1. Less-than-Best-Effort Service for Community Wireless Networks: Challenges at Three Layers 1 GAIA meeting, 89 th IETF Meeting 6. 3. 2014 Michael Welzl michawe@ifi.uio.no

2. Context: the LCDNet vision From http://publicaccesswifi.org/the-research/paws-approach/http://publicaccesswifi.org/the-research/paws-approach/ 2

3. Layer 2 LBE Outside not under control 3 Inside under control Can control: – Both ways: PHY rates, PCF? 802.11e QoS? – Download: RA algorithm, DCF parameters like CW download upload

4. RA alg. impact 4 From: Naeem Khademi, Michael Welzl, Stein Gjessing: "Experimental Evaluation of TCP Performance in Multi-rate 802.11 WLANs”, IEEE WoWMoM 2012.

5. Layer 3 LBE Shortest path routing is THE routing method – This overloads the shortest path – If there are multiple paths, LBE traffic could take a detour Tools exist: e.g. MPLS TE, ECMP… but typically still shortest paths used multi topology (MT) routing, meant for IP fast reroute, could be a good fit Small packets could be costly (power consumption) – May want to aggregate + tunnel them (TCMTF) 5

6. Layer 4 LBE End systems: LEDBAT isn’t great – Much more stuff exists – LBE != LBE… Routers / AP / Modem: AQM can differentiate (early mark/drop) Queue scheduling can differentiate (CBQ etc) 6 From: David Ros, Michael Welzl: "Assessing LEDBAT's Delay Impact", IEEE Communications Letters 17(5), pp. 1044-1047, 2013.

7. Conclusion LEDBAT isn’t enough, it’s a larger story – Research needed 7

8. Thank you! Questions?