The present document focuses on unique aspects related to network and service resiliency in a virtualised network environment. The challenges result from failures of virtualised network functions, failures of the underlying hardware and software infrastructure arising from conditions such as design faults, intrinsic wear out, operational mistakes, or other adverse conditions, e.g. natural disasters, excessive traffic demand, etc.
 
The scope of the present document includes:

• Usecase analysis for reliability and availability in a virtualised network environment.
• Analysis of service availability levels.
• Identification of requirements for maintaining network resiliency and service availability, the focus being additional requirements introduced by virtualisation. The mechanisms to be considered include the following:
  •     Network function migration within and across system boundaries.
  •     Failure detection and reporting at the various layers.
  •     Failure prediction, prevention, and remediation.
  •     State management.
  •     Solving network availability issues caused by overload/call blocking conditions.
• Engineering and deployment guidelines for maintaining network resiliency and ensuring service availability.