Tuesday, November 16, 2010

Complexity kills


The July 2010 presentation NetFlow/IPFIX Various Thoughts from the IETF 3rd NMRG Workshop on NetFlow/IPFIX Usage in Network Management describes some of the challenges that still need to be addressed in NetFlow/IPFIX. In particular the slide above describes how increased flexibility has resulted in greater complexity when trying to configure and deploy NetFlow/IPFIX monitoring systems.

In contrast, sFlow implementations have very few configuration options. While there are superficial similarities between sFlow and NetFlow/IPFIX, the two approaches to network performance management reflect profound differences between the design goals of the two standards (see Standards).

NetFlow/IPFIX was developed to export WAN traffic measurements and is typically deployed in IP routers. Configuring routers is a complex task, requiring configuration of subnets, routing protocols, WAN interfaces etc. Many of the functions in a router are implemented in software, providing a flexible platform that permits complex measurements to be made. Over time, options have been added to NetFlow/IPFIX in order to export increasingly complex measurements used to characterize WAN traffic.

sFlow evolved to provide end-to-end monitoring of high-speed layer 2/3 Ethernet switches. Ethernet switches offer plug-and-play connectivity and require very little configuration. Unlike routers, switches perform most of their functions in hardware, relying on software only to perform simple management tasks. The need to embed measurement in hardware resulted in a standard that is very simple with minimal configuration options. However, the basic sFlow measurements, while simple to configure and implement in switches, provide a rich source of information about the performance of switched networks. Instead of relying on the switches to analyze the traffic, raw data is sent to a central sFlow analyzer (see Choosing an sFlow analyzer). The sFlow architecture results in a highly scalable system that can monitor the large numbers of high-speed switch ports found in layer 2 networks (see Superlinear).

The goal of convergence is to simplify data centers, creating flexible pools of storage and computing running over a flat, high bandwidth, low latency, Ethernet fabric (see Convergence). Eliminating complexity is essential if the scalability and flexibility of a converged infrastructure is to be realized.

Microsoft's Chief Software Architect, Ray Ozzie, eloquently describes the dangers of complexity in Dawn of a New Day, "Complexity kills. Complexity sucks the life out of users, developers and IT. Complexity makes products difficult to plan, build, test and use.  Complexity introduces security challenges. Complexity causes administrator frustration."

Maintaining visibility in large scale, dynamic data center environments requires a measurement technology that is designed for the task. sFlow is a mature, multi-vendor standard supported by most switch vendors that delivers the scalable plug and play visibility needed to manage performance in converged data center environments.

Finally, the end to end visibility that sFlow provides is a critical element in building scalable systems. Measurement eliminates uncertainty and reduces the complexity of managing large systems  (see Scalability). An effective monitoring system is the foundation for automationreducing costs, improving efficiency and optimizing performance in the data center.

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