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 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 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 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 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

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 Goals

BACKUP

Overview of LoWPAN A simple low cost wireless network of devices that have limited power and relaxed throughput requirements. Conforms to IEEE 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., IEEE and *possibly* IEEE Topologies that are commonplace today include – star, mesh, and combinations of star and mesh Today LoWPAN’s are already becoming a reality LoWPAN - A different *beast* of networks compared to traditional networks !

Challenges of LoWPAN Impact Analysis AddressingRoutingSecurityNetwork 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 (<$10/unit) Stateless address generation Small or no routing tables Ease of Use, simple bootstrapping Space constraints Low bandwidth (<300kbps) Compressed addresses Low routing overhead Low packet overhead Low network overhead High density (<2-4? units/sq ft) Large address space – IPv6 Scalable and routable to *a node* RobustEasy 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

Subtleties of IEEE 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?

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 LoWPAN’s 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 BKM’s of an IPv6 stack Goals

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?