I2RS working group J. Haas Internet-Draft Juniper Intended status: Standards Track S. Hares Expires: November6,26, 2016 Huawei May5,25, 2016 I2RS Ephemeral State Requirementsdraft-ietf-i2rs-ephemeral-state-06draft-ietf-i2rs-ephemeral-state-07 Abstract This document covers requests to thenetmodNETMOD andnetconfNETCONF Working Groups for functionality to support the ephemeral state requirements to implement the I2RS architecture. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on November6,26, 2016. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Review of Requirements from I2RS architecture document . . . 3 3. Ephemeral State Requirements . . . . . . . . . . . . . . . .45 3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . .45 3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . .45 3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 53.4. Changes to4. YANG. . . . . . . . . . . . . . . . . . . . . 5 3.4.1. Suggested Yang syntax changes . . . . . . . . . . . .Features for Ephemeral State for I2RS Protocol version 1 53.5. Minimal Changes to5. NETCONF Features for Ephemeral State for I2RS Protocol version 1 .6 3.5.1. Dependencies . . . . . .. . . . . . . . . . . . . .7 3.5.2. Modified operations . . . . . . . . . . . . . . . . . 7 3.5.3. Unsupported operations . . . . . . . . . . .. . . .7 3.5.4. Interactions with existing capabilities. . . . . . .7 3.6. Changes to6 6. RESTCONF Features for Ephemeral State. . . . . . . . . 7 3.6.1. dependenciesforRESTCONF . . . . . . . . . . . .I2RS Protocol version 1 . .8 3.6.2. modification to context. . . . . . . . . . . . . . .9 3.6.3. modification to existing operations. . . . . . . . .9 3.7.7 7. Requirements regardingIdentity, Secondary-Identity andSupporting Multi-Head Control via Client Priority . . . . . . . . . . . . . . . . . . . . . . .. 9 3.7.1. Identity Requirements . . . . . . . . . . . . . . . . 9 3.7.2. Priority Requirements . . . . . . . . . . . . . . . .93.7.3.8. Multiple Message Transactions . . . . . . . . . . . . . . . .. . . .103.7.4. Subscriptions to Changed State9. Pub/Sub Requirements Expanded for Ephemeral State . . . . .11 4. Previously Considered Ideas . . . .. 11 10. IANA Considerations . . . . . . . . . . . .12 4.1. A Separate Ephemeral Data store. . . . . . . . . 11 11. Security Considerations . . . .12 4.2. Panes of Glass/Overlay. . . . . . . . . . . . . . . 11 12. Acknowledgements . .13 5. IANA Considerations. . . . . . . . . . . . . . . . . . . . 11 13. References .13 6. Security Considerations. . . . . . . . . . . . . . . . . . .13 7. Acknowledgements. . . . . 12 13.1. Normative References: . . . . . . . . . . . . . . . . .13 8.12 13.2. Informative References . . . . . . . . . . . . . . . . .. . . . . . . .148.1. Normative References: . . . . . . . .Authors' Addresses . . . . . . . . . .14 8.2. Informative References. . . . . . . . . . . . .. . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 1614 1. Introduction The Interface to the Routing System (I2RS) Working Group is chartered with providing architecture and mechanisms to inject into and retrieve information from the routing system. The I2RS Architecture document [I-D.ietf-i2rs-architecture] abstractly documents a number of requirements for implementing the I2RS requirements. Section 2 reviews 10 key requirements related to ephemeral state. The I2RS Working Group has chosen to use the YANG data modeling language [RFC6020] as the basis to implement its mechanisms. Additionally, the I2RS Working group has chosen touse there-use two existing protocols, NETCONF [RFC6241] and its similar butlighter-weightlighter- weight relative RESTCONF[I-D.ietf-netconf-restconf][I-D.ietf-netconf-restconf], as the protocols for carrying I2RS.WhileWhat does re-use of a protocol mean? Re-use means that while YANG, NETCONF and RESTCONF are a good starting basis forI2RS, there are some things neededthe I2RS protocol, the creation of the I2RS protocol implementations requires that the I2RS requirements 1. select features fromeachYANG, NETCONF, and RESTCONF per version ofthem in orderthe I2RS protocol (See sections 4, 5, and 6) 2. propose additions to YANG, NETCONF, and RESTCONF per version of the I2RS protocol for key functions (ephemeral state, protocol security, publication/subscription service, traceability), 