1. 1/12 WiSE: A Novel Efficient Transport Protocol for Wireless Networks Roberta Fracchia Joint work with C. Casetti, C. Chiasserini, M. Meo

2. 2/12 Multihoming : one SCTP host can establish an association with another SCTP host over multiple interfaces, each identified by a separate IP address SCTP: Multihoming If one of these addresses fails, the destination host can be reached through a different interface Primary Destination Address - normally used for the transmission of new packets Secondary Destination Address - to retransmit lost packets - to transmit new packets only if the primary interface is ‘inactive’

3. 3/12 WiSE: Uses efficiently multiple destination addresses: - transmits on the path with the largest available bandwidth largest available bandwidth Designed specifically for wireless networks Discriminates losses due to congestion from those due to the wireless channel: - is based on the bandwidth estimation on the default path on the default path - allows different reduction of the congestion window congestion window Wireless SCTP Extension

4. 4/12 On the primary path : accurate estimate based on received ACKs employs a time-varying low-pass filter (as TCP Westwood) WiSE: Bandwidth Estimation based on the transmission of a 6-packets train uses Heartbeats transmission tradeoffs efficiency vs. accuracy On the secondary path : 1500 bytes HB HB: Heartbeat (40 bytes) time I HB I DATA

5. 5/12 Timeout 3 dup-acks If ( generated traffic > estimated bandwidth ) ssth=BWE*RTT/pktsize cwnd=1 ssth=BWE*RTT/pktsize cwnd=ssth Timeout 3 dup-acks ssth=cwnd/2 cwnd=1 ssth=ssth/2 cwnd=ssth not Otherwise, losses are not due to congestion: BWE: estimated bandwidth RTT: minimum measured RTT the sender is causing congestion: (acts as SCTP) WiSE: CongestionControl

6. 6/12 Relaxes SCTP’s rigid “primary-secondary” path definition Transmits new packets on the path that seems in better conditions, increasing the probabilities of a successful communication if (Timeout expiration) if (primary bandwith < secondary bandwidth ) primary  secondary WiSE: PathManagement

7. 7/12 Results (ns-2) SCTP WiSE AP1 AP2 AP SCTP WiSE SCTP WiSE FTP | TCP FTP | TCP Cross Traffic Topology : Long-lived flows generated by a FTP source Packet Size: 1500 bytes

8. 8/12 Results Errors due to the wireless channel 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 0.05 0.1 0.150.20.25 0.3 Throughput (Mb/s) Average loss probability on path #1 WiSE(path #2 error-free) TCP SCTP(path #2 error-free) WiSE(path #2 = path #1) SCTP(path #2 = path #1) Capacity: wired-links=55Mb/s wireless links=11Mb/s

9. 9/12 Results Errors due to the wireless channel 0 0.05 0.1 0.150.20.25 0.3 Average loss probability on path #1 0.00 0.02 0.04 0.06 0.08 0.10 0.12 Energy per successful packet (J/pkt) WiSE(path #2 error-free) SCTP(path #2 error-free) WiSE(path #2 = path #1) SCTP(path #2 = path #1) Capacity: wired-links=55Mb/s wireless links=11Mb/s TCP

10. 10/12 Results Errors due to congestion Throughput (Mb/s) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.80.850.9 0.951 Average load 0.00 0.05 0.10 0.15 0.20 Reordering Time (s) 0.80.850.9 0.951 Average load Capacity: wired-links=10Mb/s wireless links=2Mb/s t ON =1s t ON =5s t ON =20s WiSE t ON =1s t ON =5s t ON =20s SCTP t ON =1s t ON =5s t ON =20s WiSE t ON =1s t ON =5s t ON =20s SCTP

11. 11/12 Results Average load Energy per successful packet (J/pkt) Capacity: wired-links=10Mb/s wireless links=2Mb/s 0.80.850.9 0.951 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 t ON =1s t ON =5s t ON =20s WiSE t ON =1s t ON =5s t ON =20s SCTP Errors due to congestion

12. 12/12 Conclusions is primarily designed for wireless networks We proposed a protocol that: supersedes TCP and UDP being transparent to the application outperforms both TCP and SCTP in a mixed wired/wireless environment improves energy performance