1. Network Performance versus TCP Receiver Window Size Project 2 cs533

2. Introduction TCP performance impacted by –Capacity – determines maximum bitrate –Delay – acknowledgement based Also impacted by receiver window size –Bitrate x Delay (and delay varies!) Throughput –Too big? Packet drops –Too small? Underutilization –Just right? “Sweet spot” Default OS settings TCP tuning –http://www.broadbandreports.com/

3. Description (1 of 2) Evaluate performance of two classes of applications: –Bulk download. Ex: a file download. –Interactive session. Ex: remote login and edit For each class, define the workload and parameters. –Ex: for bulk download maybe size of download –Ex: for interactive session maybe number words typed +Note! Here, we’ll study interactive session during bulk download

4. Description (2 of 2) For each workload, you are to define performance metrics at two levels: –Network level. Possible metrics include throughput, capacity, round-trip time,... –Application level. Possible metrics include download time, response time, time to complete task,... Evaluate performance for different TCP receiver window sizes –Small (1 or 2 Kbytes), medium (about 16 Kbytes), and large (about 64 Kbytes)

5. Report Design - describe your performance measurements A) how you generated your workload (ie- what programs/scripts you ran and what they did); B) how many runs of each workload you performed; C) how you measured and recorded your data; D) what the system conditions were like beyond the boundary of the system you were measuring Setup - describe your system settings A) operating system version; B) network access type; C) hardware: processor speeds, memory… Analysis – present results, beyond raw data A) appropriate tables and graphs; B) appropriate statistical analysis Conclusion - interpret results A) what they mean, what one should do for tuning Abstract –1 paragraph that abstracts whole report, write last, goes first

6. Hints (1 of 2) Enabling High Performance Data Transfers –http://www.psc.edu/networking/perf_tune.html Networking Forum FAQ –http://www.dslreports.com/faq/networking Setting receiver window sizes –Windows, use Dr. TCPDr. TCP +http://www.broadbandreports.com/drtcp –Linux, use echo 2048 > /proc/sys/net/core/rmem_max –Need to be “root” or “administrator” +See me if don’t have such a PC Remember, TCP versus round-trip time! –Can measure with ping

7. Hints (2 of 2) Gnuplot or Excel Checklist in Jain, p. 143

8. Hand-In Report Send by email