Hardware-Assisted IEEE Transmissions and Why to Avoid Them. Andreas Weigel, Volker Turau. IDCS 2015 September 2 nd, 2015

Transcription

1 Hardware-Assisted IEEE Transmissions and Why to Avoid Them Andreas Weigel, Volker Turau IDCS 2015 September 2 nd, 2015 Institute of Telematics Hamburg University of Technology TUHH

2 Introduction What is this about? CoAP Wireless Sensor Networks / IoT UDP Evaluate performance of 6LoWPAN fragmentation for large datagrams in multi-hop scenarios Simulation and testbed experiments IPv6 RPL 6LoWPAN Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 1

3 Introduction Hardware-Assisted Transmissions ATmega256RFR2 Extended Operating Mode has hardware support for... automatic backoff and CCA; automatic retries (TX_ARET) automatic acknowledgements (RX_AACK) Nice-to-have, because of: less complex code (LOC: 371 vs 1847) smaller binaries (5280 bytes ROM and 578 bytes RAM less) Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 2

4 Introduction Simulation vs. Testbed 0 21FD 21FE 21FC FF A Assembly Direct PRR [%] , ,200 Payload [Byte] Payload [Byte] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 3

5 Introduction 6LoWPAN Forwarding of Fragmented Datagrams v 1 l 0 v 2 l 1 v 3 l 2 v 4 m 1 m 2... m n m 1 m 2... m n m 1 m 2 v 1 l 0 v 2 l 1 v 3 l 2 v 4 m 1 m 2... m n m 1 m 2... m n m 1 m 2... m n... m n Assembly Mode Direct Mode Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 4

6 Introduction Extended Operating Mode IDLE RX TX BO RX TX PENDING TX RADIO Node Time RX-while-TX Time no-rx-while-tx Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 5

7 Introduction Extended Operating Mode IDLE RX TX BO RX TX PENDING TX RADIO Node Time RX-while-TX Time no-rx-while-tx Assumption: no-rx-while-tx property of Extended Operating Mode is responsible for losses! Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 5

8 Experimental Setup Approach Approaches to verify the suspicion Analytical model Adapt simulation model Realtime observation of testbed Two wireless stacks for CometOS AACK MAC (using Extended Operating Mode) Software MAC (ported TinyOS mac layer) Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 6

9 Experimental Setup Record sequence of MAC layer states of each node: Data transport and time synchronization per wire Instrument code to signal events via GPIO Ethernet/TCP RaspPi FRDM-K64F UART PC PC Basestation UART Radio Link/Static Route GPIO connection cable 3 Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 7

10 Evaluation Direct Mode - AACK MAC IDLE RX TX BO TX RADIO 1 Node Time [ms] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 8

11 Evaluation Direct Mode - Software MAC IDLE RX TX BO RX TX PENDING TX RADIO 1 Node Time [ms] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 9

12 Evaluation Results - PRR PRR in % Direct AACK MAC Software MAC Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 10

13 Evaluation Results - Fragment Counts Sum of fragment transmissions of nodes 3 and 4 Software MAC AACK MAC Requests (theo. max) Successful; Dest TX Successful; Dest non-tx Failure; Dest TX Failure; Dest non-tx 23 4 Failure; Total Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 11

14 Evaluation Results - Fragment Counts Sum of fragment transmissions of nodes 3 and 4 Software MAC AACK MAC Requests (theo. max) Successful; Dest TX Successful; Dest non-tx Failure; Dest TX Failure; Dest non-tx 23 4 Failure; Total Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 11

15 Evaluation Results - Fragment Counts Sum of fragment transmissions of nodes 3 and 4 Software MAC AACK MAC Requests (theo. max) Successful; Dest TX Successful; Dest non-tx Failure; Dest TX Failure; Dest non-tx 23 4 Failure; Total Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 11

16 Evaluation Simulation vs. Testbed revisited 0 21FD 21FC 21FF 21FE Assembly Direct Direct EOM A PRR [%] , ,200 Payload [Byte] Payload [Byte] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 12

17 Evaluation Conclusion Verified assumption in small testbed Extended Operating Mode responsible for nearly all fragment losses in multi-hop traffic scenarios Usage of similar-working mechanisms not advisable (in similar scenarios) Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 13

18 Hardware-Assisted IEEE Transmissions and Why to Avoid Them Andreas Weigel, Volker Turau Andreas Weigel IDCS 2015 September 2 nd, 2015 Phone andreas.weigel@tuhh.de Institute of Telematics Hamburg University of Technology TUHH

19 MAC Config minbe maxbe csmabackoffs maxframeretries CCA mode CCA threshold dbm Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 14

20 Results - PRR PRR in % Direct AACK MAC Direct-ARR Software MAC Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 15

21 Results - Fragment Counts Software MAC AACK MAC fragrequests (theo. max) fragsuccessdsttx ± fragsuccessdstnontx ± ± fragfaildsttx ± ± fragfaildstnontx ± ± 0.64 fragfailtotal ± ± Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 16

22 Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 17

23 TX RF RF TX END TX ACK IDLE RF TX END RF TX START TX PENDING TX START TX BO TX BO FAIL TX REQUEST TX RETRY TX FAIL, TX SUCCESS IDLE RF TX END TX REQUEST RX DONE RF RX START RF RX START RX RF TX END RX TX BO TX RADIO Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 18

24 RX DONE, RX DROPPED RF TX END RF RX START TX RF TX WAIT TX ACK RF TX START TX RETRY TX FAIL, TX SUCCESS TX RETRY RF RX END RX DONE TX BO TX RETRY TX DONE RX DONE RF TX END RF RX START TX START TX BO FAIL TX FAIL, TX SUCCESS RF RX DROPPED, RX DROPPED RX DONE, RX DROPPED, RF RX DROPPED RF RX END RX TX PD IDLE TX FAIL, TX SUCCESS, RX DROPPED, RX DONE RF RX START TX BO FAIL TX START TX START RF TX END RF RX START RX RF RX START RX DROPPED, RX DONE RF TX END RX DONE, RX DROPPED, RF RX DROPPED RX ACK TX PD RF TX START RX DL TX PD RX DL RF TX START RX ACK TX BO FAIL RX DONE TX START RX DONE IDLE RX TX BO RX TX PENDING TX RADIO Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 19

25 Direct-ARR Mode - AACK MAC (Success) IDLE RX TX BO TX RADIO 1 Node Time [ms] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 20

26 Direct-ARR Mode - AACK MAC (Failure) IDLE RX TX BO TX RADIO 1 Node Time [ms] Andreas Weigel Hardware-Assisted IEEE Transmission and Why to Avoid Them 21