]> Acklio

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Institut MINES TELECOM; IMT Atlantique

2 rue de la Chataigneraie CS 17607 35576 Cesson-Sevigne Cedex France Laurent.Toutain@imt-atlantique.fr

lpwan Working Group This document describes a YANG data model for the SCHC (Static Context Header Compression) compression and fragmentation rules. This document formalizes the description of the rules for better interoperability between SCHC instances either to exchange a set of rules or to modify some rules parameters.

Introduction SCHC is a compression and fragmentation mechanism for constrained networks defined in . It is based on a static context shared by two entities at the boundary of the constrained network. provides a non formal representation of the rules used either for compression/decompression (or C/D) or fragmentation/reassembly (or F/R). The goal of this document is to formalize the description of the rules to offer: the same definition on both ends, even if the internal representation is different. an update of the other end to set up some specific values (e.g. IPv6 prefix, destination address,...) ... illustrates the exchange of rules using the YANG data model. This document defines a YANG module to represent both compression and fragmentation rules, which leads to common representation for values for all the rules elements.

Requirements Language 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.

SCHC rules This document defines a YANG module to represent both compression and fragmentation rules, which leads to common representation for values for all the rules elements. SCHC compression is generic, the main mechanism does not refer to a specific protocol. Any header field is abstracted through an ID, a position, a direction, and a value that can be a numerical value or a string. and specify fields for IPv6 , UDP, CoAP including options definied for no serveur response and OSCORE . For the latter splits this field into sub-fields. SCHC fragmentation requires a set of common parameters that are included in a rule. These parameters are defined in . The YANG data model allows to select the compression or the fragmentation using the feature command.

Compression Rules proposes a non formal representation of the compression rule. A compression context for a device is composed of a set of rules. Each rule contains information to describe a specific field in the header to be compressed.

Identifier generation Identifier used in the SCHC YANG data model are from the identityref statement to ensure to be globally unique and be easily augmented if needed. The principle to define a new type based on a group of identityref is the following: define a main identity ending with the keyword base-type. derive all the identities used in the Data Model from this base type. create a typedef from this base type. The example () shows how an identityref is created for RCS (Reassembly Check Sequence) algorithms used during SCHC fragmentation.

Convention for Field Identifier In the process of compression, the headers of the original packet are first parsed to create a list of fields. This list of fields is matched against the rules to find the appropriate rule and apply compression. does not state how the field ID value is constructed. In examples, identification is done through a string indexed by the protocol name (e.g. IPv6.version, CoAP.version,...). The current YANG data model includes fields definitions found in , . Using the YANG data model, each field MUST be identified through a global YANG identityref.
A YANG field ID for the protocol is always derived from the fid-base-type. Then an identity for each protocol is specified using the naming convention fid-<<protocol name>>-base-type. All possible fields for this protocol MUST derive from the protocol identity. The naming convention is "fid" followed by the protocol name and the field name. If a field has to be divided into sub-fields, the field identity serves as a base. The full field-id definition is found in . A type is defined for IPv6 protocol, and each field is based on it. Note that the DiffServ bits derives from the Traffic Class identity.

Convention for Field length Field length is either an integer giving the size of a field in bits or a specific function. defines the "var" function which allows variable length fields (whose length is expressed in bytes) and defines the "tkl" function for managing the CoAP Token length field. The naming convention is "fl" followed by the function name. The field length function can be defined as an identityref as described in . Therefore, the type for field length is a union between an integer giving in bits the size of the length and the identityref.

Convention for Field position Field position is a positive integer which gives the position of a field, the default value is 1, and incremented at each repetition. value 0 indicates that the position is not important and is not considered during the rule selection process. Field position is a positive integer. The type is an uint8.

Convention for Direction Indicator The Direction Indicator (di) is used to tell if a field appears in both direction (Bi) or only uplink (Up) or Downlink (Dw). The naming convention is "di" followed by the Direction Indicator name. The type is "di-type".

Convention for Target Value The Target Value is a list of binary sequences of any length, aligned to the left. In the rule, the structure will be used as a list, with index as a key. The highest index value is used to compute the size of the index sent in residue for the match-mapping CDA (Compression Decompression Action). The index allows to specify several values: For Equal and LSB, Target Value contains a single element. Therefore, the index is set to 0. For match-mapping, Target Value can contain several elements. Index values MUST start from 0 and MUST be contiguous. If the header field contains a text, the binary sequence uses the same enconding.

Convention for Matching Operator Matching Operator (MO) is a function applied between a field value provided by the parsed header and the target value. defines 4 MO. The naming convention is "mo" followed by the MO name. The type is "mo-type"

Matching Operator arguments They are viewed as a list, built with a tv-struct (see chapter ).

Convention for Compression Decompression Actions Compression Decompression Action (CDA) identifies the function to use for compression or decompression. defines 6 CDA. The naming convention is "cda" followed by the CDA name.

