6LoWPAN Overview, Assumptions, Problem Statement

1
6LoWPANOverview, Assumptions, Problem Statement
Goals(draft-kushalnagar-lowpan-goals-assumption
s-00)

• Nandu Kushalnagar Gabriel Montenegro

2
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

3
LoWPAN architecture
4
Typical applications

• Equipment health monitoring
• Environment monitoring
• Security
• Home
• Building automation

5
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

6
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)

7
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

8
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

9
BACKUP
10
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 !
11
Challenges of LoWPAN
12
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

13
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.

14
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)

15
Why not IPv4?

• Limited address space
• NAT functionality needs gateways, etc leads to
  more cost
• Statelessness not mandated
• Gab/Geoff . any more ideas?

16
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

17
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