In a complex networking world, the difference between underlay and overlay network technologies and functionality is useful to understand.
An underlay network essentially consists of the physical infrastructure: including the switches, routers and cables that provide the foundation for all network communication - including the modern Internet. The stability and reliability of this underlay network is crucial for effective network architecture planning, communication and functionality.
Network communication is built on layers 1 to 3 of the OSI model, where technologies such as MPLS (multiprotocol label switching), DWDM (dense wavelength division multiplexing), ethernet, and numerous protocols that comprise the modern Internet are utilized. Understanding the underlay network is essential for optimal network planning, expansion, flexibility and scalability. While MPLS-based transport has been a key technology since the early 1990s, modern underlay networks increasingly rely on optical and ethernet services. These services are particularly attractive to enterprises due to their high capacity, low latency and enhanced security. They are often marketed as 'private connectivity'.
Additionally, direct connectivity to the cloud via optical transport services is ideal for companies managing large volumes of critical traffic, such as those in the gaming, finance, or manufacturing sectors.
Put simply, an overlay network is a virtual network built on top of another network, which serves as its foundation. This virtual network consists of nodes that are logically and virtually connected, and may exist only on a server, or on a dedicated box at a network site. Overlay networks come with several key attributes and components, including security features such as DDoS mitigation, quality of service (QoS), SD-WAN, encryption, bandwidth control and various protocols (e.g. BGP and VPN). All these elements enhance the communication capabilities of the underlying networks, making them more intelligent and flexible. This higher level of functionality allows for deeper customization, greater network optimization and better performance, as well as enhanced control and security.
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Underlay network |
Overlay network |
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Definition |
The physical network infrastructure, including hardware and physical connections. |
A virtual network built on top of an underlay network, using logical connections. |
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Components |
Routers, switches, physical cables, and other hardware. |
Virtual nodes, logical links, and software-defined elements. |
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Functionality |
Provides basic connectivity and data transport. |
Enhances functionality with features like security, QoS, and encryption. |
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Flexibility |
Less flexible, changes require physical modifications. |
Highly flexible, changes can be made through software configurations. |
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Customization |
Limited customization options. |
Allows for deep customization and optimization. |
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Security |
Basic security measures, often reliant on physical security. |
Advanced security features like DDoS mitigation, encryption and inbuilt firewalls |
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Protocols |
Standard networking protocols (e.g., IP, ethernet). |
Additional protocols (e.g., VPN, SD-WAN) for enhanced functionality. |
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Management |
Managed through physical network management tools. |
Managed through software-defined networking (SDN) controllers. |
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Use Cases |
Traditional networking environments, data centers, enterprise networks. |
Cloud services, virtual private networks (VPNs) and software-defined wide area networks (SD-WAN). |
SD-WAN is a virtual connectivity solution that decouples network control and management from the data plane, allowing it to function over any type of service-agnostic underlay. This underlay could range from multi-protocol label switching (MPLS) to dedicated Internet access (DIA) services. Essentially, SD-WAN operates as an overlay on top of an existing network infrastructure, enhancing the connectivity and performance across various sites.
One of the key advantages of using Arelion’s Internet backbone as an underlay is the vast capacity it offers. Additionally, with one of the largest and most robust global IP backbones, Arelion ensures your global WAN is supported with ample bandwidth and a high level of reliability, along with an enviable service level agreement (SLA).
For enterprises undergoing digital transformation, the ability to scale their network is fundamental. A robust and unified Internet underlay provides the necessary bandwidth, broad service coverage, and effective quality of service (QoS) management.
