6LoWPAN Demystified - TI
6LoWPAN demystifiedJonas OlssonSystem Applications EngineerTexas Instruments
Introduction6LoWPAN is connecting more things to the cloud. Low-power, IP-driven nodes andlarge mesh network support make this technology a great option for Internet of Things(IoT) applications. As the full name implies – “IPv6 over Low-Power Wireless PersonalArea Networks” – 6LoWPAN is a networking technology or adaptation layer that allowsIPv6 packets to be carried efficiently within small link layer frames, such as thosedefined by IEEE 802.15.4. The use of an end-to-end, IP-based infrastructure takes fulladvantage of 30 years of IP technology development, facilitating open standards andinteroperability as largely demonstrated through the daily use of the Internet and itsalmost 3 billion users.6LoWPAN is an open standard defined in RFCdata exchange between devices inside the6282 by the Internet Engineering Task Force (IETF),6LoWPAN; and 3) the generation and maintenancethe standards body that defines many of the openof the radio subnet (the 6LoWPAN network).standards used on the Internet such as UDP, TCPBy communicating natively with IP, 6LoWPANand HTTP to name a few. A powerful feature ofnetworks are connected to other networks simply6LoWPAN is that while originally conceived tousing IP routers. As shown in Figure 1, 6LoWPANsupport IEEE 802.15.4 low-power wireless networksnetworks will typically operate on the edge, actingin the 2.4-GHz band, it is now being adapted andas stub networks. This means data going into theused over a variety of other networking medianetwork is destined for one of the devices insideincluding Sub-1 GHz low-power RF, Bluetooth the 6LoWPAN. One 6LoWPAN network may beSmart, power line control (PLC) and low-power connected to other IP networks through one orWi-Fi .more edge routers that forward IP datagramsThis white paper discusses key 6LoWPAN conceptsbetween different media. Connectivity to other IPto demonstrate how it enables the use of IPv6 overnetworks may be provided through any arbitraryIEEE 802.15.4 radio links.link, such as Ethernet, Wi-Fi or 3G/4G. Because6LoWPAN only specifies operation of IPv6 over the6LoWPAN network architectureIEEE 802.15.4 standard, edge routers may alsoFigure 1 on the following page shows an examplesupport IPv6 transitionof an IPv6 network, including a 6LoWPAN meshmechanisms to connectnetwork. The uplink to the Internet is handled by the6LoWPAN networks toAccess Point (AP) acting as an IPv6 router. SeveralIPv4 networks, suchdifferent devices are connected to the AP in a typicalas NAT64 defined insetup, such as PCs, servers, etc. The 6LoWPANRFC 6146. These IPv6network is connected to the IPv6 network using antransition mechanismsedge router. The edge router handles three actions:do not require the1) the data exchange between 6LoWPAN devices6LoWPAN nodes to implement IPv4 in whole orand the Internet (or other IPv6 network); 2) localin part.6LoWPAN demystified2October 2014By communicatingnatively with IP,6LoWPAN networksare connected toother networks simplyusing IP routers
6LoWPANedge R::8R::5H::7HR::9::6R RouterH HostFigure 1. An example of an IPv6 network with a 6LoWPAN mesh networkBecause edge routers forward datagrams atthus making it possible to use embedded devicesthe network layer (see the next section aboutthat are lower cost, runs simpler software and hascommunications layers), they do not maintain anyless complex hardware. However, the IP architectureapplication-layer state. Other network architecturesdoes not preclude the use of proxies and caches to such as ZigBee , Z-wave, Bluetooth or proprietaryoptimize network performance, both of which arenetworks require stateful and sometimes complexwidely used in the Internet today.application gateways to connect to IP-basedTwo other device types are included inside a typicalnetworks, such as the Internet. These application6LoWPAN network: routers and hosts. Routersgateways must understand any application profilescan, as the name implies, route data destined tothat may be used in the network, and any changesanother node in the 6LoWPAN network. Hosts areto application protocols on the wireless nodes mustalso known as end devices and are not able toalso be accompanied by changes on the gateway.route data to other devices in the network. Host canIn contrast, IP-based border routers, like the edgealso be a sleepy device, waking up periodically torouter, remain agnostic to application protocolscheck its parent (a router) for data, enabling very lowused in the 6LoWPAN. This lowers the burden putpower consumption.on the edge router in terms of processing power,6LoWPAN demystified3October 2014