3. suggest protocol strawman as ideas for the NETCONF, RESTCONF, and YANG changes. The purpose of these requirements and the suggested protocol straw man is to provide a quick turnaround on creating the I2RS protocol. Support for ephemeral state is I2RS protocol requirement that requires datastore changes (see section 3), Yang additions (see section 4), NETCONF additions (see section 5), and RESTCONF additions (see section 6). Sections 7-9 provide details that expand upon the changes in sections 3-6 to clarify requirements discussed by the I2RS and NETCONF working groups. Sections 7 provide additional requirements that detail how write-conflicts should be resolved if two I2RS client write the same data. Section 8 provides an additional requirement that details on I2RS support of multiple message transactions. Section 9 highlights two requirements in the I2RS publication/subscription requirements [I-D.ietf-i2rs-pub-sub-requirements] that must beimplemented.expanded for ephemeral state. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. Review of Requirements from I2RS architecture document The I2RS architecture defines important high-level requirements for the I2RS protocol. The following are ten requirements that [I-D.ietf-i2rs-architecture] contains whichare important high level requirements:provide context for the ephemeral data state requirements given in sections 3-8: 1. The I2RS protocol SHOULD support highly reliable notifications (but not perfectly reliable notifications) from an I2RS agent to an I2RS client. 2. The I2RS protocol SHOULD support a high bandwidth, asynchronous interface, with real-time guarantees on getting data from an I2RS agent by an I2RS client. 3. The I2RS protocol will operate on data models whichmayMAY be protocol independent or protocol dependent. 4. I2RS Agentneeds toMUST record the client identity when a node is created or modified. The I2RS AgentneedsSHOULD to be able to read the client identity of a node and use the client identity's associated priority to resolve conflicts. The secondary identity is useful for traceability and may also be recorded. 5. Client identitywillMUST have only one priority for theclient identity.client's identifer. A collision on writes is considered an error, but the priority associated with each client identifier is utilized to compare requests from two different clients in order to modify an existing node entry. Only an entry from a client which is higher priority can modify an existing entry (First entry wins). Priority only has meaning at the time of use. 6. The Agent identity and the Client identityshouldSHOULD be passed outside of the I2RS protocol in a authentication and authorization protocol (AAA). Client priority may be passed in the AAA protocol. The values of identities are originally set by operators, and not standardized. 7. An I2RS Client and I2RS Agent MUST mutually authenticate each other based on pre-established authenticated identities. 8. Secondary identity data is read-only meta-data that is recorded by the I2RS agent associated with a data model's node is written, updated or deleted. Just like the primary identity, the secondary identityisSHOULD only be recorded when the data node is written or updated or deleted 9. I2RS agentcanMAY have a lower priority I2RS client attempting to modify a higher priority client's entry in a data model. The filtering out of lower priority clients attempting to write or modify a higher priority client's entry in a data model SHOULD be effectively handled and not put an undue strain on the I2RS agent.Note: Jeff's suggests that priority is kept at the NACM ([RFC6536])at the client level (rather than the path level or the group level) will allow these lower priority clients to be filtered out using an extended NACM approach. This is only a suggestion of a method to provide the requirement 9.10. The I2RS protocol MUST support the use of a secure transport. However, certain functions such as notifications MAY use a non- secure transport. Each model or service (notification, logging) must define within the model or service the valid uses of a non- secure transport. 