perfSONAR User Q&A and Other Discussion

[David Koski <>]

So the strange issue is that if we go to the host that has the packet loss and test from there we don't see any packet loss on the forward, we do see it on the reverse however (Which would be the opposite forward that we saw no loss on the forward).

      Dave

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David Koski

ITS ISO Communications Systems and Data Centers Operations

734-647-8993 (Office)                                                                                     734-678-5824 (Mobile)

On Mon, Jan 26, 2015 at 10:51 AM, Brian Tierney <> wrote:

If perfSONAR is reporting loss, there is probably loss. And loss is often seen in only 1 direction.

Firewalls often only effect inbound traffic, congestion is often only inbound, etc etc.

A bit more info is here: http://fasterdata.es.net/performance-testing/network-performance-howto/packet-loss/

On Mon, Jan 26, 2015 at 7:19 AM, David Koski <> wrote:

We've found that all our perfsonar systems are reporting a reverse path loss between them in the graphs - scheduled test (however the forward graph for the same path from the opposite server shows no loss).  We can't find a reason for why this is, and if "feels" like a perfsonar server issue since we have 10 systems doing the same issue.  We are seeing random packet loss that we can't explain (anywhere from consistent 80% loss to random loss between 0 and 100%).

Incidentally, while we haven't been able to confirm that this started from the 3.3 to 3.4.1 upgrades, we did notice that one of the servers did start it's reverse packet loss around the time we upgraded to 3.4.1.

As a couple of items, the servers are configured with multiple interfaces and appear properly setup under 3.4.1 for this.  The hosts are very close together as well (Around 0.3 ms).

Any one have any thoughts or perhaps a way of troubleshooting this?  Forward packet loss is constantly 0 no matter the host, reverse is always some form of packet loss (either consistent or bouncing between 0 and 100).  We haven't seen this issue going from our hosts off our network.

      Thanks

             David

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David Koski

ITS ISO Communications Systems and Data Centers Operations

734-647-8993 (Office)                                                                                     734-678-5824 (Mobile)

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Brian Tierney, http://www.es.net/tierney
Energy Sciences Network (ESnet), Berkeley National Lab
http://fasterdata.es.net