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Marvell


July 17th, 2017

Rightsizing Ethernet

By George Hervey, Principal Architect, Marvell

Implementation of cloud infrastructure is occurring at a phenomenal rate, outpacing Moore’s Law. Annual growth is believed to be 30x and as much 100x in some cases. In order to keep up, cloud data centers are having to scale out massively, with hundreds, or even thousands of servers becoming a common sight.

At this scale, networking becomes a serious challenge. More and more switches are required, thereby increasing capital costs, as well as management complexity. To tackle the rising expense issues, network disaggregation has become an increasingly popular approach. By separating the switch hardware from the software that runs on it, vendor lock-in is reduced or even eliminated. OEM hardware could be used with software developed in-house, or from third party vendors, so that cost savings can be realized.

Though network disaggregation has tackled the immediate problem of hefty capital expenditures, it must be recognized that operating expenditures are still high. The number of managed switches basically stays the same. To reduce operating costs, the issue of network complexity has to also be tackled.

Network Disaggregation
Almost every application we use today, whether at home or in the work environment, connects to the cloud in some way. Our email providers, mobile apps, company websites, virtualized desktops and servers, all run on servers in the cloud.

For these cloud service providers, this incredible growth has been both a blessing and a challenge. As demand increases, Moore’s law has struggled to keep up. Scaling data centers today involves scaling out – buying more compute and storage capacity, and subsequently investing in the networking to connect it all. The cost and complexity of managing everything can quickly add up.

Until recently, networking hardware and software had often been tied together. Buying a switch, router or firewall from one vendor would require you to run their software on it as well. Larger cloud service providers saw an opportunity. These players often had no shortage of skilled software engineers. At the massive scales they ran at, they found that buying commodity networking hardware and then running their own software on it would save them a great deal in terms of Capex.

This disaggregation of the software from the hardware may have been financially attractive, however it did nothing to address the complexity of the network infrastructure. There was still a great deal of room to optimize further.

802.1BR
Today’s cloud data centers rely on a layered architecture, often in a fat-tree or leaf-spine structural arrangement. Rows of racks, each with top-of-rack (ToR) switches, are then connected to upstream switches on the network spine. The ToR switches are, in fact, performing simple aggregation of network traffic. Using relatively complex, energy consuming switches for this task results in a significant capital expense, as well as management costs and no shortage of headaches.

Through the port extension approach, outlined within the IEEE 802.1BR standard, the aim has been to streamline this architecture. By replacing ToR switches with port extenders, port connectivity is extended directly from the rack to the upstream. Management is consolidated to the fewer number of switches which are located at the upper layer network spine, eliminating the dozens or possibly hundreds of switches at the rack level.

The reduction in switch management complexity of the port extender approach has been widely recognized, and various network switches on the market now comply with the 802.1BR standard. However, not all the benefits of this standard have actually been realized.

The Next Step in Network Disaggregation
Though many of the port extenders on the market today fulfill 802.1BR functionality, they do so using legacy components. Instead of being optimized for 802.1BR itself, they rely on traditional switches. This, as a consequence impacts upon the potential cost and power benefits that the new architecture offers.

Designed from the ground up for 802.1BR, Marvell’s Passive Intelligent Port Extender (PIPE) offering is specifically optimized for this architecture. PIPE is interoperable with 802.1BR compliant upstream bridge switches from all the industry’s leading OEMs. It enables fan-less, cost efficient port extenders to be deployed, which thereby provide upfront savings as well as ongoing operational savings for cloud data centers. Power consumption is lowered and switch management complexity is reduced by an order of magnitude

The first wave in network disaggregation was separating switch software from the hardware that it ran on. 802.1BR’s port extender architecture is bringing about the second wave, where ports are decoupled from the switches which manage them. The modular approach to networking discussed here will result in lower costs, reduced energy consumption and greatly simplified network management.

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