Overlay vs Underlay Networks

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 Tunneling (STT), Generic Routing Encapsulation (GRE), IP multicast and Network Virtualization overlays 3 (NVO3).

 

Old protocols = VLANs and MPLS, are now replaced by VXLAN which is more scalable .

Ref: https://vivadifferences.com/10-difference-between-underlay-and-overlay-networks/

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