P4 (Programming Protocol-Independent Packet Processors) is a declarative language for expressing how packets are processed by the data plane of a forwarding element, such as a networking switch. In a nutshell, P4 brings programmability to the network forwarding plane. This thesis starts by describing the challenges encountered when deploying P4 to implement MAP-T, a solution to provide IPv4 connectivity across an IPv6 backbone. This implementation has been deployed on a Cisco switch based on the Tofino programmable ASIC. This switch is sold along with a pre-built P4 program to which our implementation must be added. Hence this work has to address the challenge of merging a new functionality with a pre-built P4 program which is called Incremental Programming. Finally, this thesis addresses the challenges stemming from the fact that IP fragmentation and reassembly, which need to be supported by a MAP-T entity, cannot be implemented in P4. A heuristic to handle fragmented packets was implemented in P4 and analyzed to assess its limitation. Traffic captured on the backbone of a Tier1 Service Provider, was used to assess the algorithm. The results show that the heuristic algorithm offers an acceptable and practical trade off between complexity and loss of fragmented packets.