System stack overviewAll communications systems use a set of rules orstandards to format data and control the exchange.6LoWPAN radically changes the IoT landscape.The most common model in data communicationAs discussed, up until now a complex application-systems is the Open Systems Interconnect (OSI)layer gateway was needed to make devices suchmodel, which in a simplified model, breaks theas ZigBee, Bluetooth and proprietary systemscommunication into five fundamental layers. Figureconnect to the Internet. 6LoWPAN solves this2 shows this simplified OSI model alongside twodilemma by introducing an adaptation layer betweentypical examples of stacks used in IoT devices. Onethe IP stack’s link and network layers to enableis a device running the Wi-Fi stack, the other devicetransmission of IPv6 datagrams over IEEE 802.15.4is an IoT-connected device based on 6LoWPAN.radio links.Simplified OSI modelWi-Fi stack example6LoWPAN stack example5. Application layerHTTPHTTP, COAP, MOTT,Websocket, etc.4. Transport LayerTCPUDP, TCP (SecurityTLS/DTLS)3. Network LayerInternet Protocol (IP)IPv6, RPL6LoWPANIEEE 802.15.4 MAC2. Data Link LayerWi-Fi1. Physical LayerIEEE 802.15.4Figure 2. The OSI model, a Wi-Fi stack example and the 6LoWPAN stackThe physical layer converts data bits into signalscorrecting errors that may occur in the physical layerthat are transmitted and received over the air. Induring transmission and receiving. The data linkthe 6LoWPAN example, IEEE 802.15.4 is used.layer includes the media access layer (MAC) whichIn addition to the well-rounded 2006 version ofprovides access to the media, using features likethe standard, two important amendments exist:carrier sense multiple access – collision avoidancee and g. IEEE 802.15.4e is a MAC amendment(CSMA-CA) where the radio listens that no oneand provides enhancements such as time slottedelse is transmitting before actually sending datachannel hopping (TSCH) and coordinated sampledover the air. This layer also handles data framing.listening (CSL). Both enhancements aim to furtherIn the 6LoWPAN example, the MAC layer is IEEElower the power consumption and make the802.15.4. The 6LoWPAN adaptation layer, providinginterface more robust. The IEEE 802.15.4g is a PHYadaptation from IPv6 to IEEE 802.15.4, also resides(or physical layer) amendment and aims to providein the link layer.an additional range of radio frequency bands toThe network layer addresses and routes dataenable worldwide use even in the Sub-1 GHzthrough the network, if needed over several hops.frequency bands.IP (or Internet Protocol) is the networking protocolThe data link layer provides a reliable link betweenused to provide all devices with an IP address totwo directly connected nodes by detecting andtransport packets from one device to another.6LoWPAN demystified4October 2014
The transport layer generates communicationdirectly between end points. Instead a broker (i.e.,sessions between applications running on endserver) is used to relay messages. MQTT introducesdevices. The transport layer allows multiplethe “topic” entity; devices can publish and subscribeapplications on each device to have their ownto different topics. Once a topic is updated that acommunications channel. TCP is the dominantspecific device has subscribed to, the device willtransport protocol on the Internet. However, TCPget notified and receive the data via the broker.is a connection-based protocol (including packetDevices can use wildcards like # and * to subscribeordering) with large overhead and therefore notto a hierarchy of topics. MQTT supports severalalways suitable for devices demanding ultra-lowlayers of quality of service (QoS) making sure thatpower consumption. For those types of systems,messages are delivered. The broker can run bothUDP, a lower overhead, connectionless protocol,locally