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To flow or not to flow?

NetApp’s newest storage operating system, clustered Data ONTAP (cDOT), leverages a backend of Cisco Nexus switches for it’s cluster interconnect network.

When configuring the switch/cluster ports for use with cDOT, the best practice is to turn flow control off as per TR-4182. In fact, that happens to be the recommendation for normal data ports as well. Why is that? Before we get into that, let’s cover the basics…

What is flow control?

Flow control is a mechanism used to help manage the rate of data transfer between two devices. This is done to help prevent a source evice from overwhelming a destination device by sending more packets than the destination can handle. These scenarios can occur if a source device is faster than the destination device (CPU, RAM, NIC, etc). This can also happen if the source is intentionally trying to flood the destination via a malicious Denial of Service (DoS) attack.

Flow control can be enacted for send or receive packets, or both. It can be hardware or software based. It can occur at multiple layers of the OSI model

For a real world analogy to flow control, think of how dams work. A dam will be installed to control the flow of water on a river, usually to create lakes or reservoirs. Dams can be used to adjust the water flow to prevent flooding, depending on rainfall. Network flow control does pretty much the same thing – it prevents data floods. Read More »

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The Programmable Network: Elastic Services

In our last blog on “Advanced Flow Control” we used the metaphor of a three-dimensional collection of intersecting highways of many different kinds with a wide array of vehicles carrying various types of passengers to represent the Internet of Everything­ (IoE).  The IoE concept has come a long way since it was first coined by the Auto-ID Center. Today the concept has broadened into a catch all for current and future network-connected endpoints, from smart meters to vending machines, security cameras, all forms of transportation, and consumer electronics ─ not to mention PCs, tablets, and smartphones. People with electronic tags will one day be connected to the IoE to monitor their health. Many dogs and cats already have chips for location tracking. The opportunity for new services will be unlimited and customers will expect instant access to networking resources to launch, alter, or eliminate those services.

Instant Resources for a Spontaneous World Read More »

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The Programmable Network: Advanced Flow Control

The increasing diversity and complexity of traffic traversing the Internet of Everything­ today can be imagined as a three-dimensional collection of intersecting highways of different kinds (e.g., corporate WAN, Internet, mobile, Wi-Fi, cellular, cable, cloud), with a wide array of vehicles (e.g., PCs, tablets, smartphones) carrying various types of passengers (e.g., data, voice, video, email, SMS, Web).   Emerging traffic from the new category of machine-to-machine communications is scaling exponentially and introducing new policy triggers.

In this new environment network operators must become master traffic controllers to deal with all of the volume, diversity, and complexity. The most innovative and forward-looking experts are aggressively looking into providing more open programmatic access to their network functions and services. The goal is easier and faster control, in order to make them more agile, flexible and application interactive while at the same time optimally aligning costs with potential new revenues.

Cisco ONE Building Blocks: Controllers and Agents

Software Defined Networking (SDN) plays a key role within Read More »

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