Cut-through, corruption and CRC-stomping

Corrupted frames are the devils spawn.  A few noisy links causing frame corruption can quickly degrade network performance, and troubleshooting them is getting harder.  These integrity errors generally occur when signal noise causes a binary ‘1’ to be mistaken for a binary ‘0’ or vice-versa.  This post takes a look at integrity errors and the impacts of corrupted frames in a cut-through switched network.  Throughout this post I’ll use the term ‘CRC errors’ term to refer to frame integrity errors which were detected by CRC comparison.

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Tester not included

A few years ago, I had the chance to attend an IXIA training course in our Dublin office. I had seen the time-suck of network test gear before.  So I said,  “I’m not spending a week trying to learn a test-set.  It’ll be cool, but what’s the point. I won’t get the time to apply those skills, then I’ll forget, and it will be a wasted week.”  I declined the training.

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Get more juice from your network lab

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We have a network lab?

Spirent presented their new lab-management software, called iTest Lab Optimizer, at network field day 4 recently.  Their product name isn’t catchy, but it is very descriptive and addresses a market need.  The simple fact is that most lab networks don’t get optimised to their full potential for some of the following reasons:

  1. Nobody knows what is in the lab (or that one exists) – Inventory Management
  2. The availability of the lab devices is unknown  – Availability and scheduling
  3. The patching status of the devices is uncertain – Fixed undocumented patching.
  4. Setting up your device-under-test is hard and takes time,  so you try to prevent other users from mangling your config. – DUT config management