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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: Standards Track S. Hares 5 Expires: September 8, 2016 Huawei 6 March 7, 2016 8 I2RS Ephemeral State Requirements 9 draft-ietf-i2rs-ephemeral-state-03 11 Abstract 13 This document covers requests to the netmod and netconf Working 14 Groups for functionality to support the ephemeral state requirements 15 to implement the I2RS architecture. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on September 8, 2016. 34 Copyright Notice 36 Copyright (c) 2016 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Review of Requirements from I2RS architecture document . . . 3 53 3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 4 54 3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 4 55 3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 4 56 3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 5 57 3.4. changes to YANG . . . . . . . . . . . . . . . . . . . . . 5 58 3.5. Minimal sub-set of Changes to NETCONF . . . . . . . . . . 5 59 3.6. Requirements regarding Identity, Secondary-Identity and 60 Priority . . . . . . . . . . . . . . . . . . . . . . . . 5 61 3.6.1. Identity Requirements . . . . . . . . . . . . . . . . 5 62 3.6.2. Priority Requirements . . . . . . . . . . . . . . . . 5 63 3.6.3. Transactions . . . . . . . . . . . . . . . . . . . . 6 64 3.6.4. Subscriptions to Changed State Requirements . . . . . 7 65 4. Previously Considered Ideas . . . . . . . . . . . . . . . . . 8 66 4.1. A Separate Ephemeral Datastore . . . . . . . . . . . . . 8 67 4.2. Panes of Glass/Overlay . . . . . . . . . . . . . . . . . 9 68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 69 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 70 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 71 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 72 8.1. Normative References: . . . . . . . . . . . . . . . . . . 10 73 8.2. Informative References . . . . . . . . . . . . . . . . . 11 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 76 1. Introduction 78 The Interface to the Routing System (I2RS) Working Group is chartered 79 with providing architecture and mechanisms to inject into and 80 retrieve information from the routing system. The I2RS Architecture 81 document [I-D.ietf-i2rs-architecture] abstractly documents a number 82 of requirements for implementing the I2RS requirements. 84 The I2RS Working Group has chosen to use the YANG data modeling 85 language [RFC6020] as the basis to implement its mechanisms. 87 Additionally, the I2RS Working group has chosen to use the NETCONF 88 [RFC6241] and its similar but lighter-weight relative RESTCONF 89 [I-D.ietf-netconf-restconf] as the protocols for carrying I2RS. 91 While YANG, NETCONF and RESTCONF are a good starting basis for I2RS, 92 there are some things needed from each of them in order for I2RS to 93 be implemented. 95 2. Review of Requirements from I2RS architecture document 97 The following are ten requirements that [I-D.ietf-i2rs-architecture] 98 contains which are important high level requirements: 100 1. The I2RS protocol SHOULD support highly reliable notifications 101 (but not perfectly reliable notifications) from an I2RS agent to 102 an I2RS client. 104 2. The I2RS protocol SHOULD support a high bandwidth, asynchronous 105 interface, with real-time guarantees on getting data from an 106 I2RS agent by an I2RS client. 108 3. The I2RS protocol will operate on data models which may be 109 protocol independent or protocol dependent. 111 4. I2RS Agent needs to record the client identity when a node is 112 created or modified. The I2RS Agent needs to be able to read 113 the client identity of a node and use the client identity's 114 associated priority to resolve conflicts. The secondary 115 identity is useful for traceability and may also be recorded. 117 5. Client identity will have only one priority for the client 118 identity. A collision on writes is considered an error, but 119 priority is utilized to compare requests from two different 120 clients in order to modify an existing node entry. Only an 121 entry from a client which is higher priority can modify an 122 existing entry (First entry wins). Priority only has meaning at 123 the time of use. 125 6. The Agent identity and the Client identity should be passed 126 outside of the I2RS protocol in a authentication and 127 authorization protocol (AAA). Client priority may be passed in 128 the AAA protocol. The values of identities are originally set 129 by operators, and not standardized. 131 7. An I2RS Client and I2RS Agent mutually authenticate each other 132 based on pre-established authenticated identities. 