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Troubleshooting: Basics

It’s 2AM, the network is down, and the CEO is on the phone asking when it is going to be back up—the overnight job crucial to the business opening in the morning has failed, and the company stands to lose millions of dollars if the network is not fixed in the next hour or so. Almost every network engineer has faced this problem at least once in their career, often involving intense bouts of troubleshooting.

And yet—troubleshooting is a skill that is hardly ever taught. There are a number of computer science programs that do include classes in troubleshooting, but these tend to be mostly focused on tools, rather than technique, or focused on practical skill application. I was also trained in troubleshooting many years ago as a young recruit into the United States Air Force—but the training was, again, practical in bent, with very few theoretical components.

Note to readers: I wrote a short piece on troubleshooting here on rule11, but I have taken that piece down and replaced it with this short series on the topic. I did start writing a book on this topic many years ago, but my co-authors and I soon discovered troubleshooting was going Continue reading

One the ‘net: The Network Collective and Choosing a Routing Protocol

The Network Collective is a new and very interesting video cast of various people sitting around a virtual table talking about topics of interest to network engineers. I was on the second episode last night, and the video is already (!) posted this morning. You should definitely watch this one!

In episode 2 our panel discusses some key differences between routing protocols and the details that should be considered before choosing to implement one over another. Is there any difference between IGP routing protocols at this point? When does it make sense to run BGP in an enterprise network? Is IS-IS an old and decaying protocol, or something you should viably consider? Russ White, Kevin Myers, and the co-hosts of Network Collective tackle these questions and more.

The post One the ‘net: The Network Collective and Choosing a Routing Protocol appeared first on rule 11 reader.

MegaSwitch: an interesting new data center fabric

Data center fabrics are built today using spine and leaf fabrics, lots of fiber, and a lot of routers. There has been a lot of research in all-optical solutions to replace current designs with something different; MegaSwitch is a recent paper that illustrates the research, and potentially a future trend, in data center design. The basic idea is this: give every host its own fiber in a ring that reaches to every other host. Then use optical multiplexers to pull off the signal from each ring any particular host needs in order to provide a switchable set of connections in near real time. The figure below will be used to explain.

In the illustration, there are four hosts, each of which is connected to an electrical switch (EWS). The EWS, in turn, connects to an optical switch (OWS). The OWS channels the outbound (transmitted) traffic from each host onto a single ring, where it is carried to every other OWS in the network. The optical signal is terminated at the hop before the transmitter to prevent any loops from forming (so A’s optical signal is terminated at D, for instance, assuming the ring runs clockwise in the diagram).

The receive Continue reading

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