]> List Pagination for YANG-driven Protocols Watsen Networks
kent+ietf@watsen.net
Huawei Technologies
bill.wu@huawei.com
Ionio Systems
per.ietf@ionio.se
SUNET
olof@hagsand.se
Hewlett Packard Enterprise
flycoolman@gmail.com
OPS Area NETCONF Working Group In some circumstances, instances of YANG modeled "list" and "leaf-list" nodes may contain numerous entries. Retrieval of all the entries can lead to inefficiencies in the server, the client, and the network in between. This document defines a model for list pagination that can be implemented by YANG-driven management protocols such as NETCONF and RESTCONF. The model supports paging over optionally filtered and/or sorted entries. The solution additionally enables servers to constrain query expressions on some "config false" lists or leaf-lists.
Introduction YANG modeled "list" and "leaf-list" nodes may contain a large number of entries. For instance, there may be thousands of entries in the configuration for network interfaces or access control lists. And time-driven logging mechanisms, such as an audit log or a traffic log, can contain millions of entries. Retrieval of all the entries can lead to inefficiencies (e.g., long loading time, memory overconsuming, or crash) in the server, the client, and the network in between. For instance, consider the following:
  • A client may need to filter and/or sort list entries in order to, e.g., present the view requested by a user.
  • A server may need to iterate over many more list entries than needed by a client.
  • A network may need to convey more data than needed by a client.
Optimal global resource utilization is obtained when clients are able to cherry-pick just that which is needed to support the application-level business logic. This document defines a generic model for list pagination that can be implemented by YANG-driven management protocols such as NETCONF and RESTCONF . How the NETCONF and RESTCONF protocols support list pagination or protocols mapping is described in and , respectively. The model presented in this document supports paging over optionally filtered and/or sorted entries. Server-side filtering and sorting is ideal as servers can leverage indexes maintained by a backend storage layer to accelerate queries.
Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. The following terms are defined in and are not redefined here: client, data model, data tree, feature, extension, module, leaf, leaf-list, and server.
Conventions Various examples in this document use "BASE64VALUE=" as a placeholder value for binary data that has been base64 encoded (per ). This placeholder value is used because real base64 encoded structures are often many lines long and hence distracting to the example being presented.
Adherence to the NMDA This document is compliant with the Network Management Datastore Architecture (NMDA) . The "ietf-list-pagination" module only defines a YANG extension and augments a couple leafs into a "config false" node defined by the "ietf-system-capabilities" module.
Solution Overview The solution presented in this document broadly entails a client sending a query to a server targeting a specific list or leaf-list including optional parameters guiding which entries should be returned. Furthermore the solution is intended to leverage underlying database system capabilities, e.g. fast lookups relying on indexes, using efficient built-in selection and pagination functions. However, since there are many different database systems and configurations, the solution defines a common subset of functionality broadly available. It is also possible that a datastore's underlying database system is federated, i.e. consists of several different database systems to provide one datastore. In order to form a general solution, the possibility to configure and tune what components are available is presented. A secondary aspect of this solution entails a client sending a query parameter to a server guiding how descendent lists and leaf-lists should be returned. This parameter may be used on any target node, not just "list" and "leaf-list" nodes. Clients detect a server's support for list pagination via an entry for the "ietf-list-pagination" module (defined in ) in the server's YANG Library response. Relying on client-provided query parameters ensures servers remain backward compatible with legacy clients.
Solution Details This section is composed of the following subsections:
  • defines five query parameters clients may use to page through the entries of a single list or leaf-list in a data tree.
  • defines one query parameter that clients may use to affect the content returned for descendent lists and leaf-lists.
  • defines per schema-node tags enabling servers to indicate which "config false" lists are constrained and how they may be interacted with.
Query Parameters for a Targeted List or Leaf-List The five query parameters presented in this section are listed in processing order. This processing order is logical, efficient, and matches the processing order implemented by database systems, such as SQL. The order is as follows: a server first processes the "where" parameter (see ), then the "sort-by" parameter (see ), then a combination of the "direction" parameter (see ), with either the "offset" parameter (see ) or the "cursor" parameter (see ), and lastly the "limit" parameter (see ). The sorting can furthermore be configured with a locale for sorting. This is done by setting the "locale" parameter (see ). The feature "sort" is used to indicate support for the query parameters "locale" and "sort-by".
