6LoWPAN%20Overview,%20Assumptions,%20Problem%20Statement%20

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

• Nandu Kushalnagar Gabriel Montenegro

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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

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LoWPAN architecture
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Typical applications

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

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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

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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)

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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

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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

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BACKUP
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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 !
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Challenges of LoWPAN
Impact Analysis Addressing Routing Security Network management
Low power (1-2 years lifetime on batteries) Storage limitations, low overhead Periodic sleep aware routing, low overhead Simplicity (CPU usage), low overhead Periodic sleep aware management, low overhead
Low cost (lt10/unit) Stateless address generation Small or no routing tables Ease of Use, simple bootstrapping Space constraints
Low bandwidth (lt300kbps) Compressed addresses Low routing overhead Low packet overhead Low network overhead
High density (lt2-4? units/sq ft) Large address space IPv6 Scalable and routable to a node Robust Easy to use and scalable
IP network interaction Address routable from IP world Seamless IP routing Work end to end from IP network Compatible with SNMP, etc
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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

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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.

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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)

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Why not IPv4?

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

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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

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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