6LoWPAN Overview, Assumptions, Problem Statement & Goals (draft-kushalnagar-lowpan-goals-assumptions-00)

1. 6LoWPANOverview, Assumptions, Problem Statement & Goals(draft-kushalnagar-lowpan-goals-assumptions-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 LoWPAN’s 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 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

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 • Light weight discovery mechanisms • More?