TinyOS meets IP -- finally

Transcription

1 TinyOS meets IP -- finally David E. Culler

2 THE Question If Wireless Sensor Networks represent a future of billions of information devices embedded in the physical world, why don t they run THE standard internetworking protocol? 2

3 The Answer They should Substantially advances the state-of-the-art in both domains. Implementing IP requires tackling the general case, not just a specific operational slice Interoperability with all other potential IP network links Potential to name and route to any IP-enabled device within security domain Robust operation despite external factors Coexistence, interference, errant devices,... While meeting the critical embedded wireless requirements High reliability and adaptability Long lifetime on limited energy Manageability of many devices Within highly constrained resources 3

4 Many Advantages of IP Extensive interoperability Other wireless embedded network devices Devices on any other IP network link (WiFi, Ethernet, GPRS, Serial lines, ) Established security Authentication, access control, and firewall mechanisms Network design and policy determines access, not the technology Established naming, addressing, translation, lookup, discovery Established proxy architectures for higher-level services NAT, load balancing, caching, mobility Established application level data model and services HTTP/HTML/XML/SOAP/REST, Application profiles Established network management tools Ping, Traceroute, SNMP, OpenView, NetManager, Ganglia, Transport protocols End-to-end reliability in addition to link reliability Most industrial (wired and wireless) standards support an IP option 4

5 Challenges for IP over Header Standard IPv6 header is 40 bytes [RFC 2460] Entire MTU is 127 bytes [IEEE ] Often data payload is small Fragmentation Interoperability means that applications need not know the constraints of physical links that might carry their packets IP packets may be large, compared to max frame size IPv6 requires all links support 1280 byte packets [RFC 2460] Allow link-layer mesh routing under IP topology subnets may utilize multiple radio hops per IP hop Similar to LAN switching within IP routing domain in Ethernet Allow IP routing over a mesh of nodes Options and capabilities already well-defines Various protocols to establish routing tables 5

6 WSNs we ve all been building Client Tools External Tools Excel, Matlab Enshare, etc. GUI Legacy Data analysis Embedded Network 6 Internet Gateway Field Tools Deploy Query Command Visualize

7 6LoWPAN Format Design Orthogonal stackable header format Almost no overhead for the ability to interoperate and scale. Pay for only what you use IEEE Frame Format D pan Dst EUID 64 S pan Src EUID 64 preamble SFD Len FCF DSN Dst16 Src16 Network Header Max 127 bytes Application Data Fchk IETF 6LoWPAN Format Dispatch: coexistence Header compression Mesh (L2) routing dsp HC1 mhop IP mhop dsp HC1 Message > Frame fragmentation frag frag dsp UDP dsp HC1 HC1 7

8 6LoWPAN IPv6 Header IEEE Frame Format D pan Dst EUID 64 S pan Src EUID 64 preamble SFD Len FCF DSN Dst16 Src16 dsp Network Header Application Data Fchk IETF 6LoWPAN Format Uncompressed IPv6 address [RFC2460] 40 bytes HC1 Fully compressed: 1 byte Source address Destination address Traffic Class & Flow Label Next header : derived from link address : derived from link address : zero : UDP, TCP, or ICMP 8

9 6LoWPAN Compressed / Compressed UDP IEEE Frame Format D pan Dst EUID 64 S pan Src EUID 64 preamble SFD Len FCF DSN Dst16 Src16 Network Header Application Data Fchk IETF 6LoWPAN Format dsp HC1 IP UDP Dispatch: Compressed IPv6 HC1: Source & Dest Local, next hdr=udp IP: Hop limit UDP: 4-byte header (compressed) source port = P + 4 bits, p = (0xF0B0) destination port = P + 4 bits 9

10 6LoWPAN / Zigbee Comparison IEEE Frame Format D pan Dst EUID 64 S pan Src EUID 64 preamble SFD Len FCF DSN IETF 6LoWPAN Format Dst16 Src16 Zigbee APDU Frame Format Network Header dsp HC1 fctrl D ep IP UDP clstr prof S ep APS Application Data Fchk fctrl: Frame Control bit fields D ep: Destination Endpoint (like UDP port) clstr: cluster identifier prof: profile identifier S ep: Source Endpoint APS: APS counter (sequence to prevent duplicates) *** Typical configuration. Larger and smaller alternative forms exist. 10

11 Low Impact of 6LoWPAN on Lifetime Comparison to *Raw* Frame Energy Cost of Packet Communication vs. Data Size uas per Packet Energy Δ for fixed payload * RCV 6LoWPAN Local <= Global RCV 6LoWPAN Local <= Local RCV Raw TX 6LoWPAN Local => Global TX 6LoWPAN Local => Local TX Raw * Max Payload * fully compressed header * additional 16-byte IPv6 address Bytes of Payload 11

12 What it means for TinyOS.net? 6LoWPAN is just the beginning How bits go on the air Rest of the IETF standards mean that you can get real solutions built today. Huge array of arbitrary decisions become easy Do it like the RFC! Much easier to integrate, compare, build on, bmac, smac, tmax, xmac, zmac should use same format. Mesh-under, route-over well-defined. Route formation distinct from forwarding Whole set of issues to resolve Equivalent of sockets API to invent RIP, OSPF, IGP, EGP,. => [your routing protocol here] Geographic naming => IP address Dissemination / Agrregation Multicast Groups 12

13 and beyond TinyOS mailto: 13