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Rethinking the Network

Marten Terpstra

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Top Stories by Marten Terpstra

IP Multicast is one of those technologies that most everyone loves to hate. It’s almost the perfect example of how complicated we have made networking. Getting IP Multicast to run depends on several protocols that are all somewhat intertwined or dependent on each, their relationship sometimes explicit, sometimes implicit. Even trying to describe the basic operation is complicated. When an application or service provides information using IP multicast, it simply starts sending it onto a specific multicast group. The multicast router for the subnet of the sender sees the incoming multicast packet and will initially have no forwarding information for that stream in its forwarding hardware. The packet is passed onto the CPU of that router, which will encapsulate this packet and send it towards a special multicast router designated the Rendez-vous Point (RP). When the RP... (more)

Network Autonomy – Feedback Defined Networking

About 8 years ago at my previous employer we started a project related to Autonomic Networking. Autonomic Networking is modeled after Autonomic Computing, an IBM initiative from the early 2000s, targeted at creating self managing computing elements. The network version intends to create a framework by which network elements become largely self managed. It does so by defining discovery, awareness and analytics that build some sense of state. Once a network has a sense of its expected state, anything that alters that state can be reacted to following a set of defined or even learne... (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)

The Silence of The Lambdas

We still see quite a few eyebrows raised when we explain how we use WDM optics in our datacenter solution. In the various descriptions of the Plexxi solution it is often mentioned and referred to, but it is worth explaining what that optical infrastructure actually looks like and why it is part of our solution. One of the key attributes of the Plexxi solution is the ability to create network topologies at L1, L2 and L3 that meet the need of the workload offered, calculated based on the load on the network, and the Affinities created that describe the needs of specific applicatio... (more)

Stateless Transport Tunneling (STT) Meets the Network

Last week I walked through the packet formats for VXLAN and NVGRE specifically focused on ways by which the overlay packets provide information to the physical network that help the physical network. Some of the initial extreme thoughts that the overlay and physical network can and should be completely ignorant of each other have softened more recently and more pragmatic thoughts of collaborating layers are being articulated. At Plexxi we have often mentioned that we believe the physical network and the overlay need to be closely orchestrated to get the most benefit out of the to... (more)