Blockchain-based NAT Management for 5G Age Younchan Jung School of Information, Communications and Electronics Engineering Catholic University of Korea Bucheon-si, Gyeonggi-do, Republic of Korea Email: ycjung@catholic.ac.kr Marnel Peradilla Computer Technology Department, College of Computer Studies De La Salle University - Manila Manila, Philippines Email: marnel.peradilla@dlsu.edu.ph Abstract—Full deployment of IPv6 addressing fails because nowa- days Network Address Translation (NAT) devices are commonly used to extend internal private addressing from the global public IP addressing. The existing phone system uses the vertical model to solve issues relating to the NAT and mobility management. Also, the horizontal model has been studied, where a centralized Software-Defined network (SDN) controller is in charge of han- dling network functions such as NAT and mobility management. The goal of this paper is to propose a blockchain-based NAT management (BNATM) scheme to overcome the limitation that both the horizontal model as well as the vertical model face in relation with NAT and mobility management. Our proposal focuses on the idea that, if we use the blockchain technologies, each peer can easily obtain the necessary parameters required to handle the complicated NAT and mobility management pro- cedures. Finally, this paper analyzes the latency comparisons among the proposed BNATM scheme, existing vertical model and centralized controller-based horizontal model. Keywords–NAT management; SDN horizontal model; Blockchain; Blockchain-based management; Hash address; Transaction access. I. I NTRODUCTION The explosive growth of the Internet during 1990s signaled the danger of IP address exhaustion and also created an instant demand on IP addresses. The Internet Engineering Task Force (IETF) simultaneously introduced the IPv6 and Network Address Translation (NAT) [1] [2]. However, full deployment of IPv6 addressing fails because of the NAT’s widespread use. Currently, NAT devices are commonly installed at network edges to modify the addresses of packets crossing the NAT. LS Relay node DNS LS Relay node DNS N A T N A T STUN server Public Network Private Network Private Network Figure 1. Vertical model for NAT management NAT has one accessible public address which will be shared among End Nodes (ENs) inside the private network. NAT essentially extends internal addressing from the global IP addressing used over the Internet. NAT provides network resources to get over a shortage of the address space by mapping relatively public IP addresses to private IP addresses [3] [4]. However, the non-standardized characteristics of NAT cause traversal problems. Different NAT network products are available with different proprietary specifications. Therefore, NAT devices start to cause problems especially with the development of peer-to-peer applications [5]–[7]. Three issues are raised in implementing these application systems. First, a smart NAT management is needed in order to manage the private addressing of the local ENs in the private region and solve the NAT traversal issues. Second, the issue of mobility management, which focuses on ENs that use private IP addresses, should be solved. Most of the existing mobility management schemes only deal with the tracking of the location of the EN (that is, the addresses that are closely related to their locations) but not the use of private address [8] [9]. So, NAT management and mobility management functions need to collaborate in order that the application systems be operational. Lastly, for the joint operation of mobility management over the heterogeneous network, a significant portion of the existing work uses vertical model for network functions [10] [11]. As depicted in Figure 1, the existing vertical model for network functions for NAT management and mobility management has limitations in handling an integrated operation of heterogeneous network functions. The current trend for the NAT management and mobility management is to utilize the horizontal model of network functions [12]–[14]. The difference between the horizontal model and the vertical model depends on whether the processing of the network Infrastructure Layer Public Network Wireless Private Network Wireless Private Network Wireless Private Network Wireless Private Network Wireless Private Network Public Network Wireless Private Network Wireless Private Network Wireless Private Network NAT NAT Control Layer Centralized Software-Defined Controller NAT Management Mobility Management Centralized Software-Defined Controller NAT Management Mobility Management Control Layer Centralized Software-Defined Controller NAT Management Mobility Management Application Layer APPLICATIONS Application Layer APPLICATIONS Figure 2. Horizontal model for 5G NAT management 1 Copyright (c) IARIA, 2018. ISBN: 978-1-61208-644-6 INTERNET 2018 : The Tenth International Conference on Evolving Internet