The "where" Query Parameter
Description
The "where" query parameter specifies a filter expression that result-set entries must match.
Default Value
If this query parameter is unspecified, then no entries are filtered from the working result-set.
Allowed Values
The allowed values are XPath 1.0 expressions. The XPath context follows e.g., the context node is the target of the query, the accessible tree is "config true" lists and leaf-lists or "config false" lists and leaf-lists. Details (such as prefix bindings) are further defined at the protocol level, see and . If an XPath expression references a node identifier that does not exist in the schema, or is optional or conditional in the schema, the filter evaluates to false and nothing is filtered from the result-set. It is an error if the XPath expression for constrained "config false" lists and leaf-lists (see ), if the node identifier does not point to a node having the "indexed" extension statement applied to it (see ).
Conformance
The "where" query parameter MUST be supported for all "config true" lists and leaf-lists and SHOULD be supported for "config false" lists and leaf-lists. The supplied expression is allowed to be of arbitrary complexity. Servers MAY disable the support for some or all "config false" lists and leaf-lists as described in .
The "sort-by" Query Parameter
Description
The "sort-by" query parameter indicates the node in the working result-set (i.e., after the "where" parameter has been applied) that entries should be sorted by. Sorts are in ascending order (e.g., '1' before '9', 'a' before 'z', etc.). Missing values are sorted to the end (e.g., after all nodes having values). Sub-sorts are not supported.
Default Value
If this query parameter is unspecified, then the list or leaf-list's default order is used, per the YANG "ordered-by" statement (see ).
Allowed Values
The allowed values are node identifiers. Clients are allowed to request sorting by any data node within the result-set. It is an error if the specified node identifier does not exist in the schema, is optional or conditional in the schema or, for constrained "config false" lists and leaf-lists (see ), if the node identifier does not point to a node having the "indexed" extension statement applied to it (see ).
Conformance
The "sort-by" query parameter MUST be supported for all "config true" lists and leaf-lists and SHOULD be supported for "config false" lists and leaf-lists. Servers MAY disable the support for some or all "config false" lists and leaf-lists as described in .
The "locale" Query Parameter
Description
The "locale" query parameter indicates what locale is used when sorting the result-set. Note that the "locale" query parameter is invalid to supply without also supplying the "sort-by" query parameter. If a query supplies "locale" and not "sort-by", error-type application and error-tag "invalid-value" is returned.
Default Value
If this query parameter is unspecified, it is up to the server to select a locale for sorts. How the server chooses the locale used is out of scope for this document. The result-set includes the locale used by the server for sorts with a metadata value called "locale".
Allowed Values
The format is a free form string but SHOULD follow the language sub-tag format defined in . An example is 'sv_SE'. If a supplied locale is unknown to the server, the "locale-unavailable" SHOULD be produced in the error-app-tag in the error output. Note that all locales are assumed to be UTF-8, since character encoding for YANG strings and all known YANG modelled encodings and protocols are required to be UTF-8 . A server MUST accept a known encoding with or without trailing ".UTF-8" and MAY emit an encoding with or without trailing ".UTF-8". This means a server must handle both e.g. "sv_SE" and "sv_SE.UTF-8" equally as input, and chooses how to emit used locale as output.
Conformance
The "locale" query parameter MUST be supported for all "config true" lists and leaf-lists and SHOULD be supported for "config false" lists and leaf-lists. Servers MAY disable the support for some or all "config false" lists and leaf-lists as described in .
The "direction" Query Parameter
Description
The "direction" query parameter indicates how the entries in the working result-set (i.e., after the "sort-by" parameter has been applied) should be traversed.
Default Value
If this query parameter is unspecified, the default value is "forwards".
Allowed Values
The allowed values are:
forwards
Return entries in the forwards direction. Also known as the "default" or "ascending" direction.
backwards
Return entries in the backwards direction. Also known as the "reverse" or "descending" direction
Conformance
The "direction" query parameter MUST be supported for all lists and leaf-lists.
