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Wireless Embedded Systems (0120442x) IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN) Chaiporn Jaikaeo Department of Computer.

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Presentation on theme: "Wireless Embedded Systems (0120442x) IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN) Chaiporn Jaikaeo Department of Computer."— Presentation transcript:

1 Wireless Embedded Systems (0120442x) IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN) Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer Engineering Kasetsart University

2 Outline 6LoWPAN 6LoWPAN IPv6 overview IPv6 overview Header compression tecniques Header compression tecniques Routing Routing JenNet-IP JenNet-IP The 6lo Working Group The 6lo Working Group 2

3 6LoWPAN IPv6 over Low-power Wireless Personal Area Networks IPv6 over Low-power Wireless Personal Area Networks Nodes communicate using IPv6 packets Nodes communicate using IPv6 packets An IPv6 packet is carried in the payload of IEEE 802.15.4 data frames An IPv6 packet is carried in the payload of IEEE 802.15.4 data frames 3

4 Example 6LoWPAN Systems 4

5 IPv6 Overview Larger address space compared to IPv6 Larger address space compared to IPv6  2 32 vs. 2 128 Autoconfiguration Autoconfiguration  Supporting both stateful (DHCPv6) and stateless operations Simplified headers Simplified headers  Fixed header with optional daisy-chained headers Mandatory security Mandatory security 5

6 IPv6 Header Minimum header size = 40 bytes Minimum header size = 40 bytes  Header compression mechanism is needed 6 Ver Bit 0481216202428 0 Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address 32 64 96 128 160 192 224 256 288

7 IPv6 Extended Headers More flexible than IPv4’s option fields More flexible than IPv4’s option fields Example 1: no extended header Example 1: no extended header Example 2: with a routing header Example 2: with a routing header 7 Next header = 6 (TCP) TCP hdr + payload Next header = 43 (routing) TCP hdr + payload Next header = 6 (TCP)

8 IPv6 Addressing Global unicast addresses Global unicast addresses  Start with 001  Host ID usually incorporates MAC address 8 Prefix provided by service provider Subnet ID 4816 Host ID 001 64

9 IPv6 Address Scopes Global addresses Global addresses  Globally routable Link-local addresses Link-local addresses  Only used within directly attached network  Belonging to FE80::/10 subnet 9 0Interface ID 1111 1110 10 10 bits 96dbc9FFFE0016fe 94dbc90016fe U = 0: not unique U = 1: unique xxxxxxUx

10 IEEE 802.15.4 Revisited Allows 127 bytes MTU Allows 127 bytes MTU  Good for buffering cost and low packet error rate Supports both 16-bit and 64-bit addresses Supports both 16-bit and 64-bit addresses Supports both star and mesh topologies Supports both star and mesh topologies Usually operates in an ad hoc fashion with unreliable links Usually operates in an ad hoc fashion with unreliable links IEEE 802.15.4 networks are considered Low-power and Lossy Networks (LLN) IEEE 802.15.4 networks are considered Low-power and Lossy Networks (LLN) 10

11 6LoWPAN Adaptation Layer Needs to make IEEE 802.15.4 comply with IPv6’s MTU size of 1280 bytes Needs to make IEEE 802.15.4 comply with IPv6’s MTU size of 1280 bytes  IEEE 802.15.4’s MTU is 127 bytes  MAC header: ≤ 25 bytes  Optional security header: ≤ 21 bytes Provides three main services Provides three main services  Packet fragmentation and reassembly  Header compression  Link-layer forwarding 11

12 6LowPAN Header Stack 12

13 Header Dispatch Byte 13

14 Mesh Address Header (1) Used with mesh-under routing approach Used with mesh-under routing approach  Only performed by FFDs 14

15 Mesh Address Header (2) Hop left field is decremented by one every hop Hop left field is decremented by one every hop  Frame is discarded when hop left is 0 Address fields are unchanged Address fields are unchanged 15 ABC OriginatorFinal 802.15.4 Header Mesh Header B OrigFinalDstSrc AADData D 802.15.4 Header Mesh Header D OrigFinalDstSrc CADData

16 Mesh-under vs. Route-over Routing 16 Application Transport Network (IPv6) 6LoWPAN Adaptation 802.15.4 MAC 802.15.4 PHY Application Transport Network (IPv6) 6LoWPAN Adaptation 802.15.4 MAC 802.15.4 PHY Mesh-under routing Route-over routing Routing

17 Fragment Header Fragmentation is required when IPv6 payload size exceeds that of IEEE 802.15.4 payload limit Fragmentation is required when IPv6 payload size exceeds that of IEEE 802.15.4 payload limit All fragments are in units of 8 bytes All fragments are in units of 8 bytes 17 (in 8-byte units)

18 IPv6 Header Compression Can be either stateless or stateful Can be either stateless or stateful Independent of flows Independent of flows 18

