Commit 77d0ebc0 authored by Jay Lepreau's avatar Jay Lepreau
Browse files

Some edits for clarity and visibility.

parent cbe89168
......@@ -7,6 +7,13 @@
<h1>Linktest Tutorial</h1>
</center>
<em>Linktest is an online validation test of the network characteristics
in an Emulab experiment. It's a check that Emulab set up the network
as you requested. If you care about the fidelity of your network, you
should set linktest to run on all or some swapins, and you should read
this entire tutorial.</em>
<h2>Contents</h2>
<ul>
<li> <a href="#QuickStart">Quick Start</a>
......@@ -38,23 +45,25 @@ To run linktest, select a Linktest test level from the dropdown on the
<a href="beginexp_html.php3">Begin an Experiment</a> page.
<ul>
<li> <a href="#Level1"><b>Level 1</b> - Connectivity and Latency</a>:
For fastest response, level 1. This will check that all nodes respond
to ping and that latency is correct.
For fastest response, select level 1. Through ping, this will check
link-level connectivity and link latencies.
<br>
<li> <a href="#Level2"><b>Level 2</b> - Plus Static Routing</a>:
In addition to the above, tests static routing (if applicable).
<br>
<li> <a href="#Level3"><b>Level 3</b> - Link Loss</a>: Check link loss
characteristics. Test levels are cumulative, so this option also
includes connectivity, latency, and static routing (if
applicable).
<li> <a href="#Level3"><b>Level 3</b> - Plus Link Loss</a>: Check link loss
characteristics. Test levels are cumulative, so this option also
includes connectivity, latency, and static routing (if applicable).
<br>
<li> <a href="#Level4"><b>Level 4</b> - Bandwidth</a>: If bandwidth is
important in your experiment, select level 4. Be warned that the
bandwidth test takes up to 20 seconds per link. <b>Also note that
not all bandwidths can be accurately measured</b>. If this
<li> <a href="#Level4"><b>Level 4</b> - Plus Bandwidth</a>: If bandwidth is
important in your experiment, select level 4. Be warned that the
bandwidth test takes up to 20 seconds per link. <b>Also note that
not all bandwidths can be accurately measured</b>. If that
happens, a warning will be placed in the log file for each link
that is out of range for bandwidth testing.
</ul>
<p>
If you select a test lest level other than zero, Linktest will run
If you select a test level other than zero, Linktest will run
after the experiment completes its swapin. If a problem is found,
testbed-ops is automatically notified and a message will appear in the
activation log. You will also receive an email message to ensure that
......@@ -72,9 +81,9 @@ linktest reports failures!
</center>
<ul>
<li> Not all bandwidths can be accurately measured, and linktest will
skip links that it knows will give false results. Please check
the output, and be sure to test those links yourself if your
<li> Not all bandwidths can be accurately measured, and linktest <a href="#Level4">will
skip links</a> that it knows will give false results (e.g., slow or lossy links).
Please check the output, and be sure to test those links yourself if your
results depend on total accuracy.
<li> As with any automated testing procedure, we have to balance the desire
......@@ -83,8 +92,8 @@ linktest reports failures!
fudge on any link. <b>If your results are dependent on total
accuracy, then you should test your links yourself!</b>
<li> When using linkdelays (endnodeshaping) latency is less accurate
because of the 1ms clock resolution that the kernel runs at. At
<li> When using "endnodeshaping" (so-called linkdelays), latency is less accurate
because of the 1ms clock resolution at which the kernel runs. At
worst, latency can be off by up to 3ms, say for a roundtrip ping
packet.
......
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