The "offset" Query Parameter
Description
The "offset" query parameter indicates the number of entries in the working result-set (i.e., after the "direction" parameter has been applied) that should be skipped over when preparing the response. The "offset" query parameter MUST not be used together with "cursor" query parameter
Default Value
If this query parameter is unspecified, then no entries in the result-set are skipped, the same as when the offset value '0' is specified.
Allowed Values
The allowed values are unsigned integers. It is an error for the offset value to exceed the number of entries in the working result-set, and the "offset-out-of-range" identity SHOULD be produced in the error-app-tag in the error output when this occurs.
Conformance
The "offset" query parameter MUST be supported for all lists and leaf-lists.
The "cursor" Query Parameter
Description
The "cursor" query parameter indicates where to start the working result-set (i.e., after the "direction" parameter has been applied), the elements before the cursor are skipped over when preparing the response. Furthermore, a result set constrained with the "limit" query parameter includes metadata values called "next" and "previous", which contains cursor values to the next and previous result-sets. These next and previous cursor values are opaque index values for the underlying system's database, e.g. a key or other information needed to efficiently access the selected result-set. These "next" and "previous" metadata values work as Hypermedia as the Engine of Application State (HATEOAS) links . This means that the server does not keep any stateful information about the "next" and "previous" cursor or the current page. Due to their ephemeral nature, cursor values are never cached.
Default Value
If this query parameter is unspecified, then no entries in the result-set are skipped.
Allowed Values
The allowed values are opaque encoded positions interpreted by the server to index an element in the list, e.g. a list key or other information to efficiently access the selected result-set. It is an error to supply an unknown cursor value for the working result-set, and the "cursor-not-found" identity SHOULD be produced in the error-app-tag in the error output when this occurs.
Conformance
The "cursor" query parameter MUST be supported for all "config true" lists and SHOULD be supported for all "config false" lists. As the "cursor" query parameter support for "config false" lists is optional, the support MUST be signaled by the server per list. Servers indicate that they support the "cursor" query parameter for a "config false" list node by having the "cursor-supported" extension statement applied to it in the "per-node-capabilities" node in the "ietf-system-capabilities" model, and set to "true". Since leaf-lists might not have any unique values that can be indexed, the "cursor" query parameter is not relevant for leaf-lists. Consider the following leaf-list [1,1,2,3,5], which contains elements without uniquely indexable values. It would be possible to use the position, but then the solution would be equal to using the "offset" query parameter.
The "limit" Query Parameter
Description
The "limit" query parameter limits the number of entries returned from the working result-set (i.e., after the "offset" parameter has been applied). Any list or leaf-list that is limited includes, somewhere in its encoding, a metadata value called "remaining", a positive integer indicating the number of elements that were not included in the result-set by the "limit" operation, or the value "unknown" in case, e.g., the server determines that counting would be prohibitively expensive. If the string "unbounded" is supplied, there is no limit imposed on the result-set.
Default Value
If this query parameter is unspecified, the number of entries that may be returned is unbounded.
Allowed Values
The allowed values are unsigned 32 bit integers greater than or equal to 1, or the string "unbounded".
Conformance
The "limit" query parameter MUST be supported for all lists and leaf-lists.
Query Parameter for Descendant Lists and Leaf-Lists Whilst this document primarily regards pagination for a list or leaf-list, it begs the question for how descendent lists and leaf-lists should be handled, which is addressed by the "sublist-limit" query parameter described in this section.
The "sublist-limit" Query Parameter
Description
The "sublist-limit" parameter limits the number of entries returned for descendent lists and leaf-lists. Any descendent list or leaf-list limited by the "sublist-limit" parameter includes, somewhere in its encoding, a metadata value called "remaining", a positive integer indicating the number of elements that were not included by the "sublist-limit" parameter, or the value "unknown" in case, e.g., the server determines that counting would be prohibitively expensive. When used on a list node, it only affects the list's descendent nodes, not the list itself, which is only affected by the parameters presented in .
Default Value
If this query parameter is unspecified, the number of entries that may be returned for descendent lists and leaf-lists is unbounded.
Allowed Values
The allowed values are positive integers.
Conformance
The "sublist-limit" query parameter MUST be supported for all conventional nodes, including a datastore's top-level node (i.e., '/').
