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2011 tech priorities: Are you ready to flatten your data center network?

Industry looks to lower latency by removing a switching tier

By , Network World
January 03, 2011 06:06 AM ET

Network World - It's time to flatten those data center networks, say pundits, practitioners and profiteers. As virtualization and the movement of virtual machines around the infrastructure accelerate, so too must your network.

The best way to do that is remove switches -- a whole tier of them - in conjunction with increased port speed.

Paving the way for the flat network 

Simply jacking up server-to-switch and switch-to-switch speeds to 10G isn't enough to optimize the performance of data center networking for mobile VMs. Reducing latency by transitioning a three-tier network architecture to two, and then to one, and removing Spanning Tree as an impediment are key ingredients, too.

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. And a higher performance network includes replacing the Spanning Tree protocol in Ethernet with a new technique that enables use of multiple active links between switches. Such techniques, like the TRILL work in the IETF, are intended to overcome limitations of the Spanning Tree protocol in scale and topology re-convergence.

TRILL is intended to be a Layer 2 protocol with link state routing enhancements to enable shortest path multihop routing so users can build large-scale Ethernet and Fibre Channel-over-Ethernet data center networks. TRILL is designed to overcome the slow topology re-convergence times associated with Spanning Tree, which limits scale and is more susceptible to link failures.

Vendors are also proposing their own TRILL-like methods for flattening data center networks. Cisco's FabricPath is a "pre-standard superset" of TRILL that includes TRILL but extends its capabilities. Juniper claims its Virtual Chassis technology, which interconnects multiple Juniper switches into a single "switch" supporting hundreds of Gigabit Ethernet ports, accomplishes the same goals as TRILL -- chiefly, to collapse layers of switching in a data center network and facilitate more "east-west" communication between servers than "north-south."

Brocade's One architecture implements TRILL, while Avaya's VENA implements the IEEE's answer to TRILL, 802.1AQ Shortest Path Bridging. Alcatel-Lucent plans to add TRILL-like multichassis/virtual chassis linkage this year to its new OmniSwitch 10000. 

The New York Stock Exchange is flattening its Juniper 10G network to reduce latency and take out a layer of market feed traffic processing.

"It basically takes out one hop so...anywhere from a 10 to 20 microsecond improvement" in latency, says Andy Bach, senior vice president and global head of communications for NYSE Euronext, the owner of the New York Stock Exchange.

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