Professor PathView and Network Assessments
by December 16, 2010

Filed under: Networking Technology, Performance Monitoring

I count myself lucky that I had a professor in college who took the time to brainwash us all in the ways of network troubleshooting.

To this day, I still jolt awake in a cold sweat hearing his voice chant “physical layer! physical layer!”  As many of you know, the Physical layer is  the first layer of the OSI model, the interconnecting medium upon which telecommunications is built.

What he meant was: “Always start at the beginning” or for the more Zen: “If a tree falls in a forest on a box of cat6 cabling, is the contractor still going to use it?”

So now I am finding myself chanting this mantra at anyone who will listen. Why amI reliving my old college days?  I’ve found that my professor was right  – when troubleshooting your network or running a network assessment, you must always start at the beginning.

We have customers who are ready to tear their hair out  – not to mention their expensive network equipment – when they call us.  It can be overwhelming to review network assessments with hundreds of targets, but you can make your life easier if you start at the beginning:

Network TestingTesting:

1) Ensure your Assessment contains a healthy number of targets that represent the entire deployment (targets on various  subnets, switches, etc)

2) Test to targets from within the same segment and towards other segments

3) Test WAN links and key network locations in EACH DIRECTION

Interpreting Results:

1) Don’t Panic

2) You may find many targets that perform badly, answer these two questions:

a) What are they? (handsets, printers, switches may have variable response to heavy diagnostic testing)
b) where are they? (try to find commonality by subnet and if possible by switch – PHYSICAL LAYER!)

3) Step 2 may answer about 75% of your questions when it comes to finding bad cables, duplex conflicts, bad switch trunks,  etc, but don’t stop there!  Take a deeper dive with outstanding issues to get further diagnostics.  If single tests do not bring an issue to light, consider using real-time monitoring to find help pinpoint transient issues.

Remember, if you didn’t build the network it is that much more important that you completely understand it. By running diagnostics to dozens of targets from various locations and gathering results into one cohesive report, it becomes much easier to quickly identify key performance problems.

PHYSICAL LAYER!