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diff --git a/doc/rfc/rfc9363.txt b/doc/rfc/rfc9363.txt new file mode 100644 index 0000000..9b9f23e --- /dev/null +++ b/doc/rfc/rfc9363.txt @@ -0,0 +1,2482 @@ + + + + +Internet Engineering Task Force (IETF) A. Minaburo +Request for Comments: 9363 Acklio +Category: Standards Track L. Toutain +ISSN: 2070-1721 IMT Atlantique + March 2023 + + + A YANG Data Model for Static Context Header Compression (SCHC) + +Abstract + + This document describes a YANG data model for the Static Context + Header Compression (SCHC) 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 the parameters of some Rules. + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc9363. + +Copyright Notice + + Copyright (c) 2023 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (https://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Revised BSD License text as described in Section 4.e of the + Trust Legal Provisions and are provided without warranty as described + in the Revised BSD License. + +Table of Contents + + 1. Introduction + 2. Requirements Language + 3. Terminology + 4. SCHC Rules + 4.1. Compression Rules + 4.2. Identifier Generation + 4.3. Convention for Field Identifier + 4.4. Convention for Field Length + 4.5. Convention for Field Position + 4.6. Convention for Direction Indicator + 4.7. Convention for Target Value + 4.8. Convention for Matching Operator + 4.8.1. Matching Operator Arguments + 4.9. Convention for Compression Decompression Actions + 4.9.1. Compression Decompression Action Arguments + 4.10. Fragmentation Rule + 4.10.1. Fragmentation Mode + 4.10.2. Fragmentation Header + 4.10.3. Last Fragment Format + 4.10.4. Acknowledgment Behavior + 4.10.5. Timer Values + 4.10.6. Fragmentation Parameter + 4.10.7. Layer 2 Parameters + 5. Rule Definition + 5.1. Compression Rule + 5.2. Fragmentation Rule + 5.3. YANG Tree + 6. YANG Data Model + 7. IANA Considerations + 7.1. URI Registration + 7.2. YANG Module Name Registration + 8. Security Considerations + 9. References + 9.1. Normative References + 9.2. Informative References + Appendix A. Example + Acknowledgments + Authors' Addresses + +1. Introduction + + SCHC is a compression and fragmentation mechanism for constrained + networks defined in [RFC8724]. It is based on a static context + shared by two entities at the boundary of the constrained network. + [RFC8724] provides an informal representation of the Rules used + either for compression/decompression (C/D) or fragmentation/ + reassembly (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, and + + * an update of the other end to set up some specific values (e.g., + IPv6 prefix, destination address, etc.). + + [LPWAN-ARCH] illustrates the exchange of Rules using the YANG data + model. + + This document defines a YANG data model [RFC7950] to represent both + compression and fragmentation Rules, which leads to common + representation for values for all the Rules' elements. + +2. 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 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. + +3. Terminology + + This section defines the terminology and acronyms used in this + document. It extends the terminology of [RFC8376]. + + App: Low-Power WAN (LPWAN) Application, as defined by [RFC8376]. An + application sending/receiving packets to/from the Dev. + + Bi: Bidirectional. Characterizes a Field Descriptor that applies to + headers of packets traveling in either direction (Up and Dw; see + this glossary). + + CDA: Compression/Decompression Action. Describes the pair of + actions that are performed at the compressor to compress a header + field and at the decompressor to recover the original value of the + header field. + + Context: A set of Rules used to compress/decompress headers. + + Dev: Device, as defined by [RFC8376]. + + DevIID: Device Interface Identifier. The IID that identifies the + Dev interface. + + DI: Direction Indicator. This field tells which direction of packet + travel (Up, Dw, or Bi) a Field Descriptor applies to. This allows + for asymmetric processing, using the same Rule. + + Dw: Downlink direction for compression/decompression, from SCHC C/D + in the network to SCHC C/D in the Dev. + + FID: Field Identifier or Field ID. This identifies the protocol and + field a Field Descriptor applies to. + + FL: Field Length. This is the length of the original packet header + field. It is expressed as a number of bits for header fields of + fixed lengths or as a type (e.g., variable, token length, ...) for + Field Lengths that are unknown at the time of Rule creation. The + length of a header field is defined in the corresponding protocol + specification (such as IPv6 or UDP). + + FP: Field Position. When a field is expected to appear multiple + times in a header, the Field Position specifies the occurrence + this Field Descriptor applies to (for example, first Uri-Path + option, second Uri-Path, etc. in a Constrained Application + Protocol (CoAP) header), counting from 1. The value 0 is special + and means "don't care" (see Section 7.2 of [RFC8724]). + + IID: Interface Identifier. See the IPv6 addressing architecture + [RFC7136]. + + L2 Word: This is the minimum subdivision of payload data that the + Layer 2 (L2) will carry. In most L2 technologies, the L2 Word is + an octet. In bit-oriented radio technologies, the L2 Word might + be a single bit. The L2 Word size is assumed to be constant over + time for each device. + + MO: Matching Operator. An operator used to match a value contained + in a header field with a value contained in a Rule. + + RuleID: Rule Identifier. An identifier for a Rule. SCHC C/D on + both sides share the same RuleID for a given packet. A set of + RuleIDs are used to support SCHC F/R functionality. + + TV: Target Value. A value contained in a Rule that will be matched + with the value of a header field. + + Up: Uplink direction for compression/decompression, from the Dev + SCHC C/D to the network SCHC C/D. + +4. SCHC Rules + + SCHC compression is generic; the main mechanism