The physical diode guarantees that data flows in one direction, and nothing else. It knows nothing about TCP handshakes, sees no file structure, and because there is no return channel, ordinary protocol-based file transfer does not work over the diode alone.
For a data diode to be useful in an organization’s actual data flows, it has to be paired with software that handles protocol conversion, transfer reliability, and error recovery across the one-way connection.
link22 Diode Software is that software.
What the hardware diode leaves unsolved
The physical diode is deliberately simple. It enforces one-way transfer at the packet level. It does not see protocols, knows nothing about file structure, and cannot guarantee that a transfer arrived intact. All of that is intentional. The hardware diode is built to do one thing well and nothing else.
But real-world data flows rarely consist of raw UDP packets. Files are large, protocols are complex, and without retry capability, integrity verification, and quality guarantees, data rarely arrives correctly. The software layer handles all of that.
How Diode Software fills the gap
link22 Diode Software is a standalone software product that converts complex protocols into UDP for transport across the hardware diode, and reconstructs them on the receiving side. The technique rests on a few core mechanisms:
– Protocol conversion. TCP and similar session-based protocols are converted into one-way UDP streams. On the receiving side they are reconstructed so applications that expect TCP can receive data normally.
– Checksum verification. Because no return channel exists, integrity checking is done through computed checksums. Discrepancies are detected and handled within the software layer.
– Configurable bandwidth control and resend. Bandwidth can be reserved for priority flows, and critical data can be sent with configurable redundancy.
– Support for very large files and file libraries. The software is built for data flows that ordinary file transfer protocols do not handle gracefully.
The components in Diode Software
Diode Software is made up of three integrated components, each with a specific purpose:
Diode Transfer. File transfer across a diode. Delivered as an RPM package for RHEL 8 and 9. Handles splitting, retry, and reconstruction of files.
Secure Transfer Agent. Encrypted and signed file handling, for flows where PKI signing and integrity verification must be explicitly documented. Available for both Windows and RHEL 8.
TCP Connector. Streaming TCP data over a diode, for applications that expect a continuous TCP connection on the receiving side. RHEL 8.
Together the components cover the most common data flow patterns between security domains.
Transfer mode and mirror mode
Diode Software supports two operating modes.
Transfer mode is for discrete file transfers. A user initiates a send, the software ensures it arrives, and verifies the result.
Mirror mode is for continuous mirroring. A source directory is mirrored across the diode to a destination directory, with automatic synchronization of changes. Useful for replication of configuration files, document archives, or data storage.
Which mode fits depends on the flow rather than the architecture.
Vendor neutral
Diode Software works with hardware diodes regardless of manufacturer. This is one of the clearest differences between link22 Diode Software and proprietary all-in-one solutions.
For organizations this provides two practical advantages.
First, separation of choice. The hardware diode is chosen on its own merits (form factor, throughput, certification status), and the software layer is chosen separately. Each is evaluated against its own requirements.
Then, independent upgrades. If hardware needs to be replaced over time, the software layer does not need to be redesigned. If software requirements change, the hardware diode is not affected. This protects the investment over time.
Use cases
Diode Software is in production today at organizations handling classified information and critical OT infrastructure. Three typical contexts:
Energy and power utilities. Telemetry and process data from production facilities need to leave the OT environment toward analytics and reporting systems, without creating a return path back in.
Water and municipal services. SCADA data needs to be consolidated for overview and decision support, still without exposing control systems to the internet.
Financial and production environments. Logs and transaction data are exported from segmented networks for centralized analysis, without opening return paths.
In every case the diode is the physical guarantee, while Diode Software makes the guarantee practically usable.
Next steps
Contact link22 for a technical briefing on how Diode Software fits into your existing or planned data diode architecture. The first conversation usually focuses more on the requirements picture than on the product itself.
