<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?> <!-- generated by https://github.com/cabo/kramdown-rfc version 1.6.11 (Ruby 2.6.8) --><!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]><?rfc strict="yes"?> <?rfc compact="yes"?><rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902"docName="draft-ietf-lpwan-schc-over-nbiot-15"docName="draft-ietf-lpwan-schc-over-nbiot-15draft-ietf-lpwan-schc-over-nbiot-15" number="9391" submissionType="IETF" category="std" consensus="true"submissionType="IETF"tocInclude="true" sortRefs="true"symRefs="true">symRefs="true" updates="" obsoletes="" xml:lang="en" version="3"> <front> <title abbrev="LPWAN SCHC NB-IoT">Static Context Header Compression over Narrowband Internet of Things</title> <seriesInfo name="RFC" value="9391"/> <author initials="E." surname="Ramos" fullname="Edgar Ramos"> <organization>Ericsson</organization> <address> <postal> <street>Hirsalantie 11</street><city>02420 Jorvas,<city>Jorvas, Kirkkonummi</city> <code>02420</code> <country>Finland</country> </postal> <email>edgar.ramos@ericsson.com</email> </address> </author> <author initials="A." surname="Minaburo" fullname="Ana Minaburo"> <organization>Acklio</organization> <address> <postal> <street>1137A Avenue des Champs Blancs</street><city>35510 Cesson-Sevigne<city>Cesson-Sevigne Cedex</city> <code>35510</code> <country>France</country> </postal> <email>ana@ackl.io</email> </address> </author> <dateyear="2022" month="December" day="15"/> <area>Internet</area> <workgroup>lpwan Working Group</workgroup> <keyword>Internet-Draft</keyword>year="2023" month="April"/> <area>int</area> <workgroup>lpwan</workgroup> <abstract> <t>This document describes Static Context Header Compression andFragmentationfragmentation (SCHC) specifications,RFCRFCs 8724 andRFC8824, in combination with the 3rd Generation Partnership Project (3GPP) and the Narrowband Internet of Things (NB-IoT).</t> <t>This document has twoparts. Oneparts: one normativeto specifypart that specifies the use of SCHC overNB-IoT. AndNB-IoT and oneinformational, whichinformational part that recommends some values if 3GPPwantedwants to use SCHC inside their architectures.</t> </abstract> </front> <middle> <sectionanchor="Introduction"><name>Introduction</name>anchor="Introduction"> <name>Introduction</name> <t>This document definesthescenarios wheretheStatic Context Header Compression and fragmentation (SCHC) <xref target="RFC8724"/>and<xref target="RFC8824"/> are suitable for 3rd Generation Partnership Project (3GPP) and Narrowband Internet of Things (NB-IoT) protocol stacks.</t> <t>In the 3GPP and the NB-IoT networks, header compression efficiently brings Internet connectivity to theDevice-User EquipmentDevice UE (Dev-UE), the radio (RGW-eNB) and network (NGW-MME) gateways, and the Application Server. This document describes the SCHC parameters supportingstatic context header compression and fragmentationSCHC over the NB-IoT architecture.</t> <t>This document assumes functionality for NB-IoT of 3GPP release 15 <xreftarget="_3GPPR15"/>.target="R15-3GPP"/>. Otherwise, the text explicitly mentions other versions' functionality.</t> <t>This document has twoparts, a standardparts: normative end-to-endscenarioscenarios describing how any application must use SCHC over the 3GPP publicservice. Andservice and informational scenarios about how 3GPP could use SCHC in their protocol stack network.</t> </section> <sectionanchor="conventions-and-definitions"><name>Conventionsanchor="conventions-and-definitions"> <name>Conventions and Definitions</name><t>The<t> The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described inBCP 14BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> </section> <sectionanchor="terminology"><name>Terminology</name>anchor="terminology"> <name>Terminology</name> <t>This document will follow the terms defined in <xref target="RFC8724"/>,in<xref target="RFC8376"/>, andthe<xref target="TR23720"/>.</t><t><list style="symbols"> <t>Capillary Gateway. A capillary gateway facilitates<dl newline="false" spacing="normal"> <dt>Capillary Gateway:</dt> <dd>Facilitates seamless integration because it haswide areawide-area connectivity through cellular and provideswide areawide-area access as a proxy to other devices using LAN technologies (BT, Wi-Fi, Zigbee, orothers.)</t> <t>CIoT EPS. Cellularothers).</dd> <dt>Cellular IoT Evolved PacketSystem. It is aSystem (CIoT EPS):</dt> <dd>A functionality to improve the support of small datatransfers.</t> <t>Dev-UE. Device - User Equipment.</t> <t>DoNAS. Datatransfers.</dd> <dt>Device UE (Dev-UE):</dt> <dd>As defined in <xref target="RFC8376" sectionFormat="comma" section="3"/>.</dd> <dt>Data over Non-AccessStratum.</t> <t>EPC. EvolvedStratum (DoNAS):</dt> <dd>Sending user data within signaling messages over the NAS functional layer.</dd> <dt>Evolved PacketConnectivity. CoreConnectivity (EPC):</dt> <dd>Core network of 3GPP LTEsystems.</t> <t>EUTRAN. Evolvedsystems.</dd> <dt>Evolved Universal Terrestrial Radio AccessNetwork. RadioNetwork (EUTRAN):</dt> <dd>Radio access network of LTE-basedsystems.</t> <t>HARQ. Hybridsystems.</dd> <dt>Hybrid Automatic RepeatRequest.</t> <t>HSS. HomereQuest (HARQ):</dt> <dd>A combination of high-rate Forward Error Correction (FEC) and Automatic Repeat reQuest (ARQ) error control.</dd> <dt>Home SubscriberServer. It is aServer (HSS):</dt> <dd>A database that contains users' subscription data, including data needed for mobilitymanagement.</t> <t>IP address. IPv6management.</dd> <dt>IP address:</dt> <dd>IPv6 or IPv4 addressused.</t> <t>IWK-SCEF. InterWorkingused.</dd> <dt>InterWorking Service Capabilities ExposureFunction. It is usedFunction (IWK-SCEF):</dt> <dd>Used in roaming scenarios,itis located in the VisitedPLMNPLMN, and serves for interconnection with theSCEFService Capabilities Exposure Function (SCEF) of the HomePLMN.</t> <t>L2. Layer-2PLMN.</dd> <dt>Layer 2 (L2):</dt> <dd>L2 in the 3GPP architecturesitincludes MAC,RLCRLC, and PDCPlayerslayers; see <xreftarget="AppendixA"/>.</t> <t>LCID. Logicaltarget="AppendixA"/>.</dd> <dt>Logical ChannelID. Is theID (LCID):</dt> <dd>The logical channel instance of the corresponding MACSDU.</t> <t>MAC. MediumSDU.</dd> <dt>Medium Access Controlprotocol, part(MAC) protocol:</dt> <dd>Part ofL2.</t> <t>NAS. Non-Access Stratum.</t> <t>NB-IoT. Narrowband IoT. AL2.</dd> <dt>Non-Access Stratum (NAS):</dt> <dd>Functional layer for signaling messages that establishes communication sessions and maintains the communication while the user moves.</dd> <dt>Narrowband IoT (NB-IoT):</dt> <dd>A 3GPPLPWANLow-Power WAN (LPWAN) technology based on the LTE architecture but with additional optimization for IoT and using a Narrowband spectrumfrequency.</t> <t>NGW-CSGN. Networkfrequency.</dd> <dt>Network Gateway - CIoT Serving GatewayNode.</t> <t>NGW-CSGW. NetworkNode (NGW-CSGN):</dt> <dd>As defined in <xref target="RFC8376" sectionFormat="comma" section="3"/>.</dd> <dt>Network Gateway - Cellular ServingGateway. It routesGateway (NGW-CSGW):</dt> <dd>Routes and forwards the user data packets through the accessnetwork.</t> <t>NGW-MME. Networknetwork.</dd> <dt>Network Gateway - Mobility ManagementEntity. AnEntity (NGW-MME):</dt> <dd>An entity in charge of handling mobility of theDev-UE.</t> <t>NGW-PGW. NetworkDev-UE.</dd> <dt>Network Gateway - Packet Data NetworkGateway. AnGateway (NGW-PGW):</dt> <dd>An interface between the internalwith theand externalnetwork.</t> <t>NGW-SCEF. Networknetwork.</dd> <dt>Network Gateway - Service Capability ExposureFunction. EPCFunction (NGW-SCEF):</dt> <dd>EPC node for exposure of 3GPP network service capabilities to3rdthird partyapplications.</t> <t>NIDD. Non-IPapplications.</dd> <dt>Non-IP DataDelivery.</t> <t>PDCP. PacketDelivery (NIDD):</dt> <dd>End-to-end communication between the UE and the Application Server.