does not refer to a + specific protocol. Any header field is abstracted through a Field + Identifier (FID), a position (FP), a direction (DI), and a value that + can be a numerical value or a string. [RFC8724] and [RFC8824] + specify fields for IPv6 [RFC8200], UDP [RFC0768], and CoAP [RFC7252], + including options defined for no server response [RFC7967] and Object + Security for Constrained RESTful Environments (OSCORE) [RFC8613]. + For the latter, [RFC8824] splits this field into subfields. + + SCHC fragmentation requires a set of common parameters that are + included in a Rule. These parameters are defined in [RFC8724]. + + The YANG data model enables the compression and the fragmentation + selection using the feature statement. + +4.1. Compression Rules + + [RFC8724] proposes an informal 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. + + +-----------------------------------------------------------------+ + | Rule N | + +-----------------------------------------------------------------+| + | Rule i || + +-----------------------------------------------------------------+|| + | (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||| + |+-------+--+--+--+------------+-----------------+---------------+|/ + | | + \-----------------------------------------------------------------/ + + Figure 1: Compression Decompression Context + +4.2. Identifier Generation + + Identifiers used in the SCHC YANG data model are from the identityref + statement to ensure global uniqueness and easy augmentation 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 below (Figure 2) shows how an identityref is created for + Reassembly Check Sequence (RCS) algorithms used during SCHC + fragmentation. + + 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-crc32 { + base rcs-algorithm-base-type; + description + "CRC32 defined as default RCS in RFC 8724. This RCS is + 4 bytes 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."; + } + + Figure 2: Principle to Define a Type Based on identityref + +4.3. 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. [RFC8724] 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, + etc.). + + The current YANG data model includes field definitions found in + [RFC8724] and [RFC8824]. + + 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 subfields, the field + identity serves as a base. + + The full field-id definition is found in Section 6. A type is + defined for the IPv6 protocol, and each field is based on it. Note + that the Diffserv bits derive from the Traffic Class identity. + +4.4. Convention for Field Length + + The Field Length is either an integer giving the size of a field in + bits or a specific function. [RFC8724] defines the "var" function, + which allows variable-length fields (whose length is expressed in + bytes), and [RFC8824] 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 Section 6. Therefore, the type for the Field Length is + a union between an integer giving the size of the length in bits and + the identityref. + +4.5. Convention for Field Position + + The Field Position is a positive integer that gives the occurrence + times of a specific field from the header start. The default value + is 1 and is incremented at each repetition. Value 0 indicates that + the position is not important and is not considered during the Rule + selection process. + + The Field Position is a positive integer. The type is uint8. + +4.6. Convention for Direction Indicator + + The Direction Indicator is used to tell if a field appears in both + directions (Bi) or only uplink (Up) or Downlink (Dw). The naming + convention is "di" followed by the Direction Indicator name. + + The type is "di-type". + +4.7. 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 + the index as a key. The highest index value is used to compute the + size of the index sent in residue for the match-mapping Compression + Decompression Action (CDA). The index can specify several values: + + * For equal and most significant bits (MSBs), the Target Value + contains a single element. Therefore, the index is set to 0. + + * For match-mapping, the Target Value can contain several elements. + Index values MUST start from 0 and MUST be contiguous. + + If the header field contains text, the binary sequence uses the same + encoding. + +4.8. Convention for Matching Operator + + The Matching Operator (MO) is a function applied between a field + value provided by the parsed header and the Target Value. [RFC8724] + defines 4 MOs. + + The naming convention is "mo-" followed by the MO name. + + The type is "mo-type". + +4.8.1. Matching Operator Arguments + + They are viewed as a list, built with a tv-struct (see Section 4.7). + +4.9. Convention for Compression Decompression Actions + + The Compression Decompression Action (CDA) identifies the function to + use for compression or decompression. [RFC8724] defines 7 CDAs. + + The naming convention is "cda-" followed by the CDA name. + +4.9.1. Compression Decompression Action Arguments + + Currently no CDA requires arguments, but some CDAs may require one or + several arguments in the future. They are viewed as a list of + target-value type. + +4.10. 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 Appendix D of + [RFC8724]. + + 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. + +4.10.1. Fragmentation Mode + + [RFC8724] defines 3 fragmentation modes: + + * No ACK: This mode is unidirectional; 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. + +4.10.2. Fragmentation Header + + A data fragment header, starting with the RuleID, can be sent in the + fragmentation direction. [RFC8724] indicates that the SCHC header + may be composed of the following (cf. Figure 3): + + * a Datagram Tag (DTag) identifying the datagram being fragmented if + the fragmentation applies concurrently on several datagrams. This + field is 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 [RFC8724], and its size is defined by the Rule. + + |-- SCHC Fragment Header ----| + |-- T --|-M-|-- N --| + +-- ... -+- ... -+---+- ... -+--------...