Tag: design

  • Effectiveness – Network Truths, Principles and Fallacies

    I recently gave a 13-minute talk to the Irish Network Operators Group (INOG).  In this talk I argue that you can become more effective, and a happier engineer by standing back and reflecting. The talk discusses how you work –  with reference to some great truths, principles and fallacies. I introduce The twelve networking truths…

  • SPAN Scaling Challenge

    I’m facing a mini scaling challenge with Cisco SPAN (Switched Port ANalyzer) session and thought it would be good to share it with you fine folk. SPAN Challenge A 3750X switch is currently SPAN-ing a 10Gbps interface to a 1Gbps egress port. A server is directly attached and is using dump cap to capture a subset (5%) of…

  • Hardware – What’s the ‘holdup’?

    This post discusses power supply ‘holdup’, and how it can impact network or server hardware uptime. The holdup time or ‘output holdup time’ is the length of time that a given power supply can maintain output power to the switch or server after it’s input power supply has been cut. The dependent host will shut…

  • Planning projects instead of burning benjamins

    Engineers are often unstuck by poor planning and get hit with large financial penalties as a result. Projects can become mired in delays and complications due to unforeseen costs and expenses. There are some unavoidable bumps in the road, but most could be foreseen and eliminated in advance. I want to share a few tips based…

  • Design – Security involvement in design and audit stage

    Designed to fail Security audits are a fantastic way to improve the security of your network. A good auditor can highlight critical flaws in your design and configuration before they are launched into the big bad world. However I think there is a massive issue with security audits; they are designed to fail.

  • Does config automation demand inflexiblity?

    Imagine you’ve just designed and deployed a data center. It was hell but you are smiling. Your design is homogenous, simple and elegant. A greenfield datacenter full of shiny, identical network devices. Because the design was so consistent and repeatable you scripted the generation of the device configurations without too much hassle. This is a network with an easily…

  • Airflow is important – terminology is key

    Data center cooling and large chassis As a network engineer you need to be aware of the data-center environment where your chosen device will be deployed.  A huge wedge of the cost of running a datacenter are spent trying to keep it cool.  So preserving hot-aisle and cold-aisle airflow containment is a big deal for…

  • My 10G switch goes up to 11

    Stealing bits Nailing down the true speed of a 10GbE link can be tricky. For a start you to define ‘speed’ and ‘capacity’. Ivan Pepelnjak offers a nice summary in this post. Then there are little surprises. A former colleague of mine Fred Westermark first introduced me to the Ethernet interframe gap. I had never…

  • Network design – scale without busting your budget

    Rapid growth I read an article by Greg Ferro about twenty-percent-growth recently.  Greg makes the point that most network growth forecasts are grossly overoptimistic.   However, my experience in the service provider world is that ‘the business’ underestimates growth in most cases. Network engineers have a fiscal responsibility not to gold-plate their network designs; network gear is just…