</dd> <dt>Packet Data Convergence Protocolpart(PDCP):</dt> <dd>Part ofL2.</t> <t>PLMN. Public LandL2.</dd> <dt>Public Land-based MobileNetwork. CombinationNetwork (PLMN):</dt> <dd>A combination of wireless communication services offered by a specificoperator.</t> <t>PDU. Protocoloperator.</dd> <dt>Protocol DataUnit. AUnit (PDU):</dt> <dd>A data packet including headers that are transmitted between entities through aprotocol.</t> <t>RLC. Radioprotocol.</dd> <dt>Radio Link Protocolpart(RLC):</dt> <dd>Part ofL2.</t> <t>RGW-eNB. RadioL2.</dd> <dt>Radio Gateway - evolved NodeB. BaseB (RGW-eNB):</dt> <dd>Base Station that controls theUE.</t> <t>SDU. ServiceUE.</dd> <dt>Service DataUnit. AUnit (SDU):</dt> <dd>A data packet (PDU) fromhigher layerhigher-layer protocols used bylower layerlower-layer protocols as a payload of their ownPDUs.</t> </list></t>PDUs.</dd> </dl> </section> <sectionanchor="nb-iot-architecture"><name>NB-IoTanchor="nb-iot-architecture"> <name>NB-IoT Architecture</name> <t>TheNarrowband Internet of Things (NB-IoT)NB-IoT architecture has a complex structure. It relies on differentNGWsNetwork Gateways (NGWs) from different providers. It can send data via different paths, each with different characteristics in terms of bandwidth, acknowledgments, andlayer-2L2 reliability and segmentation.</t> <t><xref target="Figure-Archi"/> shows this architecture, where the Network Gateway - CellularInternet of ThingsIoT Serving Gateway Node (NGW-CSGN) optimizes co-locating entities in different paths. For example, a Dev-UE using the path formed by the Network Gateway - Mobility Management Entity (NGW-MME), the NGW-CSGW, and the Network Gateway - Packet Data Network Gateway (NGW-PGW) may get a limited bandwidth transmission from a few bytes/s to one thousand bytes/s only.</t> <t>Another node introduced in the NB-IoT architecture is the Network Gateway - Service Capability Exposure Function (NGW-SCEF), which securely exposes service and network capabilities to entities external to the network operator. The Open Mobile Alliance (OMA) <xref target="OMA0116"/> and the One Machine to Machine (OneM2M) <xref target="TR-0024"/> define the northbound APIs. <xref target="TS23222"/> defines architecture for the common API framework for 3GPP northboundAPIs andAPIs. <xref target="TS33122"/> defines security aspects for a common API framework for 3GPP northbound APIs. In this case, the path is small for data transmission. The main functions of the NGW-SCEF areConnectivitypath connectivity andDevice Monitoring.</t>device monitoring.</t> <figuretitle="3GPP network architecture" anchor="Figure-Archi"><artwork><![CDATA[anchor="Figure-Archi"> <name>3GPP Network Architecture</name> <artwork><![CDATA[ +---+ +---------+ +------+ |Dev| \ | +-----+ | ---| HSS | |-UE| \ | | NGW | | +------+ +---+ | | |-MME |\__ \ / +-----+ | \ +---+ \+-----+ /| | | +------+ |Dev| ----| RGW |- | | | | NGW- | |-UE| |-eNB | | | | | SCEF |---------+ +---+ /+-----+ \| | | +------+ | / \ +------+| | / |\| NGW- || +-----+ +-----------+ +---+ / | | CSGW |--| NGW-|---|Application| |Dev| | | || | PGW | | Server | |-UE| | +------+| +-----+ +-----------+ +---+ | | |NGW-CSGN | +---------+]]></artwork></figure>]]></artwork> </figure> </section> <sectionanchor="data-transmission-in-the-3gpp-architecture"><name>Dataanchor="data-transmission-in-the-3gpp-architecture"> <name>Data Transmission in the 3GPP Architecture</name> <t>NB-IoT networks deal with end-to-end user data and in-band signaling between the nodes and functions to configure, control, and monitor the system functions and behaviors. The signaling uses a different path with specific protocols, handling processes, and entities but can transport end-to-end user data for IoT services. In contrast, the end-to-end application only transports end-to-end data.</t> <t>The recommended 3GPP MTU size is 1358 bytes. The radio network protocols limit the packet sizes over the air, including radio protocol overhead, to 1600bytes,bytes; see <xref target="Radio-Parameters"/>. However, the recommended 3GPP MTU is smaller to avoid fragmentation in the network backbone due to the payload encryption size (multiple of 16) and the additional core transport overhead handling.</t> <t>3GPP standardizes NB-IoT and, in general, thecellular technologiesinterfaces andfunctions.functions of cellular technologies. Therefore, the introduction of SCHC entities to Dev-UE, RGW-eNB, and NGW-CSGN needs to be specified in the NB-IoT standard.</t> <t>This document identifies the use cases of SCHC over the NB-IoT architecture.</t><t>First,<t>The first use case is of the radio transmissionwhere, see(see <xreftarget="Radio"/>,target="Radio"/>) where the Dev-UE and the RGW-eNB can use the SCHC functionalities.</t><t>Second,<t>The second is where the packets transmitted over the control path can also use SCHC when the transmission goes over the NGW-MME orNGW-SCEF. SeeNGW-SCEF (see <xreftarget="DONAS"/>.</t>target="DONAS"/>).</t> <t>These two use cases are also valid for any 3GPP architecture and not only for NB-IoT. And as the 3GPP internal network is involved, they have been put in the informational part of this section.</t> <t>Andthird, overthe third covers the SCHC over Non-IP Data Delivery (NIDD) connection or at least up to the operator networkedge, seeedge (see <xreftarget="E2E"/>.target="E2E"/>). In this case, SCHC functionalities are available in the application layer of the Dev-UE and the Application Servers or a broker function at the edge of the operator network. NGW-PGW or NGW-SCEF transmit the packetswhichthat arenon-IPNon-IP traffic, using IP tunneling or API calls. It is also possible to benefit legacy devices with SCHC by using thenon-IPNon-IP transmission features of the operator network.</t> <t>Anon-IPNon-IP transmission refers toother layer-2an L2 transport that is different from NB-IoT.</t> <sectionanchor="normative-part"><name>Normative Part.</name> <t>Thisanchor="normative-part"> <name>Normative Scenarios</name> <t>These scenariosdoesdo not modify the 3GPP architecture or any of itscomponents, itcomponents. They only useitthe architecture asa layer-2an L2 transmission.</t> <sectionanchor="E2E"><name>SCHCanchor="E2E"> <name>SCHC over Non-IP Data Delivery (NIDD)</name> <t>This section specifies the use of SCHC overNon-IP Data Delivery (NIDD)NIDD services of 3GPP. The NIDD services of 3GPP enable the transmission of SCHC packets compressed by the application layer. The packets can be delivered between the NGW-PGW and the Application Server or between the NGW-SCEF and the Application Server, using IP-tunnels or API calls. In both cases, as compression occurs before transmission, the network will not understand the packet, and the network does not have context information of this compression. Therefore, the network will treat the packet as Non-IP traffic and deliver it to the other side without any other protocol stack element, directly overthe layer-2.</t>L2.</t> <sectionanchor="schc-entities-placing-over-nidd"><name>SCHCanchor="schc-entities-placing-over-nidd"> <name>SCHC Entities Placing over NIDD</name> <t>In the two scenarios using NIDD compression, SCHC entities are located almost on top of the stack. The NB-IoT connectivity services implement SCHC in the Dev-UE, an in the Application Server. The IP tunneling scenario requires that the Application Server send the compressed packet over an IP connection terminated by the 3GPP core network. If the transmission uses the NGW-SCEF services, it is possible to utilize an API call to transfer the SCHC packets between the core network and the Application Server. Also, an IP tunnel could be established by the Application Server if negotiated with the NGW-SCEF.