As industries become increasingly automated and stressed to seek business advantages, they often have operational constraints that make modernization and security more challenging.  Constraints exist such as low operating budgets, long operational lifetimes and infeasible network/device upgrade/modification paths.  In order to bypass these constraints with minimal risk of disruption and perform ``no harm'', network administrators have come to rely on using dual-stack approaches, which allow legacy protocols to co-exist with modern ones.  For example, if SNMP is required for managing legacy devices, and a newer protocol (NETCONF) is required for modern devices, then administrators simply modify firewall Access Control Lists (ACLs) to allow passage of both protocols.  In today's networks, firewalls are ubiquitous, relatively inexpensive, and able to support multiple protocols (hence dual-stack) while providing network security.
    
    While investigating securing legacy devices in heterogeneous networks, it was determined that dual-stack firewall approaches do not provide adequate protection beyond layer three filtering of the IP stack.  Therefore, the NETCONF/SNMP Protocol Gateway hybrid (NSPG) was developed as an alternative in environments where security is necessary, but legacy devices are infeasible to upgrade, replace, and modify.  The NSPG allows network administrators to utilize only a single modern protocol (NETCONF) instead of both NETCONF and SNMP, and enforce additional security controls without modifying existing deployments.  It has been demonstrated that legacy devices can be securely managed in a protocol-agnostic manner using low-cost commodity hardware (e.g., the RaspberryPi platform) with administrator-derived XML-based configuration policies.