Constraints on "where" and "sort-by" for "config false" Lists Some "config false" lists and leaf-lists may contain an enormous number of entries. For instance, a time-driven logging mechanism, such as an audit log or a traffic log, can contain millions of entries. In such cases, "where" and "sort-by" expressions will not perform well if the server must bring each entry into memory in order to process it. The server's best option is to leverage query-optimizing features (e.g., indexes) built into the backend database holding the dataset. However, translating arbitrary "where" expressions and "sort-by" node identifiers into syntax supported by the backend database and/or query-optimizers may prove challenging, if not impossible, to implement. Thusly this section introduces mechanisms whereby a server can:
  1. Identify which "config false" lists and leaf-lists are constrained.
  2. Identify what node-identifiers and expressions are allowed for the constrained lists and leaf-lists.
Identifying Constrained "config false" Lists and Leaf-Lists Identification of which lists and leaf-lists are constrained occurs in the schema tree, not the data tree. However, as server abilities vary, it is not possible to define constraints in YANG modules defining generic data models. In order to enable servers to identify which lists and leaf-lists are constrained, the solution presented in this document augments the data model defined by the "ietf-system-capabilities" module presented in . Specifically, the "ietf-list-pagination" module (see ) augments a boolean leaf node called "constrained" into the "per-node-capabilities" node defined in the "ietf-system-capabilities" module. The "constrained" leaf MAY be specified for any "config false" list or leaf-list. When a list or leaf-list is constrained:
  • All parts of XPath 1.0 expressions are disabled unless explicitly enabled by .
  • Node-identifiers used in "where" expressions and "sort-by" filters MUST have the "indexed" leaf applied to it (see ).
  • For lists only, node-identifiers used in "where" expressions and "sort-by" filters MUST NOT descend past any descendent lists. This ensures that only indexes relative to the targeted list are used. Further constraints on node identifiers MAY be applied in .
Indicating the Constraints for "where" Filters and "sort-by" Expressions This section identifies how constraints for "where" filters and "sort-by" expressions are specified. These constraints are valid only if the "constrained" leaf described in the previous section has been set on the immediate ancestor "list" node or, for "leaf-list" nodes, on itself.
Indicating Filterable/Sortable Nodes For "where" filters, an unconstrained XPath expressions may use any node in comparisons. However, efficient mappings to backend databases may support only a subset of the nodes. Similarly, for "sort-by" expressions, efficient sorts may only support a subset of the nodes. In order to enable servers to identify which nodes may be used in comparisons (for both "where" and "sort-by" expressions), the "ietf-list-pagination" module (see ) augments a boolean leaf node called "indexed" into the "per-node-capabilities" node defined in the "ietf-system-capabilities" module (see ). When a "list" or "leaf-list" node has the "constrained" leaf, only nodes having the "indexed" node may be used in "where" and/or "sort-by" expressions. If no nodes have the "indexed" leaf, when the "constrained" leaf is present, then "where" and "sort-by" expressions are disabled for that list or leaf-list.
The "ietf-list-pagination" Module The "ietf-list-pagination" module is used by servers to indicate that they support pagination on YANG "list" and "leaf-list" nodes, and to provide an ability to indicate which "config false" list and/or "leaf-list" nodes are constrained and, if so, which nodes may be used in "where" and "sort-by" expressions.
Data Model Overview The following tree diagram illustrates the "ietf-list-pagination" module: Comments:
  • As shown, this module augments three optional leafs into the "per-node-capabilities" node of the "ietf-system-capabilities" module.
  • Not shown is that the module also defines an "md:annotation" statement named "remaining". This annotation may be present in a server's response to a client request containing either the "limit" () or "sublist-limit" parameters ().