</t> <figuretitle="End-to End Compression.anchor="Fig--NIDD"> <name>End-to-End Compression: SCHCentities placedEntities Placed whenusingUsing Non-IP Delivery (NIDD) 3GPPServices" anchor="Fig--NIDD"><artwork><![CDATA[Services</name> <artwork><![CDATA[ +---------+ XXXXXXXXXXXXXXXXXXXXXXXX +--------+ | SCHC | XXX XXX | SCHC | |(Non-IP) +-----XX........................XX....+--*---+(Non-IP)| +---------+ XX +----+ XX | | +--------+ | | XX |SCEF+-------+ | | | | | XXX 3GPP RAN & +----+ XXX +---+ UDP | | | XXX CORE NETWORK XXX | | | | L2 +---+XX +------------+ | +--------+ | | XX |IP TUNNELING+--+ | | | | XXX +------------+ +---+ IP | +---------+ XXXX XXXX | +--------+ | PHY +------+ XXXXXXXXXXXXXXXXXXXXXXX +---+ PHY | +---------+ +--------+ Dev-UE Application Server]]></artwork></figure>]]></artwork> </figure> </section> <sectionanchor="Config"><name>Parametersanchor="Config"> <name>Parameters for Static Context Header Compression and Fragmentation (SCHC)</name> <t>These scenarios <bcp14>MAY</bcp14> use the SCHC header compression capability to improve the transmission of IPv6 packets.</t><t><list style="symbols"> <t>SCHC<ul spacing="normal"> <li><t>SCHC Contextinitialization.</t> </list></t>Initialization</t> <t>The application layer handles the staticcontext; consequently,context. Consequently, the context distribution <bcp14>MUST</bcp14> be according to the application's capabilities, perhaps utilizing IP data transmissions up to context initialization. Also, the staticcontextscontext delivery may use the same IP tunneling or NGW-SCEF services used later for the transport of SCHCpackets transport.</t> <t><list style="symbols"> <t>SCHC Rules.</t> </list></t>packets.</t></li> <li><t>SCHC Rules</t> <t>For devices acting as a capillary gateway, several rules match the diversity of devices and protocols used by the devices associated with the gateway. Meanwhile, simpler devices may have predetermined protocols and fixedparameters.</t> <t><list style="symbols"> <t>Rule ID.</t> </list></t>parameters.</t></li> <li><t>RuleID</t> <t>This scenario can dynamically set the RuleID size before the contextdelivery. Fordelivery, for example,negotiateby negotiating between the applications when choosing a profile according to the type of traffic and application deployed. Transmission optimization may require only onephysical layerPhysical Layer transmission. SCHC overhead <bcp14>SHOULD NOT</bcp14> exceed the available number of effective bits of the smallest physical TB available to optimize the transmission. The packets handled by 3GPP networks are byte-aligned. Thus, to use the smallest TB, the maximum SCHC header size is 12 bits. On the other hand, more complex NB-IoT devices (such as a capillary gateway) might require additional bits to handle the variety and multiple parameters of higher-layer protocols deployed. The configuration may be part of the agreed operation profile and content distribution. The RuleID field size may range from 2 bits, resulting in 4rulesrules, to an 8-bitvalue that would yieldvalue, yielding up to 256 rulesthat can be used with the operators and seems quite a reasonablefor use by operators. A 256-rule maximum limit seems to be quite reasonable, even for a device acting as a NAT. An application may use a larger RuleID, but it should consider the byte alignment of the expected Compression Residue. In the minimum TB size case, 2 bits of RuleID leave only 6 bits available for CompressionResidue.</t> <t><list style="symbols"> <t>SCHC MAX_PACKET_SIZE.</t> </list></t>Residue.</t></li> <li><t>SCHC MAX_PACKET_SIZE</t> <t>In these scenarios, the maximum <bcp14>RECOMMENDED</bcp14> MTU size is 1358 bytes since the SCHC packets (and fragments) are traversing the whole 3GPP network infrastructure (core and radio), not only the radio as in the IP transmissionscase.</t> <t><list style="symbols"> <t>Fragmentation.</t> </list></t>case.</t></li> <li><t>Fragmentation</t> <t>Packets larger than 1358 bytes need the SCHC fragmentation function. Since the 3GPP uses reliability functions, the No-ACK fragmentation mode <bcp14>MAY</bcp14> be enough in point-to-point connections. Nevertheless, additional considerations are described below for more complexcases.</t> <t><list style="symbols"> <t>Fragmentation modes.</t> </list></t>cases.</t></li> <li><t>Fragmentation Modes</t> <t>A global service assigns a QoS to thepackets e.g.packets, e.g., depending on the billing. Packets with very low QoS may get lost before arriving in the 3GPP radio network transmission,for example,e.g., in between the links of a capillary gateway or due to buffer overflow handling in a backhaul connection. The use of SCHC fragmentation with the ACK-on-Error mode is <bcp14>RECOMMENDED</bcp14> to secure additional reliability on the packets transmitted with a small trade-off on further transmissions to signal the end-to-end arrival of the packets if no transport protocol takes care ofretransmission.<br />retransmission.<br/> Also, the ACK-on-Error mode could be desirable to keep track of all the SCHC packets delivered. In that case, the fragmentation function could be activated for all packets transmitted by the applications. SCHC ACK-on-Error fragmentation <bcp14>MAY</bcp14> be activated in transmittingnon-IPNon-IP packets on the NGW-MME. Anon-IPNon-IP packet will use SCHC reserved RuleID for non-compressing packets as <xref target="RFC8724"/> allowsit.</t> <t><list style="symbols"> <t>Fragmentation Parameters.</t> </list></t>it.</t></li> <li><t>Fragmentation Parameters</t> <t>SCHC profile will have specific Rules for the fragmentation modes. The rule willidentify,identify which fragmentation mode is in use, andsection<xref target="Radio-Parameters"/> defines the RuleIDsize.</t>size.</t></li></ul> <t>SCHC parametrization considers thatNBIoTNB-IoT aligns the bit and uses padding and the size of the Transfer Block. SCHC will try to reduce padding to optimize the compression of the information. TheHeaderheader size needs to be a multiple of4, and the4. The Tiles <bcp14>MAY</bcp14> keep a fixed value of 4 or 8 bits to avoidpaddingpadding, except for when the transfer block equals 16 bitswhereas the Tiles may be 2 bits. The transfer block size has a wide range of values. Two configurations are <bcp14>RECOMMENDED</bcp14> for the fragmentation parameters.</t><t><list style="symbols"><ul spacing="normal"> <li> <t>For Transfer Blocks smaller than or equal to 304 bits using an 8-bit Header_size configuration, with the size of the header fields as follows:<list style="symbols"> <t>RuleID</t> <ul spacing="normal"> <li>RuleID from 1 - 3bits,</t> <t>DTagbits</li> <li>DTag 1bit,</t> <t>FCNbit</li> <li>FCN 3bits,</t> <t>Wbits</li> <li>W 1bits.</t> </list></t>bits</li> </ul> </li> <li> <t>For Transfer Blocks bigger than 304 bits using a 16-bit Header_size configuration, with the size of the header fields as follows:<list style="symbols"> <t>RulesID</t> <ul spacing="normal"> <li>RulesID from 8 - 10bits,</t> <t>DTagbits</li> <li>DTag 1 or 2bits,</t> <t>FCNbits</li> <li>FCN 3bits,</t> <t>Wbits</li> <li>W 2 or 3bits.</t> </list></t> <t>WINDOW_SIZE of 2^N-1 is <bcp14>RECOMMENDED</bcp14>.</t> <t>RCSbits</li> </ul> </li> <li>WINDOW_SIZE of (2<sup>N</sup>)-1 is <bcp14>RECOMMENDED</bcp14>.</li> <li>Reassembly Check Sequence (RCS) will follow the default size defined insection 8.2.3 of the<xreftarget="RFC8724"/>,target="RFC8724" sectionFormat="of" section="8.2.3"/>, with a length equal to the L2Word.</t> <t>MAX_ACK_REQWord.</li> <li>MAX_ACK_REQ is <bcp14>RECOMMENDED</bcp14> to be 2, but applications <bcp14>MAY</bcp14> change this value based on transmissionconditions.</t> </list></t>conditions.