deltatransfer

Deltatransfer is a data transmission method that sends only the changes between two versions of a dataset, rather than the full dataset. The technique relies on a known baseline at the destination and a computed delta that describes how to transform that baseline into the target version.

To create a delta, a delta encoding algorithm analyzes differences, often by comparing blocks or chunks and producing instructions such as insert, delete, or modify. The sender transmits the delta, and the receiver applies it to the baseline to reconstruct the new version. Popular approaches include the rsync algorithm, which uses rolling checksums to identify matching blocks, as well as formats such as bsdiff or xdelta.

Deltatransfer is widely used for software updates, data synchronization, and incremental backups, where bandwidth or update time is a concern. It is also used in content delivery and remote provisioning of devices, including firmware updates. Some systems combine delta transfer with compression to further reduce size.

Advantages include reduced bandwidth, faster deployments, and lower network load, while limitations include the need for a valid baseline, processing overhead, and potential failures if deltas become incompatible with the destination state. Security and integrity must be carefully managed, since applying incorrect deltas can corrupt data.

In related concepts, delta encoding and patching are broader ideas used in compression, version control, and software distribution. Git and other version control systems rely on delta-based representations to minimize storage and transfer sizes.