IPv6 Stack. 6LoWPAN makes this possible. IPv6 over Low-Power wireless Area Networks (IEEE )

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1 Reference: 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann What is 6LoWPAN? 6LoWPAN makes this possible - Low-power RF + IPv6 = The Wireless Embedded Internet IPv6 over Low-Power wireless Area Networks (IEEE ) Defined by IETF standards - RFC 4919, draft-ietf-6lowpan-hc and -nd IPv6 Stack - draft-ietf-roll-rpl Stateless header compression Enables a standard socket API Minimal use of code and memory Direct end-to-end Internet integration - Multiple topology options

2 Low Power Network Protocols Class WPAN WPAN WLAN LAN Lifetime (days) Powered Capacity Bandwidth (kbps) Coverage Range (m) , , (wired) Design Goals Low Power, Large Scale, Low Cost Cable Replacement Throughput Throughput

3 Protocol Stacks

4 Features of 6LowPAN Support for e.g. 64-bit and 16-bit addressing Useful with low-power link layers such as IEEE , narrowband ISM and power-line communications Efficient header compression - IPv6 base and extension headers, UDP header Network auto-configuration using neighbor discovery Unicast, multicast t and broadcast support - Multicast is compressed and mapped to broadcast Fragmentation byte IPv6 MTU -> 127 byte frames Support for IP routing (e.g. IETF RPL) Support for use of link-layer layer mesh (e.g ) 5)

5 Benefits of Benefits of 6LoWPAN Technology The benefits of 6LoWPAN include: Open, long-lived, reliable standards Easy learning-curve Transparent Internet integration Network maintainability Global scalability End-to-end ddata flows

6 IPv6 over Challenges Fragmentation - IPv6: Minimum MTU(Maximum Transmission Unit) is 1,280 bytes - IEEE : Maximum 127 bytes Head compression - IPv6: 40 bytes compressed IP Header : effective link payload is 81 bytes Routing - IPv6: A link is a single broadcast domain : a mesh of short-range range connections 21

7 Header Comparison Reference: 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

8 IPv6 Addressing Example Reference: 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

9 Route-over vs Mesh-under Routing in 6LoWPAN

10 6L WPAN R ti 6LoWPAN Routing Here we consider IP routing (Layer 3 routing) - Routing in 6LoWPAN - Single-interface routing - Simple LowPAN scenario - End-to-End data transmissions Reference: 6LoWPAN: The Wireless Embedded Internet, Shelby & Bormann

11 6LoWPAN Challenges UDP datagram, modbus, BacNET/IP,, HTML, XML,, ZCL transport header application payload Network packet 40 B + options cls flow len hops NH src IP dst IP Payload 16 B 16 B Link Layer frame 1280 Bytes MIN ctrl len src UID dst UID link payload 128 Bytes MAX Large IP Address & Header => 16 bit short address / 64 bit EUID Minimum Transfer Unit => Fragmentation Short range & Embedded => Multiple Hops chk

12 Fragmentation ti IPv6 requires underlying links to support Minimum Transmission Units (MTUs) of at least 1280 bytes The performance of large IPv6 packets fragmented over low-power wireless mesh networks is poor! - Lost fragments cause whole packet to be retransmitted - Low-bandwidth and delay of the wireless channel - 6LoWPAN application protocols should avoid fragmentation - Compression should be used on existing IP application protocols when used over 6LoWPAN if possible - IP datagram that are too large to fit in a frame are fragmented into multiple frames - Self describing for reassembly

13 28 Routing in 6LoWPAN Based on which layer the routing decision i.e. the data-gram forwarding occurs we can divide routing protocols in 6LoWPAN into two categories: - Mesh Under Routing - No IP routing - Routing within the 6LoWPAN - Route Over Routing - Routing at the IP layer - Utilizing i network-layer capabilities defined by IP Routing at two different layers may be in conflict - IETF ROLL working group - Routing Over Low-Power and Lossy networks

14 Mesh-under Scheme In mesh-under scheme, routing and forwarding are performed at link layer based on frame or the 6LoWPAN header. - Multiple link layer hops are used to complete a single IP hop To send a packet to a particular destination, - the EUI 64 bit address or the16 bit short address is used and sent it to a neighbor node to move the packet closer to the destination. All fragments of an IP packet can go through route paths and they are gathered at the destination. - All fragments are reached successfully - The adaptation layer of the destination node reassembles all fragments and creates an IP packet. - Any fragment missing in the forwarding process - The entire IP packet i.e. all fragments for this IP packet are retransmitted to the destination for recovery.

15 Route-over Scheme In route-over scheme all routing decisions are taken in the network layer where each node acts as an IP router. - The IP routing supports the forwarding of packets between these links. - The network layer takes decision using the additional encapsulated IP header. An IP packet is fragmented by the adaptation layer, fragments are sent to the next hop based on the routing table information. - The adaptation layer of the next hop checks received fragments. - All fragments are received successfully, the adaptation layer creates an IP packet from fragments and send it to the network layer. If there are one or more fragments missing then all fragments are retransmitted - If there are one or more fragments missing, then all fragments are retransmitted to one hop distance.

16 Where Should Routing Take Place? Historically, a number of interesting research initiatives on WSN - Work on Wireless Sensors Network focussed on algorithms. Most work assumed the use of MAC addresses - Layer 2 routing (mesh-under routing) Support of multiple PHY/MAC (heterogeneous networks) - IEEE , Low Power Wifi, Power Line Communications (PLC) Use IP to route - Supports multiple PHY/MAC - Moves from mesh-under (L2) to router-over(l3) over(l3)

17 Energy cost of IPv6 over IEEE The Energy Consumption on 6LowPAN

18 Technical Challenges Energy consumption is a major issue (battery powered sensors/actuators) Limited processing power Very dynamic topologies - Link failure (LP RF) - Node failures (triggered or non triggered) - Node mobility (in some environments), Data processing usually required on the node itself Sometimes deployed in harsh environments (e.g. Industrial) Potentially deployed at very large scale Must be self-managed

19 Reference: Energy Profile of a Transmission i Datasheet Analysis A. Power up oscillator & radio (Based on TI CC2420) 20mA B. Configure radio C. Clear Channel Assessment, encrypt and load TX buffer D. Transmit packet 10mA C D E E. Switch to rcv mode, listen, receive ACK A B 5 ms 10 ms

20 E C ti Analysis A l i Energy Consumption * * Payload Energy for fixed payload Reference: David E. Culler, 6LowPAN, IPSO Alliance

21 The Energy Cost of 6LowPAN Energy cost of communication has five parts - Sleep - Transmission i - Receiving - Listening (ready to receive) - Overhearing (packets overhearing form others) The increase in header size to support IP over results in a small increase in transmit and receive costs. The dominant cost is listening. - Can only receive if transmission happens when radio is on, listening. - Preamble sampling, low-power listening and related listen all the time, that will pay extra than transmission. - Use TDMA scheduling listen only when necessary. - A Ttransmission i pair must wait for transmission/listen i t slot. - Clocks must be synchronized. Increase delay to reduce energy consumption.

22 Conclusion devices have great ability to work within the resource constraints of low-power, low-memory, low-bandwidth devices provides open-systems based interoperability among low-power devices. 6LowPAN provides interoperability between low-power devices and existing IP devices, using route-over o er routing techniques. es 6LoWPAN turns IEEE into the next generation, All-IP networks.