</li> </ul> <t>The IoT devices communicate with small datatransfertransfers and use the Power Save Mode and the Idle ModeDRX,Discontinuous Reception (DRX), which govern how often the device wakes up, stays up, and is reachable. The use of the different modes allows the battery to last ten years. Table 10.5.163a in <xref target="TS24008"/>specifies a range fordefines the radiotimers as N to 3N in increments of one where thetimer values with units incrementing by N. The units of N can be 1 hour or 10 hours. The range used for IoT is of N to 3N, where N increments by one. The Inactivity Timer and the Retransmission Timer can be set based on these limits.</t> </section> </section> </section> <sectionanchor="informational-part"><name>Informational Part.</name>anchor="informational-part"> <name>Informational Scenarios</name> <t>These scenariosshowsshow how 3GPP could use SCHC for their transmissions.</t> <sectionanchor="Radio"><name>Useanchor="Radio"> <name>Use of SCHC over the Radiolink</name>Link</name> <t>Deploying SCHC over theradio linkRadio Link only would require placing it as part of the protocol stack for data transfer between the Dev-UE and the RGW-eNB. This stack is the functional layer responsible for transporting data over the wireless connection and managing radio resources. There is support for features such as reliability, segmentation, and concatenation. The transmissions use link adaptation, meaning that the system will optimize the transport format used according to the radio conditions, the number of bits to transmit, and the power and interference constraints. That means that the number of bits transmitted over the air depends on the selected Modulation and Coding Schemes(MCS).(MCSs). Transport Block (TB) transmissions happen in thephysical layerPhysical Layer at network-synchronized intervals called Transmission Time Interval (TTI). EachTransport BlockTB has a different MCS and number of bits available to transmit. The MAC layer <xref target="TR36321"/> defines theTransport Blocks' characteristics.characteristics of the TBs. The RadiolinkLink stack shown in <xref target="Fig-ProtocolArchi3"/> comprises the Packet Data Convergence Protocol (PDCP) <xref target="TS36323"/>, the Radio Link Protocol (RLC) <xref target="TS36322"/>, the Medium Access Control protocol (MAC) <xref target="TR36321"/>, and the Physical Layer <xref target="TS36201"/>.The<xref target="AppendixA"/> gives more details about these protocols.</t> <figuretitle="SCHCanchor="Fig-ProtocolArchi3"> <name>SCHC over the Radiolink" anchor="Fig-ProtocolArchi3"><artwork><![CDATA[Link</name> <artwork><![CDATA[ +---------+ +---------+ ||IP/non-IP+------------------------------+IP/non-IP+->+|IP/Non-IP+------------------------------+IP/Non-IP+->+ +---------+ | +---------------+ | +---------+ | | PDCP +-------+ PDCP | GTP|U +------+ GTP-U |->+ | (SCHC) + + (SCHC)| + + | | +---------+ | +---------------+ | +---------+ | | RLC +-------+ RLC |UDP/IP +------+ UDP/IP +->+ +---------+ | +---------------+ | +---------+ | | MAC +-------+ MAC | L2 +------+ L2 +->+ +---------+ | +---------------+ | +---------+ | | PHY +-------+ PHY | PHY +------+ PHY +->+ +---------+ +---------------+ +---------+ | C-Uu/ S1-U SGi Dev-UE RGW-eNB NGW-CSGN Radio Link]]></artwork></figure>]]></artwork> </figure> <sectionanchor="schc-entities-placing-over-the-radio-link"><name>SCHCanchor="schc-entities-placing-over-the-radio-link"> <name>Placing SCHC EntitiesPlacingover the Radio Link</name> <t>The 3GPP architecture supports Robust Header Compression (ROHC) <xref target="RFC5795"/> in the PDCP layer. Therefore, the architecture can deploy SCHC header compression entities similarly without the need for significant changes in the 3GPP specifications.</t> <t>The RLC layer has three functionalmodesmodes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). The mode of operation controls the functionalities of the RLC layer. TM only applies to signaling packets, while AM or UM carry signaling and data packets.</t> <t>The RLC layer takes care of fragmentationunlessexcept for theTransparent Mode.TM. In AM orUM modes,UM, the SCHC fragmentation is unnecessary and <bcp14>SHOULD NOT</bcp14> be used. While sending IP packets, the RadiolinkLink does not commonly use the RLCTransparent Mode.TM. However, if other protocol overhead optimizations are targeted for NB-IoT traffic, SCHC fragmentation may be used for TM transmissionmodein the future.</t> </section> </section> <sectionanchor="DONAS"><name>Useanchor="DONAS"> <name>Use of SCHC over the Non-Access Stratum (NAS)</name> <t>This section consists of IETF suggestions to the 3GPP. The NGW-MME conveys mainly signaling between the Dev-UE and the cellular network <xref target="TR24301"/>. The network transports this traffic on top of theradio link.</t>Radio Link.</t> <t>This kind of flow supports data transmissions to reduce the overhead when transmitting infrequent small quantities of data. This transmission is known as Data over Non-Access Stratum (DoNAS) or Control PlaneCellular Internet of Things (CIoT) evolved packet system (EPS)CIoT EPS optimizations. In DoNAS, the Dev-UE uses the pre-establishedsecurity andsecurity, can piggyback small uplink data into the initial uplinkmessagemessage, and uses an additional message to receive a downlink small data response.</t> <t>The NGW-MME performs the data encryption from the network side in a DoNAS PDU. Depending on the data type signaled indication (IP ornon-IPNon-IP data), the network allocates an IP address or establishes a direct forwarding path. DoNAS is regulated under rate control upon previous agreement, meaning that a maximum number of bits per unit of time is agreed upon per device subscription beforehand and configured in the device.</t> <t>The system will use DoNAS when a terminal in a power-saving state requires a short transmission and receives an acknowledgment or short feedback from the network. Depending on the size of the buffered data totransmit,be transmitted, the Dev-UE might deploy the connected modetransmissions instead, limitingtransmission instead. The connected mode would limit andcontrollingcontrol the DoNAS transmissions to predefinedthresholdsthresholds, and it would be a good resource optimization balance for the terminal and the network. The support for mobility of DoNAS is present but produces additional overhead.The<xref target="AppendixB"/> gives additional details of DoNAS.</t> <sectionanchor="schc-entities-placing-over-donas"><name>SCHCanchor="schc-entities-placing-over-donas"> <name>Placing SCHC EntitiesPlacingover DoNAS</name> <t>SCHC resides in this scenario's Non-Access Stratum (NAS) protocol layer. The same principles as forthe section<xref target="Radio"/> apply here as well. Because the NAS protocol already uses ROHC <xref target="RFC5795"/>, it can also adapt SCHC for header compression. The main difference compared to theradio link, section <xref target="Radio"/>,Radio Link (<xref target="Radio"/>) is the physical placing of the SCHC entities. On the network side, the NGW-MME resides in the core network and is the terminating node for NAS instead of the RGW-eNB.</t> <figuretitle="SCHC entities placementanchor="Fig-ProtocolArchi4"> <name>SCHC Entities Placement in the 3GPP CIOTradio protocol architectureRadio Protocol Architecture for DoNAStransmissions" anchor="Fig-ProtocolArchi4"><artwork><![CDATA[Transmissions</name> <artwork><![CDATA[ +--------+ +--------+--------+ + +--------+ | IP/ +--+-----------------+--+ IP/ | IP/ +-----+ IP/ | | Non-IP | | | | Non-IP | Non-IP | | | Non-IP | +--------+ | | +-----------------+ | +--------+ | NAS +-----------------------+ NAS |GTP-C/U +-----+GTP-C/U | |(SCHC) | | | | (SCHC) | | | | | +--------+ | +-----------+ | +-----------------+ | +--------+ | RRC +-----+RRC |S1|AP+-----+ S1|AP | | | | | +--------+ | +-----------+ | +--------+ UDP +-----+ UDP | | PDCP* +-----+PDCP*|SCTP +-----+ SCTP | | | | | +--------+ | +-----------+ | +-----------------+ | +--------+ | RLC +-----+ RLC | IP +-----+ IP | IP +-----+ IP | +--------+ | +-----------+ | +-----------------+ | +--------+ | MAC +-----+ MAC | L2 +-----+ L2 | L2 +-----+ L2 | +--------+ | +-----------+ | +-----------------+ | +--------+ | PHY +--+--+ PHY | PHY +--+--+ PHY | PHY +-----+ PHY | +--------+ +-----+-----+ +--------+--------+ | +--------+ C-Uu/ S1 SGi Dev-UE RGW-eNB NGW-MME NGW-PGW *PDCP is bypassed until AS security is activated TGPP36300.]]