DNOS

DNOS or Dell Networking Operating System is an operating system running on switches from Dell Networking. It is derived from either the PowerConnect OS (DNOS 6.x) or Force10 OS/FTOS (DNOS 9.x) and will be made available for the 10G and faster Dell Networking S-series switches, the Z-series 40G core switches and DNOS6 is available for the N-series switches.

The DNOS family comes in two main versions:

Only the PowerConnect 8100 will be able to run on DNOS 6.x: all other PowerConnect ethernet switches will continue to run its own PowerConnect OS (on top of VxWorks) while the PowerConnect W-series run on a Dell specific version of ArubaOS. The Dell Networking S- xxxx and Z9x00 series will run on DNOS where the other Dell Networking switches will continue to run FTOS 8.x firmware.

Three of the four product families from Dell Networking are using the Broadcom Trident+ ASIC's, but the company doesn't use the API's from Broadcom: the developers at Dell Networking have written their own Hardware Abstraction Layer so that DNOS 9.x can run on different hardware platforms with minimal impact for the firmware. Currently three of the four DN switch families are based on the Broadcom Trident family (while the 4th - the E-series- run on self-developed ASIC's); and two of them are running DNOS 9.x (S- and Z- series) and if the product developers want or need to use different hardware for new products they only need to develop a HAL for that new hardware and the same firmware can run on it. This keeps the company flexible and not dependent on a specific hardware-vendor and can use both 3rd party or self designed ASIC's and chipsets.

The underlying OS on which DNOS 9.x, runs, is based on NetBSD (while the DNOS 6.x runs on a Linux kernel), an implementation which is often used in embedded networking-systems. NetBSD is a very stable, open source, OS running on many different hardware platforms. By choosing for a proven technology with extended TCP functionality built into the core of the OS it reduces time during development of new products or extending the DNOS with new features.

DNOS 9.x is also modular where different parts of the OS run independent from each other within one switch: if one process would fail the impact on other processes on the switch are limited. This modular setup is also taken to the hardware level in some product-lines where a routing-module has three separate CPU's: one for management, one for L2 and one for L3 processing. This same approach is also used in the newer firmware-families from Cisco like the NX-OS for the Nexus product-line or the IOS XR for the high-end routers (the Carrier Routing Systems) from Cisco. (and unlike the original IOS: processes under IOS aren't isolated from each other). This approach is regarded not only a way to make the firmwares more resilient but also increases the security of the switches

...
Wikipedia