Example Usage
Constraining a "config false" list The following example illustrates the "ietf-list-pagination" module's augmentations of the "system-capabilities" data tree. This example assumes the "example-social" module defined in the is implemented. ds:operational /es:audit-logs/es:audit-log true /es:audit-logs/es:audit-log/es:timestamp true /es:audit-logs/es:audit-log/es:member-id true /es:audit-logs/es:audit-log/es:outcome true ]]>
YANG Module This YANG module has normative references to and . <CODE BEGINS> file "ietf-list-pagination@2026-04-02.yang" WG List: Author: Kent Watsen Author: Qin Wu Author: Per Andersson Author: Olof Hagsand Author: Hongwei Li "; description "This module is used by servers to 1) indicate they support pagination on 'list' and 'leaf-list' resources, 2) define a grouping for each list-pagination parameter, and 3) indicate which 'config false' lists have constrained 'where' and 'sort-by' parameters and how they may be used, if at all. Copyright (c) 2026 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2026-04-02 { description "Initial revision."; reference "RFC XXXX: List Pagination for YANG-driven Protocols"; } // Features feature sort { description 'This feature indicates that the parameters "locale" and "sort-by" are supported.'; } // Annotations md:annotation remaining { type union { type uint32; type enumeration { enum "unknown" { description "Indicates that the number of remaining entries is unknown to the server in case, e.g., the server has determined that counting would be prohibitively expensive."; } } } description "This annotation contains the number of elements not included in the result set (a positive value) due to a 'limit' or 'sublist-limit' operation. If no elements were removed, this annotation MUST NOT appear. The minimum value (0), which never occurs in normal operation, is reserved to represent 'unknown'. The maximum value (2^32-1) is reserved to represent any value greater than or equal to 2^32-1 elements."; reference "RFC XXXX Section 3.1.7 The 'limit' Query Parameter"; } md:annotation next { type string; description "This annotation contains the opaque encoded value of the next cursor in the pagination."; reference "RFC XXXX Section 3.1.6 The 'cursor' Query Parameter"; } md:annotation previous { type string; description "This annotation contains the opaque encoded value of the previous cursor in the pagination."; reference "RFC XXXX Section 3.1.6 The 'cursor' Query Parameter"; } md:annotation locale { if-feature "sort"; type string; description "This annotation contains the locale used when sorting. The format is a free form string but SHOULD follow the language sub-tag format defined in RFC 5646. An example is 'sv_SE'. For further details see references: RFC 5646: Tags for identifying Languages RFC 6365: Technology Used in Internationalization in the IETF"; reference "RFC XXXX Section 3.1.3 The 'locale' Query Parameter"; } // Identities identity list-pagination-error { description "Base identity for list-pagination errors."; } identity offset-out-of-range { base list-pagination-error; description "The 'offset' query parameter value is greater than the number of instances in the target list or leaf-list resource."; } identity cursor-not-found { base list-pagination-error; description "The 'cursor' query parameter value is unknown for the target list."; } identity locale-unavailable { if-feature "sort"; base list-pagination-error; description "The 'locale' query parameter input is not a valid locale or the locale is not available on the system."; } // Groupings grouping pagination-parameters { description "This grouping may be used by protocol-specific YANG modules to define a protocol-specific pagination parameters."; container list-pagination { description "List pagination parameters."; leaf where { type yang:xpath1.0; description "The 'where' parameter specifies a boolean expression that result-set entries must match. If the XPath expression references a node identifier that does not exist in the schema, or is optional or condition\ al in the schema, the filter evaluates to false and nothing is filtered from the result-set. It is an error if the XPath expression references constrained 'config false' lists and leaf-lists, if the node identifier does not point to a node having the 'indexed' extension statement applied to it (see RFC XXXX)."; } leaf locale { if-feature "sort"; type string; description "The 'locale' parameter indicates the locale which the entries in the working result-set should be collated."; } leaf sort-by { if-feature "sort"; type union { type string { // An RFC 7950 'descendant-schema-nodeid'. pattern '([A-Za-z_][A-Za-z0-9_.-]*:)?' + '[A-Za-z_][A-Za-z0-9_.-]*' + '(/[A-Za-z_]([A-Za-z0-9_.-]*:)?' + '[A-Za-z_]([A-Za-z0-9_.