></artwork></figure>]]></artwork> </figure> </section> </section> <sectionanchor="Radio-Parameters"><name>Parametersanchor="Radio-Parameters"> <name>Parameters for Static Context Header Compression and Fragmentation (SCHC) for the RadiolinkLink andDONAS use-cases.</name>DoNAS Use Cases</name> <t>If 3GPP incorporates SCHC, it is recommended that these scenarios use the SCHC header compression <xref target="RFC8724"/> capability to optimize the data transmission.</t><t><list style="symbols"> <t>SCHC<ul spacing="normal"> <li><t>SCHC Contextinitialization.</t> </list></t>Initialization</t> <t>TheRRC (RadioRadio ResourceControl)Control (RRC) protocol is the main tool used to configure the parameters of the Radiolink.Link. It will configure SCHC and the static context distribution as it has been made for ROHC operation <xref target="RFC5795"/>operation<xreftarget="TS36323"/>.</t> <t><list style="symbols"> <t>SCHC Rules.</t> </list></t>target="TS36323"/>.</t></li> <li><t>SCHC Rules</t> <t>The network operatorin these scenariosdefines the number ofrules.rules in these scenarios. For this, the network operator must know the IP traffic the device will carry. The operator might supply rules compatible with the device's use case. For devices acting as a capillary gateway, several rules match the diversity of devices and protocols used by the devices associated with the gateway. Meanwhile, simpler devices may have predetermined protocols and fixed parameters. The use of IPv6 and IPv4 may force the operator togetdevelop more rules to deal with eachcase.</t> <t><list style="symbols"> <t>RuleID.</t> </list></t>case.</t></li> <li><t>RuleID</t> <t>There is a reasonable assumption of 9 bytes of radio protocol overhead for these transmission scenarios in NB-IoT, where PDCP uses 5 bytes due to header and integrityprotection,protection and where RLC and MAC use 4 bytes. The minimum physicalTransport Blocks (TB)TBs that can withhold this overheadvaluevalue, according to the 3GPP Release 15specificationsspecification <xref target="R15-3GPP"/>, are 88, 104, 120, and 144 bits. As for <xref target="Config"/>, these scenarios must optimize thephysical layerPhysical Layer where the smallest TB is 12 bits. These 12 bits must include the Compression Residue in addition to the RuleID. On the other hand, more complex NB-IoT devices (such as a capillary gateway) might require additional bits to handle the variety and multiple parameters of higher-layer protocols deployed. In that sense, the operator may want flexibility on the number and type of rules independently supported by each device; consequently, these scenarios require a configurable value. The configuration may be part of the agreed operation profile with the content distribution. The RuleID field size may range from 2 bits, resulting in 4rulesrules, to an 8-bitvalue that would yieldvalue, yielding up to 256 rulesthat can be usedfor use with theoperators and seems quite a reasonableoperators. A 256-rule maximum limit seems to be quite reasonable, even for a device acting as a NAT. An application may use a larger RuleID, but it should consider the byte alignment of the expected Compression Residue. In the minimum TB size case, 2 bits of RuleID leave only 6 bits available for CompressionResidue.</t> <t><list style="symbols"> <t>SCHC MAX_PACKET_SIZE.</t> </list></t>Residue.</t></li> <li><t>SCHC MAX_PACKET_SIZE</t> <t>The Radio Link can handle the fragmentation of SCHC packets if needed, including reliability. Hence, the packet size is limited by the MTU that is handled by the radio protocols, which corresponds to 1600 bytes for the 3GPP Release15.</t> <t><list style="symbols"> <t>Fragmentation.</t> </list></t>15.</t></li> <li><t>Fragmentation</t> <t>For the Radiolink <xref target="Radio"/>Link (<xref target="Radio"/>) andDoNAS' <xref target="DONAS"/>DoNAS (<xref target="DONAS"/>) scenarios, the SCHC fragmentation functions are disabled. The RLC layer of NB-IoT can segment packets into suitable units that fit the selectedtransport blocksTB for transmissions of thephysical layer.Physical Layer. The block selection is made according to the link adaptation input function in the MAC layer and the quantity of data in the buffer. The link adaptation layer may produce different results at eachTime Transmission Interval (TTI),TTI, resulting in varying physicaltransport blocksTBs that depend on the network load, interference, number of bits transmitted, and QoS. Even if setting a value that allows the construction of data units following the SCHC tiles principle, the protocol overhead may be greater or equal to allowing the RadiolinkLink protocols to take care of the fragmentationintrinsically.</t> <t><list style="symbols"> <t>Fragmentationintrinsically.</t></li> <li><t>Fragmentation in RLCTransparent Mode.</t> </list></t>TM</t> <t>The RLCTransparent ModeTM mostly applies to control signaling transmissions. When RLC operates inTransparent Mode,TM, the MAC layer mechanisms ensure reliability and generate overhead. This additional reliability implies sending repetitions or automatic retransmissions.</t> <t>The ACK-Always fragmentation mode of SCHC may reduce this overhead in future operations when data transmissions may use this mode. The ACK-Always mode may transmit compressed data with fewer possible transmissions by using fixed or limitedtransport blocksTBs compatible with the tiling SCHC fragmentation handling. For SCHC fragmentationparametersparameters, see <xreftarget="Config"/>.</t>target="Config"/>.</t></li></ul> </section> </section> </section> <sectionanchor="padding"><name>Padding</name>anchor="padding"> <name>Padding</name> <t>NB-IoT and 3GPP wireless access, in general, assumes a byte-aligned payload. Therefore, thelayer 2 wordL2 Word for NB-IoT <bcp14>MUST</bcp14> be considered 8 bits, and the padding treatment should use this value accordingly.</t> </section> <sectionanchor="iana-considerations"><name>IANA considerations</name>anchor="iana-considerations"> <name>IANA Considerations</name> <t>This document has no IANA actions.</t> </section> <sectionanchor="security-considerations"><name>Security considerations</name>anchor="security-considerations"> <name>Security Considerations</name> <t>This document does not add any security considerations and followsthe<xref target="RFC8724"/> and the 3GPP access security document specified in <xref target="TS33122"/>.