LCG CI Port Architecture Specification

This document specifies the architecture of the Computer Interconnect (CI) as implemented on LCG products. It provides comprehensive technical details on the port interface to host operating systems, including the use of the Port Control Block (PCB) and a queued communication protocol. Key sections cover packet transmission characteristics, data transmission using buffer descriptors, virtual circuit management, path selection modes, and the various packet formats supported. It also includes detailed descriptions of diagnostic operations, port performance monitoring, error condition handling, and register definitions for control and status monitoring.