Differences between IOS and IOS XE

IOS

• It is a monolithic OS

• All features  are on the same file

• if  One process fail the whole box will crash

• Reboot Needed to perform an upgrade

IOS XE

• Modular software updates
• High Availability
• Linux  with IOS interface
• Configuration grouped by Process
• APIs that will make it programmable
• Platforms  ASR1k; CAT4500E/SUP7E; ASR 903: CSR1000v

IOS XE
Made of
    Consolidated packages -

•         RP Base
•         RP control
•         RP Access
•         RP Access
•         RP IOS  ---> IOS 15 code functionality
•         ESP base  FW intelligence
•         SIP Base
•         SIP SPA Share port Adapater

    Could be updated it in mass
    or individually ,
              if that's the case  you will need a provisioning file to boot it
   
    Optional packaged
        Webex Node <--- Example
       
Individual Processes

•     Logger
•     Chassis Manager  HA/RP
•     IOS
•     Pluggable Server
•     SPA driver
•     Host Manager
•     Interface Manager
•     Forwarding Manager
•     Shell Manager
•     CPP Driver/HA/SP

Impact to troubleshooting and performances

•    IOS XE (IOS 15.0) runs as a single daemon within a Linux operating system 
•   Additional system functions now run as additional, separate processes in the host OS environment
•    IOSd within the IOS XE environment supports multiple threads and multi-core CPUs
•   Wireshark and Mediatrace included, runs separately from IOS

Excluding specific platform's architecture

•  Non-IOS applications can either be tightly integrated with IOS or they could run side-by-side with IOS with very little or no interactions
•     If an application does require services from IOS, it integrates with IOS through a set of client libraries called "service points"