10 Difference Between Underlay And Overlay Networks

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What Is Overlay Network?

Overlay networking also referred to as SDN, is a method of using software to create layers of network abstraction that can be used to run multiple separate, discrete virtualized network layers on top of the physical network, often providing new application or security benefits. All nodes in an overlay network are connected with one another by means of logical or virtual links and each of these links correspond to a path in the underlying network.

Overlay network protocols include Virtual Extensible LAN (VXLAN), Network Virtualization using Generic Encapsulation (NVGRE), Stateless Transport Tunning (SST), Generic Routing Encapsulation (GRE), IP multicast and Network Virtualization overlays 3 (NVO3). Common examples of an overlay network are distributed systems such as peer-to-peer networks and client server applications because their nodes run on top of the internet.

What You Need To Know About Overlay Networks

  1. An overlay network is a logical computer telecommunications network that is built on top of another network and is supported by its infrastructure (physical components).
  2. The nodes of the overlay network are interconnected using virtual or logical links, which form an overlay topology. Though these nodes may be connected through physical links in the underlying networks.
  3. The purpose of the overlay network is to add missing functionality without a complete network redesign.
  4. Overlay networks link to the existing network through virtual or physical nodes.
  5. Two overlay nodes may be connected with a logical connection despite being several hops apart in the underlying network.
  6. The overlay network interconnects all the application nodes and provides the basic communication primitives such as flooding, random walks or point-to-point overlay message routing and multicast.
  7. Overlay network protocols include Virtual Extensible LAN (VXLAN), Network Virtualization using Generic Encapsulation (NVGRE), Stateless Transport Tunning (SST), Generic Routing Encapsulation (GRE), IP multicast and Network Virtualization overlays 3 (NVO3).
  8. Examples of overlay network deployments include Virtual private networks (VPNs), peer-to-peer (P2P) networks, continent delivery networks (CDNs), voice over IP (VoIP) services such as Skype and non-native software-defined networks.

What Is Underlay Network?

An underlay Network is a physical infrastructure above which overlay network is built. It is the underlying network responsible for delivery of packets across networks. In data center environments, the role of the physical underlay network is to provide Unicast IP connectivity from any physical device (server, storage device, router or switch) to any other physical device.

What You Need To know About

  1. Underlay network is a physical infrastructure above which overlay network is built.
  2. In data center environments, the role of the physical underlay network is to provide Unicast IP connectivity from any physical device (server, storage device, router or switch) to any other physical device.
  3. Underlay network is the underlying network responsible for delivery of packets across networks.
  4. An ideal underlay network provides low-latency, non-blocking, high-bandwidth connectivity from any point in the network to any other point in the network.
  5. The intrinsic features of the underlay network determine the efficiency of the overlay.
  6. Underlay network is designed to provide less Scalability due to technology limitation.
  7. Less scalable options of multipath forwarding. In fact using multiple paths can have associated overhead and complexity.
  8. Underlay network is responsible for delivery of Packets.

Also Read: Difference Between Peer-To-Peer Network And Client-Server

Difference Between Overlay And Underlay Network In Tabular Form

BASIS OF COMPARISON UNDERLAY NETWORK OVERLAY NETWORK
Description Underlay Network is physical infrastructure above which overlay network is built. An Overlay Network is a virtual network that is built on top of an underlying Network infrastructure/Network layer (the underlay).
Traffic Flow Transmits packets which traverse over network devices like switches and routers. Transmits packets only along the virtual links between the overlay nodes.
Deployment Time Less scalable and time consuming activity to setup new services and functions. Ability to rapidly and incrementally deploy new functions through edge-centric innovations.
Packet Control Hardware oriented. Software oriented.  
Packet Encapsulation And Overhead Packet delivery and reliability occurs at layer-3 and layer-4. Needs to encapsulate packets across source and destination, hence incurs additional overhead.
Multipath Forwarding Less scalable options of multipath forwarding. In fact using multiple paths can have associated overhead and complexity. Support for multi-path forwarding within virtual networks.
Managing Multitenancy NAT or VRF based segregation required which may face challenge in big environments. Ability to manage overlapping IP addresses between multiple tenants.
Scalability Less Scalable due to technology limitation.   Designed to provide more scalability than underlay network. E.g VLAN (Underlay Network) provides 4096 VLAN support while VXLAN (Overlay Network) provides up to 16 million identifiers.
Packet Delivery Responsible for delivery of packets. Offloaded from delivery of packets.  
Protocols Underlay protocols include Ethernet Switching, VLAN, Routing etc. Overlay network protocols include Virtual Extensible LAN (VXLAN), Network Virtualization using Generic Encapsulation (NVGRE), Stateless Transport Tunning (SST), Generic Routing Encapsulation (GRE), IP multicast and Network Virtualization overlays 3 (NVO3).  

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