RS. 97 What does re-use of a protocol mean? Re-use means that while YANG, 98 NETCONF and RESTCONF are a good starting basis for the I2RS protocol, 99 the creation of the I2RS protocol implementations requires that the 100 I2RS requirements 102 1. select features from YANG, NETCONF, and RESTCONF per version of 103 the I2RS protocol (See sections 4, 5, and 6) 105 2. propose additions to YANG, NETCONF, and RESTCONF per version of 106 the I2RS protocol for key functions (ephemeral state, protocol 107 security, publication/subscription service, traceability), 109 The purpose of these requirements is to ensure clarity during I2RS 110 protocol creation. 112 Support for ephemeral state is an I2RS protocol requirement that 113 requires datastore changes (see section 3), YANG additions (see 114 section 4), NETCONF additions (see section 5), and RESTCONF additions 115 (see section 6). 117 Sections 7-9 provide details that expand upon the changes in sections 118 3-6 to clarify requirements discussed by the I2RS and NETCONF working 119 groups. Section 7 provided additional requirements that detail how 120 write-conflicts should be resolved if two I2RS client write the same 121 data. Section 8 describes I2RS requirements for support of multiple 122 message transactions. Section 9 highlights two requirements in the 123 I2RS publication/subscription requirements [RFC7923] that must be 124 expanded for ephemeral state. 126 1.1. Requirements Language 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in RFC 2119 [RFC2119]. 132 2. Review of Requirements from I2RS architecture document 134 The I2RS architecture defines important high-level requirements for 135 the I2RS protocol. The following are requirements distilled from 136 [RFC7921] that provide context for the ephemeral data state 137 requirements given in sections 3-8: 139 1. The I2RS protocol SHOULD support an interface asynchronous 140 programmatic interface interface with properties of described in 141 section 5 of [RFC7920] (e.g. high throughput) with support for 142 target information streams, filtered evens, and thresholded 143 events (real-time events) sent by an I2RS agent to an I2RS Client 144 (Key points from section 1.1 of [RFC7921]). 146 2. I2RS agent MUST record the client identity when a node is created 147 or modified. The I2RS agent SHOULD to be able to read the client 148 identity of a node and use the client identity's associated 149 priority to resolve conflicts. The secondary identity is useful 150 for traceability and may also be recorded. (Key points from 151 section 4 of [RFC7921].) 153 3. An I2RS Client identity MUST have only one priority for the 154 client's identifier. A collision on writes is considered an 155 error, but the priority associated with each client identifier is 156 utilized to compare requests from two different clients in order 157 to modify an existing node entry. Only an entry from a client 158 which is higher priority can modify an existing entry (First 159 entry wins). Priority only has meaning at the time of use. (Key 160 points from section 7.8 of [RFC7921].) 162 4. I2RS Client's secondary identity data is read-only meta-data that 163 is recorded by the I2RS agent associated with a data model's node 164 is written. Just like the primary client identity, the secondary 165 identity SHOULD only be recorded when the data node is written. 166 (Key points from sections 7.4 of [RFC7921].) 168 5. I2RS agent MAY have a lower priority I2RS client attempting to 169 modify a higher priority client's entry in a data model. The 170 filtering out of lower priority clients attempting to write or 171 modify a higher priority client's entry in a data model SHOULD be 172 effectively handled and not put an undue strain on the I2RS 173 agent. (See section 7.8 of [RFC7921] augmented by the resource 174 limitation language in section 8 [RFC7921].) 176 3. Ephemeral State Requirements 178 In requirements Ephemeral-REQ-01 to Ephemeral-REQ-15, Ephemeral state 179 is defined as potentially including in a data model ephemeral 180 configuration and operational state which is flagged as ephemeral. 182 3.1. Persistence 184 Ephemeral-REQ-01: I2RS requires ephemeral state; i.e. state that does 185 not persist across reboots. If state must be restored, it should be 186 done solely by replay actions from the I2RS client via the I2RS 187 agent. 