Compression Decompression Action arguments Currently no CDA requires arguments, but in the future some CDA may require one or several arguments. They are viewed as a list, of target-value type.

Fragmentation rule Fragmentation is optional in the data model and depends on the presence of the "fragmentation" feature. Most of the fragmentation parameters are listed in Annex D of . Since fragmentation rules work for a specific direction, they MUST contain a mandatory direction indicator. The type is the same as the one used in compression entries, but bidirectional MUST NOT be used.

Fragmentation mode defines 3 fragmentation modes: No Ack: this mode is unidirectionnal, no acknowledgment is sent back. Ack Always: each fragmentation window must be explicitly acknowledged before going to the next. Ack on Error: A window is acknowledged only when the receiver detects some missing fragments. The type is "fragmentation-mode-type". The naming convention is "fragmentation-mode" followed by the fragmentation mode name.

Fragmentation Header A data fragment header, starting with the rule ID can be sent on the fragmentation direction. indicates that the SCHC header may be composed of (cf. ): a Datagram Tag (Dtag) identifying the datagram being fragmented if the fragmentation applies concurrently on several datagrams. This field in optional and its length is defined by the rule. a Window (W) used in Ack-Always and Ack-on-Error modes. In Ack-Always, its size is 1. In Ack-on-Error, it depends on the rule. This field is not needed in No-Ack mode. a Fragment Compressed Number (FCN) indicating the fragment/tile position within the window. This field is mandatory on all modes defined in , its size is defined by the rule.

Last fragment format The last fragment of a datagram is sent with an RCS (Reassembly Check Sequence) field to detect residual transmission error and possible losses in the last window. defines a single algorithm based on Ethernet CRC computation. The naming convention is "rcs" followed by the algorithm name. For Ack-on-Error mode, the All-1 fragment may just contain the RCS or can include a tile. The parameters defines the behavior: all-1-data-no: the last fragment contains no data, just the RCS all-1-data-yes: the last fragment includes a single tile and the RCS all-1-data-sender-choice: the last fragment may or may not contain a single tile. The receiver can detect if a tile is present. The naming convention is "all-1-data" followed by the behavior identifier.

Acknowledgment behavior The acknowledgment fragment header goes in the opposite direction of data. defines the header, composed of (see ): a Dtag (if present). a mandatory window as in the data fragment. a C bit giving the status of RCS validation. In case of failure, a bitmap follows, indicating the received tile.

For Ack-on-Error, SCHC defines when an acknowledgment can be sent. This can be at any time defined by the layer 2, at the end of a window (FCN all-0) or as a response to receiving the last fragment (FCN all-1). The naming convention is "ack-behavior" followed by the algorithm name.

Timer values The state machine requires some common values to handle correctly fragmentation. retransmission-timer gives the duration before sending an ack request (cf. section 8.2.2.4. of ). If specified, value must be strictly positive. inactivity-timer gives the duration before aborting a fragmentation session (cf. section 8.2.2.4. of ). The value 0 explicitly indicates that this timer is disabled. do not specified any range for these timers. recommends a duration of 12 hours. In fact, the value range sould be between milliseconds for real time systems to several days. To allow a large range of applications, two parameters must be specified: the duration of a tick. It is computed by this formula 2^tick-duration/10^6. When tick-duration is set to 0, the unit is the microsecond. The default value of 20 leads to a unit of 1.048575 second. A value of 32 leads to a tick duration of about 1 hour 11 minutes. the number of ticks in the predefined unit. With the default tick-duration value of 20, the timers can cover a range between 1.0 sec and 19 hours covering recommandation.

Fragmentation Parameter The SCHC fragmentation protocol specifies the the number of attempts before aborting through the parameter: max-ack-requests (cf. section 8.2.2.4. of ).

Layer 2 parameters The data model includes two parameters needed for fragmentation: l2-word-size: base fragmentation, in bits, on a layer 2 word which can be of any length. The default value is 8 and correspond to the default value for byte aligned layer 2. A value of 1 will indicate that there is no alignment and no need for padding. maximum-packet-size: defines the maximum size of a uncompressed datagram. By default, the value is set to 1280 bytes. They are defined as unsigned integer, see .

Rule definition A rule is idenfied by a unique rule identifier (rule ID) comprising both a Rule ID value and a Rule ID length. The YANG grouping rule-id-type defines the structure used to represent a rule ID. A length of 0 is allowed to represent an implicit rule. Three natures of rules are defined in : Compression: a compression rule is associated with the rule ID. No compression: this identifies the default rule used to send a packet in extenso when no compression rule was found (see section 6). Fragmentation: fragmentation parameters are associated with the rule ID. Fragmentation is optional and feature "fragmentation" should be set. The YANG data model introduces repectively these three identities : nature-compresion nature-no-compression nature-fragmentation The naming convention is "nature" followed by the nature identifier. To access a specific rule, the rule ID length and value are used as a key. The rule is either a compression or a fragmentation rule.

