Overlay technologies in data center

Everyone speaks about SDN an the benefits its brings when deploying cloud or enterprise infrastructures. But do we actually know or have any understanding what this all SDN is about? If you want be fluent in the language of virtual networking and network overlays in modern data centers you need to understand at least the following concepts:

• SDN controller (Northbound and Southbound API) (an example controller could be VMware NVP/NSX or OpenDaylighta; a list of vendor specific Northbound API)
• Openflow as Southbound API (example flow in Open vSwitch)
• Network Functions Virtualization
• Overlay and tunnels concept for cloud network inside data center (example protocols are VXLAN and STT)

In the remaining of the post we will concentrate solely on existing overlay technologies. These information was extracted from Cisco doc: Cisco Nexus 9000 Series Switches - Data Center Overlay Technologies).

Network-Based Overlay Networks

1. IEEE 802.1ad Provider Bridging or IEEE 802.1q Tunneling also known as IEEE 802.1QinQ or simply Q-in-Q
2. IEEE 802.1ah Provider Backbone Bridges (PBB) or Mac-in-Mac Tunnels
3. Cisco FabricPath allows multipath networking at Layer 2
4. TRILL - IETF Transparent Interconnection of Lots of Links is a Layer 2 multipathing technology
5. Shortest-Path Bridging (SPB) is defined in IEEE 802.1aq and is targeted as a replacement for Spanning Tree Protocol (example info based on Avaya documentation)
6. Cisco Overlay Transport Virtualization (OTV) is a Layer 2-over-Layer 3 encapsulation "MAC-in-IP" technology
7. The Cisco Location/Identifier Separation Protocol (LISP) is currently defined as a Layer 3 overlay scheme over a Layer 3 network
8. Multiprotocol Label Switching (MPLS)
9. Virtual Private LAN Service (VPLS) a Layer 2 tunneling protocols
10. Virtual Private Routed Network (VPRN) also known as BGP/MPLS or IP-VPN provides IP VPN services

Host-Based Overlay Networks

1. Virtual Extensible LAN (VXLAN) is a Layer 2 overlay scheme over a Layer 3 networ that uses IP/UDP encapsulation
2. Network Virtualization Using Generic Routing Encapsulation (NVGRE) allows creation of virtual Layer 2 topologies on top of a physical Layer 3 network
3. Stateless transport tunneling (STT) is an overlay encapsulation scheme over Layer 3 networks that use a TCP-like header