3. Ephemeral State Requirements 3.1. Persistence Ephemeral-REQ-01: I2RS requires ephemeral state; i.e. state that does not persist across reboots. If state must be restored, it should be done solely by replay actions from the I2RS client via the I2RS agent. While at first glance this may seem equivalent to the writable- running data store in NETCONF, running-config can be copied to a persistent data store, like startup config. I2RS ephemeral state MUST NOT be persisted. 3.2. Constraints Ephemeral-REQ-02: Non-ephemeral state MUST NOT refer to ephemeral state for constraint purposes; it SHALL be considered a validation error if it does. Ephemeral-REQ-03: Ephemeral state must be able to utilized temporary operational state (e.g. MPLS LSP-ID or a BGP IN-RIB) as a constraints. Ephemeral-REQ-04: Ephemeral state MAY refer to non-ephemeral state for purposes of implementing constraints. The designer of ephemeral state modules are advised that such constraints may impact the speed of processing ephemeral state commits and should avoid them when speed is essential. 3.3. Hierarchy Ephemeral-REQ-05: The ability toadd onaugment an object(or a hierarchy of objects)with appropriate YANG structures that have the property of being ephemeral.3.4. Changes toAn object defined as Yang module, schema tree, a schema node, submodule or components of a submodule (derived types, groupings, data node, RPCs, actions, and notifications". 4. YANG Features for Ephemeral State for I2RS Protocol version 1 Ephemeral-REQ-06: Yang MUST have a way to indicate in a data model that nodes have the following properties: ephemeral, writable/not- writable, status/configuration, and secure/non-secure transport.3.4.1. Suggested Yang syntax changes The minimal changes to Yang are: 1. protocol version support - "I2RS version 1", 2. ephemeral true; (key word) 3. data models indicate which component protocol is supported "NETCONF", "RESTCONF" 4. encoding support - XML or JSON 5. data models indicate which transports protocol supported:"SSH", "TLS", "TCP" (nonsecure); 6. configuration for non-secure transport 1. i2rs-transport-non-secure ok; 7. Configuration for no validation checks: ephemeral-validation no check; 1. The key word "no-check" implies the I2RS client has done all the validation and the I2RS agent is only validating the message context. The risk in this validation method 2. the key word "full" implies the I2RS Client is doing all validation normally done for a configuration node. 8. These key words can apply to ephemeral leafs, ephemeral sub- modules, ephemeral modules, and rpc allowing flexible validation levels. This validation level can also be set on an rpc command (e.g. rpc for creating a new route in the I2RS RIB). The default(If you desire examples, please see [I-D.hares-i2rs-protocol-strawman] forall I2RS ephemeral writes is full. 9. Note: Anything less than full validation runs the risk of having bad data in the I2RS ephemeral state. 3.5. Minimal Changes topotential yang syntax). 5. NETCONF Features for Ephemeral State for I2RS Protocol version 1 Ephemeral-REQ-07: The conceptual changes to NETCONFo1. protocol version support for I2RS modifications -"I2RS-version 1", o(e.g. I2RS version 1) 2. support for ephemeral model scope indication -ephemeral modules,which indicates whether a module is an ephemeral-only module, mixed config module (ephemeral and config), mixed derived state (ephemeral and config).o3. multiple message support - supports the I2RS "all ornothing", o pane of glassnothing" concept ([I-D.ietf-i2rs-architecture] section 7.9) which is the same as NETCONF "roll-back-on-error". 4. support- single ephemeral pane only. ofor the following transports protocolsupport -supported: "TCP", "SSH", "TLS", and non-secure transport (see [I-D.ietf-i2rs-protocol-security-requirements] section 3.2 in requirements SEC-REQ-09 and SEC-REQ-11 for details). NETCONF[RFC6241], yang pub-sub push [I-D.ietf-netconf-yang-push], yang module library [I-D.ietf-netconf-yang-library], call-home [I-D.ietf-netconf-call-home], and server modules [I-D.ietf-netconf-server-model] (server module mustshould beaugmentedable tosupport mutual authentication). o encoding support - XML or JSON o transports protocol supported: "TCP", "SSH", "TLS", non-secure, and others. oexpand the number of secure transport protocols supported as I2RS may add additional transport protocols. 