Compression rule A compression rule is composed of entries describing its processing. An entry contains all the information defined in with the types defined above. The compression rule described is defined by compression-content. It defines a list of compression-rule-entry, indexed by their field id, position and direction. The compression-rule-entry element represent a line of the table . Their type reflects the identifier types defined in Some checks are performed on the values: target value must be present for MO different from ignore. when MSB MO is specified, the matching-operator-value must be present

Fragmentation rule A Fragmentation rule is composed of entries describing the protocol behavior. Some on them are numerical entries, others are identifiers defined in .

YANG Tree The YANG data model described in this document conforms to the Network Management Datastore Architecture defined in .

YANG Module

file "ietf-schc@2022-08-01.yang" module ietf-schc { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-schc"; prefix schc; organization "IETF IPv6 over Low Power Wide-Area Networks (lpwan) working group"; contact "WG Web: WG List: Editor: Laurent Toutain Editor: Ana Minaburo "; description " Copyright (c) 2022 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. *************************************************************** Generic Data model for Static Context Header Compression Rule for SCHC, based on RFC 8724 and RFC8824. Include compression, no compression and fragmentation rules. This module is a YANG model for SCHC rules (RFC 8724 and RFC8824). RFC 8724 describes compression rules in a abstract way through a table. |-----------------------------------------------------------------| | (FID) Rule 1 | |+-------+--+--+--+------------+-----------------+---------------+| ||Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|| |+-------+--+--+--+------------+-----------------+---------------+| ||Field 2|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|| |+-------+--+--+--+------------+-----------------+---------------+| ||... |..|..|..| ... | ... | ... || |+-------+--+--+--+------------+-----------------+---------------+| ||Field N|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|| |+-------+--+--+--+------------+-----------------+---------------+| |-----------------------------------------------------------------| This module proposes a global data model that can be used for rule exchanges or modification. It proposes both the data model format and the global identifiers used to describe some operations in fields. This data model applies to both compression and fragmentation."; revision 2022-08-01 { description "Initial version from RFC XXXX."; reference "RFC XXX: Data Model for Static Context Header Compression (SCHC)"; } feature compression { description "SCHC compression capabilities are taken into account."; } feature fragmentation { description "SCHC fragmentation capabilities are taken into account."; } // ------------------------- // Field ID type definition //-------------------------- // generic value TV definition identity fid-base-type { description "Field ID base type for all fields."; } identity fid-ipv6-base-type { base fid-base-type; description "Field ID base type for IPv6 headers described in RFC 8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-version { base fid-ipv6-base-type; description "IPv6 version field from RFC 8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-trafficclass { base fid-ipv6-base-type; description "IPv6 Traffic Class field from RFC 8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-trafficclass-ds { base fid-ipv6-trafficclass; description "IPv6 Traffic Class field from RFC 8200, DiffServ field from RFC 3168."; reference "RFC 3168 The Addition of Explicit Congestion Notification (ECN) to IP"; } identity fid-ipv6-trafficclass-ecn { base fid-ipv6-trafficclass; description "IPv6 Traffic Class field from RFC 8200, ECN field from RFC 3168."; reference "RFC 3168 The Addition of Explicit Congestion Notification (ECN) to IP"; } identity fid-ipv6-flowlabel { base fid-ipv6-base-type; description "IPv6 Flow Label field from RFC8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-payload-length { base fid-ipv6-base-type; description "IPv6 Payload Length field from RFC8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-nextheader { base fid-ipv6-base-type; description "IPv6 Next Header field from RFC8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-hoplimit { base fid-ipv6-base-type; description "IPv6 Next Header field from RFC8200."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-devprefix { base fid-ipv6-base-type; description "Corresponds to either the source address or the destination address prefix of RFC 8200. Depending if it is respectively an uplink or a downlink message."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-deviid { base fid-ipv6-base-type; description "Corresponds to either the source address or the destination address prefix of RFC 8200. Depending if it is respectively an uplink or a downlink message."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-appprefix { base fid-ipv6-base-type; description "Corresponds to either the source address or the destination address prefix of RFC 8200. Depending if it is respectively a downlink or an uplink message."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-ipv6-appiid { base fid-ipv6-base-type; description "Corresponds to either the source address or the destination address prefix of RFC 8200. Depending if it is respectively a downlink or an uplink message."; reference "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; } identity fid-udp-base-type { base fid-base-type; description "Field ID base type for UDP headers described in RFC 768."; reference "RFC 768 User Datagram Protocol"; } identity fid-udp-dev-port { base fid-udp-base-type; description "UDP source or destination port from RFC 768, if uplink or downlink communication, respectively."; reference "RFC 768 User Datagram Protocol"; } identity fid-udp-app-port { base fid-udp-base-type; description "UDP destination or source port from RFC 768, if uplink or downlink communication, respectively."; reference "RFC 768 User Datagram Protocol"; } identity fid-udp-length { base fid-udp-base-type; description "UDP length from RFC 768."; reference "RFC 768 User Datagram Protocol"; } identity fid-udp-checksum { base fid-udp-base-type; description "UDP length from RFC 768."; reference "RFC 768 User Datagram Protocol"; } identity fid-coap-base-type { base fid-base-type; description "Field ID base type for UDP headers described in RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-version { base fid-coap-base-type; description "CoAP version from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-type { base fid-coap-base-type; description "CoAP type from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-tkl { base fid-coap-base-type; description "CoAP token length from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-code { base fid-coap-base-type; description "CoAP code from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-code-class { base fid-coap-code; description "CoAP code class from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-code-detail { base fid-coap-code; description "CoAP code detail from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-mid { base fid-coap-base-type; description "CoAP message ID from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-token { base fid-coap-base-type; description "CoAP token from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-if-match { base fid-coap-base-type; description "CoAP option If-Match from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-uri-host { base fid-coap-base-type; description "CoAP option URI-Host from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-etag { base fid-coap-base-type; description "CoAP option Etag from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-if-none-match { base fid-coap-base-type; description "CoAP option if-none-match from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-observe { base fid-coap-base-type; description "CoAP option Observe from RFC 7641."