189 While at first glance this may seem equivalent to the writable- 190 running data store in NETCONF, running-config can be copied to a 191 persistent data store, like startup config. I2RS ephemeral state 192 MUST NOT be persisted. 194 3.2. Constraints 196 Ephemeral-REQ-02: Non-ephemeral state MUST NOT refer to ephemeral 197 state for constraint purposes; it SHALL be considered a validation 198 error if it does. 200 Ephemeral-REQ-03: Ephemeral state MUST be able to have constraints 201 that refer to operational state, this includes potentially fast 202 changing or short lived operational state nodes, such as MPLS LSP-ID 203 (label switched path ID) or a BGP Adj-RIB-IN (Adjacent RIB Inboud). 204 Ephemeral state constraints should be assessed when the ephemeral 205 state is written, and if any of the constraints change to make the 206 constraints invalid after that time the I2RS agent SHOULD notify the 207 I2RS client. 209 Ephemeral-REQ-04: Ephemeral state MUST be able to refer to non- 210 ephemeral state as a constraint. Non-ephemeral state can be 211 configuration state or operational state. 213 Ephemeral-REQ-05: I2RS pub-sub [RFC7923], tracing [RFC7922], RPC or 214 other mechanisms may lead to undesirable or unsustainable resource 215 consumption on a system implementing an I2RS agent. It is 216 RECOMMENDED that mechanisms be made available to permit 217 prioritization of I2RS operations, when appropriate, to permit 218 implementations to shed work load when operating under constrained 219 resources. An example of such a work shedding mechanism is rate- 220 limiting. 222 3.3. Hierarchy 224 Ephemeral-REQ-06: YANG MUST have the ability to do the following: 226 1. to define a YANG module or submodule schema that only contains 227 data nodes with the property of being ephemeral, and 229 2. to augment a YANG model with additional YANG schema nodes that 230 have the property of being ephemeral. 232 3.4. Ephemeral Configuration overlapping Local Configuration 234 Ephemeral-REQ-07: Local configuration MUST have a priority that is 235 comparable with individual I2RS client priorities for making changes. 236 This priority will determine whether local configuration changes or 237 individual ephemeral configuration changes take precedence as 238 described in RFC7921. The I2RS protocol MUST support this mechanism. 240 4. YANG Features for Ephemeral State 242 Ephemeral-REQ-08:In addition to config true/false, there MUST be a 243 way to indicate that YANG schema nodes represent ephemeral state. It 244 is desirable to allow for, and have a way to indicate, config false 245 YANG schema nodes that are writable operational state. 247 5. NETCONF Features for Ephemeral State 249 Ephemeral-REQ-09: The changes to NETCONF must include: 251 1. Support for communication mechanisms to enable an I2RS client to 252 determine that an I2RS agent supports the mechanisms needed for 253 I2RS operation. 255 2. The ephemeral state MUST support notification of write conflicts 256 using the priority requirements defined in section 7 below (see 257 requirements Ephemeral-REQ-11 through Ephemeral-REQ-14). 259 6. RESTCONF Features for Ephemeral State 261 Ephemeral-REQ-10: The conceptual changes to RESTCONF are: 263 1. Support for communication mechanisms to enable an I2RS client to 264 determine that an I2RS agent supports the mechanisms needed for 265 I2RS operation. 267 2. The ephemeral state must support notification of write conflicts 268 using the priority requirements defined in section 7 below (see 269 requirements Ephemeral-REQ-11 through Ephemeral-REQ-14). 271 7. Requirements regarding Supporting Multi-Head Control via client 272 Priority 274 To support Multi-Headed Control, I2RS requires that there be a 275 decidable means of arbitrating the correct state of data when 276 multiple clients attempt to manipulate the same piece of data. This 277 is done via a priority mechanism with the highest priority winning. 278 This priority is per-client. 280 Ephemeral-REQ-11: The following requirements must be supported by the 281 I2RS protocol I2RS Protocol (e.g. NETCONF/RESTCONF + yang) in order 282 to support I2RS client identity and priority: 284 o the data nodes MAY store I2RS client identity and not the 285 effective priority at the time the data node is stored. 