September 14, 2009, 11:05 AM — The emergence of 10 Gigabit Ethernet, virtualization and unified switching fabrics is ushering in a major shift in data center network design: three-tier switching architectures are being collapsed into two-tier ones.
Higher, non-blocking throughput from 10G Ethernet switches allows users to connect server racks and top-of-rack switches directly to the core network, obviating the need for an aggregation layer. Also, server virtualization is putting more application load on fewer servers due to the ability to decouple applications and operating systems from physical hardware.
More application load on less server hardware requires a higher-performance network.
Moreover, the migration to a unified fabric that converges storage protocols onto Ethernet also requires a very low latency, lossless architecture that lends itself to a two-tier approach. Storage traffic cannot tolerate the buffering and latency of extra switch hops through a three-tier architecture that includes a layer of aggregation switching, industry experts say.
All of this necessitates a new breed of high-performance, low-latency, non-blocking 10G Ethernet switches now hitting the market. And it won't be long before these 10G switches are upgraded to 40G and 100G Ethernet switches when those IEEE standards are ratified in mid-2010.
"Over the next few years, the old switching equipment needs to be replaced with faster and more flexible switches," says Robin Layland of Layland Consulting, an adviser to IT users and vendors. "This time, speed needs to be coupled with lower latency, abandoning spanning tree and support for the new storage protocols. Networking in the data center must evolve to a unified switching fabric."
A three-tier architecture of access, aggregation and core switches has been common in enterprise networks for the past decade or so. Desktops, printers, servers and LAN-attached devices are connected to access switches, which are then collected into aggregation switches to manage flows and building wiring.