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-uri-port { base fid-coap-base-type; description "CoAP option Uri-Port from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-location-path { base fid-coap-base-type; description "CoAP option Location-Path from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-uri-path { base fid-coap-base-type; description "CoAP option Uri-Path from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-content-format { base fid-coap-base-type; description "CoAP option Content Format from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-max-age { base fid-coap-base-type; description "CoAP option Max-Age from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-uri-query { base fid-coap-base-type; description "CoAP option Uri-Query from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-accept { base fid-coap-base-type; description "CoAP option Accept from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-location-query { base fid-coap-base-type; description "CoAP option Location-Query from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-block2 { base fid-coap-base-type; description "CoAP option Block2 from RFC 7959."; reference "RFC 7959 Block-Wise Transfers in the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-block1 { base fid-coap-base-type; description "CoAP option Block1 from RFC 7959."; reference "RFC 7959 Block-Wise Transfers in the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-size2 { base fid-coap-base-type; description "CoAP option size2 from RFC 7959."; reference "RFC 7959 Block-Wise Transfers in the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-proxy-uri { base fid-coap-base-type; description "CoAP option Proxy-Uri from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-proxy-scheme { base fid-coap-base-type; description "CoAP option Proxy-scheme from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-size1 { base fid-coap-base-type; description "CoAP option Size1 from RFC 7252."; reference "RFC 7252 The Constrained Application Protocol (CoAP)"; } identity fid-coap-option-no-response { base fid-coap-base-type; description "CoAP option No response from RFC 7967."; reference "RFC 7967 Constrained Application Protocol (CoAP) Option for No Server Response"; } identity fid-oscore-base-type { base fid-coap-type; description "OSCORE options (RFC8613) split by RFC 8824 in sub options."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-oscore-flags { base fid-oscore-base-type; description "CoAP option oscore flags (see RFC 8824, section 6.4)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-oscore-piv { base fid-oscore-base-type; description "CoAP option oscore flags (see RFC 8824, section 6.4)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-oscore-kid { base fid-oscore-base-type; description "CoAP option oscore flags (see RFC 8824, section 6.4)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } identity fid-coap-option-oscore-kidctx { base fid-oscore-base-type; description "CoAP option oscore flags (see RFC 8824, section 6.4)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } //---------------------------------- // Field Length type definition //---------------------------------- identity fl-base-type { description "Used to extend field length functions."; } identity fl-variable { base fl-base-type; description "Residue length in Byte is sent as defined for CoAP in RFC 8824 (cf. 5.3)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } identity fl-token-length { base fl-base-type; description "Residue length in Byte is sent as defined for CoAP in RFC 8824 (cf. 4.5)."; reference "RFC 8824 Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)"; } //--------------------------------- // Direction Indicator type //--------------------------------- identity di-base-type { description "Used to extend direction indicators."; } identity di-bidirectional { base di-base-type; description "Direction Indication of bidirectionality in RFC 8724 (cf. 7.1)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity di-up { base di-base-type; description "Direction Indication of uplink defined in RFC 8724 (cf. 7.1)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity di-down { base di-base-type; description "Direction Indication of downlink defined in RFC 8724 (cf. 7.1)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } //---------------------------------- // Matching Operator type definition //---------------------------------- identity mo-base-type { description "Matching Operator: used in the rule selection process defined in RFC 8724 (cf. 7.2) to check is a Target Value matches the field's value."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity mo-equal { base mo-base-type; description "equal MO as defined in RFC 8724 (cf. 7.3)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity mo-ignore { base mo-base-type; description "ignore MO as defined in RFC 8724 (cf. 7.3)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity mo-msb { base mo-base-type; description "MSB MO as defined in RFC 8724 (cf. 7.3)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity mo-match-mapping { base mo-base-type; description "match-mapping MO as defined in RFC 8724 (cf. 7.3)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } //------------------------------ // CDA type definition //------------------------------ identity cda-base-type { description "Compression Decompression Actions. Specify the action to be applied to the field's value in a specific rule as defined in RFC8724 (cf. 7.2)"; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-not-sent { base cda-base-type; description "not-sent CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-value-sent { base cda-base-type; description "value-sent CDA as defined in RFC 8724 (cf. 7.4)."; } identity cda-lsb { base cda-base-type; description "LSB CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-mapping-sent { base cda-base-type; description "mapping-sent CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-compute { base cda-base-type; description "compute-* CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-deviid { base cda-base-type; description "DevIID CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity cda-appiid { base cda-base-type; description "AppIID CDA as defined in RFC 8724 (cf. 7.4)."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // -- type definition typedef fid-type { type identityref { base fid-base-type; } description "Field ID generic type."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef fl-type { type union { type uint64; /* positive integer, expressing length in bits */ type identityref { /* function */ base fl-base-type; } } description "Field length either a positive integer expressing the size in bits or a function defined through an identityref."