</t> </section> </middle> <back><references title='Normative References'> <reference anchor='RFC2119' target='https://www.rfc-editor.org/info/rfc2119'> <front> <title>Key words for use in RFCs to Indicate Requirement Levels</title> <author fullname='S. Bradner' initials='S.' surname='Bradner'><organization/></author> <date month='March' year='1997'/> <abstract><t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t></abstract> </front> <seriesInfo name='BCP' value='14'/> <seriesInfo name='RFC' value='2119'/> <seriesInfo name='DOI' value='10.17487/RFC2119'/> </reference> <reference anchor='RFC8174' target='https://www.rfc-editor.org/info/rfc8174'> <front> <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title> <author fullname='B. Leiba' initials='B.' surname='Leiba'><organization/></author> <date month='May' year='2017'/> <abstract><t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t></abstract> </front> <seriesInfo name='BCP' value='14'/> <seriesInfo name='RFC' value='8174'/> <seriesInfo name='DOI' value='10.17487/RFC8174'/> </reference> <reference anchor='RFC8724' target='https://www.rfc-editor.org/info/rfc8724'> <front> <title>SCHC: Generic Framework for Static Context Header Compression and Fragmentation</title> <author fullname='A. Minaburo' initials='A.' surname='Minaburo'><organization/></author> <author fullname='L. Toutain' initials='L.' surname='Toutain'><organization/></author> <author fullname='C. Gomez' initials='C.' surname='Gomez'><organization/></author> <author fullname='D. Barthel' initials='D.' surname='Barthel'><organization/></author> <author fullname='JC. Zuniga' initials='JC.' surname='Zuniga'><organization/></author> <date month='April' year='2020'/> <abstract><t>This document defines the Static Context Header Compression and fragmentation (SCHC) framework, which provides both a header compression mechanism and an optional fragmentation mechanism. SCHC has been designed with Low-Power Wide Area Networks (LPWANs) in mind.</t><t>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.</t><t>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.</t><t>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.</t></abstract> </front> <seriesInfo name='RFC' value='8724'/> <seriesInfo name='DOI' value='10.17487/RFC8724'/> </reference> <reference anchor='RFC8824' target='https://www.rfc-editor.org/info/rfc8824'> <front> <title>Static Context Header Compression (SCHC) for the Constrained Application Protocol (CoAP)</title> <author fullname='A. Minaburo' initials='A.' surname='Minaburo'><organization/></author> <author fullname='L. Toutain' initials='L.' surname='Toutain'><organization/></author> <author fullname='R. Andreasen' initials='R.' surname='Andreasen'><organization/></author> <date month='June' year='2021'/> <abstract><t>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.</t></abstract> </front> <seriesInfo name='RFC' value='8824'/> <seriesInfo name='DOI' value='10.17487/RFC8824'/> </reference><references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8724.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8824.xml"/> </references><references title='Informative References'><references> <name>Informative References</name> <referenceanchor='RFC5795' target='https://www.rfc-editor.org/info/rfc5795'>anchor="RFC5795" target="https://www.rfc-editor.org/info/rfc5795"> <front> <title>The RObust Header Compression (ROHC) Framework</title> <authorfullname='K. Sandlund' initials='K.' surname='Sandlund'><organization/></author>fullname="K. Sandlund" initials="K." surname="Sandlund"/> <authorfullname='G. Pelletier' initials='G.' surname='Pelletier'><organization/></author> <author fullname='L-E. Jonsson' initials='L-E.' surname='Jonsson'><organization/></author> <date month='March' year='2010'/> <abstract><t>The Robust Header Compression (ROHC) protocol provides an efficient, flexible, and future-proof header compression concept. It is designed to operate efficiently and robustly over various link technologies with different characteristics.</t><t>The ROHC framework, along with a set of compression profiles, was initially defined in RFC 3095. To improve and simplify the ROHC specifications, this document explicitly defines the ROHC framework and the profile for uncompressed separately. More specifically, the definition of the framework does not modify or update the definition of the framework specified by RFC 3095.</t><t>This specification obsoletes RFC 4995. It fixes one interoperability issue that was erroneously introduced in RFC 4995, and adds some minor clarifications. [STANDARDS-TRACK]</t></abstract> </front> <seriesInfo name='RFC' value='5795'/> <seriesInfo name='DOI' value='10.17487/RFC5795'/> </reference> <reference anchor='RFC8376' target='https://www.rfc-editor.org/info/rfc8376'> <front> <title>Low-Power Wide Area Network (LPWAN) Overview</title>fullname="G. Pelletier" initials="G." surname="Pelletier"/> <authorfullname='S. Farrell' initials='S.' role='editor' surname='Farrell'><organization/></author>fullname="L-E. Jonsson" initials="L-E." surname="Jonsson"/> <datemonth='May' year='2018'/> <abstract><t>Low-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.</t></abstract>month="March" year="2010"/> </front> <seriesInfoname='RFC' value='8376'/>name="RFC" value="5795"/> <seriesInfoname='DOI' value='10.17487/RFC8376'/>name="DOI" value="10.17487/RFC5795"/> </reference> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8376.xml"/> <referenceanchor="_3GPPR15" target="https://www.3gpp.org/release-15">anchor="R15-3GPP" target="https://www.3gpp.org/specifications-technologies/releases/release-15"> <front><title>The Mobile Broadband Standard</title> <author ><title>Release 15</title> <author> <organization>3GPP</organization> </author> <date month="April" year="2019"/> </front> </reference> <reference anchor="TR23720" target="https://www.3gpp.org/ftp/Specs/archive/23_series/23.720/23720-d00.zip"> <front> <title>Study on architecture enhancements for Cellular Internet of Things</title><author ><author> <organization>3GPP</organization> </author> <dateyear="2015"/>month="March" year="2016"/> </front> <refcontent>3GPP TR 23.720 V13.0.0</refcontent> </reference> <reference anchor="TS33122" target="https://www.3gpp.org/ftp//Specs/archive/33_series/33.122/33122-f30.zip"> <front> <title>Security aspects of Common API Framework (CAPIF) for 3GPP northbound APIs</title><author ><author> <organization>3GPP</organization> </author> <dateyear="2018"/>month="March" year="2019"/> </front> <refcontent>3GPP TS 33.122 V15.3.0</refcontent> </reference> <reference anchor="TR36321" target="https://www.3gpp.org/ftp/Specs/archive/36_series/36.321/36321-d20.zip"> <front> <title>Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC) protocolspecification</title> <author >specification </title> <author> <organization>3GPP</organization> </author> <date month="June" year="2016"/> </front> <refcontent>3GPP TS 36.321 V13.2.0</refcontent> </reference> <reference anchor="TS36322" target="https://www.3gpp.org/ftp/Specs/archive/36_series/36.322/36322-f01.zip"> <front> <title>Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Link Control (RLC) protocol specification</title><author ><author> <organization>3GPP</organization> </author> <date month="April" year="2018"/> </front> <refcontent>3GPP TS 36.322 V15.0.1</refcontent> </reference> <reference anchor="TS36201" target="https://www.3gpp.org/ftp/Specs/archive/36_series/36.201/36201-f10.zip"> <front> <title>Evolved Universal Terrestrial Radio Access (E-UTRA); LTE physical layer; General description</title><author ><author> <organization>3GPP</organization> </author> <date month="June" year="2018"/> </front> <refcontent>3GPP TS 36.201 V15.1.0</refcontent> </reference> <reference anchor="TR24301" target="https://www.3gpp.org/ftp//Specs/archive/24_series/24.301/24301-f80.zip"> <front><title>Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access Control (MAC)<title>Non-Access-Stratum (NAS) protocolspecification</title> <author >for Evolved Packet System (EPS); Stage 3</title> <author> <organization>3GPP</organization> </author> <date month="December" year="2019"/> </front></reference> <reference anchor="TR-0024" target="https://ftp.onem2m.org/work%20programme/WI-0037/TR-0024-3GPP_Interworking-V4_3_0.DOCX"> <front> <title>3GPP_Interworking</title> <author > <organization>OneM2M</organization> </author> <date year="2020"/> </front> </reference> <reference anchor="OMA0116" target="https://www.openmobilealliance.org/release/REST_NetAPI_Common/V1_0-20180116-A/OMA-TS-REST_NetAPI_Common-V1_0-20180116-A.pdf"> <front> <title>Common definitions for RESTful Network APIs</title> <author > <organization>OMA</organization> </author> <date year="2018"/> </front><refcontent>3GPP TS 24.301 V15.8.0</refcontent> </reference> <reference anchor="TS24008" target="https://www.3gpp.org/ftp//Specs/archive/24_series/24.008/24008-f50.zip"> <front> <title>Mobile radio interfacelayerLayer 3specification.