134 8. Secondary identity data is read-only meta-data that is recorded 135 by the I2RS agent associated with a data model's node is 136 written, updated or deleted. Just like the primary identity, 137 the secondary identity is only recorded when the data node is 138 written or updated or deleted 140 9. I2RS agent can have a lower priority I2RS client attempting to 141 modify a higher priority client's entry in a data model. The 142 filtering out of lower priority clients attempting to write or 143 modify a higher priority client's entry in a data model SHOULD 144 be effectively handled and not put an undue strain on the I2RS 145 agent. Note: Jeff's suggests that priority is kept at the NACM 146 at the client level (rather than the path level or the group 147 level) will allow these lower priority clients to be filtered 148 out using an extended NACM approach. This is only a suggestion 149 of a method to provide the requirement 9. 151 10. The I2RS protocol MUST support the use of a secure transport. 152 However, certain functions such as notifications MAY use a non- 153 secure transport. Each model or service (notification, logging) 154 must define within the model or service the valid uses of a non- 155 secure transport. 157 3. Ephemeral State Requirements 159 3.1. Persistence 161 Ephemeral-REQ-01: I2RS requires ephemeral state; i.e. state that does 162 not persist across reboots. If state must be restored, it should be 163 done solely by replay actions from the I2RS client via the I2RS 164 agent. 166 While at first glance this may seem equivalent to the writable- 167 running datastore in NETCONF, running-config can be copied to a 168 persistent data store, like startup config. I2RS ephemeral state 169 MUST NOT be persisted. 171 3.2. Constraints 173 Ephemeral-REQ-02: Non-ephemeral state MUST NOT refer to ephemeral 174 state for constraint purposes; it SHALL be considered a validation 175 error if it does. 177 Ephemeral-REQ-03: Ephemeral state must be able to utilized temporary 178 operational state which (MPLS LSP-ID or a BGP IN-RIB) as a 179 constraints. 181 Ephemeral-REQ-04: Ephemeral state MAY refer to non-ephemeral state 182 for purposes of implementing constraints. The designer of ephemeral 183 state modules are advised that such constraints may impact the speed 184 of processing ephemeral state commits and should avoid them when 185 speed is essential. 187 3.3. Hierarchy 189 Ephemeral-REQ-05: The ability to add on an object (or a hierarchy of 190 objects) that have the property of being ephemeral. An object needs 191 to be able to have (both) the property of being writable and the 192 property of the data being ephemeral (or non-ephemeral). 194 3.4. changes to YANG 196 Ephemeral-REQ-06: Yang MUST have a way to indicate in a data model 197 that nodes have the following properties: ephemeral, writable/not- 198 writable, status/configuration. 200 3.5. Minimal sub-set of Changes to NETCONF 202 Ephemeral-REQ-07: The minimal set of changes are: (TBD). 204 Potential set: TBD 206 Note: I2RS protocol design team is working to complete this set of 207 minimal changes. 209 3.6. Requirements regarding Identity, Secondary-Identity and Priority 211 3.6.1. Identity Requirements 213 Ephemeral-REQ-08:Clients shall have identifiers, and secondary 214 identifiers. 216 Explanation: 218 I2RS requires clients to have an identifier. This identifier will be 219 used by the Agent authentication mechanism over the appropriate 220 protocol. 222 The Secondary identities can be carried as part of RPC or meta-data. 223 The primary purpose of the secondary identity is for traceability 224 information which logs (who modifies certain nodes). This secondary 225 identity is an opaque value. [I-D.ietf-i2rs-traceability] provides 226 an example of how the secondary identity can be used for 227 traceability. 229 3.6.2. Priority Requirements 231 To support Multi-Headed Control, I2RS requires that there be a 232 decidable means of arbitrating the correct state of data when 233 multiple clients attempt to manipulate the same piece of data. This 234 is done via a priority mechanism with the highest priority winning. 235 This priority is per-client. 237 Ephemeral-REQ-09: The data nodes MAY store I2RS client identity and 238 not the effective priority at the time the data node is stored. The 239 I2RS Client MUST have one priority at a time. The priority MAY be 240 dynamically changed by AAA, but the exact actions are part of the 241 protocol definition as long as Collisions are handled as described in 242 Ephemeral-REQ-10, Ephemeral-REQ-11, and Ephemeral-REQ-12. 244 Ephemeral-REQ-10: When a collision occurs as two clients are trying 245 to write the same data node, this collision is considered an error 246 and priorities were created to give a deterministic result. When 247 there is a collision, a notification MUST BE sent to the original 248 client to give the original client a chance to deal with the issues 249 surrounding the collision. The original client may need to fix their 250 state. 