IOS does however support aliasing of duplicated virtual memory contents to the same physical memory. Therefore the addressable memory is limited to the physical memory of the network device on which the operating system is installed. The Cisco IOS kernel does not perform any memory paging or swapping. The entire physical memory is mapped into one virtual address space. The Cisco IOS monolithic kernel does not implement memory protection for the data of different processes. IOS considers each process a single thread and assigns it a priority value, so that high priority processes are executed on the CPU before queued low priority processes, but high priority processes can not interrupt running low priority processes. Instead the process must make a kernel call before other processes get a chance to run. There is no memory protection between processes and IOS has a run to completion scheduler, which means that the kernel does not pre-empt a running process. This means that all processes have direct hardware access to conserve CPU processing time.
The Cisco Catalyst series would for some time run the CatOS. The company acquired a number of young companies that focused on network switches, such as the inventor of the first Ethernet switch Kalpana, and as a result Cisco switches did not run the IOS. When IOS was developed, Cisco Systems' main product line were routers. Through modular extensions IOS has been adapted to increasing hardware capabilities and new networking protocols.
The IOS network operating system was developed in the 1980s for routers that had only 256 kB memory and low CPU processing power. Notable exceptions include ASA security products, which run a Linux-derived operating system, carrier routers which run IOS-XR and Cisco's Nexus switch and FC switch products which run Cisco NX-OS.
Although the IOS code base includes a cooperative multitasking kernel, most IOS features have been ported to other kernels such as QNX and Linux for use in Cisco products.
IOS is a package of routing, switching, internetworking and telecommunications functions integrated into a multitasking operating system. ( February 2015) ( Learn how and when to remove this template message)ġ5.9(3)M / August 15, 2019 2 years ago ( )Ĭisco Internetwork Operating System ( IOS) is a family of network operating systems used on many Cisco Systems routers and current Cisco network switches. Please help to improve this article by introducing more precise citations.
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