Cloud Computing--Packet Buffering for Data Center Switches

By Ori Aruj, Dune Networks

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The data center market is growing large enough to justify its own set of requirements. These are implemented in a new breed of switching products expected beginning in 2008. The requirements emerged from a cross pollination of the Enterprise and HPC switches, and include high throughput, reduced latency, dense and low-cost 10GE port machine and high speed 40GE/100GE interfaces.

Data centers consist of hundreds to many thousands of servers and several storage machines co-located within a single room or a building. The servers are interconnected using an Ethernet network. The servers connect to storage machines via a separated fiber-channel network. Traffic in the Ethernet network is typically carried via TCP. A data center presents a unique environment for TCP traffic. The rate of the links is high (1GE, 10GE, and soon 40/100GE), while server-to-server latency is low (approximately 100 microseconds or less). The network is large, thus is built from up to 3 tiers (access, distribution and core) where connection between switches at the different tiers may be oversubscribed.

Several papers studied the packet buffering size required for TCP traffic in a switch (switch and router will be used interchangeably). Unfortunately, the main focus of many of these papers is the wide area network. None of the papers discussed the data center network specifically.

This article surveys known results and applies them specifically to the data center environment.