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6LoWPANOverview, Assumptions, Problem

Statement & Goals

(draft-kushalnagar-lowpan-goals-assumptions-00)

Nandu Kushalnagar & Gabriel Montenegro

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Overview of LoWPAN

A simple low throughput wireless networkcomprising typically low cost and low powerdevices

Devices in the network typically work together toconnect 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 limitedaccessibility and user interfaces Inherently unreliable due to nature of devices in

the wireless medium

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Assumptions

Devices conform to IEEE 802.15.4-2003standard

Devices typically send small amounts ofdata

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 immediatelysuitable 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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Define adaptation (frag/reassembly) layer to matchIPv6 MTU requirements

Specify methods to do IPv6 stateless address autoconfiguration

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 forLoWPANs Specify encoding/decoding (or perhaps new protocols)

for device discovery mechanisms Document LoWPAN security threats

Goals

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BACKUP

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Overview of LoWPAN

A simple low cost wireless network of dev

ices that hav

e limitedpower 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 Networkmanagement

Low power

(1-2 years lifetime on

batteries)

Storagelimitations, lowoverhead

Periodic sleepaware routing,low overhead

Simplicity (CPUusage), lowoverhead

Periodic sleep awaremanagement, lowoverhead

Low cost

(

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Subtleties of IEEE 802.15.4

Small packet size 128 byte includingMAC, 103 bytes of payload

Uses 64 bit MAC addresses, but hasprovisions 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 technologiesalready exist, well known and proven tobe working.

The per vasive nature of IP networksallows use of existing infrastructure.

Intellectual property conditions for IP

networking technology is either morefavorable or at least better understoodthan 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 aslocation 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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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

Goals

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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 IP v6 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?