]> Juniper Networks

kwatsen@juniper.net

Yumaworks

andy@yumaworks.com

Tail-f Systems

mbj@tail-f.com

Jacobs University Bremen

j.schoenwaelder@jacobs-university.de

Operations NETMOD Working Group This document presents enhancements to YANG, NETCONF, and RESTCONF satisfying the requirements set forth in Terminology and Requirements for Enhanced Handling of Operational State.

This document presents enhancements to YANG , NETCONF , and RESTCONF satisfying the requirements set forth in Terminology and Requirements for Enhanced Handling of Operational State . A traceability matrix illustrating how each requirement is satisfied is provided in .

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 . The following terms are defined in : client datastore server The following terms are defined in : applied configuration asynchronous configuration operation derived state intended configuration operational state synchronous configuration operation

The following diagram illustrates the conceptual model presented in this document:

Key aspects illustrated in the above diagram include: The horizontal line partitions what is defined by config true and config false nodes. Above the line are data models defined by config true nodes and below the line are data models defined by config false nodes. Notably, it illustrates that the same config true nodes define the data model for both the intended configuration and the applied configuration, consistent with requirement 1-C in . The vertical line partitions the types of data models in a server. Left of the line is data that represents the intended state of the server and right of the line data that represents the operational state of the server. Notably, the intended state of the server consists only of config true nodes, whereas the operational state consists of both config true and config false nodes. This diagram illustrates that operational state is composed of both applied config and derived state, consistent with its terminology definition in .

To support the opstate requirements, one modification to YANG is necessary. This modification can be introduced as a YANG extension, as described next.

The "related-state" statement designates where related derived state nodes for a config true node can be found. This association is not needed for any descendant config false nodes, as they are already implicitly associated to the parent config true node. The "related-state" statement takes as an argument a string that is used to specify the path to a config false node holding the associated operational state. The format of the argument is the same as for the leafref's "path" statement, Section 9.9.2 in .

The following example illustrates the related-state statement in use:

Note: there is no tree diagram for this YANG module since it does not contain any protocol accessible nodes.

file "ietf-yang-related-state@2016-02-02.yang" module ietf-yang-related-state { namespace urn:ietf:params:xml:ns:yang:ietf-yang-related-state; prefix yrs; organization "IETF NETMOD (NETCONF Data Modeling Language) Working Group"; contact "WG Web: WG List: WG Chair: Tom Nadeau WG Chair: Kent Watsen WG Chair: Juergen Schoenwaelder "; description "This YANG module defines the YANG statement 'related-state'."; revision 2016-02-02 { description "Initial revision"; reference "RFC XXXXX: Terminology and Requirements for Enhanced Handling of Operational State"; } extension related-state { argument path; description "The related-state statement is used to identify a node that contains additional operational state associated for a config true node. The format of the argument is the same as for a leafref's 'path' statement. The related-state statement can be specified in the following YANG statements: o leaf o leaf-list o container o list The related-state statement allows the following YANG substatements: o description Multiple related-state statements can be given in a specific node."; } } ]]>

The following sections describe enhancements to NETCONF provided by the "ietf-netconf-opstate" YANG module.

The "ietf-netconf-opstate" YANG module enables NETCONF clients to access the contents of the applied configuration datastore by passing the value 'applied' for the <source> parameter in the <get-config> and <copy-config> operations.

To retrieve the "/interfaces" subtree from the applied configuration datastore:

]]>

The "ietf-netconf-opstate" YANG module enables NETCONF clients to control if operations that effect the intended configuration are executed synchronously or asynchronously. The operations that support this ability include: <edit-config> // only when target is "running" <copy-config> // only when target is "running" <commit> In order to control how an operation is executed, clients must pass the <sync-behavior> parameter with a value 'sync' or 'async', for synchronous or asynchronous execution respectively. When synchronous execution is requested (i.e., 'sync' is passed), the <rpc-reply> will not return until the server has fully attempted to update both the intended and applied configurations. When no errors or warnings are generated, the <rpc-reply> will only contain <ok>. When only warnings are generated, the <rpc-reply> will contain <ok> and also the <apply-warnings> flag. If any errors are generated, the <rpc-reply> will contain the standard <rpc-error>. When asynchronous execution is requested (i.e., 'async' is passed), the <rpc-reply> will return immediately, and contain an additional <sync-id> value that clients can use to correlate a subsequent 'sync-complete' notification () to determine when the asynchronous request has completed and with what result. For either synchronous or asynchronous requests, any processing semantics associated with the operation are preserved and extended to also include applying the configuration to internal server components. Notably are the <edit-config> operation's <error-option > parameter and the <commit> operation's atomic update semantic. Any rollback that may occur will restore both the intended and the applied configurations to their previous states. In order to implement the rollback behavior, for <edit-config> or <commit>, it is necessary for the server to maintain a global lock until the processing is complete. That is, either a 'sync' request returns or an 'async' request's 'sync-complete' notification has been sent. Any attempts to read or write either intended or applied configuration will be blocked until the request completes.

