# Practical Implementation of a Blockchain-Enabled SDN for Large-Scale Infrastructure Networks
## 2 Related Work
The integration of blockchain technology addresses the heightened security vulnerability in the control plane posed by SDN controllers being located in different domains. The blockchain is installed to run on every controller. By integrating blockchain, the system can use the smart contracts feature that the blockchain offers. The proposed system uses an architecture with two smart contracts defined in the same chain of the blockchain network. One of the smart contracts has the role of helping with the authorization, enabling controllers to establish trust between themselves and with the management of the controllers. The other one has the role of helping with coordination, validating if the participating controller has been authorized. Ref. [14] proposes a framework that provides authentication and auditing capabilities to tenants in multi-tenant, multi-vendor network environments. The framework uses blockchain as an addition to SDN (SD-WAN) technology in order to solve the issues of a single point of failure--central points of operation related to the centralized aspect of SDN, by a decentralized orchestration. This orchestration can be acquired by using tenant and vendor nodes from a peer-to-peer network. These nodes use the decentralized applications and smart contracts characteristics of blockchain technology. In this way, the framework manages to allow the SDN clients and vendors in the presented environment to handle services in an auditable and zero-trust-based way. The study in [15] proposes an energy trading scheme based on SDN and blockchain in order to obtain a distributed energy internet. The proposed scheme leverages SDN to obtain a separation of the operation, control and management of the energy internet that will add flexibility to it. Besides the advantages, some disadvantages of using SDN are presented, and the use of blockchain technology is suggested in order to address the issues regarding the privacy and the security of the energy transactions. The study concludes that further research is needed in order to obtain a practical solution. The work of [PERSON] et al. [16] proposes a solution to manage network bandwidth using SDN and blockchain at an ISP level, identifying three major use cases. The SDN will automatically manage QoS configurations, and the blockchain will provide a decentralized payment system. The paper provides a theoretical approach, deferringthe technical details regarding the proposed use case protocols for further investigation. The research in [17] continues this work by implementing the solution using Ethereum and POX SDN controllers. The results proved that the framework is capable of trading bandwidth resources. The SmartContractChain (SC2) [18] traffic management framework integrates flow-based control from SDN with the decentralized technology of blockchain and embedded smart contracts. Several simulations have been conducted to demonstrate the feasibility of the SC2 framework. Table 1 summarizes the related works and compares them with the proposed approach. The aforementioned related research addresses the general concepts encountered throughout the current paper. Subsequently, this section provides pertinent research findings with a focus on the technical details involved in deploying the proposed solution. The study in [19] explores the various SDN controllers and other tools that are useful in SDN experiments. The experimental work includes three network topologies with different numbers of switches and with different SDN controllers being used in order to simulate and measure throughput, jitter, latency and latency for both TCP and UDP traffic. With their work, the study provides insight related to the use of each controller. The use of Mininet as an environment for network simulation is also validated as being appropriate. In [20], different network topologies are used in order to simulate and compare the POX and Ryu SDN controllers provided in Mininet.