5. ability toselect transportsrestrict insecure transport support to specific portions of a datamodel available for managementmodels marked as valid to transfer via insecure protocol.Insecure portions must6. ephemeral state overwriting of configuration state MUST beablecontrolled by the following policy knobs (as defined by [I-D.ietf-i2rs-architecture] section 6.3 and 6.3.1): * ephemeral configuration overwrites local configuration (true/ false; normal value: true), and * Update of local configuration value supercedes and overwrites the ephemeral configuration (true/false; normal value: false). 7. The ephemeral overwriting toselect a insecure transport. o yang modules syntax changeslocal configuration described insection 3.4. 3.5.1. Dependencies 1. Yang data models, sub-modules, or modules must(8) above is considered to beflagged withthe composite of all ephemeraldata store flag, 2. Yang modulesvalues by all clients. Some may consider this approach as a single pane of glass for ephemeral state. 8. The ephemeral state must support notification of writeconflicts. 3. yang modules syntax changes describedconflicts using the priority requirements defined in section3.4. 4. Yang modules must support the following NETCONF/RESTCONF features: 1. The yang module library feature [I-D.ietf-netconf-yang-library], 2. Publication-Subscription model found3.7 below in[I-D.ietf-netconf-yang-push] 3. Server initiated connection to a client [I-D.ietf-netconf-call-home] 4. data models to configure RESTCONF/NETCONF servers [I-D.ietf-netconf-server-model], 3.5.2. Modified operations <get-config>, <edit-config> <copy-config>, <delete-config> <get> <close-session>, <kill-session> are altered to abide by ephemeral data store rules. 3.5.3. Unsupported operations <lock> and <unlock> are not supported for a target of ephemeral. 3.5.4. Interactions with existing capabilitiesrequirements Ephemeral-REQ-09 through Ephemeral-REQ-14). 9. Ephemeral data storesdoSHOULD not require support interactions withwritable- running,writable-running, candidate data store, confirmed commit, and a distinct start-up capability,Ephemeral data stores onlyThis list of requirements require the following the following existing features are supported: supporta "roll-back-on error" (I2RS all- or-nothing), URL capability and XPATH capability in sourcefor the following encodings: XML ortarget. 3.6. Changes to RESTCONFJSON. support forEphemeral State Ephemeral-REQ-08: The conceptual changes to RESTCONF are: othe following transports protocolversion support - "I2RS-version 1". o ephemeral model scope allowed - ephemeral modules, mixed config module (ephemeral and config), mixed derived state (ephemeral and config). o multiple message support - "all or nothing", o panesupported: "TCP", "SSH", "TLS". all ofglass support - "single ephemeral pane only". othe following NETCONF protocolsupport - RESTCONF [I-D.ietf-netconf-restconf],[RFC6241] specifications: * yangpub- subpub-sub push [I-D.ietf-netconf-yang-push], * yang module library [I-D.ietf-netconf-yang-library], * call-home [I-D.ietf-netconf-call-home], and * servermodulesmodel [I-D.ietf-netconf-server-model](serverwith the server module must be augmented to support mutualauthentication). o encoding support - XML or JSON o transports protocol supported: "SSH", "TLS", "TCP"(non-secure). o abilityauthentication (see [I-D.ietf-i2rs-protocol-security-requirements] section 3.1 in requirements: SEC-REQ-01 toselect insecure transportSEC-REQ-08). 6. RESTCONF Features forportion of data model. 3.6.1. dependenciesEphemeral State for I2RS Protocol version 1 Ephemeral-REQ-08: The conceptual changes to RESTCONF are: 1.Yang data models, sub-modules, or modules must be flagged with ephemeral data store flag, 2. Yang modules mustprotocol version supportnotification of write conflicts.for I2RS protocol modification (e.g. I2RS-version 1). 2. ephemeral model scope allowed - ephemeral modules, mixed config module (ephemeral and config), mixed derived state (ephemeral and config). 3.yang modules syntax changes described in section 3.4. 4. Yang modules mustsupport for both of the followingNETCONF/RESTCONF features: 1. the yang-patch featurestransport protocol suites: * HTTP over TLS (secure HTTP asspecifieddefined in[I-D.ietf-netconf-yang-patch]. 