-]*))*'; } type enumeration { enum "none" { description "Indicates that the list or leaf-list's default order is to be used, per the YANG 'ordered-by' statement."; } } } default "none"; description "The 'sort-by' parameter indicates the node in the working result-set (i.e., after the 'where' parameter has been applied) that entries should be sorted by. Sorts are in ascending order (e.g., '1' before '9', 'a' before 'z', etc.). Missing values are sorted to the end (e.g., after all nodes having values)."; } leaf direction { type enumeration { enum forwards { description "Indicates that entries should be traversed from the first to last item in the working result set."; } enum backwards { description "Indicates that entries should be traversed from the last to first item in the working result set."; } } default "forwards"; description "The 'direction' parameter indicates how the entries in the working result-set (i.e., after the 'sort-by' parameter has been applied) should be traversed."; } leaf cursor { type string; description "The 'cursor' parameter indicates where to start the working result-set (i.e. after the 'direction' parameter has been applied), the elements before the cursor are skipped over when preparing the response. Furthermore the result-set is annotated with attributes for the next and previous cursors following a result-set constrained with the 'limit' query parameter."; } leaf offset { type uint32; default 0; description "The 'offset' parameter indicates the number of entries in the working result-set (i.e., after the 'direction' parameter has been applied) that should be skipped over when preparing the response."; } leaf limit { type union { type uint32 { range "1..max"; } type enumeration { enum "unbounded" { description "Indicates that the number of entries that may be returned is unbounded."; } } } default "unbounded"; description "The 'limit' parameter limits the number of entries returned from the working result-set (i.e., after the 'offset' parameter has been applied). Any result-set that is limited includes, somewhere in its encoding, the metadata value 'remaining' to indicate the number entries not included in the result set."; } leaf sublist-limit { type union { type uint32 { range "1..max"; } type enumeration { enum "unbounded" { description "Indicates that the number of entries that may be returned is unbounded."; } } } default "unbounded"; description "The 'sublist-limit' parameter limits the number of entries for descendent lists and leaf-lists. Any result-set that is limited includes, somewhere in its encoding, the metadata value 'remaining' to indicate the number entries not included in the result set."; } } } // Protocol-accessible nodes augment "/sysc:system-capabilities/sysc:datastore-capabilities" + "/sysc:per-node-capabilities" { // Ensure the following nodes are only used for the // datastore. when "/sysc:system-capabilities/sysc:datastore-capabilities" + "/sysc:datastore = 'ds:operational'"; description "Defines some leafs that MAY be used by the server to describe constraints imposed of the 'where' filters and 'sort-by' parameters used in list pagination queries."; leaf constrained { type boolean; default false; description "Indicates that 'where' filters and 'sort-by' parameters on the targeted 'config false' list node are constrained. If a list is not 'constrained', then full XPath 1.0 expressions may be used in 'where' filters and all node identifiers are usable by 'sort-by'. Setting this to true will make the list constrained. By default this is false, i.e. a list is not constrained."; } leaf indexed { type boolean; default false; description "Indicates that the targeted descendent node of a 'constrained' list (see the 'constrained' leaf) may be used in 'where' filters and/or 'sort-by' parameters. If a descendent node of a 'constrained' list is not 'indexed', then it MUST NOT be used in 'where' filters or 'sort-by' parameters. Setting this to true will allow a constrained list to be used in 'where' filters and/or 'sort-by' parameters. By default this is false, i.e. a list constrained is not allowed for 'where' filters or 'sort-by' parameters."; } leaf cursor-supported { type boolean; default false; description "Indicates that the targeted list node supports the 'cursor' parameter. Setting this to true will enable the 'cursor' query parameter for a 'config false' list. By default this is false, i.e. the 'cursor' query parameter is disabled for 'config false' lists."; } } } ]]> <CODE ENDS>
IANA Considerations
The "IETF XML" Registry This document registers one URI in the "ns" subregistry of the IETF XML Registry maintained at . Following the format in , the following registration is requested:
The "YANG Module Names" Registry This document registers one YANG module in the YANG Module Names registry maintained at . Following the format defined in , the below registration is requested:
Security Considerations
Considerations for the "ietf-list-pagination" YANG Module This section follows the template defined in . The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. All protocol-accessible data nodes in this module are read-only and cannot be modified. Access control may be configured to avoid exposing any read-only data that is defined by the augmenting module documentation as being security sensitive. Since this module also defines groupings, these considerations are primarily for the designers of other modules that use these groupings. None of the readable data nodes defined in this YANG module are considered sensitive or vulnerable in network environments. The NACM "default-deny-all" extension has not been set for any data nodes defined in this module. This module does not define any RPCs or actions or notifications, and thus the security consideration for such is not provided here.
