Retransmits

Retransmission, and its plural form retransmits, is the act of transmitting data or content again when the original transmission failed to reach the recipient, was corrupted, or when a rebroadcast is planned.

In data communications, retransmission is a fundamental error-control mechanism. Automatic repeat request (ARQ) protocols use acknowledgments and timeouts to trigger retransmission of lost or damaged frames. Common schemes include stop-and-wait, go-back-N, and selective repeat. In transport protocols such as TCP, retransmission occurs when a segment is not acknowledged within a timeout window or when duplicate acknowledgments indicate loss. Timers, round-trip time estimates, and congestion control influence when and how aggressively retransmissions occur.

In streaming and interactive applications, retransmission decisions balance reliability with latency. Real-time protocols often avoid frequent retransmission, instead employing buffering, forward error correction, or selective negative-acknowledgment (NACK) repair. When reliable delivery is needed, systems may operate over dependable transport layers or use application-layer schemes designed for the specific service.

In broadcasting and content delivery, retransmission can refer to re-airing a program or to distributing copies of content to multiple channels or edge caches. Satellite, cable, and IP-based distribution systems may retransmit data to cover transmission errors on the link or to serve users in different regions. Retransmits also occur in storage and archival contexts when archived data is resent to users or systems on request.