6lowpan 4

6LoWPAN
Overview, Assumptions, Problem

Statement & Goals
(draft-kushalnagar-lowpan-goals-assumptions-00)
Nandu Kushalnagar & Gabriel Montenegro

Overview of LoWPAN
A simple low throughput wireless network
comprising typically low cost and low power
devices
Devices in the network typically work together to
connect the physical environment to real world
applications, e.g., wireless sensors networks
Common topologies include star, mesh, and
combinations of star and mesh
The Phy and MAC layers conform to IEEE
802.15.4-2003 standard
LoWPAN architecture
Typical applications
Equipment health monitoring
Environment monitoring
Security
Home
Building automation
6LoWPAN characteristics
Small packet size
16-bit short or IEEE 64-bit extended media
access control addresses
Low bandwidth. (250/40/20 kbps)
Topologies include star and mesh
Low power, typically battery operated
Relatively low cost
Networks are ad hoc & devices have limited
accessibility and user interfaces
Inherently unreliable due to nature of devices in
the wireless medium
Assumptions
Devices conform to IEEE 802.15.4-2003
standard
Devices typically send small amounts of
data
Typically constrained devices
(computing, power, cost, memory, etc)
Problems
No method exists to make IP run over IEEE 802.15.4
networks
Worst case .15.4 PDU 81 octets, IPv6 MTU requirements 1280
octets
Stacking IP and above layers as is may not fit within
one 802.15.4 frame
IPv6 40 octets, TCP 20 octets, UDP 8 octets + other layers
(security, routing, etc) leaving few bytes for data
Not all adhoc routing protocols may be immediately
suitable for LoWPAN
DSR may not fit within a packet, AODV needs more memory, etc
Current service discovery methods bulky for LoWPAN
Primarily XML based that needs computing, more memory, etc
Limited configuration and management necessary
Security for multi hop needs to be considered
Goals
Define adaptation (frag/reassembly) layer to match
IPv6 MTU requirements
Specify methods to do IPv6 stateless address auto
configuration
Specify/use header compression schemes.
Specify implementation considerations and best
methods of an IPv6 stack
Methods for meshing on LoWPAN below IP*
Not currently in charter
Use/adapt network management technologies for
LoWPANs
Specify encoding/decoding (or perhaps new protocols)
for device discovery mechanisms
Document LoWPAN security threats
BACKUP
Overview of LoWPAN
A simple low cost wireless network of devices that have limited
power and relaxed throughput requirements.
Conforms to IEEE 802.15.4-2003
Typical usages of LoWPAN networks are
Networking transducers (sensing & actuation, eg. smart sensors
Such usages may need in network processing)
Networking simple controls (home controls)
Networking complex controls (light & switch & motion sensor)
Standards based Phy and MAC exist for LoWPAN networks viz.,
IEEE802.15.4 and *possibly* IEEE802.15.3
Topologies that are commonplace today include star, mesh, and
combinations of star and mesh
Today LoWPANs are already becoming a reality
LoWPAN - A different *beast* of networks compared to

traditional networks !
Challenges of LoWPAN
Impact Addressing Routing Security Network
Analysis management
Low power Storage Periodic sleep Simplicity (CPU Periodic sleep aware
limitations, low aware routing, usage), low management, low
(1-2 years lifetime on overhead low overhead overhead overhead
batteries)
Low cost Stateless address Small or no Ease of Use, Space constraints
generation routing tables simple
(<$10/unit) bootstrapping
Low bandwidth Compressed Low routing Low packet Low network

addresses overhead overhead overhead
(<300kbps)
High density Large address Scalable and Robust Easy to use and
space IPv6 routable to *a scalable
(<2-4? units/sq ft) node*
IP network interaction Address routable Seamless IP Work end to end Compatible with
from IP world routing from IP network SNMP, etc
Subtleties of IEEE 802.15.4
Small packet size 128 byte including
MAC, 103 bytes of payload
Uses 64 bit MAC addresses, but has
provisions for 16 bit short addresses
Support for multiple topologies
Supports AES block cypher in several
modes (AES-CCM-64 mandatory)
Data rates between 20kbps to 250kbps
Range between 10m to 30m
Why IP?
Most of the IP based technologies
already exist, well known and proven to
be working.
The pervasive nature of IP networks
allows use of existing infrastructure.
Intellectual property conditions for IP
networking technology is either more
favorable or at least better understood
than proprietary and newer solutions.
Why IPv6?
Pros
More suitable for higher density (futuristically 2 orders of
magnitude larger than traditional networks)
Statelessness mandated
No NAT necessary (adds extra cost to the cost prohibitive WSN)
Possibility of adding innovative techniques such as
location aware addressing
Cons
Larger address width (Having efficient address compression
schemes may alleviate this con)
Complying to IPv6 node requirements (IPSec is mandated)
Why not IPv4?
Limited address space
NAT functionality needs gateways, etc
leads to more cost
Statelessness not mandated
Gab/Geoff . any more ideas?
Goals
Protocol data units may be as small as 81 bytes, far below IP and above
In all cases, reuse existing protocols before creating new ones
Address mismatch between MTU sizes of LoWPANs and IPv6
Support stateless auto configuration of IPv6 addressing (location aware?)
Specify header compression (use of existing and/or new techniques eg.
header reconstruction, header short circuiting, etc)
Define security mechanisms, security configuration and bootstrapping
Specify network management (SNMP?)
Specify routing suitable for LoWPAN networks (MANET?, topology
aware, Below L3 or above L3?, etc)
Specify methods to enable and disable IPv6 over LoWPAN.
Specify hooks within routing layer to enable in network processing
Specify light weight discovery mechanisms
Specify any changes needed for L3 + layers
Specify implementation considerations and BKMs of an IPv6 stack
Drafts of 6LoWPAN
Define a *shim* layer below IP
Fragmentation/Reassembly to satisfy IPv6 MTU of 1280 bytes
Routing including mesh
Header compression mechanisms
Header reconstruction for intra PAN communication
Header short circuiting
Header configuration to enable/disable IPv6
Define a IPv6 LoWPAN Profile
Address IPv6 node requirements
Define
L2/L3 interface mechanism
Appropriate security services
Routing considerations
Network management with SNMP
Implementation considerations
Miscellaneous (may be subsequent drafts)
Hooks from L3 for in network processing (especially critical for WSN)
Transport layer (UDP / TCP)
Security configuration
Light weight discovery mechanisms
More?

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6LoWPAN

Overview, Assumptions, Problem

Nandu Kushalnagar & Gabriel Montenegro

LoWPAN - A different beast of networks compared to

Low bandwidth Compressed Low routing Low packet Low network

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