-------+~~~~~~~~~~~~~~~~~~~~ + | RuleID | DTag | W | FCN | Fragment Payload | padding (as needed) + +-- ... -+- ... -+---+- ... -+--------...-------+~~~~~~~~~~~~~~~~~~~~ + + Figure 3: Data Fragment Header from RFC 8724 + +4.10.3. Last Fragment Format + + The last fragment of a datagram is sent with a Reassembly Check + Sequence (RCS) field to detect residual transmission errors and + possible losses in the last window. [RFC8724] 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 following parameters define 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. + +4.10.4. Acknowledgment Behavior + + The acknowledgment fragment header goes in the opposite direction of + data. [RFC8724] defines the header, which is composed of the + following (see Figure 4): + + * 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. + + |--- SCHC ACK Header ----| + |-- T --|-M-| 1 | + +-- ... -+- ... -+---+---+~~~~~~~~~~~~~~~~~~ + | RuleID | DTag | W |C=1| padding as needed (success) + +-- ... -+- ... -+---+---+~~~~~~~~~~~~~~~~~~ + + +-- ... -+- ... -+---+---+------ ... ------+~~~~~~~~~~~~~~~ + | RuleID | DTag | W |C=0|Compressed Bitmap| pad. as needed (failure) + +-- ... -+- ... -+---+---+------ ... ------+~~~~~~~~~~~~~~~ + + Figure 4: Acknowledgment Fragment Header for RFC 8724 + + 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. + +4.10.5. Timer Values + + The state machine requires some common values to handle fragmentation + correctly. + + * The Retransmission Timer gives the duration before sending an ACK + request (cf. Section 8.2.2.4 of [RFC8724]). If specified, the + value MUST be strictly positive. + + * The Inactivity Timer gives the duration before aborting a + fragmentation session (cf. Section 8.2.2.4 of [RFC8724]). The + value 0 explicitly indicates that this timer is disabled. + + [RFC8724] does not specify any range for these timers. [RFC9011] + recommends a duration of 12 hours. In fact, the value range should + be between milliseconds for real-time systems to several days for + worse-than-best-effort systems. 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 + seconds. 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 second and 19 hours, as recommended in [RFC9011]. + +4.10.6. Fragmentation Parameter + + The SCHC fragmentation protocol specifies the number of attempts + before aborting through the parameter: + + * max-ack-requests (cf. Section 8.2.2.4 of [RFC8724]) + +4.10.7. Layer 2 Parameters + + The data model includes two parameters needed for fragmentation: + + * l2-word-size: [RFC8724] base fragmentation, in bits, on a Layer 2 + Word that can be of any length. The default value is 8 and + corresponds to the default value for the 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 an uncompressed + datagram. By default, the value is set to 1280 bytes. + + They are defined as unsigned integers; see Section 6. + +5. Rule Definition + + A Rule is identified by a unique Rule Identifier (RuleID) comprising + both a RuleID value and a RuleID length. The YANG grouping rule-id- + type defines the structure used to represent a RuleID. A length of 0 + is allowed to represent an implicit Rule. + + Three natures of Rules are defined in [RFC8724]: + + * Compression: A compression Rule is associated with the RuleID. + + * No-compression: This identifies the default Rule used to send a + packet integrally when no-compression Rule was found (see + Section 6 of [RFC8724]). + + * Fragmentation: Fragmentation parameters are associated with the + RuleID. Fragmentation is optional, and the feature + "fragmentation" should be set. + + The YANG data model respectively introduces these three identities : + + * nature-compression + + * nature-no-compression + + * nature-fragmentation + + The naming convention is "nature-" followed by the nature identifier. + + To access a specific Rule, the RuleID length and value are used as a + key. The Rule is either a compression or a fragmentation Rule. + +5.1. Compression Rule + + A compression Rule is composed of entries describing its processing. + An entry contains all the information defined in Figure 1 with the + types defined above. + + The compression Rule described Figure 1 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 represents a line in Figure 1. Their type reflects the + identifier types defined in Section 4.1. + + Some checks are performed on the values: + + * When MO is ignore, no Target Value is needed; for other MOs, there + MUST be a Target Value present. + + * When MSB MO is specified, the matching-operator-value must be + present. + +5.2. Fragmentation Rule + + A fragmentation Rule is composed of entries describing the protocol + behavior. Some on them are numerical entries, others are identifiers + defined in Section 4.10. + +5.3. YANG Tree + + The YANG data model described in this document conforms to the + Network Management Datastore Architecture defined in [RFC8342]. + + module: ietf-schc + +--rw schc + +--rw rule* [rule-id-value rule-id-length] + +--rw rule-id-value uint32 + +--rw rule-id-length uint8 + +--rw rule-nature nature-type + +--rw (nature)? + +--:(fragmentation) {fragmentation}? + | +--rw fragmentation-mode + | | schc:fragmentation-mode-type + | +--rw l2-word-size? uint8 + | +--rw direction schc:di-type + | +--rw dtag-size? uint8 + | +--rw w-size? uint8 + | +--rw fcn-size uint8 + | +--rw rcs-algorithm? rcs-algorithm-type + | +--rw maximum-packet-size? uint16 + | +--rw window-size? uint16 + | +--rw max-interleaved-frames? uint8 + | +--rw inactivity-timer + | | +--rw ticks-duration? uint8 + | | +--rw ticks-numbers? uint16 + | +--rw retransmission-timer + | | +--rw ticks-duration? uint8 + | | +--rw ticks-numbers? uint16 + | +--rw max-ack-requests? uint8 + | +--rw (mode)? + | +--:(no-ack) + | +--:(ack-always) + | +--:(ack-on-error) + | +--rw tile-size? uint8 + | +--rw tile-in-all-1? schc:all-1-data-type + | +--rw ack-behavior? schc:ack-behavior-type + +--:(compression) {compression}? + +--rw entry* + [field-id field-position direction-indicator] + +--rw field-id schc:fid-type + +--rw field-length schc:fl-type + +--rw field-position uint8 + +--rw direction-indicator schc:di-type + +--rw target-value* [index] + | +--rw index uint16 + | +--rw value? binary + +--rw matching-operator schc:mo-type + +--rw matching-operator-value* [index] + | +--rw index uint16 + | +--rw value? binary + +--rw comp-decomp-action schc:cda-type + +--rw comp-decomp-action-value* [index] + +--rw index uint16 + +--rw value? binary + + Figure 5: Overview of the SCHC Data Model + +6. YANG Data Model + + <CODE BEGINS> file "ietf-schc@2023-03-01.