Rethinking the Network

Marten Terpstra

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Top Stories by Marten Terpstra

Last week Ivan Pepelnjak wrote an article about the failure domains of controller based network architectures. At the core of SDN solutions is the concept of a controller, which in most cases lives outside the network devices themselves. A controller as a central entity controlling the network (hence its name) provides very significant values and capabilities to the network. We have talked about these in this blog many times. Centralized Control When introducing a centralized entity into any inherently distributed system, the architecture of such a system needs to carefully consider failure domains and scenarios. Networks have been distributed entities, with each device more or less independent and a huge suite of protocols defined to manage the distributed state between all of them. When you think about it, it’s actually quite impressive to think about the extend o... (more)

The Network as a Complex Distributed System By @MartenT1999 | @CloudExpo

Through http://blog.ipspace.net I landed on this article on acm.org discussing the complexity of distributed systems. Through some good examples, George Neville-Neil makes it clear that creating and scaling distributed systems is very complex and “any one that tells you it is easy is either drunk or lying, and possibly both”. Networks are of course inherently distributed systems. Most everyone that has managed a good sized network before knows that like the example in the article, minor changes in traffic or connectivity can have huge implications on the overall performance of a... (more)

Brainrules: a Different Kind of Attachment

I don't read nearly as much as I should. On plane rides I tend to grab a Vince Flynn, James Patterson or David Baldacci, they are usually enough to entertain me on the way there and back. One of the more interesting books I have read in recent years that does not include murderers, spies and explosions, is "Brainrules" by John Medina. A rather good leadership seminar at my previous employer had this on its reading list, and I tore through it. John Medina is a molecular biologist and in his book he describes how our brain works by breaking it down into several areas, each describin... (more)

When Closed Is Not a Bad Thing

I remember the days when the network was open. Your PC, workstation or whatever you had on your desk could access whatever it needed (or not needed). Networking was an enabler of communication, it allowed you to put stuff onto the network, take other stuff off the network. Rather quickly most network operators figured out that the network needed some basic protection from silliness. Most of the early silliness was based in bad network implementations. Devices not responding correctly, spitting out broadcasts when they should not or just going haywire. We now call it DoS filters o... (more)

Managing Tables in Our New Virtual Reality

In traditional networks, MAC addresses are inserted into tables using standard learning techniques.  When packets arrive, if the source MAC address is not known, it is added to the MAC forwarding table for that VLAN with the ingress interface as its destination. If the destination is unknown, the packet is flooded through the VLAN, with the side effect that each switch along the way inserts the source MAC address in its own forwarding table for that VLAN. Assuming the destination actually exists, one of the flooded copies will reach its destination. The device at the destination ... (more)