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Stateful Header Compression

Stateful Header Compression. Kris Pister UC Berkeley Dust Networks. The Motivation. Working in IEEE to fix this. In many sensor networks, >90% of packets Flow along paths with lots of shared state Final destination, sometimes source Link and end-to-end crypto Source & destination ports

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Stateful Header Compression

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  1. Stateful Header Compression Kris Pister UC Berkeley Dust Networks

  2. The Motivation Working in IEEE to fix this • In many sensor networks, >90% of packets • Flow along paths with lots of shared state • Final destination, sometimes source • Link and end-to-end crypto • Source & destination ports • Route • … • Have very short “fundamental” payloads • 2B, 4B not uncommon. Data, or (data, timestamp) • Today’s minimum multi-hop overhead • Application: 0-20B • Transport+Network: 12B (HC1, HC2_UDP) • Link: 11B + 9B (security) • PHY: 6B • >10x overhead • Why fix our part?

  3. Example • Once per second, mote A wakes up and sends a packet with exactly the same • 5B: Mesh header • 3B: Dispatch, HC1, HC2 • 1B: UDP compressed ports • For a period of hours or days (thousands to millions of packets) this information doesn’t change

  4. Flow-based compression • Perhaps instead a flow label could be sent • New dispatch byte • Header compression associated with flows • Flow label index into a table with all “HCx” values • Soft state – nodes along path can reconstruct full packet if necessary • Checksums, MICs performed on full packet w/ virtual headers • Crazy talk • Both Dispatch & Flow label could come from L2 • Implicit in link type • Dozer, SCP, TSMP all have mechanisms for uniquely determining flows

  5. The Dream • Provide a continuum of header compression from 0 to 100% depending on shared state • Application • Transport • Network • Link • Requires cooperation between IEEE and IETF

  6. TSMP as an example • Time Synchronized Mesh Protocol • Basis of Wireless HART, SP100 ( 15.4E) • Sub-ms time synch across network • << 0.1% radio duty cycle maintains synch • Additional duty cycle allocated as needed by traffic • Uses a flow label to associate L2 resources and L3 routes with L4 QoS • L2 activity uniquely associated with particular flows • If it’s 8:42:06.351 AM, you must be node X with a message from node Y to node Z and the next hop is Q.

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