Contiki-NG vs VxWorks

Contiki-NG is a free, open-source operating system for resource-constrained Internet of Things devices, designed for low-power communication and standard protocols. Its code footprint is on the order of 100 kB, and memory use can be configured as low as 10 kB. The IPv6 stack includes TCP, UDP, DNS, RPL, CoAP, LWM2M, and WebSockets, with IEEE 802.15.4 and TSCH support below IPv6. Documented modules include IPv6 multicast, OMA LWM2M, secure CoAP, 6TiSCH, and SNMP. Security documentation describes DTLS with Mbed TLS, pre-shared keys or certificates, and EDHOC key exchange. Link-layer security is supported for IEEE 802.15.4 TSCH; CSMA link-layer security is described as planned. Documented hardware includes TI, Nordic, Silicon Labs, OpenMote, Tmote Sky/TelosB, and Zolertia boards. Development resources include Cooja native motes, a Renode tutorial, Docker, and native Linux and macOS toolchain setup. It is available for Linux, macOS, Windows, and self-hosted environments, and source code is distributed under the 3-clause BSD license unless otherwise specified.

VxWorks has no write-up on Specifiction yet; its figures are above.