Architecture and Technology Evolution of DCNs

The legacy DCN architecture consists of the access layer, aggregation layer, and core layer. To meet large Layer 2 and non-blocking forwarding requirements in DCs, the physical architecture evolves to a two-layer spine-leaf architecture based on the Clos architecture. Forwarding protocols on DCNs also evolve from xSTP and Layer 2 Multipathing (L2MP) to Network Virtualization over Layer 3 (NV03) protocols, among which Virtual extensible Local Area Network (VXLAN) is a typical NV03 protocol. This chapter uses the DCs of financial services companies and carriers as examples to explain the evolution process and network architecture of DCNs, and summarize DCN design principles for financial services companies and carriers.


DCs have been developing rapidly over the past few years, and because of this, virtualization, cloud (private cloud, public cloud, and hybrid cloud), big data, and SDN have become popular. Whether it is virtualization, cloud computing, or SDN technologies, network data packets must still be transmitted over physical networks. As a result, bandwidth, latency, scalability, and other physical network characteristics greatly affect the performance and function of virtual networks. A performance and scalability test report on OpenStack Neutron by Mirantis, a Silicon Valley startup, showed that transmission efficiency can be significantly improved on virtual networks through network devices with upgrade and adjustment. But before we can understand virtual networks, we must first understand physical networks. To this end, this section describes the physical architecture and technology used in DCNs.

Physical Architecture of DCNs

Network architecture design is a fundamental part of network design. Upgrading or modifying the network architecture brings huge risks and costs. Therefore, exercise caution at the beginning of DC construction when you are selecting and designing the network architecture. The physical network architecture of DCs has evolved from a traditional three-layer network architecture to a two-layer spine-leaf architecture based on the Clos architecture. This section describes how the architecture evolves.

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