252 Ephemeral-REQ-11: The requirement to support multi-headed control is 253 required for collisions and the priority resolution of collisions. 254 Multi-headed control is not tied to ephemeral state. I2RS is not 255 mandating how AAA supports priority. Mechanisms which prevent 256 collisions of two clients trying the same node of data are the focus. 258 Ephemeral-REQ-12: If two clients have the same priority, the 259 architecture says the first one wins. The I2RS protocol has this 260 requirement to prevent was the oscillation between clients. If one 261 uses the last wins scenario, you may oscillate. That was our 262 opinion, but a design which prevents oscillation is the key point. 264 Hints for Implementation 266 Ephemeral configuration state nodes that are created or altered by 267 users that match a rule carrying i2rs-priority will have those nodes 268 annotated with metadata. Additionally, during commit processing, if 269 nodes are found where i2rs-priority is already present, and the 270 priority is better than the transaction's user's priority for that 271 node, the commit should fail. An appropriate error should be 272 returned to the user stating the nodes where the user had 273 insufficient priority to override the state. 275 3.6.3. Transactions 277 Ephemeral-REQ-13: Section 7.9 of the [I-D.ietf-i2rs-architecture] 278 states the I2RS architecture does not include multi-message atomicity 279 and roll-back mechanisms. I2RS notes multiple operations in one or 280 more messages handling can handle errors within the set of operations 281 in many ways. No multi-message commands SHOULD cause errors to be 282 inserted into the I2RS ephemeral data-store. 284 Explanation: 286 I2RS suggests the following are some of the potential error handling 287 techniques for multiple message sent to the I2RS client: 289 1. Perform all or none: All operations succeed or none of them will 290 be applied. This useful when there are mutual dependencies. 292 2. Perform until error: Operations are applied in order, and when 293 error occurs the processing stops. This is useful when 294 dependencies exist between multiple-message operations, and order 295 is important. 297 3. Perform all storing errors: Perform all actions storing error 298 indications for errors. This method can be used when there are 299 no dependencies between operations, and the client wants to sort 300 it out. 302 Is important to reliability of the datastore that none of these error 303 handling for multiple operations in one more multiple messages cause 304 errors into be insert the I2RS ephemeral data-store. 306 Discussion of Current NETCONF/RESTCONF versus 308 RESTCONF does an atomic action within a http session, and NETCONF has 309 atomic actions within a commit. These features may be used to 310 perform these features. 312 I2RS processing is dependent on the I2RS model. The I2RS model must 313 consider the dependencies within multiple operations work within a 314 model. 316 3.6.4. Subscriptions to Changed State Requirements 318 I2RS clients require the ability to monitor changes to ephemeral 319 state. While subscriptions are well defined for receiving 320 notifications, the need to create a notification set for all 321 ephemeral configuration state may be overly burdensome to the user. 323 There is thus a need for a general subscription mechanism that can 324 provide notification of changed state, with sufficient information to 325 permit the client to retrieve the impacted nodes. This should be 326 doable without requiring the notifications to be created as part of 327 every single I2RS module. 329 The following requirements from the 330 [I-D.ietf-i2rs-pub-sub-requirements] apply to ephemeral state: 332 o PubSub-REQ-1: The I2RS interface SHOULD support user subscriptions 333 to data with the following parameters: push of data synchronously 334 or asynchronously via registered subscriptions. 336 o PubSSub-REQ-2: Real time for notifications SHOULD be defined by 337 the data models. 339 o PubSub-REQ-3: Security of the pub/sub data stream SHOULD be able 340 to be model dependent. 342 o PubSub-REQ-4: The Pub/Sub mechanism SHOULD allow subscription to 343 critical Node Events. Examples of critical node events are BGP 344 peers down or ISIS protocol overload bits. 346 o PubSub-REQ-5:I2RS telemetry data for certain protocols (E.g. BGP) 347 will require a hierarchy of filters or XPATHs. The I2RS protocol 348 design MUST balance security against the throughput of the 349 telemetry data. 351 o PubSub-REQ-6: I2RS Filters SHOULD be able to be dynamic. 353 o Pub-Sub-REQ-7: I2rs protocol MUST be able to allow I2RS agent to 354 set limits on the data models it will support for pub/sub and 355 within data models to support knobs for maximum frequency or 356 resolution of pub/sub data. 358 4. Previously Considered Ideas 360 4.1. A Separate Ephemeral Datastore 362 The primary advantage of a fully separate datastore is that the 363 semantics of its contents are always clearly ephemeral. It also 364 provides strong segregation of I2RS configuration and operational 365 state from the rest of the system within the network element. 