SDN via Overlay expected to be the highest revenue-generating segment!

Future Market Insights reports estimate the SDN market valued at $95 billion by 2032. The revenue growth of SDN via Overlay projected to be the highest, with an estimated CAGR of approximately 17.8% from 2022 to 2032.

But, What is SDN via Overlay?

In my previous article, Software Defined Networking (SDN), described as abstractions or layers that contribute to innovation. SDN has undergone changes since its initial development, resulting in various implementations depending on how the controller layer connects to SDN devices. There are three categories of SDN.

??Open SDN: Open SDN has a centralized control plane and uses OpenFlow protocols for its southbound API.

SDN, according to the Open Networking Foundation (ONF), involves separating the Control Plane and Data Plane. This separation allows for networking devices to control or update using the OpenFlow control protocol. In OpenFlow, a flow rule comprises a Match-Action pair. When a packet matches the rule, a corresponding action gets applied. The OpenFlow protocol uses TLS (Transport Layer Security) for communication between the controller and the switch. With this protocol, a remote controller can add, update, or remove flow entries in a switch's flow tables.

Cisco partially supports openFlow 1.0 and openFlow 1.3 features, while HP, Juniper, and Huawei have played a crucial role in openFlow and SDN development and implementation. In Google's B4 networks, openFlow controllers are used for their private Software-Defined WAN.

OpenFlow is supported by many vendors like Aruba with their 2920 series switches, Cisco with the Nexus 3K, 9K series switches, and Juniper with the EX9200 series. Check out the lists of products certified as OpenFlow? Conformant.

??API SDN (or Unopened SDN): This model uses conventional methods like Simple Network Management Protocol (SNMP) or Command-Line Interface (CLI) to invoke the functions in remote devices, like switches. Through programming interfaces, often called southbound APIs, organizations control the flow of data to and from each device.

SDN via API first implemented by Cisco, enabling API-based access to networking device features using CLIs and SNMP. The addition of a RESTful API interface creates an extra layer of abstraction and enables legacy devices to be controlled by an SDN controller using non OpenFlow standards.

NetConf is a standardized protocol for retrieving and manipulating configuration data from switches. Till now, CLI is the standard interface to interact with network devices, but this is mainly for human. The main purpose of NetConf is network automation. RestConf is an HTTP-based protocol for programmatic access to YANG-defined data using NETCONF datastore concepts.

OpenFlow was born out of the Open Networking Foundation (ONF), a non-profit consortium, but companies like Google, Microsoft, Facebook, and Amazon also contributed to the development and sale of their own APIs.

Juniper introduced the SDN controller Contrail, which employs NETCONF and XMPP protocols rather than OpenFlow.?Cisco has two SDN-via-API controllers: APIC-EM (Application Policy Infrastructure Controller-Enterprise Module) and APIC-DC (focused on Data center). Arista's Software Driven Cloud Networking (SDCN) is based on its API-centric definition of SDN. Opendaylight (ODL) is a hybrid that uses OpenFlow and southbound APIs, such as NETCONF and BGP-LS/PCE-P, to control network devices.

??Overlay SDN: This model creates virtual network topologies on physical infrastructure, supporting layer2 or layer3 networks. To put it simply, overlays created by building a virtual network on top of a physical one.

The Network Hypervisor software abstracts network hardware, enabling virtual networks independent from the physical network.

In SDN, the virtual network traffic flows over the physical network infrastructure, with hypervisors injecting and receiving traffic in the overlay network. The key mechanism in this mode of SDN is network encapsulation, where one data structure hidden within another. The network hypervisor, based on information programmed by the controller, sends the encapsulated packet. This process referred as MAC in IP tunneling because the entire MAC frame encapsulated.

By utilizing APIs, applications can manage the establishment of virtual networks by assigning hardware resources like ports, VLANs, VXLANs, TCAMs, and bandwidth. Applications can also manage and monitor flows without knowledge of physical topology or exact flow locations in the physical network.

Different vendors use different encapsulation technologies with pros and cons, but the underlying idea is the same. VMware and Cisco use Virtual eXtensible Local-Area Network (VXLAN), while Microsoft prefers Network Virtualization using Generic Routing Encapsulation (NVGRE). VMware's Network Virtual Platform (NVP) was a popular hypervisor-based overlay SDN offering.

With Software for Open Networking in the Cloud (SONiC), Microsoft pioneered an open-source framework that allows running on diverse network AISCs using the Switch Abstraction Interface (SAI). SAI can be combined with any SDN model to establish a uniform interface for managing network switches. Each approach has its merits, and the choice depends on specific use cases and requirements.

Meta opted for the Open Compute Project (OCP) Switch Abstraction Interface (SAI) as the standardized and open API for their data center network hardware.

Key Takeways:

SDN is transitioning from early adoption to the early mainstream. Google, Meta, and Microsoft are among the cloud providers that have embraced and widely deployed it. Moreover, well-known network operators such as AT&T and NTT openly talk about deploying SDN-based solutions, particularly in the context of access networks. Enterprises have started adopting SDN for managing edge services provided by cloud providers. Network virtualization and SD-WAN have achieved notable success in the enterprise sector.

Sources: [1] Demystifying SDN part 3: SVN via Overlay by Javier Guillermo. [2] Why Overlay SDN by enterprisenetworkingplanet. [3] Future Market Insights reports on SDN [4] NetConf vs RestConf by Prasenjit Mana [5] What is Software Defined Networking by IBM