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef di-type { type identityref { base di-base-type; } description "Direction in LPWAN network, up when emitted by the device, down when received by the device, bi when emitted or received by the device."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef mo-type { type identityref { base mo-base-type; } description "Matching Operator (MO) to compare fields values with target values."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef cda-type { type identityref { base cda-base-type; } description "Compression Decompression Action to compression or decompress a field."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // -- FRAGMENTATION TYPE // -- fragmentation modes identity fragmentation-mode-base-type { description "Define the fragmentation mode."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity fragmentation-mode-no-ack { base fragmentation-mode-base-type; description "No-ACK of RFC8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity fragmentation-mode-ack-always { base fragmentation-mode-base-type; description "ACK-Always of RFC8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity fragmentation-mode-ack-on-error { base fragmentation-mode-base-type; description "ACK-on-Error of RFC8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef fragmentation-mode-type { type identityref { base fragmentation-mode-base-type; } description "Define the type used for fragmentation mode in rules."; } // -- Ack behavior identity ack-behavior-base-type { description "Define when to send an Acknowledgment ."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity ack-behavior-after-all-0 { base ack-behavior-base-type; description "Fragmentation expects Ack after sending All-0 fragment."; } identity ack-behavior-after-all-1 { base ack-behavior-base-type; description "Fragmentation expects Ack after sending All-1 fragment."; } identity ack-behavior-by-layer2 { base ack-behavior-base-type; description "Layer 2 defines when to send an Ack."; } typedef ack-behavior-type { type identityref { base ack-behavior-base-type; } description "Define the type used for Ack behavior in rules."; } // -- All-1 with data types identity all-1-data-base-type { description "Type to define when to send an Acknowledgment message."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity all-1-data-no { base all-1-data-base-type; description "All-1 contains no tiles."; } identity all-1-data-yes { base all-1-data-base-type; description "All-1 MUST contain a tile."; } identity all-1-data-sender-choice { base all-1-data-base-type; description "Fragmentation process chooses to send tiles or not in All-1."; } typedef all-1-data-type { type identityref { base all-1-data-base-type; } description "Define the type used for All-1 format in rules."; } // -- RCS algorithm types identity rcs-algorithm-base-type { description "Identify which algorithm is used to compute RCS. The algorithm also defines the size of the RCS field."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity rcs-RFC8724 { base rcs-algorithm-base-type; description "CRC 32 defined as default RCS in RFC8724. This RCS is 4 byte-long."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef rcs-algorithm-type { type identityref { base rcs-algorithm-base-type; } description "Define the type for RCS algorithm in rules."; } // --------- TIMER DURATION ------------------- grouping timer-duration { leaf ticks-duration { type uint8; default "20"; description "Duration of one tick in micro-seconds: 2^ticks-duration/10^6 = 1.048s."; } leaf ticks-numbers { type uint16; description "Timer duration = ticks-numbers * 2^ticks-duration / 10^6."; } description "Used by inactivity and retransmission timer. Allows a precision from micro-second to year by sending the tick-duration value. For instance: tick-duration / smallest value highest value v 20: 00y 000d 00h 00m 01s.048575<->00y 000d 19h 05m 18s.428159 21: 00y 000d 00h 00m 02s.097151<->00y 001d 14h 10m 36s.856319 22: 00y 000d 00h 00m 04s.194303<->00y 003d 04h 21m 13s.712639 23: 00y 000d 00h 00m 08s.388607<->00y 006d 08h 42m 27s.425279 24: 00y 000d 00h 00m 16s.777215<->00y 012d 17h 24m 54s.850559 25: 00y 000d 00h 00m 33s.554431<->00y 025d 10h 49m 49s.701119 Note that the smallest value is also the incrementation step, so the timer precision. "; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // -------- RULE ENTRY DEFINITION ------------ grouping tv-struct { description "Defines the target value element. If the header field contains a text, the binary sequence uses the same encoding. field-id allows the conversion to the appropriate type."; leaf index { type uint16; description "Index gives the position in the matching-list. If only one element is present, index is 0. Otherwise, index is the the order in the matching list, starting at 0."; } leaf value { type binary; description "Target Value content as a untyped binary value."; } reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } grouping compression-rule-entry { description "These entries defines a compression entry (i.e. a line) as defined in RFC 8724. +-------+--+--+--+------------+-----------------+---------------+ |Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act| +-------+--+--+--+------------+-----------------+---------------+ An entry in a compression rule is composed of 7 elements: - Field ID: The header field to be compressed. - Field Length : Either a positive integer of a function. - Field Position: A positive (and possibly equal to 0) integer. - Direction Indicator: An indication in which direction compression and decompression process is effective. - Target value: A value against which the header Field is compared. - Matching Operator: The comparison operation and optional associate parameters. - Comp./Decomp. Action: The compression or decompression action, and optional parameters. "; leaf field-id { type schc:fid-type; mandatory true; description "Field ID, identify a field in the header with a YANG referenceid."; } leaf field-length { type schc:fl-type; mandatory true; description "Field Length, expressed in number of bits if the length is known when the Rule is created or through a specific function if the length is variable."; } leaf field-position { type uint8; mandatory true; description "Field position in the header is an integer. Position 1 matches the first occurrence of a field in the header, while incremented position values match subsequent occurences. Position 0 means that this entry matches a field irrespective of its position of occurence in the header. Be aware that the decompressed header may have position-0 fields ordered differently than they appeared in the original packet."; } leaf direction-indicator { type schc:di-type; mandatory true; description "Direction Indicator, indicate if this field must be consider for rule selection or ignored based on the direction (bi directionnal, only uplink, or only downlink)."; } list target-value { key "index"; uses tv-struct; description "A list of value to compare with the header field value. If target value is a singleton, position must be 0. For use as a matching list for the mo-match-mapping matching operator, positions should take consecutive values starting from 1."; } leaf matching-operator { type schc:mo-type; must "../target-value