Rethinking the Network

Marten Terpstra

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Top Stories by Marten Terpstra

The past few years have seen a dramatic improvement in the latency in network switches. Single ASIC based switches can all pretty much switch packets in less than a microsecond. Current 10GE switching silicon provides anywhere from 300 to 800 nanoseconds, specialized silicon shaves that to less than 200 nanoseconds when limiting the amount of searching that needs to be done by reducing the size of lookup tables. Even other solutions play some smart tricks by providing forwarding hints for intermediate switches make those lookups take less than 50 nanoseconds. Modular switches inherently have a higher latency. Line cards on modular switches typically have multiple ASICs, those ASICs are connected through a single or multi stage fabric. Each step takes time, resulting in latencies varying from around a microsecond when a packet stays on the same ASIC, to possibly 5-... (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)

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)

Many Waze to Cambridge

I work mostly in Plexxi’s office in Nashua, NH. That is about a 12-minute commute for me, backroads only through two sleepy towns. Very convenient and a great improvement over my previous commute. Every now and again I make the trek out to our Cambridge office and it is painful. About 40 miles and around 45 minutes of mostly highway on a good day; early morning this is easily a 90-minute exercise, and finding myself on the road for two hours is not unusual. I am not very attached to a GPS, but whenever I travel a distance or know I am going to hit traffic, I turn on Waze on my p... (more)

Overlay Entropy

There have been many articles describing overlay networks in the past few quarters. It's a relatively straightforward concept, not far removed from some of the older VPN technologies very popular a while ago. The actual transport of packets is probably the simplest, it is the control plane that is much harder to construct and therefore explain. It is therefore also that the control plane in overlay networks has seen the most innovation and change, and is likely to change some more in standard and proprietary ways in the next little while. A perfect example is the use of IP Multic... (more)