</title> <author >specification; Core network protocols; Stage 3</title> <author> <organization>3GPP</organization> </author> <date month="December" year="2018"/> </front> <refcontent>3GPP TS 24.008 V15.5.0</refcontent> </reference> <reference anchor="TS36323" target="https://www.3gpp.org/ftp/Specs/archive/36_series/36.323/36323-d20.zip"> <front> <title>Evolved Universal Terrestrial Radio Access (E-UTRA); Packet Data Convergence Protocol (PDCP) specification</title><author ><author> <organization>3GPP</organization> </author> <date month="June" year="2016"/> </front> <refcontent>3GPP TS 36.323 V13.2.0</refcontent> </reference> <reference anchor="TS36331" target="https://www.3gpp.org/ftp//Specs/archive/36_series/36.331/36331-f51.zip"> <front> <title>Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification</title><author ><author> <organization>3GPP</organization> </author> <dateyear="2018"/>month="April" year="2019"/> </front> <refcontent>3GPP TS 36.331 V15.5.1</refcontent> </reference> <reference anchor="TS23222" target="https://www.3gpp.org/ftp/Specs/archive/23_series/23.222/23222-f60.zip"> <front><title>Common<title>Functional architecture and information flows to support Common API Framework for 3GPP NorthboundAPIs</title> <author >APIs; Stage 2</title> <author> <organization>3GPP</organization> </author> <date month="September" year="2022"/> </front> <refcontent>3GPP TS 23.222 V15.6.0</refcontent> </reference> <reference anchor="TR-0024" target="https://ftp.onem2m.org/work%20programme/WI-0037/TR-0024-3GPP_Interworking-V4_3_0.DOCX"> <front> <title>3GPP_Interworking</title> <author> <organization>OneM2M</organization> </author> <date month="March" year="2020"/> </front> <refcontent>TR-0024-V4.3.0</refcontent> </reference> <reference anchor="OMA0116" target="https://www.openmobilealliance.org/release/REST_NetAPI_Common/V1_0-20180116-A/OMA-TS-REST_NetAPI_Common-V1_0-20180116-A.pdf"> <front> <title>Common definitions for RESTful Network APIs</title> <author> <organization>Open Mobile Alliance</organization> </author> <date month="January" year="2018"/> </front> <refcontent>Version 1.0</refcontent> </reference> </references> </references> <sectionanchor="AppendixA"><name>NB-IoTanchor="AppendixA"> <name>NB-IoT User Planeprotocol architecture</name>Protocol Architecture</name> <sectionanchor="packet-data-convergence-protocol-pdcp-ts36323"><name>Packetanchor="packet-data-convergence-protocol-pdcp-ts36323"> <name>Packet Data Convergence Protocol(PDCP) <xref target="TS36323"/></name>(PDCP)</name> <t>Each of the Radio Bearers(RB)(RBs) is associated with one PDCPentity.entity <xref target="TS36323"/>. Moreover, a PDCP entity is associated with one or two RLCentitiesentities, depending on the unidirectional orbi-directionalbidirectional characteristics of the RB and RLC mode used. A PDCP entity is associated with either a control plane or a user plane with independent configuration and functions. The maximum supported size for NB-IoT of a PDCP SDU is 1600 octets. The primary services and functions of the PDCP sublayer for NB-IoT for the user plane include:</t><t><list style="symbols"> <t>Header<ul spacing="normal"> <li>Header compression and decompression using ROHC <xreftarget="RFC5795"/></t> <t>Transfertarget="RFC5795"/></li> <li>Transfer of user and control data to higher and lowerlayers</t> <t>Duplicatelayers</li> <li>Duplicate detection oflower layerlower-layer SDUs when re-establishing connection (when RLC with Acknowledge Mode is in use for User Planeonly)</t> <t>Cipheringonly)</li> <li>Ciphering anddeciphering</t> <t>Timer-baseddeciphering</li> <li>Timer-based SDU discard inuplink</t> </list></t>uplink</li> </ul> </section> <sectionanchor="radio-link-protocol-rlc-ts36322"><name>Radioanchor="radio-link-protocol-rlc-ts36322"> <name>Radio Link Protocol(RLC) <xref target="TS36322"/></name>(RLC)</name> <t>RLC <xref target="TS36322"/> isa layer-2an L2 protocol that operates between theUEUser Equipment (UE) and the base station (eNB). It supports the packet delivery from higher layers to MAC, creating packets transmitted over the air, optimizing theTransport BlockTB utilization. RLC flow of data packets is unidirectional, and it is composed of a transmitter located in the transmission device and a receiver located in the destination device. Therefore, to configurebi-directionalbidirectional flows, two sets of entities, one in each direction (downlink and uplink), must be configured and effectively peered to each other. The peering allows the transmission of control packets(ex.,(e.g., status reports) between entities. RLC can be configured for a data transfer in one of the following modes:</t><t><list style="symbols"> <t>Transparent<ul spacing="normal"> <li><t>Transparent Mode(TM). RLC(TM)</t> <t>RLC does not segment or concatenate SDUs from higher layers in this mode and does not include any headertowith the payload. RLC receives SDUs from upper layers when acting as a transmitter and transmits directly to its flow RLC receiver via lower layers. Similarly, upon reception, a TM RLC receiver wouldonly deliver without processingnot process the packets and only deliver them to higherlayers upon reception.</t> <t>Unacknowledgedlayers.</t></li> <li><t>Unacknowledged Mode(UM). This(UM)</t> <t>This mode provides support for segmentation and concatenation of payload. The RLC packet's size depends on the indication given at a particular transmission opportunity by the lower layer (MAC) and is octet-aligned. The packet delivery to the receiver does not include reliability support, and the loss of a segment from a packet means a complete packet loss. Also, inthe case of lower layerlower-layer retransmissions, there is no support for re-segmentation in caseof change ofthe radio conditionstriggeringchange and trigger the selection of a smallertransport block.TB. Additionally, it provides PDU duplication detection and discards,reordering of out-of-sequence,out-of-sequence reordering, and lossdetection.</t> <t>Acknowledgeddetection.</t></li> <li><t>Acknowledged Mode(AM). In(AM)</t> <t>In addition to the same functions supported by UM, this mode also adds a moving windows-based reliability service on top of thelower layerlower-layer services. It also supports re-segmentation, and it requires bidirectional communication to exchange acknowledgmentreportsreports, called RLC StatusReportReports, and to trigger retransmissions. This model also supportsprotocol errorprotocol-error detection. The mode used depends on the operator configuration for the type of data to be transmitted. For example, data transmissions supporting mobility or requiring high reliability would be most likely configured using AM. Meanwhile, streaming and real-time data would be mapped to a UMconfiguration.</t> </list></t>configuration.</t></li> </ul> </section> <sectionanchor="medium-access-control-mac-tr36321"><name>Mediumanchor="medium-access-control-mac-tr36321"> <name>Medium Access Control(MAC) <xref target="TR36321"/></name>(MAC)</name> <t>MAC <xref target="TR36321"/> provides a mapping between the higher layers abstraction called Logical Channels (which are comprised by the previously describedprotocols toprotocols) and the PhysicallayerLayer channels (transport channels). Additionally, MAC may multiplex packets from different Logical Channels and prioritizewhatwhich ones to fit into oneTransport BlockTB if there is data and space available to maximize data transmission efficiency. MAC also provides error correction and reliability support through Hybrid Automatic Repeat reQuest (HARQ), transport format selection, and scheduling informationreportingreported from the terminal to the network. MAC also adds the necessary padding and piggyback controlelementselements, whenpossible andpossible, as well as the higher layers data.