The Emergence of Hybrid-SDN

• Tofino (Barefoot Networks, 2016)
  
• Tofino 2 (Barefoot Networks, 2018)
  
• Tofino 3 (Intel, 2021)
  
• A Programmable ASIC has been released that allows some of the functions of the Control Plane, previously managed by the SDN Controller, to be implemented directly on SDN switches equipped with this ASIC through separate programming.
• The first official Programmable ASIC is Barefoot Networks' Tofino.
• Barefoot Networks' Tofino supports controlling the ASIC using P4, an open-source programming language.
• P4 (Programming Protocol-independent Packet Processors)
  • A high-level language designed for programming the behavior of the network data
    plane.
  • P4 aims to maximize the flexibility and programmability of network hardware by allowing the processing methods of network packets to be defined in software.
• If a function to add tags to data packets is introduced, these tags could enable the measurement of network quality, such as packet load and delays, as the data packets traverse network devices.
• A top-down control method is now feasible, where data packets entering the switch can be processed autonomously by the switch itself, without the control or configuration from the SDN controller.
• The advent of Programmable ASICs has transformed the structure of SDN into a Hybrid-SDN, a middle ground between traditional networks and SDN.
  
• According to one study, Hybrid-SDN switches, which can autonomously apply self-learning forwarding rules when control plane rules do not match, can reduce the load on the control plane.