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: <https://datatracker.ietf.org/wg/lpwan/about/> + WG List: <mailto:lp-wan@ietf.org> + Editor: Laurent Toutain + <mailto:laurent.toutain@imt-atlantique.fr> + Editor: Ana Minaburo + <mailto:ana@ackl.io>"; + description + "Copyright (c) 2023 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 9363 + (https://www.rfc-editor.org/info/rfc9363); 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 the Static Context Header Compression + Rule for SCHC, based on RFCs 8724 and 8824. Including + compression, no-compression, and fragmentation Rules. + + This module is a YANG data model for SCHC Rules (RFCs 8724 and + 8824). RFC 8724 describes compression Rules in an 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 specifies a global data model that can be used for + Rule exchanges or modification. It specifies 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 2023-03-01 { + description + "Initial version from RFC 9363."; + reference + "RFC 9363 A YANG 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."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; + } + + identity fid-ipv6-trafficclass { + base fid-ipv6-base-type; + description + "IPv6 Traffic Class field."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; + } + + identity fid-ipv6-trafficclass-ds { + base fid-ipv6-trafficclass; + description + "IPv6 Traffic Class field: Diffserv field."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification, + 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: ECN field."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification, + 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."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; + } + + identity fid-ipv6-payload-length { + base fid-ipv6-base-type; + description + "IPv6 Payload Length field."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; + } + + identity fid-ipv6-nextheader { + base fid-ipv6-base-type; + description + "IPv6 Next Header field."; + reference + "RFC 8200 Internet Protocol, Version 6 (IPv6) Specification"; + } + + identity fid-ipv6-hoplimit { + base fid-ipv6-base-type; + description + "IPv6 Next Header field."; + 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 on whether it is 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 IID of RFC 8200 depending on whether it is 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 on whether it is an + uplink or a downlink 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 IID of RFC 8200 depending on whether it is an uplink + or a downlink 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, 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, if uplink or downlink + communication, respectively."; + reference + "RFC 768 User Datagram Protocol"; + } + + identity fid-udp-length { + base fid-udp-base-type; + description + "UDP length."; + reference + "RFC 768 User Datagram Protocol"; + } + + identity fid-udp-checksum { + base fid-udp-base-type; + description + "UDP length."; + reference + "RFC 768 User Datagram Protocol"; + } + + identity fid-coap-base-type { + base fid-base-type; + description + "Field ID base type for UDP headers described."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-version { + base fid-coap-base-type; + description + "CoAP version."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-type { + base fid-coap-base-type; + description + "CoAP type."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-tkl { + base fid-coap-base-type; + description + "CoAP token length."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-code { + base fid-coap-base-type; + description + "CoAP code."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-code-class { + base fid-coap-code; + description + "CoAP code class."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-code-detail { + base fid-coap-code; + description + "CoAP code detail."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-mid { + base fid-coap-base-type; + description + "CoAP message ID."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-token { + base fid-coap-base-type; + description + "CoAP token."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option { + base fid-coap-base-type; + description + "Generic CoAP option."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-if-match { + base fid-coap-option; + description + "CoAP option If-Match."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-uri-host { + base fid-coap-option; + description + "CoAP option Uri-Host."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-etag { + base fid-coap-option; + description + "CoAP option ETag."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-if-none-match { + base fid-coap-option; + description + "CoAP option if-none-match."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-observe { + base fid-coap-option; + description + "CoAP option Observe."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-uri-port { + base fid-coap-option; + description + "CoAP option Uri-Port."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-location-path { + base fid-coap-option; + description + "CoAP option Location-Path."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-uri-path { + base fid-coap-option; + description + "CoAP option Uri-Path."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-content-format { + base fid-coap-option; + description + "CoAP option Content Format."