通訊技術的迅速進步促使了第五代(5th Generation, 5G)行動網路的出現。5G系統架構採用軟體定義的網路和網路功能虛擬化，實現了靈活且可擴充的5G核心網路。然而，隨著連線需求和可靠度要求的增加，以及5G行動網路強調高頻寬和低延遲的特性，5G核心網路在效率和安全性方面面臨挑戰。為了探討5G核心網路如何應對這些挑戰，在本論文中，我們使用了3個開源5G核心網路：free5GC、Open5GS和OpenAirInterface，對控制平面和使用者平面的效能進行了實驗評估。
在控制平面上，我們對存取與行動管理功能(Access and Mobility Management Function, AMF)和網路功能資源庫功能(Network function Repository Function, NRF)進行了實驗。在AMF部分，我們設計了兩個場景來針對連線需求測試使用者裝置(User Equipment, UE)註冊的效率。第一個場景是觀察不同規模的UE註冊在開源5G核心網路的效能，第二個場景是重複的UE註冊請求對AMF的影響。在NRF部分，我們探索了3個開源5G核心網路中NRF的實現進度，並利用HTTP/2協議的漏洞進行了阻斷服務攻擊來探討核心網路的可靠度。
在使用者平面上，我們測量3個開源核心網路的服務品質，包含UE和數據網路之間的上行/下行吞吐量和往返時間，並比較3個開源5G核心網路在不同鏈路延遲和UE數量連線時的傳輸速率以及封包往返時間的表現。這些實驗結果顯示了3個開源5G核心網路在不同規模的UE註冊效率和UE連線數的吞吐量，給開發人員在系統效能上可以優化的方向，並且透過攻擊結果提出在控制平面中可以加強的安全性，以提高開源5G核心網路的可靠性。

The rapid advancement of communication technologies has brought about the 5th Generation (5G) mobile networks, enabling a flexible and scalable 5G Core Network (CN). However, with the increasing requirements for connectivity needs and reliability, as well as the emphasis on the high bandwidth and low latency in the 5G mobile networks, both efficiency and security challenges arise. To study the relevant implementations, we conduct experiments about the performance of the Control Plane (CP) and User Plane (UP) using 3 open-source 5G CNs, free5GC, Open5GS, and OpenAirInterface (OAI) in this thesis.
On the CP, we conduct experiments on the Access and Mobility Management Function (AMF) and Network Repository Function (NRF). On the AMF, two scenarios of User Equipment (UE) registration are used. The first scene is the performance of UE registrations with different scales. The second is the impact of duplicate UE registration requests on the AMF. On the NRF, we explore the construction progress of the NRF and use HTTP/2 protocol vulnerabilities to examine the reliability of the CN. On the UP, we measure the uplink/downlink throughput and round-trip time with different link delays and numbers of UE. These experimental results demonstrate the differences in registration efficiency and transmission rate for various sizes of UE among the 3 open-source 5G CNs. Our findings help developers optimize system performance and suggest security improvements for more reliable open-source 5G CNs.

[1] 3GPP, “System architecture for the 5G System (5GS),” Technical Specification (TS) 23.501 (Rel. 17), Dec. 2023.
[2] free5GC, “free5gc,” [Online]. Available: https://github.com/free5gc/free5gc.
[3] Open5GS, “open5gs,” [Online]. Available: https://github.com/open5gs/open5gs.
[4] OpenAirInterface, “cn5g,” [Online]. Available: https://gitlab.eurecom.fr/oai/cn5g.
[5] 3GPP, “Procedures for the 5G System (5GS),” Technical Specification (TS) 23.502 (Rel. 17), Dec. 2023.
[6] 3GPP, “Technical Realization of Service Based Architecture,” Technical Specification (TS) 29.500 (Rel. 18), Sep. 2023.
[7] 3GPP, “Network Function Repository Services,” Technical Specification (TS) 29.510 (Rel. 17), Sep. 2023.
[8] open5gs, “open5gs/src/nrf/nf-sm.c,” [Online]. Available: https://github.com/open5gs/open5gs/blob/02d302b15aa316a1f39cb7d9592c96c9ff73f18b/src/nrf/nf-sm.c.
[9] oai, “oai-cn5g-nrf/src/nrf_app/nrf_app.cpp,” [Online]. Available: https://gitlab.eurecom.fr/oai/cn5g/oai-cn5g-nrf/-/blob/master/src/nrf_app/nrf_app.cpp.
[10] free5gc, “nrf/internal/sbi/producer/nf_management.go,” [Online]. Available: https://github.com/free5gc/nrf/blob/72c93a38cb17930f87901c28f3eb51277ce55d39/internal/sbi/producer/nf_management.go.
[11] ITU-R, “Minimum requirements related to technical performance for IMT-2020 radio interface(s),” Report M.2410-0, Nov. 2017.
[12] 3GPP, “Architecture enhancements for control and user plane separation of EPC nodes,” Technical Specification (TS) 23.214 (Rel. 17), Jun. 2021.
[13] 3GPP, “System architecture for the 5G System (5GS),” Technical Specification (TS) 23.501 (Rel. 15), Mar. 2022.
[14] S. Sheikhi and P. Kostakos, “DDoS attack detection using unsupervised federated learning for 5G networks and beyond,” in 2023 Joint European Conference on Networks and Communications 6G Summit (EuCNC/6G Summit), Gothenburg, Sweden, Jun. 2023, pp. 442-447.