in an IP intranet and on the Internet andcan be a better option. Secure transport layersmultiple brokers are supported interacting in theexamples include TLS (transport layer security)same system. Several public brokers are availablerunning atop TCP and DTLS, which is based on UDP.and many of the cloud service providers provideFinally, the application layer is responsible forMQTT access. There are many more applicationdata formatting. It also makes sure that data islayer protocols available that can run over the TCP/transported in application-optimal schemes. AUDP. Those listed here specifically target low-powerbroadly used application layer on the Internet isIoT applications.HTTP running over TCP. HTTP uses XML, whichInternet Protocol version 6 (IPv6)over IEEE 802.15.4is a text-based language with a large overhead.Therefore, it is not optimal to use HTTP in many6LoWPAN systems. However, HTTP can still beToday’s Internet (and many standalone IP networks)very useful for communications between 6LoWPANis mainly based on IPv4 and uses 32-bit addresses,and the Internet. For this reason, the industry andwhich limits the address space to 4,294,967,296community have developed alternative applicationunique addresses. As addresses were assignedlayer protocols, such as the constrained applicationto users (and devices), the number of unassignedprotocol (COAP), a message protocol running overaddresses naturally decreased. IPv4 addressUDP with a bit-optimized REST mechanism veryexhaustion occurred on Feb. 3, 2011, although itsimilar to HTTP. COAP is defined by IETF in RFChad been significantly delayed by address changes7252 and defines retransmissions, confirmablesuch as network address translation (NAT).and non-confirmable messages, support for sleepyThis limitation of IPv4 stimulated the developmentdevices, block transfers, subscription support andof IPv6 in the 1990s, which has been in commercialresource discovery. COAP is also easy to map todeployment since 2006. IPv6 covers an addressHTTP via proxies.space of 2128 and 3.4*1038 unique addresses. ThisAnother application layer protocol that should beshould be enough for Internet to scale for decadesmentioned is message queue telemetry transportto come – even with the promise of the Internet of(MQTT), an open-source protocol that was inventedThings, which according to estimates might includeby IBM. MQTT is a publish/subscribe type of50 billion connected devices by the year 2020.protocol running over TCP. Data is not transported6LoWPAN demystified5October 2014
To recognize the increase in bandwidth, IPv62. Since IEEE 802.15.4 is both low power and lowincreases the minimum maximum transmission unitthroughput, in addition to the use of RF as media,(MTU) from 576 to 1280 bytes. IPv6 also reflectsit is more prone to spurious interference, linkchanges and advances in link layer technologiesfailures and asymmetric links (A can hear B, but Bthe Internet uses. Ethernet is the dominant linkcannot hear A). Those characteristics require thetechnology and its throughput has increasednetwork layer to be adaptive and responsive at theover the years. Wi-Fi mirrors Ethernet capabilitiessame time as low power and efficient.supporting similar-sized MTU and very high link3. The most common network topology forrates. Both Ethernet and Wi-Fi operate in the6LoWPAN is a low-power mesh network. Thiscontext of ample power and highly capable devices.negates the assumption that a link is a singleOn the other hand, IEEE 802.15.4 was designedbroadcast domain, something that is veryto serve a different market; long-lived applicationsimportant since the very foundation of IPv6 suchthat require large numbers of low-cost, ultra-low-as neighbor discovery relies on it.power devices. The throughput under this standardThe above issues are all addressed in the 6LoWPANis limited to 250 kbps, and the frame length isstandard.limited to 127 bytes to ensure low packet and biterror rates in a lossy RF environment. Additionally,The 6LoWPAN adaptation layerIEEE 802.15.4 uses two addresses: a 16-bit shortWhen sending data over MAC and PHY layers, anaddress and an EUI-64 extended address. Theseadaptation layer is always used. For example, RFCaddresses reduce header overhead and minimize2464 