To edit the "/interfaces" subtree from the applied configuration datastore:

async Ethernet0/0 1500 4123 ]]>

The "ietf-netconf-opstate" YANG module enables NETCONF clients to request a server to return the difference between datastores (running, startup, candidate, and applied). The <get-diff> RPC takes two 'source' parameters as input and, based on the value of the 'format' paramter, returns either an <edit-config> document (Section 7.2 in ) or a YANG-patch document (), that transforms the first datastore into the second datastore.

This example assumes a YANG module has a data model like:

With a value in the candidate datastore of 'us-east-dc-fw-1' and value in the running datastore 'us-eass-dc-fw-1' (notice the typo):

yang-patch candidate running 202 edit1 replace /example-module:system/hostname us-east-dc-fw-1 ]]>

The "ietf-netconf-opstate" YANG module enables NETCONF clients to request a server to return operational state data. This RPC is similar to the <get-config> RPC (Section 7.1 in ), but for operational state instead of configuration. The <get-state> RPC takes two optional parameters. The first parameter is a choice between the values <applied/> and <derived/>, which selects if only these types of nodes should be returned. The second parameter is a filter just like the one used by the <get-config> RPC, including the optional support for XPath expressions.

The following example depicts a request that returns all the derived state (i.e. config false) nodes under the "users" subtree.

]]>

The

The following example depicts a notification for a that returns all the derived state (i.e. config false) nodes under the "users" subtree.

2007-07-08T00:02:00Z 4123 ]]>

The tree diagram for the "ietf-netconf-opstate" YANG module:

The "ietf-netconf-opstate" YANG module:

