Network Design for Greenfield Data Centers

In recent years, economic volatility has done little to slow demand for supporting digital business infrastructure. While new data center construction slowed initially, 2021 saw robust expansion. When data center operators begin the process of defining the makeup of these new networks, there are some important practical design questions they need to answer, with the key considerations being general architecture, distance needs, data rate requirements, fiber types, and cost.?

With a greenfield project, network designers may be starting from scratch with only an empty room or even just a concrete foundation. A greenfield project differs from brownfield data center upgrades, which face added constraints from the network infrastructure in place, such as the existing cable type or cabling layout. Brownfield upgrades can also be more constrained by time since updates to an operating data center may involve network disruption and downtime.?

In a greenfield data center project there will be a significantly higher up-front investment as compared to updating an existing network, but there is an opportunity to create the right network architecture from the start since thereare fewer existing impediments when making technology and design choices.The only real constraints in these projects are size, power, and money.?

Design Considerations

The first decision to make for a new data center network is to choose the right architecture. This involves asking questions like: “What are the business needs of the data center?" and "What are the workloads and processes that will run in the data center?” While these questions are bigger than just the physical layer, they do lead to size and speed decisions that shape the makeup of the cabling system.?

The type of data center architecture will affect the speed requirements of the network and the transceiver types most applicable to the design. Over the past 10 years, a split has formed between enterprise and cloud provider data centers when it comes to network migration patterns. For example, in previous years, cloud provider networks have operated at 40 Gb/s uplinks to the switch and 10 Gb/s from switch to server. These networks are now moving to 100 Gb/s uplinks and 25 Gb/s downlinks to the server, with some even preparing to migrate to 200 and 400 Gb/s uplinks and 50 and 100 Gb/s at the server.

Next, data managers need to determine which fiber type is appropriate for each tier. In data center architecture there will be different layer 1 network tiers, and each will have different reach requirements. For example, the transceiver and fiber cabling choices for a Top-of-Rack (ToR) design — which typically have 2- or 3-meter connections — can be very different than the connections for an End-of-Row or Spine design. Extended reach is possible, however when considering extended reach applications, it is prudent to have a full understanding of current and future data applications, target application transceiver specifications, and a careful analysis of the performance capabilities of the passive cabling infrastructure.

Trunk cabling selection is the next key decision when constructing a new data center. Today, most data center connectors are either LC or MPO connectors. LC duplex connectors are currently the most popular fiber connection type. The duplex connector is easy to manage from a polarity perspective, and its established popularity makes it readily available. A common question we hear is “Will LC connections work when upgrading to data rates beyond 25 Gb/s?”

While there are LC solutions for connecting networks at 40 Gb/s and 100 Gb/s, the duplex options that use LC connections will typically require multiplexing technologies like CWDM, which can raise the price of transceivers. Beyond 10 Gb/s, parallel optics with MPOs allow for breakout options that create easy connections between higher speed ports and multiple lower speed ports.

These considerations are only the beginning when it comes to designing a greenfield data center. If you would like to learn even more about specific data rate and transceiver choices, cabling topology, and link cost considerations, check out our full white paper.

This is an article from CrossTalk, a newsletter from Leviton Network Solutions. Check out all of the articles in our latest issue.