defines how an IPv6 packet is encapsulated inmemory requirements. In addition, 6LoWPANan Ethernet frame. The same is also used for IEEEoperates most commonly over multiple hops802.11 Wi-Fi. For 6LoWPAN, RFC 6282 definesforming a low-power mesh network, a fundamentalhow an IPv6 data frame is encapsulated over andifference from Ethernet- or Wi-Fi-based networks.IEEE 802.15.4 radio link.Finally, devices used to implement 6LoWPAN aretypically constrained in terms of resources, havingThe main focus of the IETF working group,about 16 kB RAM and 128 kB ROM.6LoWPAN WG, was to optimize the transmission ofIPv6 packets over low-power and lossy networksDue to the above resource constraints and(LLNs) such as IEEE 802.15.4 and led to the6LoWPAN multi-hop topology, supporting IPv6 overpublication of RFC 6282 specifying;IEEE 802.15.4 networks present several challenges; Header compression, which compresses1. IPv6 datagrams are not a natural fit for IEEEthe 40-byte IPv6 and 8-byte UDP headers by802.15.4 networks. Low throughput, limitedassuming the usage of common fields. Headerbuffering and datagrams that are one-tenth offields are elided when they can be derivedIPv6 minimum MTU make header compressionfrom the link layer. The way the headers can beand data fragmentation a necessity. Forcompressed is one of the factors that led to theexample IEEE 802.15.4 link headers can limitstandard only supporting IPv6 and not IPv4.the effective possible payload to 81 bytes. ThisNote that there is nothing stopping one frommakes IPv6 (40 bytes), TCP (20 bytes) and UDPrunning TCP in a 6LoWPAN system, but TCP(8 bytes) headers seem way too large.6LoWPAN demystifiedheader compression is not part of RFC 6282.6October 2014
Fragmentation and reassembly. The datainformation that can be derived from other layers, suchlink of IEEE 802.15.4 with a frame length ofas the IPv6 addresses and UDP/IPv6 length fields.maximum 127 bytes does not match the MTUof IPv6, which is 1280 bytes. It should be notedHeader compressionthat the frame format of IEEE 802.15.4g doesThe traditional way of performing IP headernot have the same limitation.compression is status based, which is used atpoint-to-point connections where a flow between Stateless auto configuration. Stateless autoconfiguration is the process where devicestwo end points is stable. This implementation isinside the 6LoWPAN network automaticallyvery effective in static networks with stable links.generate their own IPv6 address. There areCommunication over multiple hops requires hop-methods to avoid the case where two devicesby-hop compression/decompression. The routingget the same address; this is called duplicateprotocols (e.g., RPL) normally running in 6LoWPANaddress detection (DAD).systems obtain receiver diversity by rerouting,which would require state migration and henceThroughout the 6LoWPAN adaptation layer, theseverely reduce the compression efficiency. Forkey concept is to use stateless or shared-contextdynamically changing networks, with multiple hopscompression to elide header fields. This canand infrequent transmissions like a 6LoWPANcompress all headers (adaptation, network andradio network, another method has to be applied.transport layers) down to a few bytes. It is possibleInstead in 6LoWPAN stateless and shared-contextto compress header fields since they often carrycompression is used, which does not require anycommon values. Common values occur due tostate and lets routing protocols dynamically choosefrequent use of a subset of IPv6 functionality, namelyroutes without affecting compression ratio.UDP, TCP and ICMP. Assumptions regarding sharedcontext can also be made, such as a commonIn the example in Figure 3, three communicationnetwork prefix for the whole 6LoWPAN system. Thescenarios are displayed:6LoWPAN adaptation layer also removes duplicatedIPv6 headerVerTrafficclassFlow labelPayloadlengthNextheaderHoplimitSource address64-bit prefix, 64-bit HD1. Compressed header, :CAFE:00FF:FE00:02002 bytes2. Compressed header, plimitDestination address64-bit HD2001::4455:84C6:39BB:A2DD12 bytes3. Compressed header, nation address64-bit prefix, 64-bit HDCIDHoplimit2001::4455:84C6:39BB:A2DDDestination address64-bit prefix, 64-bit HDSource address64-bit prefixFigure 3. 6LoWPAN IPv6 header compression examples6LoWPAN demystified7October 201420 bytes40 bytes
