10.5. 10.2 Network Model 10.2.1 Slice Failure Detection Process The main processes during the lifecycle of a RAN slice should include deployment, oper- ation, and termination [21], as shown in Figure 10.1. We depict the process where a RAN slice failure is detected. The controller receives a slice reconfiguration request that contains service specific requirements, e.g. quality-of-service (QoS) (latency and guaranteed band- width), mobility, security, reliability, and connectivity requirements. Owing to this, different technologies and primitives are involved in NFV and packet forwarding, and the controller decomposes a slice reconfiguration request into a VNF reconfiguration request and a path reconfiguration request in Step 5a and 5b. By analyzing the VNF requirements, the VNF 10.2 Network Model VNF pools SDN-based infrastructure Controller (New) (old) selection Receive a network slice request 1a. VNF requirements 1b. Path requirements 2. VNF configuration 3. <VNF ID, context> 4a. VNF successfully 4b. Flow table allocated entries established Detect a network slice failure 5a. VNF reconfiguration 5b. Path reconfig- request uration request 6. Context migration 7. <VNF ID, context update> 8a. VNF successfully 8b. Flow table entries reallocated established Release a network slice 9a. VNF release 9b. Path release 10. VNF resource release Figure 10.1 The main processes of the lifecycle of a RAN slice. selection module reconfigures an appropriate set of VNFs in the VNFs pool in Step 6. The VNF selection module migrates the context to the new VNF, where the context includes VNF type, capability, property, and requirement following the TOSCA standard [22]. The VNF ID and context update confirmation massage are sent back to the VNF selection mod- ule in Step 7. A RAN slice failure is recovered once the controller receives feedbacks from the VNF selection modules and open flow switches in the SDN-based infrastructure in Step 8a and 8b, respectively. In Section 10.2.2, the system model for robust RAN slicing mecha- nisms a