2. The yang module library feature [I-D.ietf-netconf-yang-library], 3. Publication-Subscription model foundRESTCONF [I-D.ietf-netconf-restconf] section 2), * HTTP used in[I-D.ietf-netconf-yang-push] 4. Server initiated connection toaclient [I-D.ietf-netconf-call-home] 5. data models to configure RESTCONF/NETCONF servers [I-D.ietf-netconf-server-model], 3.6.2. modification to contextnon-secure fashion (See [I-D.ietf-i2rs-protocol-security-requirements], section 3.2, requirements SEC-REQ-09 and SEC-REQ-11 for details), and * RESTCONFmustSHOULD be able tosupport ephemeral data with an ephemeral context that supports "edit-collision" features that include timestamp, Entity tag, andexpand the transports supported as as future I2RS protocol versions may support other transports. 4. The ability tocompare I2RS client- priorities. 3.6.3. modificationrestrict insecure transports toexisting operations The following modificationspecific portions of a data model marked as valid to transfer via an insecure protocol. 5. Support for theexisting operations are required: 1. OPTIONS - provide indicationdevelopment ofephemeral in modules, 2. HEAD - ablea RESTCONF based yang pub-sub push based on the requirements in [I-D.ietf-i2rs-pub-sub-requirements] and equivalent toget HEAD of ephemeral or config module orthehead of groups ofnetconf . [I-D.ietf-netconf-yang-push] 6. ephemeralorstate overwriting of configurationnodes in a module. 3. GET,Post,PUT, Patch, Delete, Query Parameters - muststate MUST beable to handle a context="Ephemeral". 4.controlled by the following policy knobs (as defined by [I-D.ietf-i2rs-architecture] section 6.3 and 6.3.1) * Ephemeraldatabase must support publication notifications or errors as event stream,configuration overwrites local configuration (true/ false; normal value:true), andsubscribing to portions* Update ofthat event stream. (see [I-D.ietf-netconf-yang-push] 3.7. Requirements regarding Identity, Secondary-Identity and Priority 3.7.1. Identity Requirements Ephemeral-REQ-09:Clients shall have identifierslocal configuration value supercedes andsecondary identifiers. Explanation: I2RS requires clients to have an identifier. This identifier will be used by the Agent authentication mechanism overoverwrites theappropriate protocol.ephemeral configuration (true/false; normal value:false). 7. TheSecondary identities canephemeral state overwriting a local configuration described above is considered to becarried as part of rpc or meta-data [I-D.ietf-netmod-yang-metadata]. The primary purpose ofthesecondary identity is for traceability information which logs (who modifies certain nodes). This secondary identity is an opaque value. [I-D.ietf-i2rs-traceability] provides an examplecomposite ofhow the secondary identity can be used for traceability. 3.7.2. Priority Requirements To support Multi-Headed Control, I2RS requires that there beall ephemeral state values by all clients. Some may consider this adecidable meanssingle "pane ofarbitratingglass" for thecorrectephemeral values. 8. RESTCONF support ephemeral state MUST support notification ofdata when multiple clients attempt to manipulatewrite conflicts using thesame piecepriority requirements (see section 3.7 below, specifically requirements Ephemeral-REQ-09 through Ephemeral-REQ-14). Expansion ofdata. Thisexisting "edit-collision" features (timestamp and Entity tag) to include I2RS client- priorities isdone via a priority mechanism withpreferred since I2RS client-Agents exchange MAY wish to use thehighest priority winning. This priority is per-client. Ephemeral-REQ-09: Theexisting edit-collision features in RESTCONF. 9. Ephemeral datanodes MAY store I2RS client identity andstores SHOULD notthe effective priority at the time therequire support for interactions with writeable-running, candidate datanode is stored.stores, confirmed commit, and a distinct start-up capability. This requirement also requires that RESTCONF support all of the following specifications: 1. support for the following encodings: XML or JSON. 2. all of the following curren RESTCONF specifications: 1. RESTCONF [I-D.ietf-netconf-restconf], 2. the yang-patch features as specified in [I-D.ietf-netconf-yang-patch], 3. yang module library [I-D.ietf-netconf-yang-library] as defined in RESTCONF [I-D.ietf-netconf-restconf] section 3.3.3), 4. call-home [I-D.ietf-netconf-call-home], 5. zero-touch [I-D.ietf-netconf-zerotouch], and 6. server modules [I-D.ietf-netconf-server-model] (server module must be augmented to support mutual authentication). 