1. Communication between two devices insidesequence at the end. When data packets arethe same 6LoWPAN network, using link-localre-assembled, the additional information added isaddresses, the IPv6 header can be compressedremoved and the packets are restored to their initialto only 2 bytes.IPv6 format. The fragmentation sequence is differentbased on what type of routing is used (different2. Communication destined to a device outsideof the 6LoWPAN network and the prefix forrouting techniques are discussed later). In the casethe external network is known, where the IPv6of mesh-under routing, fragments are reassembledheader can be compressed to 12 bytes.at their final destination only, while in the case ofroute-over networks data packets are reassembled3. Similar to 2, but without knowing the prefix ofthe external device, that gives an IPv6 header ofat every hop. Thus in a router-over network each20 bytes.hop has to have enough resources to store allfragments. Whereas in a mesh-under system, aThe best case (1) in this example is not useful forlot of network traffic is generated quickly since allsending application data (as it can only be usedfragments are passed immediately. If any fragmentsto send data to direct neighbors), however beingare missing (in a mesh-under system) during theable to compress headers on data interchangedreassemble, the complete packet needs to bebetween two near-by devices is important especiallyre-transmitted. If possible, fragmentation shouldfor the routing protocol. The worst case (3) still givesbe avoided as long as possible since it negativelya 50 percent compression ratio. In the example,impacts the battery life of a device. Therefore,it is assumed that the interface ID (IID) is derivedkeeping the payload low (includes selecting thefrom the MAC address of the device. It shall alsoappropriate application level protocols) and usingbe noted that UDP header compression is partheader compression are of the utmost importance.of the 6LoWPAN standard as stated earlier in thisdocument, but not displayed in this example.Header formatsFragmentation and reassembly6LoWPAN uses stacked headers and, analogousto IPv6, extension headers. 6LoWPAN headersIn order to enable the transmission of IPv6 framesdefine the capability of each sub-header. Threeover IEEE 802.15.4 radio links, the IPv6 framessub-headers are defined: mesh addressing,need to be divided into several smaller segments.fragmentation and header compression. MeshFor this purpose, additional data in the headers areaddressing supports layer-two (data link) forwardinggenerated to reassemble the packets in the correctand fragmentation supports the transmission ofIEEE 802.15.4 headerIPv6 headercompressionIPv6 payloadIEEE 802.15.4 headerFragment headerIPv6 headercompressionIPv6 payloadIEEE 802.15.4 headerMesh addressingheaderFragment headerIPv6 headercompressionFigure 4. 6LoWPAN stacked headers6LoWPAN demystified8October 2014IPv6 payload
IPv6 MTU. The header format is defined by usingnetwork. The mesh address header includesthe header type field placed at the beginning ofthree fields: hop limit, source address andeach header. The header stack is easy to parse anddestination address. The hop limit field is usedallows for sub-headers to be removed if not needed.to limit the number of hops for forwarding. TheThe fragmentation header is elided for packets thatfield is decremented at each hop. Once the countfit into one single IEEE 802.15.4 frame. The meshreaches zero the packet is dropped. The sourceheader is not used when sending data over oneand destination address fields indicate the IP endhop only.points. Both are IEEE 802.15.4 addresses andThe fragment header is used when the payload ismay be short or extended as defined in the IEEEtoo large to fit in a single IEEE 802.15.4 frame. The802.15.4 standard. The mesh address header’sfragment header contains three fields; datagramlength is between 5 and 17 bytes, depending on thesize, datagram tag and datagram offset. Datagramaddressing mode in use.size describes the total (un-fragmented) payload.RoutingDatagram tag identifies the set of fragments andis used to match fragments of the same