19 HC1 Compression (1) Optimized for link-local addresses Optimized for link-local addresses Based on the following observations Based on the following observations  Version is always 6  IPv6 address’s interface ID can be inferred from MAC address  Packet length can be inferred from frame length  TC and flow label are commonly 0  Next header is TCP, UDP, or ICMP 19 Ver Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address

20 HC1 Compression (2) 20

21 HC2 Compression Compress UDP header Compress UDP header Length field can be inferred from frame length Length field can be inferred from frame length Source and destination ports are shortened into 4 bits each Source and destination ports are shortened into 4 bits each  Given that ports fall in the well-known range of 61616 – 61631 21

22 HC1 + HC2 Compression 22

23 IPHC Compression (1) HC1 and HC2 are only optimized for link- local addresses HC1 and HC2 are only optimized for link- local addresses  Globally routable addresses must be carried non-compressed IPHC will be the main compression technique for 6LoWPAN IPHC will be the main compression technique for 6LoWPAN  HC1 and HC2 will likely be deprecated 23

24 IPHC Compression (2) TF: Traffic class and flow label TF: Traffic class and flow label NH: Next header NH: Next header HLIM: Hop limit (0  NC, 1  1,2  64,3  255) HLIM: Hop limit (0  NC, 1  1,2  64,3  255) CID: Context Identifier CID: Context Identifier SAC/DAC: Src/Dst address (stateful or stateless) SAC/DAC: Src/Dst address (stateful or stateless) SAM/DAM: Src/Dst mode SAM/DAM: Src/Dst mode 24

25 IPHC’s Context Identifier Can be used to derive source and destination addresses Can be used to derive source and destination addresses Not specified how contexts are stored or maintained Not specified how contexts are stored or maintained 25

26 RPL – Routing Protocol for Low-power and Lossy Networks

27 Low-power and Lossy Networks Abbr. LLN Abbr. LLN Packet drops and link failures are frequent Packet drops and link failures are frequent Routing protocol should not over-react to failures Routing protocol should not over-react to failures Not only applied to wireless networks Not only applied to wireless networks  E.g., power-line communication 27 Packet delivery ratio

28 Routing Requirements IETF formed a working group in 2008, called ROLL (Routing over Low-power and Lossy Networks) to make routing requirements IETF formed a working group in 2008, called ROLL (Routing over Low-power and Lossy Networks) to make routing requirements Major requirements include Major requirements include  Unicast/multicast/anycast  Adaptive routing  Contraint-based routing  Traffic characteristics  Scalability  Auto-configuration and management  Security 28

29 LLN Example 29

30 Different Objective Functions 30 - Minimize low and fair quality links - Avoid non-encrypted links - Minimize latency - Avoid poor quality links and battery-powered node

31 RPL Protocol IPv6 Routing Protocol for Low-power and Lossy Networks IPv6 Routing Protocol for Low-power and Lossy Networks Designed to be highly modular for flexibility Designed to be highly modular for flexibility Employing distance vector mechanism Employing distance vector mechanism 31

32 DODAG (Destination Oriented Directed Acyclilc Graph) is created DODAG (Destination Oriented Directed Acyclilc Graph) is created  Based on the objective function RPL Operations 32 1 1211 2324 13 2122 3534333231 424144434546 LBR 1 1211 2324 13 2122 3534333231 424144434546 LBR

33 Multiple DODAGs (1) Provide alternate routes for different requirements Provide alternate routes for different requirements 33

34 Multiple DODAGs (2) 34 - Low latency- High reliability (no battery-powered node)

35 JenNet IP Jennic’s implementation of 6LoWPAN Jennic’s implementation of 6LoWPAN Supports tree topology Supports tree topology Routing is performed over a tree Routing is performed over a tree 35

36 The 6lo Working Group Works on IPv6 over networks of constrained nodes, such as Works on IPv6 over networks of constrained nodes, such as  IEEE 802.15.4  ITU-T G.9959  Bluetooth LE https://datatracker.ietf.org/wg/6lo/charter/ 36

37 References G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler. Transmission of IPv6 Packets over IEEE 802.15.4 Networks, RFC 4494, September 2007. G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler. Transmission of IPv6 Packets over IEEE 802.15.4 Networks, RFC 4494, September 2007. NXP Laboratories. JenNet-IP WPAN Stack User Guide (JN-UG-3080 v1.3). 2013. NXP Laboratories. JenNet-IP WPAN Stack User Guide (JN-UG-3080 v1.3). 2013. Jean-Philippe Vasseur and Adam Dunkels. Interconnecting Smart Objects with IP: The Next Internet. Morgan Kaufmann. 2010. Jean-Philippe Vasseur and Adam Dunkels. Interconnecting Smart Objects with IP: The Next Internet. Morgan Kaufmann. 2010. 37


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