  In this paper, we present an implementation of CLNP ground-to-ground packet
processing for ATN in Linux kernel version 2.6. We present the big picture of
CLNP packet processing, the details of input, routing, and output processing
functions, and the implementation of each function based on ISO 8473-1. The
functions implemented in this work are PDU header decomposition, header format
analysis, header error detection, error reporting, reassembly, source routing,
congestion notification, forwarding, composition, segmentation, and transmit to
device functions. Each function is initially implemented and tested as a
separated loadable kernel module. These modules are successfully loaded into
Linux kernel 2.6.
