A Review of 6LoWPAN Routing Protocols Presented by Ee Gee Keng - PowerPoint PPT Presentation

A Review of 6LoWPAN Routing Protocols Presented by Ee Gee Keng Department of Computer and Communication Systems Faculty of Engineering University Putra Malaysia

Outline • Introduction • 6LoWPAN Overview • 6LoWPAN Adaptation Layer Mechanisms And Header Types • Existing Routing Protocols in 6LoWPAN • Comparison of 6LoWPAN Routing Protocols • Conclusion

Introduction Personal Area Network (PAN) IPv6 vs IEEE 802.15.4 Wireless IPv4 (PHY and MAC) Sensor 6LoWPAN Network (WSN) Low power Wireless Personal Area Network Ex: ZigBee (LoWPAN)

WSN vs 6LoWPAN NAT devices obviated !

6LoWPAN Overview -Provides a WSN node with IP communication capabilities. -RFD (end device) FFD (router) Gateway IP-enabled devices

6LoWPAN Protocol Stack Adaptation layer Header compression, fragmentation, reassembly ! IPv6 packet (1280 bytes) MAC frame size (25+102= 127 bytes)

IEEE 802.15.4 PHY and MAC - specifies when the devices may access the channel for communication. - 4 frame structures for MAC layer: beacon frame, data frame, acknowledgement frame and MAC command frame. - A beacon frame - to transmit beacons. - A data frame - data transfers. - Acknowledgement frame - confirm successful frame reception. - MAC command frame - handling all MAC peer entity control - dictates how the IEEE 802.15.4 devices may communicate with transfers. each other over a wireless channel. - The IEEE 802.15.4 standard total 27 channels defined in PHY layer. Channel 0 Channels 1-10 2 MHz 868MHz / 915MHz PHY General MAC frame format in PHY frame 868.3 MHz 902 MHz 928 MHz 20Kb/s 40Kb/s 2.4 GHz Channels 11-26 5 MHz PHY 250Kb/s

6LoWPAN Adaptation Layer Mechanisms • Header compression, fragmentation and layer-two forwarding. • 4 basic 6LoWPAN header types: - HC1 header ( IPv6 Header Compression Header) First two bits of header - Fragmentation header are used to - Mesh header identify - Dispatch header • Header stacking principle is used. - Device only uses specific 6LoWPAN defined headers to send its packet.

6LoWPAN Adaptation Layer Mechanisms a) HC1 header - Used to compress those header fields to a few bits while reserving an escape value for the less common ones appear. -> reduce transmission overhead ! IPv6 6LoWPAN Header Field header Explanation HC1 length length Version 4 bits ------ Assuming communicating with IPv6. Traffic class 8 bits 0 = Not compressed. The field is in full size. 1 bit Flow label 20 bits 1 = Compressed. The traffic class and flow label are both zero. Can be derived from MAC frame length or adaptation layer datagram size Payload length 16 bits ------ (6LoWPAN fragmentation header). Compressed whenever the packet uses UDP, TCP or Internet Control Message Next header 8 bits 2 bits Protocol version 6 (ICMPv6). Hop limit 8 bits 8 bits The only field always not compressed. Source address 128 bits 2 bits If Both source and destination IPv6 addresses are in link local, their 64-bit network prefix are compressed into a single bit each with a value of one. Another single bit is set to one to indicate that 64-bit interface identifier are elided if the destination can Destination derive them from the corresponding link-layer address in the link-layer frame or 128 bits 2 bits address mesh addressing header when routing in a mesh. HC2 encoding ------ 1 bit Another compression scheme follows a HC1 header. Total 40 bytes 2 bytes Fully compressed, the HC1 encoding reduces the IPv6 header to two bytes.

6LoWPAN Adaptation Layer Mechanisms b) Fragmentation header - Datagram size - specify the size of the entire IP packet before adaptation-layer fragmentation. - Datagram tag - identify all of the fragments of a single original packet. - An extra byte in subsequent fragmentation is used for datagram offset field. 1 1 0 0 0 Datagram size (11 bits) Datagram tag (16 bits) C) Mesh header - Accomplish intra-PAN routing. 1 0 O F Hops left (4 bits) Originator address (16-64 bits) Final address (16-64 bits) Hops left Originator address 1 0 O F 0xF Final address (16-64 bits) (8 bits) (16-64 bits)

6LoWPAN Adaptation Layer Mechanisms d) Dispatch header - Used to define the type of header to follow. - Only 5 of the 64 dispatch header types have thus far been defined. 0 1 Dispatch (6 bits) 0 1 0x3F Dispatch (8 bits) The following bits are IPv6 uncompressed header 01 000001 The following bits are IPv6 HC1 compressed encoding 01 000010 The following bits are broadcast header 01 010000 The following 8 bits are an additional field for dispatch value. 01 111111

6LoWPAN Adaptation Layer Mechanisms 6LoWPAN header sequences - Header stacking principle headers present only if needed ! IEEE 802.15.4 Mesh Broadcast Fragmentation Dispatch Compressed Payload frame addressing header header header IP header 6LoWPAN routing header - To achieve full routing functionality. - Mesh-under (intra-PAN) vs route-over (inter-PAN). Dispatch Header ( new 6-bit sequence) Routing header Payload

6LoWPAN Routing classification Mesh Under - Performs its routing at adaptation layer. - Performs no IP routing within LoWPAN. - Based on MAC address (16-bit or 64-bit). Route Over -Performs its routing at network layer. -Performs IP routing. -IP address = IPv6 prefix + interface identifier => automatically (stateless auto-configuration) Mesh Under Route Over -Each node serves as an IP router.

Existing 6LoWPAN Routing a) 6LoWPAN Ad-hoc On-Demand Distance Vector (LOAD) AODV protocol message exchange LOAD protocol message exchange Modification done in LOAD: - Destination sequence number is not used. - For ensure loop freedom, only destination generates RREP. - new routing metric : link quality indication (LQI) is used. - Link Layer Notification (LLN) instead of Hello message.

Existing 6LoWPAN Routing b) Dynamic MANET On-demand for 6LoWPAN Routing (DYMO-low) Differences with LOAD : -16-bit destination sequence number is used. - local repair and route cost accumulation are not used.

Existing 6LoWPAN Routing c) Hierarchical Routing (HiLow) Uses 16-bit short address as interface identifier instead of 64-bit as AODV and LOAD PAN => memory saving and larger coordinator scalability. Parent Nodes 17 18 Child Nodes

Comparison of 6LoWPAN Routing AODV DYMO- LOAD HiLow (WSN) low RERR message Use Use Use No use Sequence number Use No use Use No use Precursor list Use No use No use No use Hop count Use Optional Optional Use Hello message Use No use Use No use Local repair Use Use No use No use Energy Usage High Low Low Low Memory usage High Medium Medium Low Mobility Mobile Mobile Mobile Static Scalability Low Low Low High Routing delay High Low High Low Convergence to Fast Fast Fast Slow topology change

Conclusion • With the knowledge of the 6LoWPAN header encapsulation, the new routing header can be added in the 6LoWPAN packet to achieve full routing functionality. • Existing 6LoWPAN routing protocols such as LOAD, DYMO-low and HiLow are reviewed. • There are always some tradeoffs between the routing protocols. A suitable routing protocol only can be chosen based on the application that it involves.

Thank You