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-max-age { + base fid-coap-option; + description + "CoAP option Max-Age."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-uri-query { + base fid-coap-option; + description + "CoAP option Uri-Query."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-accept { + base fid-coap-option; + description + "CoAP option Accept."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-location-query { + base fid-coap-option; + description + "CoAP option Location-Query."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-block2 { + base fid-coap-option; + description + "CoAP option Block2."; + reference + "RFC 7959 Block-Wise Transfers in the Constrained + Application Protocol (CoAP)"; + } + + identity fid-coap-option-block1 { + base fid-coap-option; + description + "CoAP option Block1."; + reference + "RFC 7959 Block-Wise Transfers in the Constrained + Application Protocol (CoAP)"; + } + + identity fid-coap-option-size2 { + base fid-coap-option; + description + "CoAP option Size2."; + reference + "RFC 7959 Block-Wise Transfers in the Constrained + Application Protocol (CoAP)"; + } + + identity fid-coap-option-proxy-uri { + base fid-coap-option; + description + "CoAP option Proxy-Uri."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-proxy-scheme { + base fid-coap-option; + description + "CoAP option Proxy-Scheme."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-size1 { + base fid-coap-option; + description + "CoAP option Size1."; + reference + "RFC 7252 The Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-no-response { + base fid-coap-option; + description + "CoAP option No response."; + reference + "RFC 7967 Constrained Application Protocol (CoAP) + Option for No Server Response"; + } + + identity fid-oscore-base-type { + base fid-coap-option; + description + "OSCORE options (RFC8613) split in suboptions."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP)"; + } + + identity fid-coap-option-oscore-flags { + base fid-coap-option; + description + "CoAP option OSCORE flags."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP) (see + Section 6.4)"; + } + + identity fid-coap-option-oscore-piv { + base fid-coap-option; + description + "CoAP option OSCORE flags."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP) (see + Section 6.4)"; + } + + identity fid-coap-option-oscore-kid { + base fid-coap-option; + description + "CoAP option OSCORE flags."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP) (see + Section 6.4)"; + } + + identity fid-coap-option-oscore-kidctx { + base fid-coap-option; + description + "CoAP option OSCORE flags."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP)(see + Section 6.4)"; + } + + //---------------------------------- + // 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 bytes is sent as defined for CoAP."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP) (see + Section 5.3)"; + } + + identity fl-token-length { + base fl-base-type; + description + "Residue length in bytes is sent as defined for CoAP."; + reference + "RFC 8824 Static Context Header Compression (SCHC) for the + Constrained Application Protocol (CoAP) (see + Section 4.5)"; + } + + //--------------------------------- + // Direction Indicator type + //--------------------------------- + + identity di-base-type { + description + "Used to extend Direction Indicators."; + } + + identity di-bidirectional { + base di-base-type; + description + "Direction Indicator of bidirectionality."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.1)"; + } + + identity di-up { + base di-base-type; + description + "Direction Indicator of uplink."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.1)"; + } + + identity di-down { + base di-base-type; + description + "Direction Indicator of downlink."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.1)"; + } + + //---------------------------------- + // Matching Operator type definition + //---------------------------------- + + identity mo-base-type { + description + "Matching Operator: used in the Rule selection process + to check if a Target Value matches the field's value."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.2)"; + } + + identity mo-equal { + base mo-base-type; + description + "equal MO."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.3)"; + } + + identity mo-ignore { + base mo-base-type; + description + "ignore MO."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.3)"; + } + + identity mo-msb { + base mo-base-type; + description + "MSB MO."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.3)"; + } + + identity mo-match-mapping { + base mo-base-type; + description + "match-mapping MO."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.3)"; + } + + //------------------------------ + // 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."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.2)"; + } + + identity cda-not-sent { + base cda-base-type; + description + "not-sent CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-value-sent { + base cda-base-type; + description + "value-sent CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-lsb { + base cda-base-type; + description + "Least Significant Bit (LSB) CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-mapping-sent { + base cda-base-type; + description + "mapping-sent CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-compute { + base cda-base-type; + description + "compute-* CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-deviid { + base cda-base-type; + description + "DevIID CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + identity cda-appiid { + base cda-base-type; + description + "Application Interface Identifier (AppIID) CDA."