Building a 100G Data Center Leaf-Spine Network

As AI advances, data center computing power is further squeezed. Traditional data center networks can no longer meet the high bandwidth, low latency, and scalability requirements of AI development. To address this issue and accommodate the massive east-west traffic generated by AI computing, engineers are choosing leaf-spine network architectures for next-generation high-performance data centers. This article will introduce you to 100G leaf-spine networks, their topology, and their architecture, to help you better understand high-performance data center networks.

1. What is a Data Center Leaf-Spine Network Architecture?

In high-performance data centers, the leaf-spine architecture is constructed using a two-layer structure (leaf switches + spine switches). This means the entire network consists of only two layers, directly connected to each other, achieving a flat design.

In a leaf-spine architecture, the leaf switches are at the bottom layer, connecting end nodes and aggregating all traffic. The spine switches are at the top layer, providing high-speed interconnection between leaf switches and enabling connections between any two servers in the network. This structure simplifies the network topology and supports horizontal scalability, easily adapting to growth from hundreds to thousands of servers.

2. Advantages of the Leaf-Spine Network Architecture in Data Centers

In traditional data centers, the three-tier network structure (access layer, aggregation layer, core layer) suffers from multi-hop forwarding, low bandwidth utilization, and poor scalability in large-scale environments. The leaf-spine network architecture improves and addresses these issues while retaining the advantages of the three-tier network structure. It also offers the following advantages:

2.1 Low Latency and Predictable Performance

In a leaf-spine network architecture, traffic transmission paths are fixed and minimized, passing through a maximum of two switches and three hops to reach their destination. This results in low, stable, and predictable performance, making it ideal for latency-sensitive and performance-demanding applications such as high-frequency trading and AI training.

2.2 High Bandwidth

The leaf-spine network architecture eliminates the aggregation layer bottleneck found in traditional three-tier networks. East-west traffic can be transmitted over multiple parallel spine links without interfering with each other, fully utilizing the switch transmission bandwidth and resulting in very high cross-link bandwidth across the entire network.

2.3 Powerful Scalability

Compared to the traditional three-tier network architecture of data centers, the leaf-spine network architecture of high-performance data centers offers powerful scalability, making horizontal network expansion much simpler. As the number of end nodes in a network increases, the total bandwidth between leaf switches becomes insufficient to handle the increased traffic. In traditional three-layer networks, this requires network replanning. However, a leaf-spine network architecture allows network expansion by simply adding new spine and leaf switches horizontally and connecting them to all existing leaf switches. This expansion is extremely convenient, requiring no disruption to existing network services or complete replanning of the entire network cabling.

2.4 Zero-Latency Switchover in the Event of Network Failures

In a leaf-spine network architecture, there is no single point of failure. If any link, leaf, or spine switch fails, traffic is automatically rerouted through alternative paths, achieving zero-latency failover, ensuring normal network service operation and minimizing losses caused by service interruption.

3. Typical Topology Design for a 100G Leaf-Spine Network

3.1 100G Leaf-Spine Network Topology

The leaf-spine network architecture utilizes a fully meshed topology. This fully meshed topology ensures that every leaf switch is connected to all spine switches, creating sufficient network redundancy and achieving a near 1:1 network convergence ratio. This ensures zero congestion between two devices in the network and packet forwarding capacity close to the switch backplane bandwidth.

3.2 Leaf-Spine Network Hardware Selection

In a leaf-spine network, spine switches are responsible for traffic conversion across the entire network. They require high backplane bandwidth and high-speed forwarding to deliver high bandwidth and low latency. Layer-3 managed switches with 100G/400G ports are preferred. Heat dissipation and reliability should also be considered to ensure stable core layer operation and minimize network failures.

Leaf switches are responsible for end-node access and traffic aggregation across the entire network. They require high port density and support for advanced network features. 48-port/96-port 100G Layer-3 managed switches are preferred. Support for advanced network features such as VXLAN, VXLAN-EVPN, and OSPF are also recommended. These features will greatly assist in subsequent network expansion and operations. For links between network end nodes and leaf switches, typically within a network cabinet, with an average distance of less than 5 meters, 100G DACs are a priority. Their low power consumption and low cost perfectly suit the confined, underheated environment of the cabinet, reducing power and heat dissipation pressures.

For links between leaf and spine switches, typically within data centers, with distances typically less than 2 km, 100G LR4s are prohibitively expensive. Therefore, 100G CWDM4 optical modules, designed specifically for data center networks, are a priority. Their 2km transmission distance meets the interconnection needs within the data center and are more affordable.

4. Deployment and Operations Key Points

Cabinet Planning: 100G DACs are recommended for internal cabinets to facilitate operation and maintenance; 100G CWDM4 modules are recommended for internal cabinets and data centers to reduce financial pressures.

Module Code Compatibility Verification: When purchasing optical modules in bulk, verify the performance and compatibility of the first fiber to avoid purchasing substandard modules that could slow data center construction.

Automated Deployment: Utilize Ansible, Python, or the vendor's Fabric management platform for batch configuration and deployment. Operations and Maintenance Monitoring: Enable device DDM optical power monitoring, SNMP trap alarms, and centralized log management.

5. Summary

In high-performance data centers, building a 100G leaf-spine network is not just a speed upgrade; it also comprehensively enhances architecture, management, and automation capabilities. Through appropriate topology planning, device selection, and protocol design, you can achieve enhanced scalability and maintainability while maintaining high performance, making it the preferred network architecture for high-performance data centers. YXFiber, a professional optical module manufacturer, offers full-rate optical modules from 1G to 800G and one-stop network solution design, making it your ideal partner for network construction.