If you want an overview of of the state-of-the-art open source networking stack, you can check this last year FOSDEM 2019 presentation by one of the developers of BISDN [1]. Somehow I don't think they mentioned SONiC in their presentation though.

I teach computer networking lab but for now we need to resort using dual boot Linux Switch Appliance (LISA) that uses custom kernel and another vanilla kernel running Quagga on multi-port Ethernet embedded PC. The good thing is that both LISA and Quagga use CLI environment similar to familiar Cisco switch/router IOS. I really wish there is an open source alternative offering that can seamlessly support layer 2 and layer 3 without dual boot, perhaps using Software Defined Networking (SDN) concept with an intuitive CLI.

Recently the new Shortest Path Bridging (SPB) has been integrated with 802.1Q since 2018 (bye-bye TRILL). I reckon any reasonably good Linux based open source layer 2 and 3 network OS player will be extremely popular overnight for enterprise, consumer and education. Together with eBPF this thing should be flying on the new off-the-shelf whitebox supporting 40Gbps multi-port Ethernet. Imagine a LAN or Metro LAN party with this beast :-)

[1]https://archive.fosdem.org/2019/schedule/event/from_closed_t...