Why SDN Is Revolutionizing Public Cloud Networks – Insights and Real-World Cases

Theme Overview

Although the concept of Software‑Defined Networking (SDN) has been around for many years, its commercial deployment in production environments has exceeded expectations, especially among public‑cloud providers facing rapid business growth.

SDN and Public Cloud

As data centers transition to cloud architectures, network platforms must meet increasing challenges:

Support compute virtualization, provide sufficient access bandwidth, large MAC tables, and a "big Layer‑2" environment for VM migration.

Offer flexibility for resource deployment, rapid network adjustments, and free migration of network attributes.

Enable automated business deployment by integrating with cloud management platforms for end‑to‑end automation.

Traditional technologies such as IRF virtualization, Trill/FabricPath cannot satisfy these requirements, leading to the emergence of overlay technologies.

Overlay adds a logical network on top of the physical infrastructure based on business needs.

Overlay networks can be dynamically created to free virtual networks from physical constraints. IETF has defined three major overlay solutions: VXLAN, NVGRE, and STT, with VXLAN becoming the de‑facto industry standard.

Traditional VXLAN requires multicast routing in the underlay and management of VNI‑multicast group mappings, which hampers large‑scale deployments. Introducing an SDN controller to handle the VXLAN control plane is now the mainstream solution.

Transforming Traditional Networks to SDN

Key considerations include:

Not all devices support SDN; a thorough equipment evaluation is required.

Devices can operate in both IP forwarding and flow‑based modes, allowing a smooth transition.

SDN does not heavily consume network bandwidth.

Initial packets, ARP replies, and flow‑table installations typically stay below 300 Mbps (our controller handles 500 Kpps of Packet‑In).

By integrating traditional switches, vSwitches, NFV, and security appliances, SDN enables on‑demand provisioning of both physical and virtual resources, meeting needs such as centralized operations, flexible deployment, resource pooling, massive tenant scaling, tenant isolation, and reliable security.

The advantages of SDN have driven its commercial adoption beyond expectations.

Separating control and forwarding expands application scenarios, and as the SDN ecosystem matures, its development will accelerate.

NFV‑Based Products

Current NFV offerings include virtual routers (vSR), virtual firewalls (vFW), virtual load balancers (vLB), virtual wireless controllers (vAC), and virtual BRAS (vBRAS), all with mature products.

In public‑cloud VPCs, vSR can be deployed as a resource pool to serve as a VPN gateway for enterprise cloud access.

This diagram illustrates a typical NFV application scenario:

Some customers use vSR as a BGP route reflector to steer WAN traffic.

NFV development is faster abroad than in China, but domestic demand is rapidly growing.

SDN for Network Operations

Beyond data‑center deployment, SDN is being applied to operations, e.g., Baidu’s probe servers that send test packets from both ends of a link to assess quality. However, fixed‑path routing prevents full path coverage.

Using SDN, probe packets can be steered along all available paths to evaluate each link’s quality.

The SDN controller can generate probe packets, issue Packet‑Out to devices, and use OpenFlow to control their forwarding. Each forwarding device copies the packet and sends a Packet‑In back to the controller for comparison, yielding link‑quality metrics.

The southbound interface uses standard OpenFlow, making vendor differences irrelevant. An open‑source Opendaylight controller can host an operations app for visualizing data‑center network paths.

Overlay technology emerged to meet the "big Layer‑2" demand in cloud environments and to provide flexible networking. The underlay supplies connectivity and multi‑link load balancing without special topology constraints, requiring only reliable Layer‑3 forwarding.

Public‑cloud providers have the most urgent SDN needs; integrating SDN controllers with cloud platforms enables end‑to‑end automated service delivery, which is the primary value for cloud vendors.

While public‑cloud use cases are limited, private‑cloud adoption is accelerating, with financial institutions such as Industrial, Construction, and Agricultural Banks exploring SDN‑based network platforms.

Company’s SDN Solution Highlights

Our SDN controller, first demonstrated at an Internet conference in October, addresses traditional VXLAN overlay issues. Recent advances have improved controller cluster stability, supporting large‑scale deployments with high reliability and fail‑over mechanisms.

Operational features include radar detection and VM simulation for overlay visualization.

Solution offerings cover private‑cloud, elastic public‑cloud compute, and VPC services, already deployed at scale in Tencent Cloud and Alibaba Cloud.

Key controller characteristics:

Built on the Opendaylight open architecture, supporting OpenFlow, NETCONF, OVSDB, and PCEP southbound interfaces.

Uses OpenFlow for flow‑table distribution, NETCONF for switch configuration, and OVSDB for vSwitch configuration.

Northbound interfaces include standard RESTful APIs and Java APIs for integration with cloud management platforms and third‑party ecosystems.

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