We also know there are known unknowns – Network troubleshooting

Such as WAN link utilisation.

Users were complaining that network performance was slow across the 80M WAN link.  How did they know?  Citrix users mostly …

So I ask our telecommunications provider, “is our link congested?”

‘No, 60% utilisation.  Here’s a graph of the network performance:”


Can you see what’s wrong?  Well there’s a couple of things, it’s a sample image for example.  But if you knew we were running Netware 3 & 4, you’d expect to see IPX/SPX traffic.  Which were the protocol layers our users were mostly using.

“Where is it?”, I ask.

‘Oh, we don’t measure IPX/SPX traffic, it’s only IP.’

My estimate, based on running a network sniffer, was that IPX/SPX was using 30% of the WAN link.

My recommendations were:

  • remove IPX/SPX
    (difficult, talking Netware 3 & 4 here)
  • upgrading the WAN link.

“Reports that say that something hasn’t happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don’t know we don’t know.”  – Donald Rumsfeld