IOS XE is a new generation of IOS. The command in IOS XE is so similar to IOS. So if you used to know about IOS, it's no problem for you in IOS XE. IOS that runs on routers is a monolithic kernel that runs all of the necessary modules in the same memory space. If one process on your router have problem, It will affect the hold router. It's a critical problem for current network enviroment. For IOS XE, Cisco abstracted the system functions out of the main kernel and into separate processes. That means if one of them goes down, it won’t take the core kernel with it.
One more importance note is IOS XE developed in the modular approach on both hardware and software. Because of it’s modular design however, IOS XE allows the different planes to be run as their own individual processes, and even allows these processes to be run on different pieces of hardware. This also enhances redundancy, high availability, and you can balance the workload of the processes across multiple processor cores. As you see below, It is the packages of IOS XE, you can upgrade any package as you need. it will not affect to the other package.
- RPBase: Provides the operating system software for the Route Processor.
- RPControl: Controls the control plane processes that interface between the IOS process and the rest of the platform.
- RPAccess: Exports processing of restricted components, such as Secure Socket Layer (SSL), Secure Shell (SSH), and other security features.
- RPIOS: Provides the Cisco IOS kernel, which is where IOS features are stored and run. Each consolidated package has a different RPIOS.
- ESPBase: Provides the ESP operating system and control processes, and the ESP software.
- SIPBase: Controls the SIP operating system and control processes.
- SIPSPA: Provides the SPA driver and Field Programmable Device (FPD) images.
- Chassis Manager : Responsible for all chassis management functions, including management of the HA state, environmental monitoring, and FRU state control.
- Host Manager : Provides an interface between the IOS process and many of the information-gathering functions of the underlying platform kernel and operating system.
- Logger : Provides IOS facing logging services to processes running on each FRU.
- Interface Manager : Provides an interface between the IOS process and the per-SPA interface processes on the SIP.
- IOS: The IOS process implements all forwarding and routing features for the router.
- Forwarding Manager: Manages the downloading of configuration to each of the ESPs and the communication of forwarding plane information, such as statistics, to the IOS process.
- Pluggable Services: The integration point between platform policy application, such as authentication and the IOS process.
- Shell Manager: Provides all user interface features and handling related to features in the nonIOS image of the consolidated package, which are also the features available in diagnostic mode when the IOS process fails.
- SPA driver process: Provides an isolated process driver for a specific SPA.
- CPP driver process: Manages the CPP hardware forwarding engine on the ESP.
- CPP HA process: Manages HA state for the CPP hardware forwarding engine.
- CPP SP process: Performs high-latency tasks for the CPP-facing functionality in the ESP instance of the Forwarding Manager process.