With the increase of IOT devices worldwide, Software-Defined Networking (SDN) has emerged as a critical tool to optimize and manage congested IP networks. The challenges faced with such networks are achieving optimal resource allocation and traceability. Network operators face network security attacks (eg. MITM) causing a breach in Service-Level Agreements (SLA). Traditional solutions have aimed to improve this using algorithms and additional hardware. This paper presents DecOp, a new methodology in operating a network based on peers instead of a centralized algorithm using Blockchain (BC). BC is a growing technology that is used primarily in the financial industry (eg. BITCON and ETHEREUM) because of its ability to bring dependable consensus amongst several users using distributed ledgers. DecOp makes use of the existing platforms infrastructure to process and store network configurations. This allows for a modular solution that can be implemented and verified with varying platforms. We designed a new method to allocate resources by integrating SDN and BC using the designed Secure Service Contract (SSC) chaincode, Secure Network Operator (SNO) chaincode, and modular communication middleware. This provides a dependable traceability by storing changes to the network state in an immutable ledger. A prototype is developed and tested with Hyperledger Fabric as the BC platform and OpenDaylight as the SDN Controller. Evaluation results focus on system performance versus the BC Network size, from 12 to 40 peers.