A reliable data channel is a network communications channel through which transferred data can be assumed free of corrupted bits, packet loss, and delivered in the intended order.
Reliable data channels are paramount to the larger concept of Reliable Data Transfer and represent fundamental underpinnings of services such as Transmission Control Protocol (TCP) that provide such reliability-guarantees to application layer services.
Reliable data channels typically reside on the transport layer which, by nature, sits atop inherently unreliable channels such as the network layer (best-effort delivery) and link layer. Further complicating the issue is the uncertainty of network structure beyond the transport layer.
After leaving the transport layer, data may traverse a single network link or a global network consisting of many links. Reliable data channels must develop reliable data transfer protocols to help address such concerns.