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doc/networking/networktasks.t

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+@c
+@c  Written by Eric Norum
+@c
+@c  COPYRIGHT (c) 1988-1998.
+@c  On-Line Applications Research Corporation (OAR).
+@c  All rights reserved.
+@c
+@c  $Id$
+@c
+
+@chapter Network Task Structure and Data Flow
+
+A schematic diagram of the tasks and message @b{mbuf} queues in a
+simple RTEMS networking application is shown in the following
+figure:
+
+@ifset use-ascii
+@example
+@group
+NO ASCII VERSION OF THE TASKING FIGURE IS AVAILABLE
+@end group
+@end example
+@end ifset
+
+@ifset use-tex
+@c for now use the ascii version
+@example
+@group
+NO TEX VERSION OF THE TASKING FIGURE IS AVAILABLE
+@end group
+@end example
+@end ifset
+
+@ifset use-html
+@html
+<IMG SRC="networking.gif" ALIGN=CENTER 
+     ALT="Network Task Structure and Data Flow">
+@end html
+@end ifset
+
+
+The transmit task  for each network interface is normally blocked waiting
+for a packet to arrive in the transmit queue.  Once a packet arrives, the
+transmit task may block waiting for an event from the transmit interrupt
+handler.  The transmit interrupt handler sends an RTEMS event to the transmit
+task to indicate that transmit hardware resources have become available.
+
+The receive task for each network interface is normally blocked waiting
+for an event from the receive interrupt handler.  When this event is received
+the receive task reads the packet and forwards it to the network stack
+for subsequent processing by the network task.
+
+The network task processes incoming packets and takes care of
+timed operations such as handling TCP timeouts and
+aging and removing routing table entries.
+
+The `Network code' contains routines which may run in the context of
+the user application tasks, the interface receive task or the network task.
+A network semaphore ensures that
+the data structures manipulated by the network code remain consistent.