tcpipd(1M)
NAME
tcpipd − TCP/IP daemon
SYNOPSIS
/usr/etc/tcpipd
DESCRIPTION
tcpipd can be started to handle the reception of IP packets. This kernel daemon will handle processing for the IP protocol, as well as processing for the TCP or UDP protocol layers. When tcpipd is not started, packet processing for received packets is done in a software interrupt routine. This software interrupt is labeled "Network software interrupt" in the configuration file, and is one of the lowest priority interrupts in the system.
tcpipd is started by uncommenting the appropriate line in /etc/rc. System administrators may wish to review the run options specified in /etc/rc and change them as needed. Note that once tcpipd is initiated, it can not be killed.
When tcpipd is not used, packet received processing will be done at the highest priority on the processor where the network interrupt routine is serviced. This is because an interrupt routine will always be executed before any user-level activity on a given processor. The length of the processing for packet received processing is very indeterminate, since multiple packets can be processed within the same interrupt. Received packet processing is an expensive operation, which will also prevent a high priority process from running when the event the process was waiting for has occurred.
When the tcpipd program is used to process received packets, the priority of the daemon can be set so that the most important real-time processes on that processor have a higher priority than packet receive processing. Care must be taken in setting the priorities of tasks to be higher than the tcpipd program, since packets can be dropped or a packet may be retransmitted if the tcpipd process is prevented from running for lengthy periods of time. Processes which require a high degree of responsiveness should have priorities higher than tcpipd.
tcpipd will fail if it is not started by the super-user or an instantiation of tcpipd exists.
SEE ALSO
ttyd(1M), softclockd(1M),
CX/RT Reference Manual
CX/UX Networking