Hop Recording and Forwarding State Logging: Two Implementations for Path Tracking in P4 Full information on the path travelled by packets is extremely important for network management and network security. We implemented two path tracking methods in hardware with P4. The first approach tracks a packetu0027s path by recording each node along the path of a packet (hop recording). The complete path a packet took can be extracted from the packet in the last node of the path. The second approach tracks a packetu0027s path by logging the forwarding state of a network (forwarding state logging). The complete path can be reconstructed based on the node where the packet entered a network. We conducted experiments with the two implemented approaches and showed that the paths of the packets are reconstructed correctly. The advantage of using P4 is that the control plane only gets involved when the path of a packet is reconstructed. We finally show how our work provides a working tool in P4 networks that can be used to gain deep insights in traffic patterns.

Toward Comprehensive Network Verification: Practices, Challenges and Beyond Guaranteeing that large scale networks are always operated as policy goals dictate is critical for network availability, security, and performance. The problem is challenging, as it should not only assure the correctness of policy configurations across various network devices, but also guarantee the faithfulness of policy enforcement on actual packet forwarding behaviors. In this article, we provide a systematic overview of the direction of network verification, which covers both verification of network configurations and assurance of device actual behaviors. In particular, we summarize stateoftheart designs with focuses from early stateless data planes with switchesrouters to more recent stateful ones containing middleboxes. After analyzing and comparing these works, we also specify future directions in the verification of stateful networks.