or derived-from-or-self(., 'mo-ignore')" { error-message "mo-equal, mo-msb and mo-match-mapping need target-value"; description "target-value is not required for mo-ignore."; } must "not (derived-from-or-self(., 'mo-msb')) or ../matching-operator-value" { error-message "mo-msb requires length value"; } mandatory true; description "MO: Matching Operator"; } list matching-operator-value { key "index"; uses tv-struct; description "Matching Operator Arguments, based on TV structure to allow several arguments. In RFC 8724, only the MSB matching operator needs arguments (a single argument, which is the number of most significant bits to be matched)."; } leaf comp-decomp-action { type schc:cda-type; mandatory true; description "CDA: Compression Decompression Action."; } list comp-decomp-action-value { key "index"; uses tv-struct; description "CDA arguments, based on a TV structure, in order to allow for several arguments. The CDAs specified in RFC 8724 require no argument."; } reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // --Rule nature identity nature-base-type { description "A rule, identified by its RuleID, are used for a single purpose. RFC 8724 chap 6. defines 2 natures: compression, no compression and fragmentation."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity nature-compression { base nature-base-type; description "Identify a compression rule, as defined in chap 6 of RFC 8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity nature-no-compression { base nature-base-type; description "Identify a no compression rule, as defined in chap 6 of RFC 8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } identity nature-fragmentation { base nature-base-type; description "Identify a fragmentation rule, as defined in chap 6 of RFC 8724."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } typedef nature-type { type identityref { base nature-base-type; } description "defines the type to indicate the nature of the rule."; } grouping compression-content { list entry { must "derived-from-or-self(../rule-nature, 'nature-compression')" { error-message "Rule nature must be compression"; } key "field-id field-position direction-indicator"; uses compression-rule-entry; description "A compression rule is a list of rule entries, each describing a header field. An entry is identified through a field-id, its position in the packet and its direction."; } description "Define a compression rule composed of a list of entries."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } grouping fragmentation-content { description "This grouping defines the fragmentation parameters for all the modes (No-ACK, ACK-Always and ACK-on-Error) specified in RFC 8724."; leaf fragmentation-mode { type schc:fragmentation-mode-type; must "derived-from-or-self(../rule-nature, 'nature-fragmentation')" { error-message "Rule nature must be fragmentation"; } mandatory true; description "Which fragmentation mode is used (No-Ack, ACK-Always, ACK-on-Error)."; } leaf l2-word-size { type uint8; default "8"; description "Size, in bits, of the layer 2 word."; } leaf direction { type schc:di-type; must "derived-from-or-self(., 'di-up') or derived-from-or-self(., 'di-down')" { error-message "Direction for fragmentation rules are up or down."; } mandatory true; description "Should be up or down, bidirectional is forbidden."; } // SCHC Frag header format leaf dtag-size { type uint8; default "0"; description "Size, in bits, of the DTag field (T variable from RFC8724)."; } leaf w-size { when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error') or derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-always') "; type uint8; description "Size, in bits, of the window field (M variable from RFC8724)."; } leaf fcn-size { type uint8; mandatory true; description "Size, in bits, of the FCN field (N variable from RFC8724)."; } leaf rcs-algorithm { type rcs-algorithm-type; default "schc:rcs-RFC8724"; description "Algorithm used for RCS. The algorithm specifies the RCS size."; } // SCHC fragmentation protocol parameters leaf maximum-packet-size { type uint16; default "1280"; description "When decompression is done, packet size must not strictly exceed this limit, expressed in bytes."; } leaf window-size { type uint16; description "By default, if not specified 2^w-size - 1. Should not exceed this value. Possible FCN values are between 0 and window-size - 1."; } leaf max-interleaved-frames { type uint8; default "1"; description "Maximum of simultaneously fragmented frames. Maximum value is 2^dtag-size. All DTAG values can be used, but at most max-interleaved-frames must be active at any time."; } container inactivity-timer { uses timer-duration; description "Duration is seconds of the inactivity timer, 0 indicates that the timer is disabled."; } container retransmission-timer { uses timer-duration; when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error') or derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-always') "; description "Duration in seconds of the retransmission timer."; } leaf max-ack-requests { when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error') or derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-always') "; type uint8 { range "1..max"; } description "The maximum number of retries for a specific SCHC ACK."; } choice mode { case no-ack; case ack-always; case ack-on-error { leaf tile-size { when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error')"; type uint8; description "Size, in bits, of tiles. If not specified or set to 0, tiles fill the fragment."; } leaf tile-in-all-1 { when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error')"; type schc:all-1-data-type; description "Defines whether the sender and receiver expect a tile in All-1 fragments or not, or if it is left to the sender's choice."; } leaf ack-behavior { when "derived-from-or-self(../fragmentation-mode, 'fragmentation-mode-ack-on-error')"; type schc:ack-behavior-type; description "Sender behavior to acknowledge, after All-0, All-1 or when the LPWAN allows it."; } } description "RFC 8724 defines 3 fragmentation modes."; } reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // Define rule ID. Rule ID is composed of a RuleID value and a // Rule ID Length grouping rule-id-type { leaf rule-id-value { type uint32; description "Rule ID value, this value must be unique, considering its length."; } leaf rule-id-length { type uint8 { range "0..32"; } description "Rule ID length, in bits. The value 0 is for implicit rules."; } description "A rule ID is composed of a value and a length, expressed in bits."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } // SCHC table for a specific device. container schc { list rule { key "rule-id-value rule-id-length"; uses rule-id-type; leaf rule-nature { type nature-type; mandatory true; description "Specify the rule's nature."; } choice nature { case fragmentation { if-feature "fragmentation"; uses fragmentation-content; } case compression { if-feature "compression"; uses compression-content; } description "A rule is for compression, for no-compression or for fragmentation."; } description "Set of rules compression, no compression or fragmentation rules identified by their rule-id."; } description "A SCHC set of rules is composed of a list of rules which are used for compression, no-compression or fragmentation."; reference "RFC 8724 SCHC: Generic Framework for Static Context Header Compression and Fragmentation"; } } ]]>

