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Wireless Embedded Systems (0120442x) IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN). Chaiporn Jaikaeo [email protected] Department of Computer Engineering Kasetsart University. Outline. 6LoWPAN IPv6 overview Header compression tecniques Routing JenNet -IP

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wireless embedded systems 0120442x ipv6 over low power wireless personal area networks 6lowpan

Wireless Embedded Systems(0120442x) IPv6 over Low-Power Wireless Personal Area Networks(6LoWPAN)

Chaiporn Jaikaeo

[email protected]

Department of Computer EngineeringKasetsart University

outline
Outline
  • 6LoWPAN
  • IPv6 overview
  • Header compression tecniques
  • Routing
  • JenNet-IP
  • The 6lo Working Group
6lowpan
6LoWPAN
  • IPv6 over Low-power Wireless Personal Area Networks
  • Nodes communicate using IPv6 packets
  • An IPv6 packet is carried in the payload of IEEE 802.15.4 data frames
ipv6 overview
IPv6 Overview
  • Larger address space compared to IPv6
    • 232 vs. 2128
  • Autoconfiguration
    • Supporting both stateful (DHCPv6) and stateless operations
  • Simplified headers
    • Fixed header with optional daisy-chained headers
  • Mandatory security
ipv6 header
IPv6 Header
  • Minimum header size = 40 bytes
    • Header compression mechanism is needed

Bit

0

4

8

12

16

20

24

28

0

Ver

Traffic Class

Flow Label

32

Payload Length

Next Header

Hop Limit

64

Source Address

96

128

160

192

Destination Address

224

256

288

ipv6 extended headers
IPv6 Extended Headers
  • More flexible than IPv4’s option fields
  • Example 1: no extended header
  • Example 2: with a routing header

Next header = 6 (TCP)

TCP hdr + payload

Next header = 43 (routing)

Next header = 6 (TCP)

TCP hdr + payload

ipv6 addressing
IPv6 Addressing
  • Global unicast addresses
    • Start with 001
    • Host ID usually incorporates MAC address

001

Prefix provided byservice provider

Subnet ID

Host ID

48

16

64

ipv6 address scopes
IPv6 Address Scopes
  • Global addresses
    • Globally routable
  • Link-local addresses
    • Only used within directly attached network
    • Belonging to FE80::/10 subnet

0

Interface ID

1111 1110 10

96

db

c9

FF

FE

00

16

fe

10 bits

xxxxxxUx

U = 0: not uniqueU = 1: unique

94

db

c9

00

16

fe

ieee 802 15 4 revisited
IEEE 802.15.4 Revisited
  • Allows 127 bytes MTU
    • Good for buffering cost and low packet error rate
  • Supports both 16-bit and 64-bit addresses
  • Supports both star and mesh topologies
  • Usually operates in an ad hoc fashion with unreliable links
  • IEEE 802.15.4 networks are considered Low-power and Lossy Networks (LLN)
6lowpan adaptation layer
6LoWPAN Adaptation Layer
  • 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
    • Packet fragmentation and reassembly
    • Header compression
    • Link-layer forwarding
mesh address header 1
Mesh Address Header (1)
  • Used with mesh-under routing approach
    • Only performed by FFDs
mesh address header 2
Mesh Address Header (2)
  • Hop left field is decremented by one every hop
    • Frame is discarded when hop left is 0
  • Address fields are unchanged

802.15.4Header

MeshHeader

802.15.4Header

MeshHeader

B

A

A

D

Data

D

C

A

D

Data

Dst

Src

Orig

Final

Dst

Src

Orig

Final

Originator

Final

A

B

C

D

mesh under vs route over routing
Mesh-under vs. Route-over Routing

Application

Application

Transport

Transport

Network (IPv6)

Network (IPv6)

Routing

6LoWPAN Adaptation

6LoWPAN Adaptation

802.15.4 MAC

802.15.4 MAC

802.15.4 PHY

802.15.4 PHY

Mesh-under routing

Route-over routing

fragment header
Fragment Header
  • Fragmentation is required when IPv6 payload size exceeds that of IEEE 802.15.4 payload limit
  • All fragments are in units of 8 bytes

(in 8-byte units)

ipv6 header compression
IPv6 Header Compression
  • Can be either stateless or stateful
  • Independent of flows
hc1 compression 1
HC1 Compression (1)
  • Optimized for link-local addresses
  • 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

Ver

Traffic Class

Flow Label

Payload Length

Next Header

Hop Limit

Source Address

Destination Address

hc2 compression
HC2 Compression
  • Compress UDP header
  • Length field can be inferred from frame length
  • Source and destination ports are shortened into 4 bits each
    • Given that ports fall in the well-known range of 61616 – 61631
iphc compression 1
IPHC Compression (1)
  • 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
    • HC1 and HC2 will likely be deprecated
iphc compression 2
IPHC Compression (2)
  • TF: Traffic class and flow label
  • NH: Next header
  • HLIM: Hop limit (0NC, 11,264,3255)
  • CID: Context Identifier
  • SAC/DAC: Src/Dst address (stateful or stateless)
  • SAM/DAM: Src/Dst mode
iphc s context identifier
IPHC’s Context Identifier
  • Can be used to derive source and destination addresses
  • Not specified how contexts are stored or maintained
low power and lossy networks
Low-power and Lossy Networks
  • Abbr. LLN
  • Packet drops and link failures are frequent
  • Routing protocol should not over-react to failures
  • Not only applied to wireless networks
    • E.g., power-line communication

Packet delivery ratio

routing requirements
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
    • Unicast/multicast/anycast
    • Adaptive routing
    • Contraint-based routing
    • Traffic characteristics
    • Scalability
    • Auto-configuration and management
    • Security
different objective functions
Different Objective Functions

- Minimize low and fair quality links

- Avoid non-encrypted links

- Minimize latency

- Avoid poor quality links and battery-powered node

rpl protocol
RPL Protocol
  • IPv6 Routing Protocol for Low-power and Lossy Networks
  • Designed to be highly modular for flexibility
  • Employing distance vector mechanism
rpl operations
RPL Operations
  • DODAG (Destination Oriented Directed Acyclilc Graph) is created
    • Based on the objective function

LBR

LBR

1

1

11

12

13

11

12

13

21

22

23

24

21

22

23

24

31

32

33

34

35

31

32

33

34

35

41

42

43

44

45

46

41

42

43

44

45

46

multiple dodags 1
Multiple DODAGs (1)
  • Provide alternate routes for different requirements
multiple dodags 2
Multiple DODAGs (2)

- High reliability (no battery-powered node)

- Low latency

jennet ip
JenNet IP
  • Jennic’simplementation of 6LoWPAN
  • Supports tree topology
  • Routing is performed over a tree
the 6lo working group
The 6lo Working Group
  • 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/

references
References
  • 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.
  • Jean-Philippe Vasseur and Adam Dunkels. Interconnecting Smart Objects with IP: The Next Internet. Morgan Kaufmann. 2010.
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