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Challenges of Sleeping Nodes

Challenges of Sleeping Nodes. Margaret Wasserman Painless Security, LLC mrw@painless-security.com. What Are Sleeping Nodes?. Small, low-cost, battery-powered nodes often “sleep” to extend battery life Keep just enough of the system on to wake up on schedule

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Challenges of Sleeping Nodes

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  1. Challenges of Sleeping Nodes Margaret Wasserman Painless Security, LLC mrw@painless-security.com

  2. What Are Sleeping Nodes? • Small, low-cost, battery-powered nodes often “sleep” to extend battery life • Keep just enough of the system on to wake up on schedule • Radio receiver and transmitter are off • All high-power chips (radio chips, CPU) are off • Wake up periodically to perform functions • Sensors: Take/report sensor readings • Actuators: Poll for events/messages, take appropriate actions • Devices may sleep 99% of the time, or more

  3. Protocol Challenges • Sleeping nodes are not “always on” • Increasing number of IETF protocols expect nodes to be “always on”, including IPv6 ND & DAD. • Most multicast protocols don’t work well for sleeping nodes • Costs of leaving and rejoining a network or application may be prohibitive • IP no longer provides best-effort delivery • Need to determine you are on the same network before using IP address(es) -- DNA, DHCP • Need to reestablish Neighbor Cache entries before sending packets • Verbose Protocols • Every round trip requires receiver to stay on for another RTT • Congestion concerns are not the only reason to limit message size • Longer packets take more energy to transmit

  4. Possible Solutions • “Always On” assumption • Consider alternative paradigm for sleeping nodes • End-node polling vs. sending events/messages as they happen? • Gateways/Routers proxy for nodes that sleep (Proxy ND, etc.) • High cost to rejoin network • Goal is to determine that a mobile node has not moved to another network • Why isn’t detection of the same layer 2 network good enough? • Same SSID, L2 security credentials work, etc. • Verbose Protocols • Minimize round trips and required messages • Consider compressed or succinct message formats • COAP, XML compression, etc. • Use UDP with one-way messages when appropriate

  5. Which Protocols? • At minimum, Internet Protocol (IPv4 & v6) should continue to work on these nodes • IPv4 & ARP work (minus some optional add-ons) • IPv6 has challenges, especially in ND • Essentially, many optional add-ons in IPv4 are now required in all IPv6 implementations • Address autoconfiguration, DNA, IGMP/Multicast, DAD, etc. • Device-to-device, configuration, management, service discovery • DNS, DHCP, SNMP, NETCONF, DNS-SD, SDP, etc. • Some applications assume a human at both ends, and won’t be used on sleeping devices • Instant messaging, voice, multimedia, etc. • But, are we sure? (consider HTML & Jabber)

  6. Wider Applicability • Described as problem for low-cost, battery-powered, wireless sensors and actuators, but principals may apply to other nodes • Could extend laptop, touch pad or cell phone battery life • Could reduce energy consumption of wall-powered nodes Just because the energy is available, doesn’t mean we should squander it!

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