ltpclock - Online in the Cloud

PROGRAM:

NAME

ltpclock - LTP daemon task for managing scheduled events

SYNOPSIS

ltpclock

DESCRIPTION

ltpclock is a background "daemon" task that periodically performs scheduled LTP
activities. It is spawned automatically by ltpadmin in response to the 's' command that
starts operation of the LTP protocol, and it is terminated by ltpadmin in response to an
'x' (STOP) command.

Once per second, ltpclock takes the following action:

First it manages the current state of all links ("spans"). In particular, it checks
the age of the currently buffered session block for each span and, if that age exceeds
the span's configured aggregation time limit, gives the "buffer full" semaphore for
that span to initiate block segmentation and transmission by ltpmeter.

In so doing, it also infers link state changes ("link cues") from data rate changes as
noted in the RFX database by rfxclock:

If the rate of transmission to a neighbor was zero but is now non-zero, then
transmission to that neighbor is unblocked. The applicable "buffer empty"
semaphore is given if no outbound block is being constructed (enabling start of a
new transmission session) and the "segments ready" semaphore is given if the
outbound segment queue is non-empty (enabling transmission of segments by the link
service output task).

If the rate of transmission to a neighbor was non-zero but is now zero, then
transmission to that neighbor is blocked -- i.e., the semaphores triggering
transmission will no longer be given.

If the imputed rate of transmission from a neighbor was non-zero but is now zero,
then all timers affecting segment retransmission to that neighbor are suspended.
This has the effect of extending the interval of each affected timer by the length
of time that the timers remain suspended.

If the imputed rate of transmission from a neighbor was zero but is now non-zero,
then all timers affecting segment retransmission to that neighbor are resumed.

Then ltpclock retransmits all unacknowledged checkpoint segments, report segments, and
cancellation segments whose computed timeout intervals have expired.

EXIT STATUS

"0" ltpclock terminated, 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
ltpadmin to restart ltpclock.

"1" ltpclock was unable to attach to LTP protocol operations, probably because ltpadmin
has not yet been run.

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