payload.Routing is the ability to send a data packet fromDatagram offset identifies the fragment’s offsetone device to another device, sometimes overwithin the un-fragmented payload. The fragmentmultiple hops. Depending on what layer the routingheader length is 4 bytes for the first header and 5mechanism is located, two categories of routingbytes for all subsequent headers.are defined: mesh-under or route-over. Mesh-underuses the layer-two (link layer) addresses (IEEEThe mesh address header is used to forward802.15.4 MAC or short address) to forward datapackets of multiple hops inside a 6LoWPANsourceRoute-over (layer three) forwardingdestination5. Application layer5. Application layer5. Application layer5. Application layer4. Transport Layer4. Transport Layer4. Transport Layer4. Transport Layer3. Network Layer3. Network Layer3. Network Layer3. Network Layer2. Data Link Layer2. Data Link Layer2. Data Link Layer2. Data Link Layer1. Physical Layer1. Physical Layer1. Physical Layer1. Physical LayerMesh-under (layer two) forwardingsourcedestination5. Application layer5. Application layer5. Application layer5. Application layer4. Transport Layer4. Transport Layer4. Transport Layer4. Transport Layer3. Network Layer3. Network Layer3. Network Layer3. Network Layer2. Data Link Layer2. Data Link Layer2. Data Link Layer2. Data Link Layer1. Physical Layer1. Physical Layer1. Physical Layer1. Physical LayerFigure 5. Mesh-under and route-over packet forwarding6LoWPAN demystified9October 2014
packets; while route-over uses layer three (networka routing table and a neighbor table. The routinglayer) addresses (IP addresses).table is used to look up routes to devices, and theIn a mesh-under system, routing of data happensneighbor table is used to keep track of a node’stransparently, hence mesh-under networks aredirect neighbors. In non-storing mode the only deviceconsidered to be one IP subnet. The only IP routerwith a routing table is the edge router, hence sourcein such a system is the edge router. One broadcastrouting is used. Source routing means that thedomain is established to ensure compatibilitypacket includes the complete route (or hops) it needswith higher layer IPv6 protocols such as duplicateto take to reach the destination. For example, whenaddress detection. These messages have to besending data from one device to another devicesent to all devices in the network, resulting in highinside the same 6LoWPAN network, data is first sentnetwork load. Mesh-under networks are best suitedfrom the source device to the edge router, the edgefor smaller and local networks.router in turn makes a lookup in its routing table andadds the complete route to the destination in theIn route-over networks the routing takes place at thepacket. Storing mode imposes higher requirementsIP level as described above, thus each hop in suchon the devices acting as routers (i.e., they need tonetworks represents one IP router. The usage of IPhave resources enough to store the routing androuting provides the foundation to larger and moreneighbor tables), while using non-storing modepowerful and scalable networks, since every routerthe overhead increases with the number of hops amust implement all features supported by a normalpacket needs to traverse to reach the destination.IP router such as DAD, etc. The most widely usedrouting protocol for route-over 6LoWPAN networksAuto configuration and neighbordiscoverytoday is RPL (pronounced “ripple”) as defined byIETF in RFC 6550. Compared to mesh-under,Auto configuration is the autonomous generation ofroute-over features the advantage that most of thea device’s IPv6 address. The process is essentiallyprotocols used on a standard TCP/IP stack todaydifferent between IPv4 and IPv6. In IPv6 it allows acan be implemented and used as is. RFC 6550device to automatically generate its IPv6 addressspecifies the IPv6 routing protocol for low-power andwithout any outside interaction with a DHCPlossy networks (RPL), which provides a mechanismserver or such. To get an address, a host canwhereby multipoint-to-point traffic from devices insidecommunicate via neighbor discovery protocolthe 6LoWPAN network towards a central control(NDP), however many of the NDP features are alsopoint (e.g., a