permessage

Permessage is a term used in networking and messaging to denote that a particular operation, parameter, or property is applied to each individual message in a sequence, rather than to the connection, stream, or batch as a whole. The concept emphasizes message-boundary awareness, enabling independent processing, error containment, and easier retransmission semantics.

Typical uses of per-message processing include compression, encryption, signing, or metadata tagging that are applied on a per-message basis. In WebSocket communications, an extension named permessage-deflate demonstrates the concept by compressing the payload of each WebSocket message independently rather than maintaining a shared compression state across multiple messages. This independence allows messages to be compressed and decompressed without cross-message dependencies, though optional negotiation and contextual settings (such as whether dictionaries are reused across messages) can influence performance.

Per-message semantics are also relevant to security and data integrity, where each message can be encrypted or authenticated separately. This can improve isolation between messages and simplify error handling, at the cost of potential redundancy or higher computational overhead.

Design considerations: per-message processing imposes boundaries that facilitate streaming and error recovery but may reduce opportunities for global optimizations. Protocol designers must balance compression efficiency, encryption overhead, and the requirement to preserve message boundaries.

See also: permessage-deflate; WebSocket extension; per-message encryption; message framing.