Implementation Status This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in . The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to , "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". Openschc is implementing the conversion between the local rule representation and the representation conform to the data model in JSON and CBOR (following -08 draft).

IANA Considerations This document registers one URIs and one YANG modules.

  URI Registration This document requests IANA to register the following four URIs in the "IETF XML Registry" :

• URI:  urn:ietf:params:xml:ns:yang:ietf-schc

• Registrant Contact:  The IESG.

• XML:  N/A; the requested URI is an XML namespace.

  YANG Module Name Registration This document registers the following one YANG modules in the "YANG Module Names" registry .

• name:           ietf-schc

• namespace:      urn:ietf:params:xml:ns:yang:ietf-schc

• prefix:         schc

• reference:      RFC XXXX Data Model for Static Context Header Compression (SCHC)

Security Considerations 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. This data model formalizes the rules elements described in for compression and fragmentation. As explained in the architecture document , a rule can be read, created, updated or deleted in response to a management request. These actions can be done between two instances of SCHC or between a SCHC instance and a rule repository.

|Rule |<--|--------> (-------) update |Manager| NETCONF, RESTCONF or CORECONF . read delete +=======+ request . +-------+ <===| R & D |<=== ===>| C & F |===> +-------+ ]]>

The rule contains some sensible informations such as the application IPv6 address. An attacker by changing a rule content may block the communication or intercept the traffic. Therefore, the identity of the requester must be validated. This can be done through certificates or access lists. The full tree is sensitive, since it represents all the elements that can be managed. This module aims to be encapsulated into a YANG module including access control and identities.

