Rethinking the Network

Marten Terpstra

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Top Stories by Marten Terpstra

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 total network solution. And orchestration != ECMP. In addition to VXLAN and NVGRE, Stateless Transport Tunneling (STT) is an encapsulation mechanism used by VMware, mostly for communication between server based vSwitches. It is a bit more involved and complicated than VXLAN and NVGRE, mostly ... (more)

Attention: Overlay Tunnel Construction Ahead

A while ago I wrote a few articles describing the various tunnel protocols used for network virtualization between vSwitches on servers, and between vSwitches and physical network gateways. These are the mechanisms that construct overlay networks on top of a physical network. VMWare uses STT as the tunneling mechanism between vSwitches on servers and VXLAN to communicate with gateways to the non virtualized world. NVGRE is used mostly by Microsoft, and is an extension to GRE tunneling that has been around for a while. Each one of these mechanisms have their pros and cons. They ... (more)

Red Sox, Pumpkins and Packet Encapsulation

[This is not really about the Red Sox or pumpkins this Halloween, but how could I not use those in the title? Go Red Sox] I left an awful teaser at the end of my article last week. In Brent Salisbury's original article that triggered some of these additional virtualization thoughts, he articulated two very clear differences between native network based L2 virtualization mechanisms and the mechanisms that are being provided by overlay solutions based mostly in server vSwitch infrastructure. These two fundamental functions are MAC learning and tunnel encapsulation. In today's post... (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)

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)