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 heard of this before and felt a bit cheated to be honest.  Since when do ‘bits’ need a rest. Pfff.

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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 too damn expensive.  But you can over-optimise for cost.  It is incredibly frustrating to overhaul and scale-up a network within a year of the initial deployment.    The end-result is additional capital cost, more engineer effort and resultant opportunity costs.

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Video – 10G Fiber Transceivers – Network Sherpa

I’ve just recorded a quick video about 10Gbps fiber transceivers, There’s a first for everything I guess.  It’s a cheat sheet which describes the different transceivers, where they’re commonly found and the connectors you use.

I’d love to hear your take on the video.  Too long… too short, music too cheesy (yeah I know!), etc.   All constructive feedback is welcomed.

TCAM-based forwarding engines


Ternary Content Addressable Memory, or TCAM,  is a critical component of a modern router. It is a powerful and fast hardware lookup engine for IP Prefixes.  It is also complex, expensive and power hungry.  Not surprisingly, there never seems to be never enough on whatever system you use.

TCAM has historically been used to perform hardware-table-lookups of Access-list, Netflow or QoS tables in routers and switches.   Most of these implementations from your favorite brand name vendors use one or more external TCAM chips to perform these lookups. Continue reading