7. Requirements regarding Supporting Multi-Head Control via Client Priority To support Multi-Headed Control, I2RS requires that there be a decidable means of arbitrating the correct state of data when multiple clients attempt to manipulate the same piece of data. This is done via a priority mechanism with the highest priority winning. This priority is per-client. Ephemeral-REQ-09: The data nodes MAY store I2RSClient MUSTclient identity and not the effective priority at the time the data node is stored. Per SEC-REQ-07 in section 3.1 of [I-D.ietf-i2rs-protocol-security-requirements], an identifier must have just one priority. Therefore, the data nodes MAY store I2RS client identity and not the effective priority of the I2RS client ata time.the time the data node is stored. The priority MAY be dynamically changed by AAA, but the exact actions are part of the protocol definition as long as collisions are handled as described in Ephemeral-REQ-10, Ephemeral-REQ-11, and Ephemeral-REQ-12. Ephemeral-REQ-10: When a collision occurs as two clients are trying to write the same data node, this collision is considered an error and priorities were created to give a deterministic result. When there is a collision, a notification MUST BE sent to the original client to give the original client a chance to deal with the issues surrounding the collision. The original client may need to fix their state. Ephemeral-REQ-11: The requirement to support multi-headed control is required for collisions and the priority resolution of collisions. Multi-headed control is not tied to ephemeral state. I2RS is not mandating how AAA supports priority. Mechanisms which prevent collisions of two clients trying the same node of data are the focus. Ephemeral-REQ-12: If two clients have the same priority, the architecture says the first one wins. The I2RS protocol has this requirement to prevent was the oscillation between clients. If one uses the last wins scenario, you may oscillate. That was our opinion, but a design which prevents oscillation is the key point.Hints for Implementation Ephemeral configuration state nodes that are created or altered by users that match a rule carrying i2rs-priority will have those nodes annotated with meta data. Additionally, during commit processing, if nodes are found where i2rs-priority is already present, and the priority is better than the transaction's user's priority for that node, the commit should fail. An appropriate error should be returned to the user stating the nodes where the user had insufficient priority to override the state. 3.7.3.8. Multiple Message Transactions Ephemeral-REQ-13: Section 7.9 of the [I-D.ietf-i2rs-architecture] states the I2RS architecture does not include multi-message atomicity and roll-back mechanisms. I2RS notes multiple operations in one or more messages handling can handle errors within the set of operations in many ways. No multi-message commands SHOULD cause errors to be inserted into the I2RS ephemeral data-store. Explanation: I2RS suggests the following are some of the potential error handling techniques for multiple message sent to the I2RS client: 1. Perform all or none: All operations succeed or none of them will be applied. This useful when there are mutual dependencies. 2. Perform until error: Operations are applied in order, and when error occurs the processing stops. This is useful when dependencies exist between multiple-message operations, and order is important. 3. Perform all storing errors: Perform all actions storing error indications for errors. This method can be used when there are no dependencies between operations, and the client wants to sort it out. Is important to reliability of the data store that none of these error handling for multiple operations in one more multiple messages cause errors into be insert the I2RS ephemeral data-store. Discussion of Current NETCONF/RESTCONF versus RESTCONF does an atomic action within a http session, and NETCONF has atomic actions within a commit. These features may be used to perform these features. I2RS processing is dependent on the I2RS model. The I2RS model must consider the dependencies within multiple operations work withina model. 