A YANG Data Model for Static Context Header Compression (SCHC)Acklio1137A avenue des Champs BlancsCesson-Sevigne Cedex35510Franceana@ackl.ioInstitut MINES TELECOM; IMT Atlantique2 rue de la Chataigneraie CS 17607Cesson-Sevigne Cedex35576FranceLaurent.Toutain@imt-atlantique.fr
int
lpwanHeader CompressionFragmentationSCHC RuleIPv6UDPCoAPOSCOREThis 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.
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the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
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errata, and how to provide feedback on it may be obtained at
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Table of Contents
. Introduction
. Requirements Language
. Terminology
. SCHC Rules
. Compression Rules
. Identifier Generation
. Convention for Field Identifier
. Convention for Field Length
. Convention for Field Position
. Convention for Direction Indicator
. Convention for Target Value
. Convention for Matching Operator
. Matching Operator Arguments
. Convention for Compression Decompression Actions
. Compression Decompression Action Arguments
. Fragmentation Rule
. Fragmentation Mode
. Fragmentation Header
. Last Fragment Format
. Acknowledgment Behavior
. Timer Values
. Fragmentation Parameter
. Layer 2 Parameters
. Rule Definition
. Compression Rule
. Fragmentation Rule
. YANG Tree
. YANG Data Model
. IANA Considerations
. URI Registration
. YANG Module Name Registration
. Security Considerations
. References
. Normative References
. Informative References
. Example
Acknowledgments
Authors' Addresses
IntroductionSCHC 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 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.).
illustrates the exchange of Rules using the YANG data model.This document defines a YANG data model 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.
TerminologyThis section defines the terminology and acronyms used in this document.
It extends the terminology of .
App:
Low-Power WAN (LPWAN) Application, as defined by . 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 .
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 ).
IID:
Interface Identifier. See the IPv6 addressing architecture .
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.
SCHC RulesSCHC 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. and specify fields for IPv6 , UDP , and CoAP , including options defined for no server response and Object Security for Constrained RESTful Environments (OSCORE) . For the latter, splits this field into subfields.SCHC fragmentation requires a set of common parameters that are included in a Rule. These parameters are defined in .The YANG data model enables the compression and the fragmentation selection using the feature statement.Compression Rules 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.Identifier GenerationIdentifiers 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 () shows how an identityref is created for Reassembly Check Sequence (RCS) algorithms used during SCHC fragmentation.Convention for Field IdentifierIn 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, etc.).The current YANG data model includes field definitions found in and .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 . 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.Convention for Field LengthThe 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 the Field Length is a union between an integer giving the size of the length in bits and the identityref.Convention for Field PositionThe 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.Convention for Direction IndicatorThe 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".Convention for Target ValueThe 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.Convention for Matching OperatorThe Matching Operator (MO) is a function applied between a field value provided by the parsed header and the Target Value. defines 4 MOs.The naming convention is "mo-" followed by the MO name.The type is "mo-type".Matching Operator ArgumentsThey are viewed as a list, built with a tv-struct (see ).Convention for Compression Decompression ActionsThe Compression Decompression Action (CDA) identifies the function to use for compression or decompression.
defines 7 CDAs.The naming convention is "cda-" followed by the CDA name.Compression Decompression Action ArgumentsCurrently 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.Fragmentation RuleFragmentation is optional in the data model and depends on the presence of the "fragmentation" feature.Most of the fragmentation parameters are listed in .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 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.Fragmentation HeaderA data fragment header, starting with the RuleID, can be sent in the fragmentation direction.
indicates that the SCHC header may be composed of the following (cf. ):
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 , and its size is defined by the Rule.
Last Fragment FormatThe 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. 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.Acknowledgment BehaviorThe acknowledgment fragment header goes in the opposite direction of data. defines the header, which is composed of the following (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 ValuesThe state machine requires some common values to handle fragmentation correctly.
The Retransmission Timer gives the duration before sending an ACK request (cf. ). If specified, the value MUST be strictly positive.