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context + Header Compression and Fragmentation (see + Section 7.4)"; + } + + // -- 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 identityref { + base fl-base-type; + } + description + "Function used to indicate Field Length."; + 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, or 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 field 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 compress 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 mode."; + 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 mode."; + 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 mode."; + 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-crc32 { + base rcs-algorithm-base-type; + description + "CRC32 defined as default RCS in RFC 8724. This RCS is + 4 bytes 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."; + } + + // -------- 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 + order in the matching list, starting at 0."; + } + leaf value { + type binary; + description + "Target Value content as an untyped binary value."; + } + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation"; + } + + grouping compression-rule-entry { + description + "These entries define 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 or a function + - Field Position: a positive (and possibly equal to 0) + integer + - Direction Indicator: an indication in which direction the + 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 + identity reference."; + } + leaf field-length { + type union { + type uint8; + 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 + occurrences. + Position 0 means that this entry matches a field + irrespective of its position of occurrence 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 + considered for Rule selection or ignored based on the + direction (bidirectional, only uplink, or only + downlink)."; + } + list target-value { + key "index"; + uses tv-struct; + description + "A list of values 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, index should take consecutive values starting + from 0."; + } + 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."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 7.3)"; + } + 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; + must "../target-value or + derived-from-or-self(., 'cda-value-sent') or + derived-from-or-self(., 'cda-compute') or + derived-from-or-self(., 'cda-appiid') or + derived-from-or-self(., 'cda-deviid')" { + error-message + "cda-not-sent, cda-lsb, and cda-mapping-sent need + target-value"; + description + "target-value is not required for some CDA."; + } + mandatory true; + description + "CDA: Compression Decompression Action."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 7.4)"; + } + 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."; + } + } + + // --Rule nature + + identity nature-base-type { + description + "A Rule, identified by its RuleID, is used for a single + purpose. RFC 8724 defines 3 natures: + compression, no-compression, and fragmentation."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 6)"; + } + + identity nature-compression { + base nature-base-type; + description + "Identify a compression Rule."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 6)"; + } + + identity nature-no-compression { + base nature-base-type; + description + "Identify a no-compression Rule."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 6)"; + } + + identity nature-fragmentation { + base nature-base-type; + description + "Identify a fragmentation Rule."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation (see Section 6)"; + } + + 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, or + 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 + "MUST be up or down, bidirectional MUST NOT be used."; + } + // SCHC Frag header format + leaf dtag-size { + type uint8; + default "0"; + description + "Size, in bits, of the DTag field (T variable from + RFC 8724)."; + } + 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 + RFC 8724)."; + } + leaf fcn-size { + type uint8; + mandatory true; + description + "Size, in bits, of the FCN field (N variable from + RFC 8724)."; + } + leaf rcs-algorithm { + type rcs-algorithm-type; + default "schc:rcs-crc32"; + 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, the FCN value is 2^w-size - 1. + This value should not be exceeded. 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 more than + max-interleaved-frames MUST NOT be active at any time."; + } + container inactivity-timer { + leaf ticks-duration { + type uint8; + default "20"; + description + "Duration of one tick in microseconds: + 2^ticks-duration/10^6 = 1.048s."; + } + leaf ticks-numbers { + type uint16 { + range "0..max"; + } + description + "Timer duration = ticks-numbers*2^ticks-duration / 10^6."; + } + + description + "Duration in seconds of the Inactivity Timer; 0 indicates + that the timer is disabled. + + Allows a precision from microsecond to year by sending the + tick-duration value. For instance: + + tick-duration: smallest value <-> highest value + + 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."; + } + container retransmission-timer { + leaf ticks-duration { + type uint8; + default "20"; + description + "Duration of one tick in microseconds: + 2^ticks-duration/10^6 = 1.048s."; + } + leaf ticks-numbers { + type uint16 { + range "1..max"; + } + description + "Timer duration = ticks-numbers*2^ticks-duration / 10^6."; + } + 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. + See the Inactivity 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 or 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 RuleID. RuleID is composed of a RuleID value and a + // RuleID length + + grouping rule-id-type { + leaf rule-id-value { + type uint32; + description + "RuleID value. This value must be unique, considering its + length."; + } + leaf rule-id-length { + type uint8 { + range "0..32"; + } + description + "RuleID length, in bits. The value 0 is for implicit + Rules."; + } + description + "A RuleID 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 compression, no-compression, or fragmentation + Rules identified by their rule-id."; + } + description + "A SCHC set of Rules is composed of a list of Rules that are + used for compression, no-compression, or fragmentation."; + reference + "RFC 8724 SCHC: Generic Framework for Static Context Header + Compression and Fragmentation"; + } + } + <CODE ENDS> + + Figure 6: SCHC YANG Data Model + +7. IANA Considerations + + This document registers one URI and one YANG data model. + +7.1. URI Registration + + IANA registered the following URI in the "IETF XML Registry" + [RFC3688]: + + URI: urn:ietf:params:xml:ns:yang:ietf-schc + Registrant Contact: The IESG. + XML: N/A; the requested URI is an XML namespace. + +7.2. YANG Module Name Registration + + IANA has registered the following YANG data model in the "YANG Module + Names" registry [RFC6020]. + + name: ietf-schc + namespace: urn:ietf:params:xml:ns:yang:ietf-schc + prefix: schc + reference: RFC 9363 + +8. 