287 o Per SEC-REQ-07 in section 4.3 of 288 [I-D.ietf-i2rs-protocol-security-requirements], an I2RS Identifier 289 MUST have just one priority. The I2RS protocol MUST support the 290 ability to have data nodes store I2RS client identity and not the 291 effective priority of the I2RS client at the time the data node is 292 stored. 294 o The priority MAY be dynamically changed by AAA, but the exact 295 actions are part of the protocol definition as long as collisions 296 are handled as described in Ephemeral-REQ-12, Ephemeral-REQ-13, 297 and Ephemeral-REQ-14. 299 Ephemeral-REQ-12: When a collision occurs as two I2RS clients are 300 trying to write the same data node, this collision is considered an 301 error. The I2RS priorities are used to provide a deterministic 302 resolution to the conflict. When there is a collision, and the data 303 node is changed, a notification (which includes indicating data node 304 the collision occurred on) MUST BE sent to the original client to 305 give the original client a chance to deal with the issues surrounding 306 the collision. The original client may need to fix their state. 308 Explanation: RESTCONF and NETCONF updates can come in concurrently 309 from alternative sources. Therefore the collision detection and 310 comparison of priority needs to occur for any type of update. 312 For example, RESTCONF tracks the source of configuration change via 313 the entity-Tag (section 3.5.2 of [I-D.ietf-netconf-restconf]) which 314 the server returns to the client along with the value in GET or HEAD 315 methods. RESTCONF requires that this resource entity-tag be updated 316 whenever a resource or configuration resource within the resource is 317 altered. In the RESTCONF processing, when the resource or a 318 configuration resource within the resource is altered, then the 319 processing of the configuration change for two I2RS clients must 320 detect an I2RS collision and resolve the collision using the priority 321 mechanism. 323 Ephemeral-REQ-13: Multi-headed control is required for collisions and 324 the priority resolution of collisions. Multi-headed control is not 325 tied to ephemeral state. I2RS protocol MUST NOT mandate the internal 326 mechanism for how AAA protocols (E.g. Radius or Diameter) or 327 mechanisms distribute priority per identity except that any AAA 328 protocols MUST operate over a secure transport layer (See Radius 329 [RFC6614] and Diameter [RFC6733]. Mechanisms that prevent collisions 330 of two clients trying to modify the same node of data are the focus. 332 Ephemeral-REQ-14: A deterministic conflict resolution mechanism MUST 333 be provided to handle the error scenario that two clients, with the 334 same priority, update the same configuration data node. The I2RS 335 architecture gives one way that this could be achieved, by specifying 336 that the first update wins. Other solutions, that prevent 337 oscillation of the config data node, are also acceptable. 339 8. Multiple Message Transactions 341 Ephemeral-REQ-15: Section 7.9 of the [RFC7921] states the I2RS 342 architecture does not include multi-message atomicity and roll-back 343 mechanisms. The I2RS protocol implementation MUST NOT require the 344 support of these features. As part of this requirement, the I2RS 345 protocol should support: 347 multiple operations in one messge; an error in one operation MUST 348 NOT stop additional operations from being carried out nor can it 349 cause previous operations to be rolled back. 351 multiple operations in multiple messages, but multiple message 352 commands error handling MUST NOT insert errors into the I2RS 353 ephemeral state. 355 9. Pub/Sub Requirements Expanded for Ephemeral State 357 I2RS clients require the ability to monitor changes to ephemeral 358 state. While subscriptions are well defined for receiving 359 notifications, the need to create a notification set for all 360 ephemeral configuration state may be overly burdensome to the user. 362 There is thus a need for a general subscription mechanism that can 363 provide notification of changed state, with sufficient information to 364 permit the client to retrieve the impacted nodes. This should be 365 doable without requiring the notifications to be created as part of 366 every single I2RS module. 