server on the Internet) as well as point-included in RPL. The procedure described here isto-multipoint traffic from the central control point tovalid for RPL also, and involves four message types:the devices inside the 6LoPWAN are supported. Router solicitation (RS)Support for point-to-point traffic is also available. Router advertisement (RA)However, RPL is not the optimum choice for such Neighbor solicitation (NS)traffic, since the data in many cases needs to be Neighbor advertisement (NA)transported via the edge router. RPL supports twodifferent routing modes; storing mode and n on-IPv6 neighbor discovery (ND) lets a device discoverstoring mode. In storing mode, all devices in theneighbors, maintain reachability information,6LoWPAN network configured as routers maintainconfigure default routes, and propagate configuration6LoWPAN demystified10October 2014
Securityparameters. The RS message includes, among otherthings, the IPv6 prefix of the network. All routers inSecurity is a must for IoT systems and alwaysthe network periodically send out these messages. Ifpresents a challenge. Due to the nature of IoTa host wants to participate in a 6LoWPAN network, itwith many nodes that in many cases have veryassigns itself a link-local unicast address (FE80::IID),constrained performance, there are also morethen sends this address in an NS message to allentry points for an outside attacker. Another criticalother participants in the subnet to check if theaspect is that data flowing in a typical IoT system isaddress is being used by someone else. If it doesnot just “data,” the damage potential is much highernot hear an NA message within a defined timeframe,since the data flowing in the system can be used toit assumes that the address is unique. Thisopen the door to you house or turn on/off alarmsprocedure is called duplicate address detection,remotely, for example.DAD. Now, to get the network prefix, the host sendsState-of-the-art security schemes are necessary toout an RS message to the router to get the correctbe ahead of the pack. 6LoWPAN takes advantageprefix. Using these four messages, a host is able toof the strong AES-128 link layer security definedassign itself a worldwide unique IPv6 address.in IEEE 802.15.4. The link layer security providesUsing source address auto configuration, each hostlink authentication and encryption. In addition togenerates a link-local IPv6 address using its IEEElink layer security, transport layer security (TLS)802.15.4 EUI-64 address, 16-bit short addressmechanisms have been shown to work great inor both. In a mesh-under configuration, the link-6LoWPAN systems. TLS, as defined in RFC 5246,local scope covers the entire 6LoWPAN network,runs over TCP. For constrained environments andeven over multiple hops, and a link-local addresssystems where UDP is chosen as the transportis sufficient for communication happening in thelayer protocol, the RFC 6347 (datagram transport6LoWPAN. The only time a routable IPv6 addresslayer security) can be used to provide security atis needed is when communicating outside of thethe transport layer. However, it should be noted6LoWPAN network. In a route-over configuration, athat implementing TLS/DTLS requires the devicelink-local address is sufficient to communicate withto have necessary resources, such as a hardwarenodes that are within radio coverage, but a routableencryption engine to enable the use of advancedaddress is required to communicate with devicescipher suites, etc. A device especially developed forseveral hops away.this purpose is TI’s CC2538 wireless MCU, whichFor all unicast addresses, it is most efficient tointegrates a powerful ARM Cortex -M3 CPUderive them from the local IEEE EUI-64 address.and an IEEE 802.15.4 radio. The device has up to6LoWPAN’s binding between link, adaptation and512kB Flash and 32kB RAM, and also features aIP headers allows them to be elided and removeshardware encryption engine capable of supportingthe need for address resolution, thus resulting inTLS/DTLS.smaller headers. Similarly, au
6LoWPAN demystified 2 October 2014 Introduction 6LoWPAN is connecting more things to the cloud. Low-power, IP-driven nodes and large mesh network support m
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