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 [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer + is the secure transport layer, and the mandatory-to-implement secure + transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer + is HTTPS, and the mandatory-to-implement secure transport is TLS + [RFC8446]. + + The Network Configuration Access Control Model (NACM) [RFC8341] + 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. + + There are a number of data nodes defined in this YANG module that are + writable/creatable/deletable (i.e., config true, which is the + default). These data nodes may be considered sensitive or vulnerable + in some network environments. Write operations (e.g., edit-config) + to these data nodes without proper protection can have a negative + effect on network operations. These are the subtrees and data nodes + and their sensitivity/vulnerability: + + /schc: All the data nodes may be modified. The Rule contains + sensitive information, such as the application IPv6 address where + the device's data will be sent after decompression. An attacker + may try to modify other devices' Rules by changing the application + address and may block communication or allows traffic + eavesdropping. Therefore, a device must be allowed to modify only + its own rules on the remote SCHC instance. The identity of the + requester must be validated. This can be done through + certificates or access lists. Modification may be allowed + regarding the Field Descriptor (i.e., IPv6 addresses field + descriptors should not be modified, but UDP dev port could be + changed). + + Some of the readable data nodes in this YANG module may be considered + sensitive or vulnerable in some network environments. It is thus + important to control read access (e.g., via get, get-config, or + notification) to these data nodes. These are the subtrees and data + nodes and their sensitivity/vulnerability: + + /schc: By reading a module, an attacker may learn the traffic + generated by a device and can also learn about application + addresses or REST API. + +9. References + +9.1. Normative References + + [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, + DOI 10.17487/RFC0768, August 1980, + <https://www.rfc-editor.org/info/rfc768>. + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <https://www.rfc-editor.org/info/rfc2119>. + + [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, + DOI 10.17487/RFC3688, January 2004, + <https://www.rfc-editor.org/info/rfc3688>. + + [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for + the Network Configuration Protocol (NETCONF)", RFC 6020, + DOI 10.17487/RFC6020, October 2010, + <https://www.rfc-editor.org/info/rfc6020>. + + [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., + and A. Bierman, Ed., "Network Configuration Protocol + (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, + <https://www.rfc-editor.org/info/rfc6241>. + + [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure + Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, + <https://www.rfc-editor.org/info/rfc6242>. + + [RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6 + Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, + February 2014, <https://www.rfc-editor.org/info/rfc7136>. + + [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained + Application Protocol (CoAP)", RFC 7252, + DOI 10.17487/RFC7252, June 2014, + <https://www.rfc-editor.org/info/rfc7252>. + + [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF + Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, + <https://www.rfc-editor.org/info/rfc8040>. + + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, <https://www.rfc-editor.org/info/rfc8174>. + + [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", STD 86, RFC 8200, + DOI 10.17487/RFC8200, July 2017, + <https://www.rfc-editor.org/info/rfc8200>. + + [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration + Access Control Model", STD 91, RFC 8341, + DOI 10.17487/RFC8341, March 2018, + <https://www.rfc-editor.org/info/rfc8341>. + + [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., + and R. Wilton, "Network Management Datastore Architecture + (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, + <https://www.rfc-editor.org/info/rfc8342>. + + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol + Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, + <https://www.rfc-editor.org/info/rfc8446>. + + [RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz, + "Object Security for Constrained RESTful Environments + (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019, + <https://www.rfc-editor.org/info/rfc8613>. + + [RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC. + Zuniga, "SCHC: Generic Framework for Static Context Header + Compression and Fragmentation", RFC 8724, + DOI 10.17487/RFC8724, April 2020, + <https://www.rfc-editor.org/info/rfc8724>. + + [RFC8824] Minaburo, A., Toutain, L., and R. Andreasen, "Static + Context Header Compression (SCHC) for the Constrained + Application Protocol (CoAP)", RFC 8824, + DOI 10.17487/RFC8824, June 2021, + <https://www.rfc-editor.org/info/rfc8824>. + +9.2. Informative References + + [LPWAN-ARCH] + Pelov, A., Thubert, P., and A. Minaburo, "LPWAN