1. Speaker : Che-Wei Chang
Optimizing Protocol Parameters to Large Scale PC Cluster and Evaluation of its Effectiveness with Parallel Data Mining
Speaker : Che-Wei Chang

2. Outline Introduction Features Communication performance
Optimization of transport layer protocol parameters
Parallel data mining application
Conclusion

3. Introduction(1/2)
ATM ( Asynchronous Transfer Mode ) technology is one of the strong candidates as a de facto standard of high speed communication networks.
Several features of an ATM connected PC cluster consists of 100 PCs are examined.

4. Introduction(2/2)
Characteristics of a transport layer protocol for the interconnection network are discussed.
The proposed method is evaluated using a parallel data mining application, and considerably good performance scale-up is achieved up to 100 PCs.

5. Features(1/3) We have constructed a large scale PC cluster.
ATM is used as a communication network in our cluster.
We used data intensive applications for the evaluation of the PC cluster.

6. Features(2/3) Figure 1. PC cluster pilot system
Table 1. Each node of PC cluster

7. Features(3/3)
Figure 2. An overview of the PC cluster

8. Communication performance(1/3)
Use TCP protocol in Solaris OS, whose parameters can be changed with user-level command.
In this experiment, point-to-point throughput is measured when a maximum TCP window size is changed on the cluster.
Two suites of experiments are performed: MSS(Maximum Segment Size) is set to be 8192 bytes and 1024 bytes, respectively.

9. Communication performance(2/3)
throughput is not a smooth curve
Figure 3. Point-to-point throughput

10. Communication performance(3/3)
TCP header’s window size bits limitation
Figure 4. Number of transmission
packet (MSS=8192[bytes])
Figure 5. Number of transmission
packet (MSS=1024[bytes])

11. Optimization of transport layer protocol parameters(1/5)
Even if the amount of broadcast data is not large, a lot of collisions happen in a large scale ATM connected PC cluster, if timing of the broadcasting is the same at all nodes.
A network becomes heavily congested, cells are discarded at the ATM switch and TCP retransmission should happen as a result.

12. Optimization of transport layer protocol parameters(2/5)
Several experiments are executed on 100 nodes of the PC cluster, in order to investigate retransmission characteristics.
maximum interval of TCP retransmission
MAX
=60000[msec]
Minimum interval of TCP retransmission
MIN
=200[msec]

13. Optimization of transport layer protocol parameters(3/5)
It takes an exponential back-off value.
24 sec
12 sec
6 sec
Figure 6. Execution time of the broadcasting
program (MIN = 200[msec])

14. Optimization of transport layer protocol parameters(4/5)
Figure 7. Execution time of the broadcasting
program (MAX = MIN + 100[msec])

15. Optimization of transport layer protocol parameters(5/5)
Figure 8. Amount of retransmission
(MAX =MIN [msec])
Figure 9. Amount of retransmission
(MAX =MIN [msec])

16. Parallel data mining application(1/2)
Figure 10. Execution time of HPA program.

17. Parallel data mining application(2/2)
Figure 11. Speedup ratio of HPA program.

18. Conclusion
Retransmission caused by cell loss at the ATM switch was analyzed.
Default TCP protocol could not provide good performance, since a lot of collisions occur in all-to-all broadcasting executed.
Using a TCP parameters according to the proposed optimization, sufficient performance improvement has been achieved with parallel data mining on 100 PCs.

19. Thanks For Your Attention.