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Network Vendors Tout Fabric-Based Designs

Cisco’s FabricPath and HP’s FlexNetwork mark a shift in network architectures across the board

Every big network vendor is now touting an architecture that challenges the traditional three-tier design. Cisco and Hewlett-Packard are introducing equipment and design changes that increase the size of the Layer 2 collision domain to enable greater virtual workload mobility. Network managers are being offered a choice between known, proven designs and unknown, flattened architectures. And these new architectures require new switch chassis along with new line and supervisor cards.

No network manager will be fired for adhering to risk-avoiding orthodox networks. The question is, in the face of sweeping changes offered by virtualisation and cloud computing, can traditional networks remain competitive?

For example, the widely used and well-understood STP (Spanning Tree Protocol) makes switched networks possible. At a basic level, STP enables switches to be plugged into other switches so that redundant paths are available to prevent a single point of failure, but loops, which are fatal to network operation, are prevented. Creating smaller collision domains inside a larger broadcast domain worked in networks where applications were installed on single, physical host systems.

However, when VMware vSphere was introduced, these smaller domains also limited where virtual machines could migrate because VMs must have access to the same subnets on the source and destination physical hosts. Thus, business-continuity strategies are usually limited to a single physical location and are, therefore, much more likely to fail.

Emerging Network Concepts

Two architectures, one from Cisco and the other from HP, offer a range of hardware, protocol and management changes. It’s worth noting that other network-equipment manufacturers are also offering architecture options including Brocade’s Ethernet fabrics, Extreme’s Open Fabric and Juniper Networks’ just released QFabric.

Starting in 2008, Cisco introduced the Nexus 7000 data centre switch chassis, a new operating system called NX-OS and a family of Nexus switches. The FabricPath architecture came the following year and in 2010 OTV (Overlay Transport Virtualisation), which extends Layer 2 functionality between data centres, was released. Along with these switch and protocol changes Cisco released its UCS (Unified Computing System) server hardware, thus setting the stage for a substantial change in network architecture and the current competitive struggle with HP.

Last month at Interop, HP announced the A10500 switch, basically a competitor to the Catalyst 6500 family, and the A12500, which is roughly analogous to the Cisco 7000. HP also unveiled its FlexNetwork architecture including FlexFabric for the data centre. It almost goes without saying that HP has long made data centre servers.

Aging protocols are being jostled by emerging network concepts that could morph into the standards that will run on networks in short order. Besides working to move beyond STP, a research project called OpenFlow — an experimental, open standard intended for future switches, routers and wireless access points — seeks to be the basis for software-defined networks where hardware elements support optimised traffic flows that eliminate bottlenecks that current protocols such as OSPF (Open Shortest Path First) can introduce. And all of these protocols will require better network-management oversight.

Cisco is often chided for having too many disparate management tools while HP has a well-established place in the enterprise operations-management field. Both companies are using the network architecture changes as an opportunity to recreate management as a competitive advantage, which is all to the good for IT managers. Cisco is reducing the number of management tools by consolidating functions while HP started shipping IMC5 release (Intelligent Management Center, version 5) at Interop.

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