How to flatten a data centre network

Shrinking a three-layer data centre network to two may be an easy job for a small company, but what if you’re a global financial services corporation?

It can be done, say consultants from Juniper Networks Inc., who recently showed a Toronto audience of enterprise networking managers how they did it for a U.S. financial institution a medical research institute.

The technology isn’t the point. The need to do it is.

“We need to minimize how traffic flows and the amount of [network] devices it has to traverse,” explained John Dathan, Juniper’s enterprise general manager for Canada.

Most networks have a core, a distribution layer and an access layer. However, most experts agree the middle layer doesn’t add much value –it just connects devices on either side of it. “The way networks have evolved today the core layer can serve as the core and the aggregation layer,” says Dathan.

The result is increased efficiency because there are fewer routers and switches, which, obviously lowers the network’s cost.

Major networking equipment manufacturers have been urging customers for over a year to cut their data centre tiers down to two levels using new techniques to link the layers, says Zeus Kerravala, a vice-president of research at Yankee Group. The increased use of virtualization has been a key driver, he said.

Cisco Systems Inc., with its FabricPath technology and Brocade Communications Systems Inc. with its Virtual Cluster Switching architecture are following the IETF’s Transparent Interconnection of Lots of Links (TRILL) standard. Juniper calls its technology Virtual Chassis. Last week Avaya Inc. revealed its solution called Vena, built around the emerging IEEE 802.1AQ Shortest Path Bridging standard.

“I think there’s a lot of interest from enterprises [in reducing data centre network layers],” Kerrvala said. “The fact remains that if a company is looking to do more advanced things with virtualization like vMotion [the ability to move virtual partitions on the fly] the network’s the main bottleneck and this help alleviate that.”

In Juniper’s case studies, the unnamed U.S.-based financial institution, dubbed ‘Acme Financial’ for privacy reasons, had 20,000 staffers in 200 offices around the world and an IT budget of about US$200 million.

When a new CIO came in, he had a number of goals including consolidating data centres, leveraging the network to compete against larger firms and creating a private cloud for delivering virtual desktops to the institution’s financial traders.

An important problem to solve was network latency, which could be devastating to a firm that relied on links to stock markets around the globe. The result was sensitive traffic was being delayed for crucial milliseconds by non-sensitive data. A complex security policy didn’t help.

Getting rid of the access layer meant replacing chassis-based switches with top-of-rack switches, using virtual LANs, shifting to an IP/MPLS network and imposing advanced quality of service were among the strategies used to eliminate the middle layer.

By using loop-free virtual LANs in the second layer, the need for spanning tree protocol was eliminated, thus improving data centre scalability.

The Los Angeles-based Laboratory of Neuro Imaging (LONI), is a facility that not only images the human neuro system but acts as a service provider to over 1,000 researchers around the world who connect to its data centre. The use images and data sets of up to several hundred gigabytes in size.

LONI’s biggest problem was throughput. The spanning tree protocol disabled to to half of the bandwidth, up to half of the ports interconnected with switches and the unnecessary layers added latency. Scaling up the servers was increasingly difficult.

Again, eliminating the middle network layer – this time by placing an Ethernet edge router at the core – and updated switches at the access layer — was the heart of the solution.

There isn’t a single solution for chopping a layer off a data centre, Juniper’s presenters stressed.

“It’s not all that difficult once you get your head around the design and how you’re going to do it,” said Dathan.