References Normative References Informative References Architectural Styles and the Design of Network-based Software Architectures
Vector Tests This normative appendix section illustrates every notable edge condition conceived during this document's production. Test inputs and outputs are provided in a manner that is both generic and concise. Management protocol specific documents need only reproduce as many of these tests as necessary to convey peculiarities presented by the protocol. Implementations are RECOMMENDED to implement the tests presented in this document, in addition to any tests that may be presented in protocol specific documents.
Example YANG Module The vector tests assume the "example-social" YANG module defined in this section. This module has been specially crafted to cover every notable edge condition, especially with regards to the types of the data nodes. Following is the tree diagram for the "example-social" module: /members/member/member-id | +--rw posts | | +--rw post* [timestamp] | | +--rw timestamp yang:date-and-time | | +--rw title? string | | +--rw body string | +--rw favorites | | +--rw uint8-numbers* uint8 | | +--rw uint64-numbers* uint64 | | +--rw int8-numbers* int8 | | +--rw int64-numbers* int64 | | +--rw decimal64-numbers* decimal64 | | +--rw bits* bits | +--ro stats | +--ro joined yang:date-and-time | +--ro membership-level enumeration | +--ro last-activity? yang:date-and-time +--ro audit-logs +--ro audit-log* [] +--ro timestamp yang:date-and-time +--ro member-id string +--ro source-ip inet:ip-address +--ro request string +--ro outcome boolean ]]> Following is the YANG for the "example-social" module:
Example Data Set The examples assume the server's operational state as follows. The data is provided in JSON only for convenience and, in particular, has no bearing on the "generic" nature of the tests themselves.
Example Queries The following sections are presented in reverse query-parameters processing order. Starting with the simplest (limit) and ending with the most complex (where). All the vector tests are presented in a protocol-independent manner. JSON is used only for its conciseness. The "members" list in the example data set is "ordered-by system" and the queries without explicit "sort-by" below return them in this given order. Note that the order of the result-set without explicit "sort-by" is implementation specific for "ordered-by system" lists.
The "limit" Parameter Noting that "limit" must be a positive number, the edge condition values are '1', '2', num-elements-1, num-elements, and num-elements+1. These vector tests assume the target "/example-social:members/member=alice/favorites/uint8-numbers", which has six values, thus the edge condition "limit" values are: '1', '2', '5', '6', and '7'.
limit=1 REQUEST RESPONSE
limit=2 REQUEST RESPONSE
limit=5 REQUEST RESPONSE
limit=6 REQUEST RESPONSE
limit=7 REQUEST RESPONSE
The "offset" Parameter Noting that "offset" must be an unsigned number less than or equal to the num-elements, the edge condition values are '0', '1', '2', num-elements-1, num-elements, and num-elements+1. These vector tests again assume the target "/example-social:members/member=alice/favorites/uint8-numbers", which has six values, thus the edge condition "limit" values are: '0', '1', '2', '5', '6', and '7'.
offset=0 REQUEST RESPONSE
offset=1 REQUEST RESPONSE
offset=2 REQUEST RESPONSE
offset=5 REQUEST RESPONSE
offset=6 REQUEST RESPONSE
offset=7 REQUEST RESPONSE
The "cursor" Parameter Noting that "cursor" is an opaque encoded value represented by a string, which addresses an element in a list. These vector tests assume the target "/example-social:members/member" which has five members.
cursor=&limit=2 REQUEST RESPONSE
cursor="YWxpY2U="&limit=2 REQUEST RESPONSE
cursor="am9l"&limit=2 REQUEST RESPONSE
cursor="BASE64VALUE=" REQUEST The cursor used does not exist in the datastore. RESPONSE
The "direction" Parameter Noting that "direction" is an enumeration with two values, the edge condition values are each defined enumeration. These vector tests again assume the target "/example-social:members/member=alice/favorites/uint8-numbers". The number of elements is relevant to the edge condition values.
direction=forwards REQUEST RESPONSE
direction=backwards REQUEST RESPONSE
The "sort-by" Parameter Noting that the "sort-by" parameter is a node identifier, there is not so much "edge conditions" as there are "interesting conditions". This section provides examples for some interesting conditions.
