This part of ISO/IEC 11518 specifies a physical-level, point-to-point, full-duplex, link interface for reliable, flow-controlled transmission of user data at 6 400 Mbit/s per direction, across distances of up to 1 km. A parallel copper cable interface for distances of up to 40 m is specified. Connections to a separate longer-distance optical interface are provided. Small fixed-size micropackets provide an efficient, low-latency structure for small transfers, and a component for large transfers.

Specifications are included for:

? automatic retransmission to correct flawed data;

? the format of a small data transfer unit called a micropacket;

? a message structure that includes routing information for network applications;

? end-to-end, as well as link-to-link, checksums;

? the timing requirements of the parallel signals;

? a parallel interface using copper coaxial cable;

? connections to a separate local optical interface;

? a link-level protocol tuned for a maximum distance of 1 km.