2.3 Summary

Hosts, which communicate with peers, implement their networking software functions over a host operating system like UNIX. The functions can be in the user mode or kernel mode. STREAMS is an example of a framework for building networking stacks in the UNIX environment. The performance of host-based networking software is not high, due to several reasons-restrictions of the operating system, legacy code, kernel- to user-mode transitions, and so on.

Embedded communications devices typically use a real-time operating system as the platform for building their software functions. The RTOSes may be available from vendors or built in house. Using a commercial RTOS with standard APIs permits application portability. Memory considerations like booting, flash, and DRAM versus SRAM are all important in embedded communications systems.

An implementation of the system will require clear partitioning of the control plane, data plane, and management plane. In the data plane, both fast-path and slow-path processing will need to be identified. Hardware acceleration via ASICs and NPs can be used for specific functions in the data plane fast path.