NAME

udpclo - UDP-based BP convergence layer output task

SYNOPSIS

udpclo round_trip_time remote_hostname[:remote_port_nbr]

DESCRIPTION

udpclo is a background "daemon" task that extracts bundles from the queues of bundles ready for transmission via UDP to a remote node's UDP socket at remote_hostname and remote_port_nbr, encapsulates those bundles in UDP datagrams, and sends those datagrams to that remote UDP socket.

Because UDP is not itself a "reliable" transmission protocol (i.e., it performs no retransmission of lost data), it may be used in conjunction with BP custodial retransmission. BP custodial retransmission is triggered only by expiration of a timer whose interval is nominally the round-trip time between the sending BP node and the next node in the bundle's end-to-end path that is expected to take custody of the bundle; notionally, if no custody signal citing the transmitted bundle has been received before the end of this interval it can be assumed that either the bundle or the custody signal was lost in transmission and therefore the bundle should be retransmitted. The value of the custodial retransmission timer interval (the expected round-trip time between the sending node and the anticipated next custodian) must be provided as a run-time argument to udpclo. If the value of this parameter is zero, custodial retransmission is disabled.

udpclo is spawned automatically by bpadmin in response to the 's' (START) command that starts operation of the Bundle Protocol, and it is terminated by bpadmin in response to an 'x' (STOP) command. udpclo can also be spawned and terminated in response to START and STOP commands that pertain specifically to the UDP convergence layer protocol.

EXIT STATUS

"0"

udpclo terminated normally, for reasons noted in the ion.log file. If this termination was not commanded, investigate and solve the problem identified in the log file and use bpadmin to restart udpclo.
"1"

udpclo terminated abnormally, for reasons noted in the ion.log file. Investigate and solve the problem identified in the log file, then use bpadmin to restart udpclo.

FILES

No configuration files are needed.

ENVIRONMENT

No environment variables apply.

DIAGNOSTICS

The following diagnostics may be issued to the ion.log log file:

udpclo can't attach to BP.

bpadmin has not yet initialized Bundle Protocol operations.
No memory for UDP buffer in udpclo.

ION system error. Check errtext, correct problem, and restart UDP.
No such udp duct.

No UDP outduct with duct name remote_hostname[:<remote_port_nbr>] has been added to the BP database. Use bpadmin to stop the UDP convergence-layer protocol, add the outduct, and then restart the UDP protocol.
CLO task is already started for this engine.

Redundant initiation of udpclo.
CLO can't open UDP socket

Operating system error. Check errtext, correct problem, and restart udpclo.
CLO write() error on socket

Operating system error. Check errtext, correct problem, and restart udpclo.
Bundle is too big for UDP CLA.

Configuration error: bundles that are too large for UDP transmission (i.e., larger than 65535 bytes) are being enqueued for udpclo. Change routing.

BUGS

Report bugs to <https://github.com/nasa-jpl/ION-DTN/issues>