In the context of applying SDN switches in various scenarios, a concise yet flexible summary is often used. It's important to note that the SDN switch discussed here does not necessarily refer to an OpenFlow-based switch. Instead, it is more common for traditional switches to incorporate a Cloud Agent. Providing an open API—such as JSON-RPC or REST API—can be a more practical approach for integration and deployment.
SDN technology has been evolving for several years, and cloud computing has an even longer history. The combination of these two technologies has become a powerful application for SDN, gaining significant attention over the past few years. Consulting firms have increasingly recognized the potential of SDN, with market growth being consistent. The focus on market share here mainly refers to the use of SDN in cloud networking environments.
When it comes to the application of SDN in cloud networks, there are generally two main approaches: the "soft" approach represented by VMware and the "hard" approach represented by Cisco. The soft approach involves implementing network virtualization logic directly within the hypervisor on the server, with the physical network acting only as a transport layer. On the other hand, the hard approach places the core network virtualization logic within the physical network, typically at the top-of-rack (TOR) switch. If this is not feasible, it may be placed on dedicated devices. Both approaches have their strengths and attract different user bases.
However, the real world is rarely unipolar or bipolar—it is inherently multipolar. Many unconventional requirements exist in actual networks that cannot be effectively addressed by these two approaches, or even if they can, the solutions may not be optimal in terms of implementation complexity, performance, or cost. As a provider of long-term hardware SDN solutions, I'd like to share how real-world hardware SDN switches can address specific scenarios in cloud networks, whether public or private. Private clouds, in particular, often involve more customized needs.
It should be noted that some scenarios can be achieved using Cisco’s ACI, as its fundamental concept is based on using hardware SDN to support network virtualization. However, many users choose not to adopt ACI due to factors such as high cost, vendor lock-in, or a preference for more flexible solutions. While ACI is a strong solution, it's not the only option, and from a technical perspective, I personally appreciate its design.
**Customization Requirements for SDN Controllers and Switches in Cloud Computing Networks**
There are common misunderstandings about how SDN switches are applied in cloud computing networks. Two of the most frequent misconceptions are: first, people often ask which controller we use and whether it can integrate with OpenDaylight, Ryu, or ONOS. Second, they assume that any SDN switch can support cloud computing scenarios regardless of the vendor. These misunderstandings stem from a lack of understanding that SDN requires application-specific customization. Unlike general-purpose tools, cloud computing networks are often designed with a single function in mind—fulfilling specific cloud requirements. In some cases, the controller might even be embedded within the cloud platform itself, such as in OpenStack Neutron. Therefore, a general-purpose SDN controller is not suitable for cloud environments, and vice versa.
Similarly, the idea that any SDN switch can support cloud networking is also incorrect. Just as controllers need to be tailored for cloud use, SDN switches must also be customized. This is why specialized, deeply integrated solutions are necessary. For example, Shengke Network has developed specific controller and switch functions tailored for cloud computing scenarios.
**Scenario 1: Using Hardware SDN Switches to Improve Performance**
In this scenario, network virtualization is implemented using Tunnel Overlay. However, the performance impact of vSwitch handling tunnel operations (like VxLAN or NvGRE) can be significant, leading to reduced throughput, increased latency, and jitter. To address this, an SDN TOR switch can offload these performance-intensive tasks, allowing the server-side vSwitch to remain unchanged. The SDN TOR switch acts as an extension of the vSwitch, and in some cases, it can even handle distributed Layer 3 gateway functions, making it deeply involved in network virtualization.
This model is not universally accepted, but it has proven effective in several small and medium-sized private clouds and a well-known IDC cloud. The performance and stability improvements have been significant, as shown in the diagram below.
[Image: Analysis of the role of SDN switches in cloud computing networks in different scenarios]
**Scenario 2: Using a Hardware SDN Switch to Access Physical Servers**
Many believe all servers in cloud data centers are virtualized, but this is far from the truth. In reality, many public and private clouds still rely heavily on physical servers. Some servers lack virtualization capabilities, while others run resource-heavy applications where VM performance is unreliable. Others are custom-built, or customers prefer not to share them physically for security reasons. These are real and valid demands.
While VLANs can manage isolation, tunneling introduces challenges. Configuring VTEP on the server is one option, but it affects performance. Another is to install a special vSwitch, which increases workload and uncertainty. For these cases, many providers, including VMware, use a hardware SDN switch as a VTEP Gateway to connect physical servers to the virtual network without requiring changes on the server side. This requires the SDN switch to support both tunnel bridging and routing, which many standard switches do not. Cisco ACI supports this, but it comes at a cost. Shengke’s SDN switches, however, support both features from the start and are widely deployed in public clouds.
[Image: Scenario architecture with SDN switches]
**Scenario 3: Using a Hardware SDN Switch to Connect a Hardware Firewall**
Hardware firewalls are commonly used in cloud environments, especially in private and hosted clouds. Some customers insist on using their own hardware firewalls, which must be connected to the cloud network. Traditional methods like ACLs don’t work well in dynamic environments where VMs are constantly created and moved. SDN switches excel here by enabling dynamic policy enforcement. When tunnels are used, the SDN switch can terminate the tunnel and convert it to VLAN for the firewall, ensuring seamless integration.
Shengke’s SDN switches support unique VLANs per port, avoiding the limitations of traditional VLANs and addressing scalability concerns.
**Scenario 4: Supporting Multiple Hypervisors with Hybrid Networking**
The challenge arises when supporting multiple hypervisors, particularly when integrating VMware with open-source platforms like KVM or Xen. VMware is closed-source, and its integration with cloud platforms can be complex. Customers want to maintain existing VMware infrastructure while adopting newer technologies like VPC. An effective solution is to use an SDN switch to access VMware servers, converting VLANs to tunnels and enabling firewall integration. This approach has been successfully deployed in industry cloud environments, offering flexibility without the cost of NSX.
[Image: Architecture for hybrid hypervisor networking]
**Scenario 5: Deploying VLANs on Demand with a Hardware SDN Switch**
While not everyone prioritizes VLANs, some customers do. In small private clouds, VLANs are often used for simplicity and performance. However, managing VLANs dynamically during VM migrations can be challenging. Pre-configuring all possible VLANs on every port leads to inefficiencies and security risks. A better solution is to use an SDN switch to dynamically configure VLANs as needed, improving efficiency and reducing unnecessary traffic.
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