CLTP is a simple, unreliable datagram protocol which is accessed via the
SOCK_DGRAM abstraction for the ISO protocol family. CLTP sockets are connectionless, and are normally used with the
sendto(2) and
recvfrom(2) calls, though the
connect(2) call may also be used to fix the destination for future packets (in which case the
recv(2) or
read(2) and
send(2) or
write(2) system calls may be used).
CLTP address formats are identical to those used by TP. In particular CLTP provides a service selector in addition to the normal ISO NSAP. Note that the CLTP selector space is separate from the TP selector space (i.e. a CLTP selector may not be “connected” to a TP selector).
Options at the CLNP network level may be used with CLTP; see
clnp(4).