Methods and apparatus for performing in-service software upgrade for a network device using system virtualization

A method for modifying software in a network system, comprising:

• creating a second virtual machine (“VM”) on a control card in response to a program modification signal;
• loading a second version of program to the second VM while maintaining a first version of program running on a first VM for providing network management;
• migrating program execution for network management from the first version of program operated on the first VM to the second version of program operated on the second VM;
• and
• facilitating in-service software upgrade (“I SSU”) for at least one data-path module in response to the first version and second version of programs,
• wherein creating the second VM on the control card includes establishing a new operating system operating as a new virtual entity running concurrently with the first VM on a processing card,
• wherein loading the second version of program to the second VM while maintaining a first version of program running on a first VM for providing network management includes installing a new release of software to a virtual process running on the second VM while allowing existing software running on the first VM to continue providing network management, and
• wherein migrating program execution for network management includes gradually transitioning hardware resource from the first VM to the second VM in accordance with a predefined resource allocation schedule.