perfSONAR User Q&A and Other Discussion

[Brian Candler <>]

I am trying to understand some things about maddash configuration.

(1) If you set up a full mesh, then you see something like this:

   A B C

A  . 1 X
B  2 . X
C  X X .

Each intersection box shows two values - for example if you hover over box (1) you see results for A->B and B->A. The box is also split into two colours for the two results.

However at box (2) you also see results for A->B and B->A, *and these may be different*. The grid is not symmetrical.

The only thing I can think of is that one box is showing test results stored in the measurement archive on host A, and the other is showing the test results stored in the measurement archive on host B. Is that correct? How does one know which MA each box is showing?

(2) Does this also imply that if you set up a full mesh, all the tests will be done twice? For example, host A schedules and stores tests A->B and B->A, whilst host B also schedules and stores tests from A->B and B->A?

Isn't that wasteful, or is it an intentional form of redundancy to make sure a test is being done somewhere?

(3) If you look at the sample grid at
http://ps-dashboard.es.net/index.cgi?grid=ESnet%20-%20ESnet%20to%20ESnet%20Packet%20Loss%20Testing
it is 30x30 but not quite symmetrical:

- albq-owamp.es.net appears on the left but not the top
- sdsc-owamp.es.net appears on the top but not the left

Is this actually a disjoint mesh rather than a full mesh? If so, why would it be configured that way?

(4) Looking at the same example I also note that some tests are visible at the intersection (A,B) but not (B,A). In the second direction the square is white. It is not orange ("Unable to retrieve data") or grey ("Check has not yet run")

e.g.
aofa (left) slac (top) shows values green and red. Clicking on this shows some stored results (although only a single packet loss figure, not the two figures implied by the green and red)

slac (left) aofa (top) is white. Clicking on this does nothing.

I cannot work out at all what's going on here at all.

Many thanks for any clues.

Cheers,

Brian Candler.