In your hybrid testbed, you integrated GNS3 and Mininet to emulate realistic network behaviors. What were the specific technical challenges you faced when synchronizing the RESTCONF-based fault detection across these two different emulation environments, and how did you ensure consistent slice isolation during the transition to a backup path?
The primary technical challenge in integrating GNS3 and Mininet was unified topology visibility. Although OVS nodes in GNS3 and Mininet operate independently, they must appear as a single integrated topology from the OpenDaylight controllers perspective. We addressed this by leveraging GNS3s Cloud Node to bridge the ODL controller and Mininet platform into the GNS3 infrastructure. Since all OVS nodes connect to the same ODL controller via OpenFlow, RESTCONF API topology queries return a unified view encompassing both domains.
Regarding fault detection synchronization, our Slice Manager periodically polls the ODL controllers topology information through the RESTCONF API. The ODL controller centrally manages OpenFlow connection states across both domains, effectively abstracting cross-domain synchronization at the controller level. As shown in Algorithm 1, we compare consecutive topology snapshots using set difference operations to detect missing nodes, and this mechanism applies uniformly regardless of which domain the fault occurs in.
For ensuring consistent slice isolation during backup path transitions, we employed a VLAN-based isolation mechanism. Each slice is distinguished by a unique VLAN ID: VLAN 100 for Slice 1 and VLAN 200 for Slice 2. During the flow rule migration process in Algorithm 2, both REMOVE_FLOWS and INSTALL_FLOWS operations selectively target flows based on the slice ID, which corresponds to the VLAN tag. This ensures that only the affected slices forwarding entries are modified while other slices remain unaffected. As validated in Figure 5 through Wireshark packet captures, VLAN 200 traffic successfully migrated from OVS 2 to OVS 3 while maintaining VLAN segmentation throughout the failover process.
