# Programmable Data Plane Applications in 5G and Beyond Architectures: A Systematic Review
## 4 Findings and Discussion
### Characteristics of the Reviewed work
The second UPF is designed to run on hardware switches, maximizing bandwidth and minimizing latency. It leverages microservices to provide additional functionality, such as buffering traffic for idle mobile devices. [PERSON] et al. [55] propose the design of a 5G multi-access proxy's user plane based on the MP-DCCP (multi-path datagram congestion control protocol) protocol, which extends DCCP to support multipath communication. To implement this design, the authors use a P4 smart NIC. [PERSON] et al. [56] implement 5G UPF prototypes, one of which utilizes a P4 smart NIC to offload both data plane processing (e.g., GTP encapsulation/decapsulation and oversubscribed session queuing) and control plane signaling (e.g., control plane packet processing and data plane rule installation). In a follow-up work [57], the authors propose AccelUPF, a high-performance 5G UPF that offloads user plane functionality to a programmable switch, achieving significant acceleration in data plane processing. It also offloads PFCP (packet forwarding control protocol) message processing from the control plane, dividing it between the hardware and software components to optimize performance. The fast path on hardware is assigned to the more common and simpler patterns of PFCP messages, while the software handles the more complex and infrequent messages. CeUPF [58] adopts a hybrid architecture that combines software and hardware elements to optimize the performance of user plane functions. Specifically, some actions, such as traffic steering and datagram forwarding, are offloaded to programmable hardware. While other messages that the hardware cannot process are directed back to the software user plane. This offloading is achieved using a P4-based hardware switch and a smart NIC. [PERSON] et al. [59] conducted a comparative analysis of XDP, DPDK, and P4 as processing acceleration technologies in uRLLC scenarios. In their study, they implemented UPF surrogates to handle GTP processes for each technology. Specifically, they used a P4 FPGA board as the device under test to evaluate the performance of the P4-based UPF. [PERSON] et al. [60] develop a 5G-MEC testbed for the purpose of gathering data related to cybersecurity. To achieve high throughput in this architecture, P4 switches are utilized specifically for the handling of UDP traffic. [PERSON] et al. [61] utilize a P4 Smart NIC to implement the UPF function for 5G and beyond networks. The device performs forwarding and tunneling, while more complex functions such as buffering and flow processing are assigned to a host-based UPF. [PERSON] et al. [62] present an implementation of SRv6 as a transport protocol for 5G network slicing utilizing P4 switches. The proposed solution is evaluated in terms of performance against the widely used GTP protocol. BRAINE [63] proposes a MEC solution for 5G. This framework deploys multiple P4 switches to perform INT, user plane offloading, and DoS attack detection. [PERSON] et al. [64] implement a MEC router based on a P4 switch to provide ultra-low latency services in a distributed computing environment. The router performs GTP match and encapsulation/decapsulation actions, which minimize the load on host CPU cores. Synergy [65] is a high-performance UPF on P4 smart NICs with monitoring capabilities for user session data prediction and handover optimization. Efficient buffering of data packets during handover and paging events is accomplished by employing a two-level flow-state access mechanism, which results in low latency for both control and data planes while maintaining high packet forwarding throughput. The prediction of handover events is achieved through the utilization of a recurrent neural network model. Velox [66; 67] is a network of P4 switches designed to interconnect 5G RAN and core networks for industrial scenarios. It enables switches to process cellular control (NGAP) and cellular data packets (GTP) while introducing the concept of intra-cellular optimization to reduce latency between two devices on the same network.