1. Multipath Congestion Control Wenpeng Zhou Instructor Andrei Gurtov

2. Contents  Introduction  Related works  Multipath TCP congestion control (MPTCP)  Vertical handover  Conclusions

3. Introduction  Increase end-to-end throughput  Better load balancing  Improve security  Cause packet reordering Host B Host A

4. Related work  Split a single connection into multipath, for example, MPLS  There are multipath. Only primary path is considered  Multipath can be used simultaneously.  Packet reordering is a big problem.

5. Multipath TCP (MPTCP) Protocol (1/5)  Transmission timer  Acknowledgement  Congestion window assignment  Architecture

6. Transmission timer (2/5)  Reordering can trigger unnecessary retransmit/fast recovery.  DUPACK is not qualified in multipath.  We use transmission timer to reduce fast retransmit.

7. Acknowledgement (3/5)  Cumulative acknowledgement degrades TCP performance.  Selective acknowledgement such as SACK

8. Congestion window assignment (4/5)  Different routes have different RTT  We focus on Relative Forward Delay (RFD)

9. Architecture (5/5) Every active receiving interface sends SACK Sending side Function block

10. Vertical handover Two solutions  Overbuffering  Explicit handover notification When handover happens, update RTT and RFD and retransmit the lost packets.

11. Conclusions  MPTCP reduces reordering to some extend  We can use MPTCP to vertical handover  Finding a bottleneck is not an easy task  Can we integrate MPTCP with HIP?