Router Security Strategies: Securing IP Network Traffic Planes

Appendix C. Cisco IOS to IOS XR Security Transition

Cisco IOS has been the mainstay for all Cisco routers for more than 20 years. This monolithic operating system, which disassociates the software architecture from hardware, has proven resilient to massive upgrades in both hardware and software technologies over the years. The term monolithic means that Cisco IOS runs as a single image and all processes share the same memory space, and that it uses a non-preemptive scheduler. In support of carrier-class IP networks, including continuous system operation and unprecedented service flexibility, the Cisco IOS XR operating system was pioneered for the Cisco CRS-1 and 12000 series platforms. Cisco IOS XR uses a real-time microkernel operating system ...