file "ietf-netconf-opstate@2016-02-02.yang" module ietf-netconf-opstate { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-opstate"; prefix ncos; import ietf-netconf { // RFC 6241 prefix nc; } import ietf-yang-patch { // RFC YYYY prefix yp; } organization "IETF NETMOD (NETCONF Data Modeling Language) Working Group"; contact "WG Web: WG List: WG Chair: Tom Nadeau WG Chair: Kent Watsen WG Chair: Juergen Schoenwaelder "; description "This YANG module does the following: - enables get-config and copy-config to access applied datastore - enables edit-config, copy-config, and commit to be executed either synchronously or asynchronously - defines 'get-diff' operation to diff datastores - defines 'get-state' operation to return just state data - defines 'sync-complete' notification for async requests"; revision 2016-02-02 { description "Initial revision"; reference "RFC XXXXX: Terminology and Requirements for Enhanced Handling of Operational State"; } // features feature sync { description "Indicates the server supports the 'sync' value for the parameter in the operations , , and ."; } feature async { description "Indicates the server supports the 'async' value for the parameter in the operations , , and ."; } // The following two augmentations enable 'applied' to be passed as a // argument in the and operations. augment /nc:get-config/nc:input/nc:source/nc:config-source { description "Allows 'applied' to be passed in "; leaf applied { type empty; description "Indicates that the applied configuration should be returned"; } } augment /nc:copy-config/nc:input/nc:source/nc:config-source { description "Allows 'applied' to be passed in "; leaf applied { type empty; description "Indicates that the applied configuration should be returned"; } } // The following two groupings define input and output parameters that // are subsequently augmented into the edit-config, copy-config, and // commit operations. grouping sync-behavior-input { description "This grouping is augmented into the edit-config, copy-config, and commit operations"; leaf sync-behavior { type enumeration { enum "sync" { if-feature sync; description "Request the server to not return a response until both the intended and applied configurations have been updated."; } enum "async" { if-feature async; description "Request the server to not wait for the configuration to be applied before returning a response. The response will contain the 'sync-id' leaf. Later, after both the intended and applied configurations have been updated, the server will send the 'sync-complete' notification using the same sync-id value."; } } description "This value specifies whether the server should process the request synchronously or asynchronously."; } } grouping sync-behavior-output { description "This grouping is augmented into the edit-config, copy-config, and commit operations. The additional output is only returned when 'sync-behavior' is specified, and thus does not alter legacy behavior."; choice request-type { description "This choice makes it explicit which content is possibly returned for the two 'sync-behavior' values."; case sync { leaf apply-warning { type empty; description "Indicates that a warning was generated when applying the intended configuration to internal server components (e.g., due to missing hardware) and hence the applied configuration differs from the intended configuration."; } } case async { leaf sync-id { type string; description "A server-specified value to identify the asynchronous request. This value is returned whenever 'async' is passed in the request. The server must ensure that it is a unique value over some reasonable amount of time."; } } } } // The following six augmentations are used to insert the // sync-behavior-input and sync-behavior-output nodes into // the edit-config, copy-config, and commit operations. augment /nc:edit-config/nc:input { description "Allows 'sync-behavior' to be passed in . When specified, the 'error-option' value is interpreted as spanning both the updating of the intended and applied configurations. Notably, when rollback-on-error is set, both the intended and applied configurations are restored to their initial states on error."; uses sync-behavior-input { when "nc:target/nc:running" { description "only available when target is 'running'"; } } } augment /nc:edit-config/nc:output { description "Allows 'apply-warning' and 'sync-id' to be returned for operations."; uses sync-behavior-output; } augment /nc:copy-config/nc:input { description "Allows 'sync-behavior' to be passed in "; uses sync-behavior-input { when "nc:target/nc:running" { description "only available when target is 'running'"; } } } augment /nc:copy-config/nc:output { description "Allows 'apply-warning' and 'sync-id' to be returned for operations."; uses sync-behavior-output; } augment /nc:commit/nc:input { description "Allows 'sync-behavior' to be passed in the operation. The operation's atomic behavior is extended to include both the updating of the intended and applied configurations."; uses sync-behavior-input; } augment /nc:commit/nc:output { description "Allows 'apply-warning' and 'sync-id' to be returned for operations."; uses sync-behavior-output; } // The following grouping is used by the get-diff RPC grouping get-diff-source { description "This grouping is used by the 'get-diff' RPC's two input parameters."; choice config-source { mandatory true; description "The configuration datastore to use as a source."; leaf candidate { if-feature nc:candidate; type empty; description "The candidate configuration is the config source."; } leaf running { type empty; description "The running configuration is the config source."; } leaf startup { if-feature nc:startup; type empty; description "The startup configuration is the config source."; } leaf applied { type empty; description "The applied configuration is the config source."; } } } // The following RPC returns the diff between two datastores rpc get-diff { description "Get the difference between two datastores in the form of a YANG Patch (see RFC YYYY) that transforms 'source1' into 'source2'. Specifying the same datastore for both sources always returns an empty diff."; input { leaf format { type enumeration { enum edit-config { description ""; } enum yang-patch { description ""; } } description "Selects output format"; } container source1 { description "the first of two datastores to compare"; uses get-diff-source; } container source2 { description "the second of two datastores to compare"; uses get-diff-source; } } output { choice format { case edit-config { anyxml data {description "";} } case yang-patch { uses yp:yang-patch; } description ""; } } } // The following RPC returns just operational state nodes from // the server. rpc get-state { description "Retrieve operational state from the server. Operational state is composed of both applied configuration and derived state. Applied configuration is the subset of config true nodes that is operational. Derived state is composed of just the config false nodes."; reference "RFC 6241, Section 7.7"; input { choice type { description "An optional parameter to select if only applied configuration or derived state nodes should be returned. If not specified, then all node types are returned."; leaf applied { type empty; description "Only return matching applied configuration nodes"; } leaf derived { type empty; description "Only return matching derived state nodes"; } } anyxml filter { mandatory true; description "This parameter specifies the portion of the applied configuration and derived state data to retrieve. "; nc:get-filter-element-attributes; } } output { anyxml data { description "Copy of the running datastore subset and/or state data that matched the filter criteria (if any). An empty data container indicates that the request did not produce any results."; } } } // This following notification is used to alert clients when // an asynchronous operation request has completed. notification sync-complete { description "Sent by the server when an asynchronous operation request has completed."; leaf sync-id { type string; mandatory true; description "The server-specified unique identifier returned to the client that requested the asynchronous operation."; } choice response { mandatory true; leaf ok { type empty; description "Indicates that the request processed successfully."; } leaf apply-warning { type empty; description "Indicates that a warning was generated when applying the intended configuration to internal server components (e.g., due to missing hardware) and hence the applied configuration differs from the intended configuration."; } container rpc-error { leaf error-type { type enumeration { enum transport { description "transport"; } enum rpc { description "rpc"; } enum protocol { description "protocol"; } enum application { description "application"; } } mandatory true; description "error-type"; } leaf error-tag { type nc:error-tag-type; mandatory true; description "error-tag"; } leaf error-severity { type nc:error-severity-type; mandatory true; description "error-severity"; } leaf error-app-tag { type string; description "error-app-tag"; } leaf error-path { type string; description "error-path"; } leaf error-message { type string; description "error-message"; } container error-info { leaf session-id { type uint32; description "session-id"; } leaf bad-attribute { type string; description "bad-attribute"; } leaf bad-element { type string; description "bad-element"; } leaf ok-element { type string; description "ok-element"; } leaf err-element { type string; description "err-element"; } leaf noop-element { type string; description "noop-element"; } leaf bad-namespace { type string; description "bad-namespace"; } description "error-info"; } description "rpc-error"; } description "response"; } } } ]]>