</t> <figuretitle="Exampleanchor="Fig--MAC"> <name>Example of User Planepacket encapsulationPacket Encapsulation fortwo transport blocks" anchor="Fig--MAC"><artwork><![CDATA[Two Transport Blocks</name> <artwork><![CDATA[ <Max. 1600 bytes> +---+ +---+ +------+ Application |AP1| |AP1| | AP2 |(IP/non-IP)(IP/Non-IP) |PDU| |PDU| | PDU | +---+ +---+ +------+ | | | | | | PDCP +--------+ +-------- +-----------+ |PDCP|AP1| |PDCP|AP1| |PDCP| AP2 | |Head|PDU| |Head|PDU| |Head| PDU | +--------+ +--------+ +--------+--\ | | | | | | | | |\ `--------\ +---------------------------+ | |(1)| `-------\(2)\ RLC |RLC |PDCP|AP1|RLC |PDCP|AP1| +-------------+ +----|---+ |Head|Head|PDU|Head|Head|PDU| |RLC |PDCP|AP2| |RLC |AP2| +-------------|-------------+ |Head|Head|PDU| |Head|PDU| | | | | | +---------|---+ +--------+ | | | LCID1 | | / / / / / / / / _/ _// _/ _/ / LCID2 / | | | | | / _/ _/ / ___/ | | | | || | | / / +------------------------------------------+ +-----------+---+ MAC |MAC|RLC|PDCP|AP1|RLC|PDCP|AP1|RLC|PDCP|AP2| |MAC|RLC|AP2|Pad| |Hea|Hea|Hea |PDU|Hea|Hea |PDU|Hea|Hea |PDU| |Hea|Hea|PDU|din| |der|der|der | |der|der | |der|der | | |der|der| |g | +------------------------------------------+ +-----------+---+ TB1 TB2 (1) Segment One (2) Segment Two]]></artwork></figure>]]></artwork> </figure> </section> </section> <sectionanchor="AppendixB"><name>NB-IoTanchor="AppendixB"> <name>NB-IoT Data over NAS (DoNAS)</name> <t>The Access Stratum (AS) protocol stack used by DoNAS is specific because the radio network still needs to establish the security associations and reduce the protocoloverhead,overhead so that the PDCP(Packet Data Convergence Protocol)is bypassed until the AS security is activated.RLC (Radio Link Control protocol) uses, byBy default, RLC uses theAM mode, butAM. However, depending on the network's features and the terminal,itRLC may change to other modes by the network operator. For example, thetransparent modeTM does not add any headerornor process the payload to reduce the overhead, but the MTU would be limited by thetransport blockTB used to transmit the data, which is a couple of thousand bits maximum. If UM (only terminals compatible with 3GPP Release 15compatible terminals)<xref target="R15-3GPP"/>) is used, the RLC mechanisms of reliability are disabled, and only the reliability provided by the MAC layer by HARQ is available. In this case, the protocol overhead might be smaller than the AM case because of the lack of statusreportingreporting, butwiththe overhead would have the same support for segmentation up to 1600 bytes. NAS packets are encapsulated within an RRC(Radio Resource Control)<xref target="TS36331"/> message.</t> <t>Depending on the data type indication signaled (IP ornon-IPNon-IP data), the network allocates an IP address or establishes a direct forwarding path. DoNAS is regulated under rate control upon previous agreement, meaning that a maximum number of bits per unit of time is agreed upon per device subscription beforehand and configured in the device. The use of DoNAS is typically expected when a terminal in a power-saving state requires a short transmission and is receiving an acknowledgment or short feedback from the network. Depending on the size of buffered data totransmit,be transmitted, the UE might be instructed to deploy the connected mode transmissions instead, limiting and controlling the DoNAS transmissions to predefined thresholds and a good resource optimization balance for the terminal and the network. The support for mobility of DoNAS is present but produces additional overhead.</t> <figuretitle="DoNAS transmission sequenceanchor="Fig--DONAS"> <name>DoNAS Transmission Sequence from an Uplinkinitiated access" anchor="Fig--DONAS"><artwork><![CDATA[Initiated Access</name> <artwork><![CDATA[ +--------+ +--------+ +--------+ | | | | | | +-----------------+ | UE | | C-BS | | C-SGN | |Roaming Scenarios| +----|---+ +--------+ +--------+ | +--------+ | | | | | | | | +----------------|------------|+ | | P-GW | | | Attach | | +--------+ | +------------------------------+ | | | | | | | | | +------|------------|--------+ | | | | |RRCConnection Establishment|connection establishment| | | | | |with NAS PDU transmission | | | | | |& Ack Rsp | | | | | +----------------------------+ | | | | | | | | | | | |Initial UE | | | | | |message | | | | | |----------->| | | | | | | | | | | | +---------------------+| | | | | |Checks Integrity || | | | | |protection, decrypts || | | | | |data || | | | | +---------------------+| | | | | | Small data packet | | | |-------------------------------> | | | Small data packet | | | |<------------------------------- | | +----------|---------+ | | | | | Integrity protection,| | | | | | encrypts data | | | | | | +--------------------+ | | | | | | | | | | |Downlink NAS| | | | | |message | | | | | |<-----------| | | | +-----------------------+ | | | | |SmallData Delivery,data delivery, | | | | | |RRC connection release | | | | | +-----------------------+ | | | | | | | | +-----------------+]]></artwork></figure>]]></artwork> </figure> <figuretitle="Exampleanchor="Fig--ProtocolArchi5"> <name>Example of User Planepacket encapsulationPacket Encapsulation for Data overNAS" anchor="Fig--ProtocolArchi5"><artwork><![CDATA[NAS</name> <artwork><![CDATA[ +---+ +---+ +---+ +----+ Application |AP1| |AP1| |AP2| |AP2 |(IP/non-IP)(IP/Non-IP) |PDU| |PDU| |PDU| ............... |PDU | +---+ +---+ +---+ +----+ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |/ / | \ | | NAS /RRC +--------+---|---+----+ +---------+ |NAS/|AP1|AP1|AP2|NAS/| |NAS/|AP2 | |RRC |PDU|PDU|PDU|RRC | |RRC |PDU | +--------+-|-+---+----+ +---------| | | | | | | |\ | | | |<--Max. 1600 bytes-->|__ |_ | | | \__ \___ \_ \ | | \ \ \__ \ | | \ | | \_ +---------------|+-----|----------+ \ \ RLC |RLC | NAS/RRC ||RLC | NAS/RRC | +----|-------+ |Head| PDU(1/2)||Head | PDU (2/2)| |RLC |NAS/RRC| +---------------++----------------+ |Head|PDU | | | | \ | +------------+ | | LCID1 | \ | | / | | | \ \ | | | | | \ \ | | | | | \ \ \ | +----+----+----------++-----|----+---------++----+---------|---+ MAC |MAC |RLC | RLC ||MAC |RLC | RLC ||MAC | RLC |Pad| |Head|Head| PAYLOAD ||Head |Head| PAYLOAD ||Head| PDU | | +----+----+----------++-----+----+---------++----+---------+---+ TB1 TB2 TB3]]></artwork></figure>]]></artwork> </figure> </section> <sectionanchor="acknowledgements"><name>Acknowledgements</name>anchor="acknowledgements" numbered="false"> <name>Acknowledgements</name> <t>The authors would like to thank (in alphabetic order):Carles Gomez, Antti Ratilainen, Tuomas Tirronen, Pascal Thubert, Éric Vyncke.</t><contact fullname="Carles Gomez"/>, <contact fullname="Antti Ratilainen"/>, <contact fullname="Pascal Thubert"/>, <contact fullname="Tuomas Tirronen"/>, and <contact fullname="Éric Vyncke"/>.</t> </section> </back><!-- ##markdown-source: H4sIADLdmmMAA+197XbbxrbYfz7FNF69piKSkijbcXxOsy5NybZ6LJkRqePk 1q0vSA5J1CTAA4CSFTP937fos7Qv1v01XwAoy4lzzzq9ZVYsYgjMzN6zZ3/v QbvdbuRFlEzfR8s00c9UkW10I15n9C0vuoeH3x92G9N0kkQr+HmaRbOiHeti 1l6ub6KknU8Wk3Z6rbN2Mo7Ton30uBFlOnqmzpJCZ4kuGjfzZ+r14G3vQr1N sw9xMlcvs3Szbny4cTe1T7DfxiQqnqm8mDbyzXgV53mcJsXtGoY9Ox29aKzj Zw2l8ttVpmf5M/XwVucPsSHNilJLkcWTwl1P0tU68huKdGIuGkVcLGGEYREV 8UT1YUT9sVCvdDTVGVyu1pmmiSgEUl1EWZbejAFhdu4qnanRAuDKG9F4nOlr A+6w/6qvLp63z9IRIYEQVkJCtCkWafas0VZxAhCcdtRltEpzmCPj+3Q6jzLb lmbQzSkAl+dpwoBqDXC9irM8WkZJEWt1dIQQx8XtM3XYfdQ9VP85za6jvKX+ EmcfPqTJZrWKCSebpMjgphdxAk9OoUmvonj5TGkcspPhkP+sZawOoNDMsddR 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