3.7.4. Subscriptions to Changed State Requirements I2RS clients require the ability to monitor changes to ephemeral state. While subscriptions are well defined for receiving notifications, the need to create a notification set for all ephemeral configuration state may be overly burdensome to the user. There is thus a need for a general subscription mechanism that can provide notification of changed state, with sufficient information to permit the client to retrieve the impacted nodes. This should be doable without requiring the notifications to be created as part of every single I2RS module. The following requirements from the [I-D.ietf-i2rs-pub-sub-requirements] apply to ephemeral state: o PubSub-REQ-1: The I2RS interface SHOULD support user subscriptions to data with the following parameters: push of data synchronously or asynchronously via registered subscriptions. o PubSub-REQ-2: Real time for notifications SHOULD be defined by the data models. o PubSub-REQ-3: Security of the pub/sub data stream SHOULD be able to be model dependent. o PubSub-REQ-4: The Pub/Sub mechanism SHOULD allow subscription to critical Node Events. Examples of critical node events are BGP peers down or ISIS protocol overload bits. o PubSub-REQ-5:I2RS telemetry data for certain protocols (E.g. BGP) will require a hierarchy of filters or XPATHs. The I2RS protocol design MUST balance security against the throughput of the telemetry data. o PubSub-REQ-6: I2RS Filters SHOULD be able to be dynamic. o PubSub-REQ-7: I2rs protocol MUST be able to allow I2RS agent to set limits on the data models it will support for pub/sub and within data models to support knobs for maximum frequency or resolution of pub/sub data. 4. Previously Considered Ideas 4.1. A Separate Ephemeral Data store The primary advantage of a fully separate data store is that the semantics of its contents are always clearly ephemeral. It also provides strong segregation of I2RS configuration and operational state from the rest of the system within the network element. The most obvious disadvantage of such a fully separate data store is that interaction with the network element's operational or configuration state becomes significantly more difficult. As an example, a BGP I2RS use case would be the dynamic instantiation of a BGP peer. While it is readily possible to re-use any defined groupings from an IETF-standardized BGP module in such an I2RS ephemeral data store's modules, one cannot currently reference state from one data store to another For example, XPath queries are done in the context document of the data store in question and thus it is impossiblea model. 9. Pub/Sub Requirements Expanded foranEphemeral State I2RSmodel to fulfil a "must" or "when" requirement inclients require theBGP module inability to monitor changes to ephemeral state. While subscriptions are well defined for receiving notifications, thestandard data stores. To implement suchneed to create amechanism would require appropriate semanticsnotification set forXPath. 4.2. Panes of Glass/Overlay I2RSall ephemeral configuration state may be overly burdensome to the user. There isgenerally expectedthus a need for a general subscription mechanism that can provide notification of changed state, with sufficient information to permit the client to retrieve the impacted nodes. This should bedisjoint from persistent configuration. In some cases, extending persistent configuration with ephemeral attributes is expecteddoable without requiring the notifications to beuseful. A case that is considered potentially useful but problematic was explored wascreated as part of every single I2RS module. The publication/subscription requirements for I2RS are in [I-D.ietf-i2rs-pub-sub-requirements], and theabilityfollowing general requirements SHOULD be understood to"overlay" persistent configuration withbe expanded to to include ephemeralconfiguration. In this overlay scenario, persistentstate: o Pub-Sub-REQ-01: The Subscription Service MUST support subscriptions against ephemeral data in operational data stores, configuration data stores or both. o Pub-Sub-REQ-02: The Subscription Service MUST support filtering so thatwas not shadowed bysubscribed updates under a target node might publish only ephemeral data in operational data or configurationcould be "read through". There were two perceived disadvantages to this mechanism: The general complexity with managing the overlay mechanism itself. Consistency issues with validation should thedata, or publish both ephemeralstate be lost, perhaps on reboot. In such a case, the previously shadowed persistent state may no longer validate. 