perfSONAR User Q&A and Other Discussion

[Zhi-Wei Lu <>]

Hi all,

 

We are experiencing some strange issue (ip fragmentation) for our perfSonar bandwidth test with MTU=9000.  For perfSonar machines with clean MTU=9000 path,  our band width tests between the pair of perfSonar boxes work fine.  However, if the path between the two perfSonar boxes have MTU=1500 devices (such as firewalls or packet shape), only one way test would work.

 

For example, from our box p0 (bebind 1500 MTU security device) to perfsonar.nersc.gov

bwctl –c perfsonar.nersc.gov  would fail, while

bwctl –s perfsonar.nersc.gov would work

 

From our box pb (on the border) with a clean 9K MTU path to perfsonar.nersc.gov, both tests work.

Test between out boxes pb and p0 would exhibit the one way behavior as well, as there is MTU=1500 device in the path.

 

I though that IP fragmentation is enabled on the Linux boxes (CentOS 6.5), yet why I am getting this one way traffic behavior? Are there kernel/application parameters that I can set to correct the issue that we are encountering.

 

If I set MTU=1500 on p0, tests to any site work both ways.  Thank you.

 

Zhi-Wei Lu

IET-CR-Network Operations Center

University of California, Davis

(530) 752-0155