367 The most obvious disadvantage of such a fully separate datastore is 368 that interaction with the network element's operational or 369 configuration state becomes significantly more difficult. As an 370 example, a BGP I2RS use case would be the dynamic instantiation of a 371 BGP peer. While it is readily possible to re-use any defined 372 groupings from an IETF-standardized BGP module in such an I2RS 373 ephemeral datastore's modules, one cannot currently reference state 374 from one datastore to anothe 375 For example, XPath queries are done in the context document of the 376 datastore in question and thus it is impossible for an I2RS model to 377 fulfil a "must" or "when" requirement in the BGP module in the 378 standard data stores. To implement such a mechanism would require 379 appropriate semantics for XPath. 381 4.2. Panes of Glass/Overlay 383 I2RS ephemeral configuration state is generally expected to be 384 disjoint from persistent configuration. In some cases, extending 385 persistent configuration with ephemeral attributes is expected to be 386 useful. A case that is considered potentially useful but problematic 387 was explored was the ability to "overlay" persistent configuration 388 with ephemeral configuration. 390 In this overlay scenario, persistent configuration that was not 391 shadowed by ephemeral configuration could be "read through". 393 There were two perceived disadvantages to this mechanism: 395 The general complexity with managing the overlay mechanism itself. 397 Consistency issues with validation should the ephemeral state be 398 lost, perhaps on reboot. In such a case, the previously shadowed 399 persistent state may no longer validate. 401 5. IANA Considerations 403 There are no IANA requirements for this document. 405 6. Security Considerations 407 The security requirements for the I2RS protocol are covered in 408 [I-D.hares-i2rs-auth-trans] document. 410 7. Acknowledgements 412 This document is an attempt to distill lengthy conversations on the 413 I2RS mailing list for an architecture that was for a long period of 414 time a moving target. Some individuals in particular warrant 415 specific mention for their extensive help in providing the basis for 416 this document: 418 o Alia Atlas 420 o Andy Bierman 422 o Martin Bjorklund 423 o Dean Bogdanavich 425 o Rex Fernando 427 o Joel Halpern 429 o Thomas Nadeau 431 o Juergen Schoenwaelder 433 o Kent Watsen 435 8. References 437 8.1. Normative References: 439 [I-D.hares-i2rs-auth-trans] 440 Hares, S., Migault, D., and J. Halpern, "I2RS Security 441 Related Requirements", draft-hares-i2rs-auth-trans-05 442 (work in progress), August 2015. 444 [I-D.ietf-i2rs-architecture] 445 Atlas, A., Halpern, J., Hares, S., Ward, D., and T. 446 Nadeau, "An Architecture for the Interface to the Routing 447 System", draft-ietf-i2rs-architecture-13 (work in 448 progress), February 2016. 450 [I-D.ietf-i2rs-pub-sub-requirements] 451 Voit, E., Clemm, A., and A. Prieto, "Requirements for 452 Subscription to YANG Datastores", draft-ietf-i2rs-pub-sub- 453 requirements-05 (work in progress), February 2016. 455 [I-D.ietf-i2rs-rib-info-model] 456 Bahadur, N., Kini, S., and J. Medved, "Routing Information 457 Base Info Model", draft-ietf-i2rs-rib-info-model-08 (work 458 in progress), October 2015. 460 [I-D.ietf-i2rs-traceability] 461 Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to 462 the Routing System (I2RS) Traceability: Framework and 463 Information Model", draft-ietf-i2rs-traceability-07 (work 464 in progress), February 2016. 466 [I-D.ietf-netmod-yang-metadata] 467 Lhotka, L., "Defining and Using Metadata with YANG", 468 draft-ietf-netmod-yang-metadata-04 (work in progress), 469 February 2016. 471 8.2. Informative References 473 [I-D.ietf-netconf-restconf] 474 Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 475 Protocol", draft-ietf-netconf-restconf-09 (work in 476 progress), December 2015. 478 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 479 Requirement Levels", BCP 14, RFC 2119, 480 DOI 10.17487/RFC2119, March 1997, 481 . 483 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 484 the Network Configuration Protocol (NETCONF)", RFC 6020, 485 DOI 10.17487/RFC6020, October 2010, 486 . 488 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 489 and A. Bierman, Ed., "Network Configuration Protocol 490 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 491 . 493 [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration 494 Protocol (NETCONF) Access Control Model", RFC 6536, 495 DOI 10.17487/RFC6536, March 2012, 496 . 498 Authors' Addresses 500 Jeff Haas 501 Juniper 503 Email: jhaas@juniper.net 505 Susan Hares 506 Huawei 507 Saline 508 US 510 Email: shares@ndzh.com