In modern times, companies rely heavily on networks that link their offices, telecommuters, applications, data centers, and cloud services from different geographic locations. The farther their environments spread, the more difficult it becomes to operate within the framework of a traditional WAN. Static routing may become problematic when changes happen in terms of congestion, delay, packet loss, or application needs.
SD-WAN or software-defined wide area networking refers to an alternative approach based on software that gives companies an opportunity to manage various network links and make routing decisions according to application needs and current network state.
When wondering how does SD-WAN work in practice, it is necessary to find out how all these elements interact with each other.
What Is SD-WAN?
SD-WAN is a technology that allows management of wide area networks using software-defined mechanisms. SD-WAN technology decouples traffic management from the underlying connections of the network, providing the administrator with more control over data transfers across the network.
The company may use different connectivity services in its branches, such as broadband, dedicated circuits, or mobile connections. Instead of managing each service separately, SD-WAN will manage them all under predefined policies.
It will recognize applications, measure network conditions, and decide which connection should be used for specific traffic types. As a result, the network will be more flexible compared to one based on static routing architecture.
How Does SD-WAN Work?
The simple procedure includes four major steps: classification of traffic, measurement of network condition, implementation of policies, and path selection.
When the traffic is introduced to an SD-WAN environment, it identifies the kind of application or traffic that it is. It also analyzes the various possible paths in the network based on metrics like latency, jitter, packet loss, and bandwidth.
Then, the system evaluates them against existing policies. An application such as real-time collaboration, for instance, could need lower latency and less packet loss. A file transfer would have less stringent demands and can go through another connection.
The SD-WAN solution will then send traffic through an appropriate path. In case of changes in conditions, it can always make a new decision based on the configuration rules.
This ongoing process enables the traffic management to be adaptive to real conditions in the network instead of following only predefined paths.
Core Components of an SD-WAN Architecture
While different implementations exist, there are some elements that typically constitute an SD-WAN infrastructure.
SD-WAN Edge
The edge component is a component that runs at a branch office or any other remote site. It forwards traffic and imposes the rules by which various flows will make use of the connections that are available.
Centralized Management
Centralized management offers the capability to deploy and manage policies at different sites.
Underlay Network
An underlay includes the actual or virtual links used to transmit traffic. Organizations can employ various connectivity solutions based on their location, availability of resources, performance, and costs.
Overlay Network
An overlay represents logical links over the underlying network. A secure tunnel can be created to connect locations, making it possible to establish central policies for traffic transfer.
Traffic Policies
Policies represent the way applications and traffic classes can make use of network resources. These policies may take into account the application priority, performance requirements, and security.
How Intelligent Traffic Management Works
The biggest benefit of SD-WAN lies in the use of current data for routing decisions.
Suppose that there is a branch office and two connectivity options are available. With the static routing system, the important traffic may still use the same route even if it is congested. The SD-WAN system allows monitoring of the connection and comparison of the status with performance parameters.
Once packet loss or latency exceeds a particular threshold, the system can reroute traffic to another route. When the condition gets better, policies may decide on returning traffic to its original route.
This does not imply that each and every SD-WAN solution will select the fast path without fail. This is because the administrators will specify the criteria and conditions, and the software will apply them consistently.
It can be considered an extension of traffic engineering techniques used in network traffic, where traffic is managed based on the capacity and performance of the network.
SD-WAN Compared With Traditional WAN
The difference between SD-WAN and a traditional WAN is primarily about how network resources are controlled and managed.
| Area | Traditional WAN | SD-WAN |
| Routing | Often based on predefined routes | Policy-driven and condition-aware |
| Connectivity | Frequently centered on dedicated links | Can combine different connection types |
| Management | Configuration may be distributed | Centralized policy management |
| Path selection | Usually more static | Can respond to changing conditions |
| Application handling | Limited depending on design | Can apply application-aware policies |
| Scalability | More manual administration | Policies can be applied across locations |
| Visibility | May require multiple tools | Centralized monitoring is common |
The distinction becomes more important as organizations add branches, cloud applications, remote users, and multiple connectivity providers.
Why Organizations Use SD-WAN
The reason why organizations think about SD-WAN is that there might be problems managing the network or there will be variation in application performance from one location to another.
Some common use cases where SD-WAN is used by organizations include:
- Connection of physically scattered offices via several network links.
- Prioritization of important applications over others.
- Running applications hosted on the Internet from branch offices.
- Using different routes if the main route fails.
- Managing traffic uniformly at several different branches.
Another important aspect that organizations may take into consideration is connectivity. The organization may have several different network links but no efficient way to manage them. SD-WAN can help in this regard.
What Happens During a Network Failure?
The other vital aspect of SD-WAN is network resilience. In case there is a loss of active connection or it does not adhere to predefined criteria, the SD-WAN solution can pick another suitable route.
As an illustration, the branch may choose to direct its traffic via one connection but at the same time have another connection that it can use as an alternative if necessary.
It will all depend on the settings that one opts for; it might be possible for an organization to use the connection mainly for redundancy or direct its traffic via several connections based on types of traffic.
SD-WAN and Network Security
Traffic management cannot be fully separated from security. Distributed networking generates more pathways to connect users, branches, applications, and services, making consistent security controls necessary.
SD-WAN architectures could include encrypted tunnels, segmentation, access control, and many other types of security controls depending on the architecture and implementation.
Organizations thus need to consider SD-WAN within the larger context of network and security strategies. For an effective implementation, it is crucial to make appropriate choices regarding application access, segmentation, monitoring, identity, encryption, and policy enforcement.
The SD-WAN service architecture gives further technical background on application flows, policies, underlay connectivity, SD-WAN edges, and policy-based traffic management.
What Should Organizations Consider Before Deployment?
SD-WAN can simplify network administration, but deployment still requires planning. Organizations should understand their existing infrastructure before deciding how to introduce the technology.
Important considerations include:
- Current network connections and their performance characteristics.
- Critical applications and their latency or bandwidth requirements.
- Existing routing and security architecture.
- Number of locations and expected future expansion.
- Monitoring and troubleshooting requirements.
- Policies for failover and traffic prioritization.
It is also useful to establish measurable objectives before deployment. Simply adding multiple connections does not guarantee better performance. The organization needs policies that connect network behavior with actual business and application requirements.
The Future of Intelligent WAN Management
As organizations use cloud applications, distributed workforce, remote offices and internet-based services, the network traffic is constantly evolving. Today users are not bound by a centralized application access point any more.
Thus intelligent traffic management becomes more and more relevant. SD-WAN creates a system of management and coordination of various paths with the help of policy enforcement via software, reacting to the changes.
The key point here is not to have several connections. Much more important is to manage these connections in an intelligent way, knowing the needs of the applications, the state of networks and applying policies.
For those who are planning to look into their WAN strategies, SD-WAN can be a good introduction.
FAQs
1. Does SD-WAN replace traditional WAN?
Not necessarily. SD-WAN can be used on top of the current WAN connections and control how data flows over them. It just redefines the method of connectivity rather than replacing the infrastructure.
2. Can SD-WAN improve application performance?
SD-WAN can enhance application performance through intelligent path selection based on configured policies and network status. The outcome depends on the connectivity, applications, architecture, and implementation.
3. Does SD-WAN require multiple network connections?
No. Multiple connections are not mandatory for every deployment. However, having more than one path can provide additional flexibility for traffic management, redundancy, and failover.
4. Can SD-WAN be used by small businesses?
Yes, SD-WAN can be used by organizations of various sizes. The applicability of SD-WAN technology is determined by such aspects as number of locations, complexity of the network, applications, connectivity, security requirements, and others.