the target node's type The section provides three examples, one for a "leaf-list" and two for a "list", with one using a direct descendent and the other using an indirect descendent.
type is a "leaf-list" This example illustrates when the target node's type is a "leaf-list". Note that a single period (i.e., '.') is used to represent the nodes to be sorted. This test again uses the target "/example-social:members/member=alice/favorites/uint8-numbers", which is a leaf-list. REQUEST RESPONSE
type is a "list" and sort-by node is a direct descendent This example illustrates when the target node's type is a "list" and a direct descendent is the "sort-by" node. This vector test uses the target "/example-social:members/member", which is a "list", and the sort-by descendent node "member-id", which is the "key" for the list. REQUEST RESPONSE
type is a "list" and sort-by node is an indirect descendent This example illustrates when the target node's type is a "list" and an indirect descendent is the "sort-by" node. This vector test uses the target "/example-social:members/member", which is a "list", and the sort-by descendent node "stats/joined", which is a "config false" descendent leaf. Due to "joined" being a "config false" node, this request would have to target the "member" node in the <operational> datastore. REQUEST RESPONSE
The "where" Parameter The "where" is an XPath 1.0 expression, there are numerous edge conditions to consider, e.g., the types of the nodes that are targeted by the expression.
match of leaf-list's values This example selects the uint8-numbers greater than 7 in the member alice's favorites. REQUEST 7] Sort-by: - Direction: - Offset: - Limit: - ]]> RESPONSE
match on descendent string containing a substring This example selects members that have an email address containing "@example.com". REQUEST RESPONSE
match on decendent timestamp starting with a substring This example selects members that have a posting whose timestamp begins with the string "2020". REQUEST RESPONSE
The "locale" Parameter The "locale" parameter may be used on any target node. If this parameter is omitted, there is no default value and it is up to the server to choose a locale. This locale is then reported in the result-set as the "locale" metadata value. Note that for ordered-by user lists and leaf-lists "locale" is not relevant, since the order is set by the user. For ordered-by system lists and leaf-lists, the server MAY report "locale" if the order that the server has chosen follows a valid locale, If "locale" is used on an ordered-by user list, error-type "application" and error-tag "invalid-value" is returned. If an ordered-by system target is not ordered according to any locale, the server omits the locale from the response. REQUEST RESPONSE REQUEST RESPONSE REQUEST RESPONSE REQUEST This example targets an "ordered-by user" list. RESPONSE REQUEST This example supplies "locale" but not "sort-by". RESPONSE
The "sublist-limit" Parameter The "sublist-limit" parameter may be used on any target node.
target is a list entry This example uses the target node '/example-social:members/member=alice' in the <intended> datastore. This example sets the sublist-limit value '1', which returns just the first entry for all descendent lists and leaf-lists. Note that, in the response, the "remaining" metadata value is set on the first element of each descendent list and leaf-list having more than one value. REQUEST Target: /example-social:members/member=alice Sublist-limit: 1 Pagination Parameters: Where: - Sort-by: - Direction: - Offset: - Limit: - ]]> RESPONSE
target is a datastore This example uses the target node <intended> datastore. This example sets the sublist-limit value '1', which returns just the first entry for all descendent lists and leaf-lists. Note that, in the response, the "remaining" metadata value is set on the first element of each descendent list and leaf-list having more than one value. REQUEST Target: / Sublist-limit: 1 Pagination Parameters: Where: - Sort-by: - Direction: - Offset: - Limit: - ]]> RESPONSE
Combinations of Parameters
All six parameters at once REQUEST Target: /example-social:members/member Sublist-limit: 1 Pagination Parameters: Where: stats/joined[starts-with(timestamp,'2020')] Sort-by: member-id Direction: backwards Offset: 2 Limit: 2 ]]> RESPONSE
Acknowledgements This work has benefited from the discussions of RESTCONF resource collection over the years, in particular, which provides enhanced filtering features for the retrieval of data nodes with the GET method and which document large size data handling challenge. The authors would like to thank the following for lively discussions on list (ordered by first name): Andy Bierman, Martin Björklund, Robert Varga, Rob Wills, and Rob Wilton. The authors would also like to thank Jen Linkova for the OPS Directorate review.