Acknowledgements The authors would like to thank Dominique Barthel, Carsten Bormann, Ivan Martinez, Alexander Pelov for their careful reading and valuable inputs. A special thanks for Joe Clarke, Carl Moberg, Tom Petch, Martin Thomson, and Eric Vyncke for their explanations and wise advices when building the model.

In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation.CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460. Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950. This document defines Object Security for Constrained RESTful Environments (OSCORE), a method for application-layer protection of the Constrained Application Protocol (CoAP), using CBOR Object Signing and Encryption (COSE). OSCORE provides end-to-end protection between endpoints communicating using CoAP or CoAP-mappable HTTP. OSCORE is designed for constrained nodes and networks supporting a range of proxy operations, including translation between different transport protocols.Although an optional functionality of CoAP, OSCORE alters CoAP options processing and IANA registration. Therefore, this document updates RFC 7252. This document defines the Static Context Header Compression and fragmentation (SCHC) framework, which provides both a header compression mechanism and an optional fragmentation mechanism. SCHC has been designed with Low-Power Wide Area Networks (LPWANs) in mind.SCHC compression is based on a common static context stored both in the LPWAN device and in the network infrastructure side. This document defines a generic header compression mechanism and its application to compress IPv6/UDP headers.This document also specifies an optional fragmentation and reassembly mechanism. It can be used to support the IPv6 MTU requirement over the LPWAN technologies. Fragmentation is needed for IPv6 datagrams that, after SCHC compression or when such compression was not possible, still exceed the Layer 2 maximum payload size.The SCHC header compression and fragmentation mechanisms are independent of the specific LPWAN technology over which they are used. This document defines generic functionalities and offers flexibility with regard to parameter settings and mechanism choices. This document standardizes the exchange over the LPWAN between two SCHC entities. Settings and choices specific to a technology or a product are expected to be grouped into profiles, which are specified in other documents. Data models for the context and profiles are out of scope. This document defines how to compress Constrained Application Protocol (CoAP) headers using the Static Context Header Compression and fragmentation (SCHC) framework. SCHC defines a header compression mechanism adapted for Constrained Devices. SCHC uses a static description of the header to reduce the header's redundancy and size. While RFC 8724 describes the SCHC compression and fragmentation framework, and its application for IPv6/UDP headers, this document applies SCHC to CoAP headers. The CoAP header structure differs from IPv6 and UDP, since CoAP uses a flexible header with a variable number of options, themselves of variable length. The CoAP message format is asymmetric: the request messages have a header format different from the format in the response messages. This specification gives guidance on applying SCHC to flexible headers and how to leverage the asymmetry for more efficient compression Rules. The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK] This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model.This document obsoletes RFC 6536. This document describes a simple process that allows authors of Internet-Drafts to record the status of known implementations by including an Implementation Status section. This will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature.This process is not mandatory. Authors of Internet-Drafts are encouraged to consider using the process for their documents, and working groups are invited to think about applying the process to all of their protocol specifications. This document obsoletes RFC 6982, advancing it to a Best Current Practice. There can be machine-to-machine (M2M) scenarios where server responses to client requests are redundant. This kind of open-loop exchange (with no response path from the server to the client) may be desired to minimize resource consumption in constrained systems while updating many resources simultaneously or performing high-frequency updates. CoAP already provides Non-confirmable (NON) messages that are not acknowledged by the recipient. However, the request/response semantics still require the server to respond with a status code indicating "the result of the attempt to understand and satisfy the request", per RFC 7252.This specification introduces a CoAP option called 'No-Response'. Using this option, the client can explicitly express to the server its disinterest in all responses against the particular request. This option also provides granular control to enable expression of disinterest to a particular response class or a combination of response classes. The server MAY decide to suppress the response by not transmitting it back to the client according to the value of the No-Response option in the request. This option may be effective for both unicast and multicast requests. This document also discusses a few examples of applications that benefit from this option. YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). The Static Context Header Compression and fragmentation (SCHC) specification (RFC 8724) describes generic header compression and fragmentation techniques for Low-Power Wide Area Network (LPWAN) technologies. SCHC is a generic mechanism designed for great flexibility so that it can be adapted for any of the LPWAN technologies.This document defines a profile of SCHC (RFC 8724) for use in LoRaWAN networks and provides elements such as efficient parameterization and modes of operation. Acklio Cisco Systems Acklio This document defines the LPWAN SCHC architecture.