5.and operational data. 10. IANA Considerations There are no IANA requirements for this document.6.11. Security Considerations The security requirements for the I2RS protocol are covered in [I-D.ietf-i2rs-protocol-security-requirements] document.7.The security requirements for the I2RS protocol environment are in [I-D.ietf-i2rs-security-environment-reqs]. 12. Acknowledgements This document is an attempt to distill lengthy conversations on the I2RS mailing list for an architecture that was for a long period of time a moving target. Some individuals in particular warrant specific mention for their extensive help in providing the basis for this document: o Alia Atlas o Andy Bierman o Martin Bjorklund o Dean Bogdanavich o Rex Fernando o Joel Halpern o Thomas Nadeau o Juergen Schoenwaelder o Kent Watsen8.13. References8.1.13.1. Normative References: [I-D.ietf-i2rs-architecture] Atlas, A., Halpern, J., Hares, S., Ward, D., and T. Nadeau, "An Architecture for the Interface to the Routing System", draft-ietf-i2rs-architecture-15 (work in progress), April 2016. [I-D.ietf-i2rs-protocol-security-requirements] Hares, S., Migault, D., and J. Halpern, "I2RS Security Related Requirements", draft-ietf-i2rs-protocol-security-requirements-03requirements-06 (work in progress),MarchMay 2016. [I-D.ietf-i2rs-pub-sub-requirements] Voit, E., Clemm, A., and A. Prieto, "Requirements for Subscription to YANG Datastores", draft-ietf-i2rs-pub-sub-requirements-07requirements-09 (work in progress), May 2016. [I-D.ietf-i2rs-security-environment-reqs] Migault, D., Halpern, J., and S. Hares, "I2RS Environment Security Requirements", draft-ietf-i2rs-security- environment-reqs-01 (work in progress), April 2016. [I-D.ietf-i2rs-traceability] Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to the Routing System (I2RS) Traceability: Framework and Information Model",draft-ietf-i2rs-traceability-09draft-ietf-i2rs-traceability-11 (work in progress), May 2016. [I-D.ietf-netconf-call-home] Watsen, K., "NETCONF Call Home and RESTCONF Call Home", draft-ietf-netconf-call-home-17 (work in progress), December 2015. [I-D.ietf-netconf-restconf] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", draft-ietf-netconf-restconf-13 (work in progress), April 2016. [I-D.ietf-netconf-server-model] Watsen, K. and J. Schoenwaelder, "NETCONF Server and RESTCONF Server Configuration Models", draft-ietf-netconf- server-model-09 (work in progress), March 2016. [I-D.ietf-netconf-yang-library] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module Library", draft-ietf-netconf-yang-library-06 (work in progress), April 2016. [I-D.ietf-netconf-yang-patch] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch Media Type", draft-ietf-netconf-yang-patch-08 (work in progress), March 2016. [I-D.ietf-netconf-yang-push] Clemm, A., Prieto, A., Voit, E., Tripathy, A., and E. Einar, "Subscribing to YANG datastore push updates", draft-ietf-netconf-yang-push-02 (work in progress), March 2016. [I-D.ietf-netconf-zerotouch] Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning for NETCONF or RESTCONF based Management", draft-ietf- netconf-zerotouch-08 (work in progress), April 2016. [I-D.ietf-netmod-yang-metadata] Lhotka, L., "Defining and Using Metadata with YANG", draft-ietf-netmod-yang-metadata-07 (work in progress), March 2016. [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <http://www.rfc-editor.org/info/rfc6241>.8.2.13.2. Informative References [I-D.hares-i2rs-protocol-strawman] Hares, S., Bierman, A., and a. amit.dass@ericsson.com, "I2RS protocol strawman", draft-hares-i2rs-protocol- strawman-02 (work in progress), May 2016. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, <http://www.rfc-editor.org/info/rfc6020>. [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, <http://www.rfc-editor.org/info/rfc6536>. Authors' Addresses Jeff Haas Juniper Email: jhaas@juniper.net Susan Hares Huawei Saline US Email: shares@ndzh.com