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&rfc2119; &rfc6241; &rfc6020; YumaWorks Tail-f Systems Juniper Networks YumaWorks Tail-f Systems Juniper Networks

This section explains how the requirements specified in are satisfied by the solution presented in this document. The following outline mimics the outline in the requirements draft: Ability to interact with both intended and applied configuration A NETCONF client can ask the operational components of a server (e.g., line cards) for the configuration that they are currently using either by using the <get-config> RPC with the <source> value "applied", or by using the <get-state> RPC with the <applied> parameter. A NETCONF client is only able to read applied configuration. Neither the <get-config> nor <get-state> RPCs enable modification and no other RPC targets the applied datastore directly. The data model for the intended and applied configurations are identical. A fundamental aspect of the solution defined in this document is that config true nodes simultaneously define both Ensuring that the applied configuration values match the intended configuration values is the responsibility of an implementation more so than the solution presented in this document. Support for both synchronous and asynchronous configuration operations (see terms) A server may only support synchronous configuration operations by only advertising the 'sync' feature. A server may only support asynchronous configuration operations by only advertising the 'async' feature. A server may support both synchronous and asynchronous configuration operations by advertising both the 'sync' and 'async' features. A NETCONF client may select on a per-operation basis if a request should be processed synchronously and asynchronously using the <sync-behavior> parameter. NETCONF clients can use the <get-diff> RPC to determine the difference between the intended and applied configurations. This solution handles errors by extending existing semantics for the <edit-config>, <get-config>, and <commit> operations to include also the application of the configuration to the operational components of the system. For synchronous operations, errors or warnings are returned in the <rpc-reply>, whereas for asynchronous operations, errors or warnings are returned in the <sync-complete> notification. This solution supports the rollback-on-error semantics in <edit-config> (for servers that support the :rollback capability) and in <commit> (for servers that support the :candidate capability). Separation of the applied configuration and derived state aspects of operational state; ability to retrieve them independently and together A NETCONF client can retrieve only the applied configuration of operational state either by using the "applied" source target in the <get-config> operation or by using the 'applied' argument in the <get-state> operation. A NETCONF client can retrieve only the derived state aspects of operational state by using the 'derived' argument in the <get-state> operation. A NETCONF client may retrieve both the applied configuration and derived state aspects of operational state together by not passing either the 'applied' or 'derived' arguments in the <get-state> operation. Ability to relate configuration with its corresponding operational state Mapping intended config nodes to corresponding applied config nodes is automatic, as the same paths are used to access the same nodes in both trees. The ability to relate intended config nodes to associated derived state nodes is provided by the "related-state" YANG statement (). The "related-state" statement is programmatically consumable, being defined using a YANG statement. Backwards compatibility NETCONF and RESTCONF servers can be upgraded to one that supports this solution without breaking backwards compatibility as all the changes made to NETCONF and RESTCONF require a client to explicitly opt into it, by passing some new input parameter in the requests that it may send to a server. NETCONF and RESTCONF clients coded to support this solution can differentiate servers that support opstate from those that don't, by examining if the servers support the ietf-netconf-opstate or ietf-restconf-opstate modules.