[15] V. Jain et al., “L25GC: a low latency 5G core network based on high-performance NFV platforms,” in Proceedings of the ACM SIGCOMM 2022 Conference, New York, NY, USA, Aug. 2022, pp. 143-157.
[16] R. Reddy, M. Gundall, C. Lipps, and H. D. Schotten, “Open source 5G core network implementations: A qualitative and quantitative analysis,” in 2023 IEEE International Black Sea Conference on Communications and Networking (BlackSeaCom), Istanbul, Turkiye, Jul. 2023, pp. 253-258.
[17] M. Chepkoech, N. Mombeshora, B. Malila, and J. Mwangama, “Evaluation of open-source mobile network software stacks: A guide to low-cost deployment of 5G testbeds,” in 2023 18th Wireless On-Demand Network Systems and Services Conference (WONS), Madonna di Campiglio, Italy, Jan. 2023, pp. 56-63.
[18] G. Amponis et al., “Threatening the 5G core via PFCP DoS attacks: the case of blocking UAV communications,” EURASIP J. Wirel. Commun. Netw., vol. 2022, no. 1, pp. 1-27, Dec. 2022.
[19] S. Woo, J. Park, S. Kwon, K. Park, J. Kim, and J.-H. Lee, “Simulation of data hijacking attacks for a 5G-advanced core network,” in 2023 Joint European Conference on Networks and Communications 6G Summit (EuCNC/6G Summit), Gothenburg, Sweden, Jun. 2023, pp. 538-542.
[20] O.-M. Ungureanu and C. Vlădeanu, “Leveraging the cloud-native approach for the design of 5G nextgen core functions,” in 2022 14th International Conference on Communications (COMM), Bucharest, Romania, Jun. 2022, pp. 1-7.
[21] G. Lando, L. A. F. Schierholt, M. P. Milesi, and J. A. Wickboldt, “Evaluating the performance of open source software implementations of the 5G network core,” in NOMS 2023-2023 IEEE/IFIP Network Operations and Management Symposium, Miami, FL, USA, May 2023, pp. 1-7.
[22] H. C. Rudolph, A. Kunz, L. L. Iacono, and H. V. Nguyen, “Security challenges of the 3GPP 5G service based architecture,” IEEE Communications Standards Magazine, vol. 3, no. 1, pp. 60-65, Mar. 2019.
[23] Q. Tang, O. Ermis, C. D. Nguyen, A. D. Oliveira, and A. Hirtzig, “A systematic analysis of 5G networks with a focus on 5G core security,” IEEE Access, vol. 10, pp. 18 298-18 319, Feb. 2022.
[24] N. Wehbe, H. A. Alameddine, M. Pourzandi, E. Bou-Harb, and C. Assi, “A security assessment of HTTP/2 usage in 5G service-based architecture,” IEEE Communications Magazine, vol. 61, no. 1, pp. 48-54, Nov. 2023.
[25] A. H. Vasoukolaei, D. Sattar, and A. Matrawy, “TLS performance evaluation in the control plane of a 5G core network slice,” in 2021 IEEE Conference on Standards for Communications and Networking (CSCN), Thessaloniki, Greece, Dec. 2021, pp. 155-160.
[26] Y.-C. Li et al., “A runtime anomaly detector via service communication proxy for 5G mobile networks,” in IEEE INFOCOM 2023 - IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Hoboken, NJ, USA, May 2023, pp. 1-2.
[27] X. Hu, C. Liu, S. Liu, W. You, and Y. Zhao, “Signalling security analysis: Is HTTP/2 secure in 5G core network?” in 2018 10th International Conference on Wireless Communications and Signal Processing (WCSP), Hangzhou, China, Oct. 2018, pp. 1-6.
[28] E. Chatzoglou, V. Kouliaridis, G. Kambourakis, G. Karopoulos, and S. Gritzalis, “A hands-on gaze on HTTP/3 security through the lens of HTTP/2 and a public dataset,” Comput. Secur., vol. 125, no. C, pp. 103 051-103 067, Feb. 2023.
[29] K. Seemakhupt and K. Piromsopa, “When should we use HTTP2 multiplexed stream?” in 2016 13th International Joint Conference on Computer Science and Software Engineering (JCSSE), Khon Kaen, Thailand, Jul. 2016, pp. 1-4.
[30] IMPERVA, “HTTP/2: In-depth analysis of the top four flaws of the next generation web protocol,” [Online]. Available: https://www.imperva.com/docs/Imperva_HII_HTTP2.pdf.
[31] Z. Salazar, H. N. Nguyen, W. Mallouli, A. R. Cavalli, and E. Montes de Oca, “5Greplay: a 5G network traffic fuzzer - application to attack injection,” in Proceedings of the 16th International Conference on Availability, Reliability and Security, New York, NY, USA, Aug. 2021, pp. 1-8.
[32] O.-M. Dumitru-Guzu and C. Vlădeanu, “Analysis of potential threats in nextgen 5G core,” in 2022 International Symposium on Electronics and Telecommunications (ISETC), Timisoara, Romania, Nov. 2022, pp. 1-4.
[33] S. Park, S. Kwon, Y. Park, D. Kim, and I. You, “Session management for security systems in 5G standalone network,” IEEE Access, vol. 10, pp. 73 421-73 436, Jun. 2022.
[34] aligungr, “UERANSIM,” [Online]. Available: https://github.com/aligungr/UERANSIM.
[35] CVE, “CVE-2023-44487,” [Online]. Available: https://www.cve.org/CVERecord?id=CVE-2023-44487.