368 The publication/subscription requirements for I2RS are in [RFC7923], 369 and the following general requirements SHOULD be understood to be 370 expanded to include ephemeral state: 372 o Pub-Sub-REQ-01: The Subscription Service MUST support 373 subscriptions against ephemeral state in operational data stores, 374 configuration data stores or both. 376 o Pub-Sub-REQ-02: The Subscription Service MUST support filtering so 377 that subscribed updates under a target node might publish only 378 ephemeral state in operational data or configuration data, or 379 publish both ephemeral and operational data. 381 o Pub-Sub-REQ-03: The subscription service MUST support 382 subscriptions which are ephemeral. (E.g. An ephemeral data model 383 which has ephemeral subscriptions.) 385 10. IANA Considerations 387 There are no IANA requirements for this document. 389 11. Security Considerations 391 The security requirements for the I2RS protocol are covered in 392 [I-D.ietf-i2rs-protocol-security-requirements] document. The 393 security requirements for the I2RS protocol environment are in 394 [I-D.ietf-i2rs-security-environment-reqs]. 396 12. Acknowledgements 398 This document is an attempt to distill lengthy conversations on the 399 I2RS mailing list for an architecture that was for a long period of 400 time a moving target. Some individuals in particular warrant 401 specific mention for their extensive help in providing the basis for 402 this document: 404 o Alia Atlas, 406 o Andy Bierman, 408 o Martin Bjorklund, 410 o Dean Bogdanavich, 412 o Rex Fernando, 414 o Joel Halpern, 416 o Thomas Nadeau, 418 o Juergen Schoenwaelder, 420 o Kent Watsen, 422 o Robert Wilton, and 424 o Joe Clarke, 426 13. References 428 13.1. Normative References: 430 [I-D.ietf-i2rs-protocol-security-requirements] 431 Hares, S., Migault, D., and J. Halpern, "I2RS Security 432 Related Requirements", draft-ietf-i2rs-protocol-security- 433 requirements-17 (work in progress), September 2016. 435 [I-D.ietf-i2rs-security-environment-reqs] 436 Migault, D., Halpern, J., and S. Hares, "I2RS Environment 437 Security Requirements", draft-ietf-i2rs-security- 438 environment-reqs-01 (work in progress), April 2016. 440 [I-D.ietf-netconf-restconf] 441 Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 442 Protocol", draft-ietf-netconf-restconf-17 (work in 443 progress), September 2016. 445 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 446 and A. Bierman, Ed., "Network Configuration Protocol 447 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 448 . 450 [RFC6614] Winter, S., McCauley, M., Venaas, S., and K. Wierenga, 451 "Transport Layer Security (TLS) Encryption for RADIUS", 452 RFC 6614, DOI 10.17487/RFC6614, May 2012, 453 . 455 [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, 456 Ed., "Diameter Base Protocol", RFC 6733, 457 DOI 10.17487/RFC6733, October 2012, 458 . 460 [RFC7920] Atlas, A., Ed., Nadeau, T., Ed., and D. Ward, "Problem 461 Statement for the Interface to the Routing System", 462 RFC 7920, DOI 10.17487/RFC7920, June 2016, 463 . 465 [RFC7921] Atlas, A., Halpern, J., Hares, S., Ward, D., and T. 466 Nadeau, "An Architecture for the Interface to the Routing 467 System", RFC 7921, DOI 10.17487/RFC7921, June 2016, 468 . 470 [RFC7922] Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to 471 the Routing System (I2RS) Traceability: Framework and 472 Information Model", RFC 7922, DOI 10.17487/RFC7922, June 473 2016, . 475 [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements 476 for Subscription to YANG Datastores", RFC 7923, 477 DOI 10.17487/RFC7923, June 2016, 478 . 480 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 481 RFC 7950, DOI 10.17487/RFC7950, August 2016, 482 . 484 13.2. Informative References 486 [I-D.hares-i2rs-protocol-strawman] 487 Hares, S. and a. amit.dass@ericsson.com, "I2RS protocol 488 strawman", draft-hares-i2rs-protocol-strawman-03 (work in 489 progress), July 2016. 491 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 492 Requirement Levels", BCP 14, RFC 2119, 493 DOI 10.17487/RFC2119, March 1997, 494 . 496 Authors' Addresses 498 Jeff Haas 499 Juniper 501 Email: jhaas@juniper.net 503 Susan Hares 504 Huawei 505 Saline 506 US 508 Email: shares@ndzh.com