The Inactivity Timer gives the duration before aborting a fragmentation session (cf. ). The value 0 explicitly indicates that this timer is disabled.
does not specify any range for these timers. 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: 2tick-duration/106. 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 .
Fragmentation ParameterThe SCHC fragmentation protocol specifies the number of attempts before aborting through the parameter:
max-ack-requests (cf. )
Layer 2 ParametersThe data model includes two parameters needed for fragmentation:
l2-word-size: 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 .Rule DefinitionA 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 :
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 ).
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.Compression RuleA 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 represents a line in . Their type reflects the identifier types defined in
.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.
Fragmentation RuleA fragmentation Rule is composed of entries describing the protocol behavior. Some on them are numerical entries,
others are identifiers defined in .YANG TreeThe YANG data model described in this document conforms to the
Network Management Datastore Architecture defined in .YANG Data ModelIANA ConsiderationsThis document registers one URI and one YANG data model.URI RegistrationIANA registered the following URI 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 RegistrationIANA has registered the following YANG data model in the "YANG Module Names" registry .
name:
ietf-schc
namespace:
urn:ietf:params:xml:ns:yang:ietf-schc
prefix:
schc
reference:
RFC 9363
Security ConsiderationsThe 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.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.
ReferencesNormative ReferencesUser Datagram ProtocolKey words for use in RFCs to Indicate Requirement LevelsIn 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.The IETF XML RegistryThis 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 - A Data Modeling Language for the Network Configuration Protocol (NETCONF)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]Network Configuration Protocol (NETCONF)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]Using the NETCONF Protocol over Secure Shell (SSH)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]Significance of IPv6 Interface IdentifiersThe IPv6 addressing architecture includes a unicast interface identifier that is used in the creation of many IPv6 addresses. Interface identifiers are formed by a variety of methods. This document clarifies that the bits in an interface identifier have no meaning and that the entire identifier should be treated as an opaque value. In particular, RFC 4291 defines a method by which the Universal and Group bits of an IEEE link-layer address are mapped into an IPv6 unicast interface identifier. This document clarifies that those two bits are significant only in the process of deriving interface identifiers from an IEEE link-layer address, and it updates RFC 4291 accordingly.The Constrained Application Protocol (CoAP)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.RESTCONF ProtocolThis 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).Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 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.Internet Protocol, Version 6 (IPv6) SpecificationThis document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.Network Configuration Access Control ModelThe 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.Network Management Datastore Architecture (NMDA)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.The Transport Layer Security (TLS) Protocol Version 1.3This 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.Object Security for Constrained RESTful Environments (OSCORE)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.SCHC: Generic Framework for Static Context Header Compression and FragmentationThis 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.Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)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.Informative ReferencesLPWAN Static Context Header Compression (SCHC) ArchitectureAcklioCisco SystemsAcklio This document defines the LPWAN SCHC architecture.
Work in ProgressThe YANG 1.1 Data Modeling LanguageYANG 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).Constrained Application Protocol (CoAP) Option for No Server ResponseThere 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.Low-Power Wide Area Network (LPWAN) OverviewLow-Power Wide Area Networks (LPWANs) are wireless technologies with characteristics such as large coverage areas, low bandwidth, possibly very small packet and application-layer data sizes, and long battery life operation. This memo is an informational overview of the set of LPWAN technologies being considered in the IETF and of the gaps that exist between the needs of those technologies and the goal of running IP in LPWANs.Static Context Header Compression and Fragmentation (SCHC) over LoRaWANThe 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.ExampleThe informal Rules given are represented in XML, as shown in .AcknowledgmentsThe authors would like to thank , , , and for their careful reading and valuable inputs. A special thanks for
, , , ,
and for their explanations and wise advice when building the model.Authors' AddressesAcklio1137A avenue des Champs BlancsCesson-Sevigne Cedex35510Franceana@ackl.ioInstitut MINES TELECOM; IMT Atlantique2 rue de la Chataigneraie CS 17607Cesson-Sevigne Cedex35576FranceLaurent.Toutain@imt-atlantique.fr