Network Kernel Architectures
and Implementation
(01204423)
IPv6 over Low-Power Wireless
Personal Area Networks
(6LoWPAN)
Chaiporn Jaikaeo
chaiporn.j@ku.ac.th
Department of Computer Engineering
Kasetsart University
Outline
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6LoWPAN
IPv6 overview
Header compression tecniques
Routing
JenNet-IP
The 6lo Working Group
2
6LoWPAN
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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
3
Example 6LoWPAN Systems
4
IPv6 Overview

Larger address space compared to IPv6
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Autoconfiguration
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Supporting both stateful (DHCPv6) and
stateless operations
Simplified headers


232 vs. 2128
Fixed header with optional daisy-chained
headers
Mandatory security
5
IPv6 Header

Minimum header size = 40 bytes

Header compression mechanism is needed
Bit 0
0
32
4
Ver
8
12
Traffic Class
Payload Length
16
20
24
28
Flow Label
Next Header
Hop Limit
64
96
128
Source Address
160
192
224
256
Destination Address
288
6
IPv6 Extended Headers
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More flexible than IPv4’s option fields
Example 1: no extended header
Next header = 6 (TCP)

TCP hdr + payload
Example 2: with a routing header
Next header = 43 (routing)
Next header = 6 (TCP)
TCP hdr + payload
7
IPv6 Addressing

Global unicast addresses

Start with 001
001
Prefix provided by
Subnet ID
service provider
48

16
Host ID
64
Host ID usually incorporates MAC address
8
IPv6 Address Scopes
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Global addresses
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Globally routable
Link-local addresses
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Only used within directly attached network
Belonging to FE80::/10 block
0
1111 1110 10
10 bits
Interface ID
96 db c9 FF FE 00 16 fe
xxxxxxUx
U = 0: not unique
U = 1: unique
94 db c9 00 16 fe
For Ethernet addresses: U=0 Global, U=1: Local
See http://upload.wikimedia.org/wikipedia/commons/9/94/MAC-48_Address.svg
9
IEEE 802.15.4 Revisited
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Allows 127 bytes MTU
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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)
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6LoWPAN Adaptation Layer
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Needs to make IEEE 802.15.4 comply with
IPv6’s MTU size of 1280 bytes
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IEEE 802.15.4’s MTU is 127 bytes
MAC header: ≤ 25 bytes
Optional security header: ≤ 21 bytes
Provides three main services
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Packet fragmentation and reassembly
Header compression
Link-layer forwarding
11
6LowPAN Header Stack
12
Header Dispatch Byte
13
Mesh Address Header (1)
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Used with mesh-under routing approach
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Only performed by FFDs
14
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

802.15.4
Header
B
A
Dst
Src
Mesh
Header
A
802.15.4
Header
D
Orig Final
Data
Mesh
Header
D
C
A
Dst
Src
Originator
A
D
Data
Orig Final
Final
B
C
D
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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
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Fragment Header
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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)
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IPv6 Header Compression
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Can be either stateless or stateful
Independent of flows
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HC1 Compression (1)
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Optimized for link-local addresses
Ver
Traffic Class
Payload Length
Flow Label
Next Header
Hop Limit
Source Address
Destination Address
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Based on the following observations
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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
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HC1 Compression (2)
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HC2 Compression
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Compress UDP header
Length field can be inferred from frame
length
Source and destination ports are shortened
into 4 bits each
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Given that ports fall in the well-known range of
61616 – 61631
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HC1 + HC2 Compression
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IPHC Compression (1)
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HC1 and HC2 are only optimized for linklocal addresses
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Globally routable addresses must be carried
non-compressed
IPHC will be the main compression
technique for 6LoWPAN
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HC1 and HC2 will likely be deprecated
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IPHC Compression (2)
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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
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IPHC’s Context Identifier
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Can be used to derive source and
destination addresses
Not specified how contexts are stored or
maintained
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RPL – Routing Protocol for
Low-power and Lossy Networks
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Abbr. LLN
Packet drops and link
failures are frequent
Routing protocol
should not over-react
to failures
Not only applied to
wireless networks

Packet delivery ratio
Low-power and Lossy Networks
E.g., power-line
communication
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Routing Requirements
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IETF formed a working group in 2008, called
ROLL (Routing over Low-power and Lossy
Networks) to make routing requirements
Major requirements include
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Unicast/multicast/anycast
Adaptive routing
Contraint-based routing
Traffic characteristics
Scalability
Auto-configuration and management
Security
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LLN Example
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Different Objective Functions
- Minimize low and fair quality links
- Avoid non-encrypted links
- Minimize latency
- Avoid poor quality links and
battery-powered node
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RPL Protocol
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IPv6 Routing Protocol for Low-power and
Lossy Networks
Designed to be highly modular for flexibility
Employing distance vector mechanism
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RPL Operations
DODAG (Destination Oriented Directed Acyclic Graph) is
created
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Based on the objective function
LBR
LBR
1
1
11
41
12
21
22
31
32
42
13
23
33
43
11
24
34
44
35
45
46
41
12
21
22
31
32
42
13
23
33
43
24
34
44
35
45
46
32
Multiple DODAGs (1)
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Provide alternate routes for different
requirements
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Multiple DODAGs (2)
- High reliability
(no battery-powered node)
- Low latency
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JenNet IP
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Jennic’s implementation of 6LoWPAN
Supports tree topology
Routing is performed over a tree
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The 6lo Working Group
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Works on IPv6 over networks of
constrained nodes, such as
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IEEE 802.15.4
ITU-T G.9959
Bluetooth LE
https://datatracker.ietf.org/wg/6lo/charter/
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References
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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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