Static + Context Header Compression (SCHC) Architecture", Work in + Progress, Internet-Draft, draft-ietf-lpwan-architecture- + 02, 30 June 2022, <https://datatracker.ietf.org/doc/html/ + draft-ietf-lpwan-architecture-02>. + + [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", + RFC 7950, DOI 10.17487/RFC7950, August 2016, + <https://www.rfc-editor.org/info/rfc7950>. + + [RFC7967] Bhattacharyya, A., Bandyopadhyay, S., Pal, A., and T. + Bose, "Constrained Application Protocol (CoAP) Option for + No Server Response", RFC 7967, DOI 10.17487/RFC7967, + August 2016, <https://www.rfc-editor.org/info/rfc7967>. + + [RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN) + Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018, + <https://www.rfc-editor.org/info/rfc8376>. + + [RFC9011] Gimenez, O., Ed. and I. Petrov, Ed., "Static Context + Header Compression and Fragmentation (SCHC) over LoRaWAN", + RFC 9011, DOI 10.17487/RFC9011, April 2021, + <https://www.rfc-editor.org/info/rfc9011>. + +Appendix A. Example + + The informal Rules given Figure 7 are represented in XML, as shown in + Figure 8. + + /-------------------------\ + |Rule 6/3 110 | + |---------------+---+--+--+----------------+-------+----------------\ + |IPV6.VER | 4| 1|BI| 6|EQUAL |NOT-SENT | + |IPV6.TC | 8| 1|BI| 0|EQUAL |NOT-SENT | + |IPV6.FL | 20| 1|BI| 0|IGNORE |NOT-SENT | + |IPV6.LEN | 16| 1|BI| |IGNORE |COMPUTE-LENGTH | + |IPV6.NXT | 8| 1|BI| 58|EQUAL |NOT-SENT | + |IPV6.HOP_LMT | 8| 1|BI| 255|IGNORE |NOT-SENT | + |IPV6.DEV_PREFIX| 64| 1|BI|200104701f2101d2|EQUAL |NOT-SENT | + |IPV6.DEV_IID | 64| 1|BI|0000000000000003|EQUAL |NOT-SENT | + |IPV6.APP_PREFIX| 64| 1|BI| |IGNORE |VALUE-SENT | + |IPV6.APP_IID | 64| 1|BI| |IGNORE |VALUE-SENT | + \---------------+---+--+--+----------------+-------+----------------/ + /-------------------------\ + |Rule 12/11 00001100 | + !=========================+=========================================\ + !^ Fragmentation mode : NoAck header dtag 2 Window 0 FCN 3 UP ^! + !^ No Tile size specified ^! + !^ RCS Algorithm: RCS_CRC32 ^! + \===================================================================/ + /-------------------------\ + |Rule 100/8 01100100 | + | NO-COMPRESSION RULE | + \-------------------------/ + + Figure 7: Rules Example + + <?xml version='1.0' encoding='UTF-8'?> + <schc xmlns="urn:ietf:params:xml:ns:yang:ietf-schc"> + <rule> + <rule-id-value>6</rule-id-value> + <rule-id-length>3</rule-id-length> + <rule-nature>nature-compression</rule-nature> + <entry> + <field-id>fid-ipv6-version</field-id> + <field-length>4</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-equal</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>AAY=</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-trafficclass</field-id> + <field-length>8</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-equal</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>AA==</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-flowlabel</field-id> + <field-length>20</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-ignore</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>AA==</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-payload-length</field-id> + <field-length>16</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-ignore</matching-operator> + <comp-decomp-action>cda-compute</comp-decomp-action> + </entry> + <entry> + <field-id>fid-ipv6-nextheader</field-id> + <field-length>8</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-equal</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>ADo=</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-hoplimit</field-id> + <field-length>8</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-ignore</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>AP8=</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-devprefix</field-id> + <field-length>64</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-equal</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>IAEEcB8hAdI=</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-deviid</field-id> + <field-length>64</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-equal</matching-operator> + <comp-decomp-action>cda-not-sent</comp-decomp-action> + <target-value> + <index>0</index> + <value>AAAAAAAAAAM=</value> + </target-value> + </entry> + <entry> + <field-id>fid-ipv6-appprefix</field-id> + <field-length>64</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-ignore</matching-operator> + <comp-decomp-action>cda-value-sent</comp-decomp-action> + </entry> + <entry> + <field-id>fid-ipv6-appiid</field-id> + <field-length>64</field-length> + <field-position>1</field-position> + <direction-indicator>di-bidirectional</direction-indicator> + <matching-operator>mo-ignore</matching-operator> + <comp-decomp-action>cda-value-sent</comp-decomp-action> + </entry> + </rule> + <rule> + <rule-id-value>12</rule-id-value> + <rule-id-length>11</rule-id-length> + <rule-nature>nature-fragmentation</rule-nature> + <direction>di-up</direction> + <rcs-algorithm>rcs-crc32</rcs-algorithm> + <dtag-size>2</dtag-size> + <fcn-size>3</fcn-size> + <fragmentation-mode> + fragmentation-mode-no-ack + </fragmentation-mode> + </rule> + <rule> + <rule-id-value>100</rule-id-value> + <rule-id-length>8</rule-id-length> + <rule-nature>nature-no-compression</rule-nature> + </rule> + </schc> + + Figure 8: XML Representation of the Rules + +Acknowledgments + + The authors would like to thank Dominique Barthel, Carsten Bormann, + Ivan Martinez, and Alexander Pelov for their careful reading and + valuable inputs. A special thanks for Joe Clarke, Carl Moberg, Tom + Petch, Martin Thomson, and Éric Vyncke for their explanations and + wise advice when building the model. + +Authors' Addresses + + Ana Minaburo + Acklio + 1137A avenue des Champs Blancs + 35510 Cesson-Sevigne Cedex + France + Email: ana@ackl.io + + + Laurent Toutain + Institut MINES TELECOM; IMT Atlantique + 2 rue de la Chataigneraie CS 17607 + 35576 Cesson-Sevigne Cedex + France + Email: Laurent.Toutain@imt-atlantique.fr |