According to Cisco's product literature, IOS XR shares very little infrastructure with the other IOS trains, and is instead built upon a "
preemptive,
memory protected,
multitasking,
microkernel-based operating system". The microkernel was formerly provided by
QNX; versions 6.0 up to 7.5.2 use the
Wind River Linux distribution. From version 7.6.1 and onwards, the kernel has been switched to
OpenEmbedded. IOS XR aims to provide the following advantages over the earlier IOS trains: • Improved
high availability (largely through support for
hardware redundancy and fault containment methods such as protected memory spaces for individual processes and process restartability) • Better scalability for large hardware configurations (through a
distributed software infrastructure and a two-stage
forwarding architecture) • A
package based software distribution model (allowing optional features such as
multicast routing and
MPLS to be installed and removed while the router is in service) • The ability to install package upgrades and
patches (potentially while the router remains in service) • A web-based
GUI for system management (making use of a generic,
XML management interface) ==History==