1. Copyright © 2011, MBL@CS.NCTU A Flow-based Hybrid Mechanism to Improve Performance in NOX and wireless OpenFlow switch networks Bruno Van Den Bossche, Bart De Vleeschauwer, Tom Verdickt, Filip De Turck, Bart Dhoedt, Piet Demeester Journal of Network and Computer Applications, vol. 32, no. 6, 2009

2. Copyright © 2011, MBL@CS.NCTU Outline Overview Introduction Problem description Main Approach Related Works Evaluation Conclusions Reference

3. Copyright © 2011, MBL@CS.NCTU Overview In this paper, we propose a flow-based hybrid mechanism to improve performance in NOX and wireless OpenFlow switch networks. The main idea of this scheme is that when the transmission of a OpenFlow switch fails, one of neighbor OpenFlow switches transmits the lost frame for the failed one.

4. Copyright © 2011, MBL@CS.NCTU Introduction If the packet does not match a flow entry or OpenFlow switch fails to transmit its data, OpenFlow switch requests the path to the NOX. However, if OpenFlow switch requests the path to NOX whenever it fails to transmit its data, it will be a big overhead in wireless OpenFlow switch networks with a bad channel quality.

5. Copyright © 2011, MBL@CS.NCTU Problem Description Retransmission of failed data allows other OpenFlow switches to lose their channel access chances and increases the number of Packet-In Message overheads such as packet header, ID assigned by data-path, full length of frame and acknowledgement (ACK) transmission.

6. Copyright © 2011, MBL@CS.NCTU Main Approach Each OpenFlow switch naturally overhears the transmitted packets of other OpenFlow switches toward the same destination, it buffers the packets that is not yet acknowledged in overhear table. Own data table Overhear table

7. Copyright © 2011, MBL@CS.NCTU Main Approach Channel Condition α<= β and x<=y α: the total flow size for sending β: the maximum flow threshold x : the SNR of failed OpenFlow switch y : the SNR of current OpenFlow switch

8. Copyright © 2011, MBL@CS.NCTU Main Approach Cooperative part between OpenFlow Switches

9. Copyright © 2011, MBL@CS.NCTU Main Approach Compensation part by NOX

10. Copyright © 2011, MBL@CS.NCTU Related Works [1] designed a novel relay-enabled DCF protocol to exploit the physical layer multirate capability. Data can be transmitted with different rates and some data packets may be delivered faster through a relay. [1] novel relay- enabled DCF protocol Flow-based Hybrid Mechanism overhead Insufficient to decrease the number of MAC/PHY overhead Aggregate scheme used in flow transmission to NOX

11. Copyright © 2011, MBL@CS.NCTU Evaluation

12. Copyright © 2011, MBL@CS.NCTU

13. Conclusion It shows that in environments where the packet is likely to be lost more, the throughput gain of our proposed scheme performs better.

14. Copyright © 2011, MBL@CS.NCTU Reference [1]Natasha Gude, Teemu Koponen, Justin Pettit, Ben Pfaff, Martín Casado, Nick McKeown and Scott Shenker, “NOX: Towards an Operating System for Networks”, ACM Sigcomm Computer Communication Review 2008.