Datagrams Under UNIX IPC Domain in 4.2BSD
gwyn%brl-vld at sri-unix.UUCP
gwyn%brl-vld at sri-unix.UUCP
Sun Jan 22 00:59:10 AEST 1984
From: Doug Gwyn (VLD/VMB) <gwyn at brl-vld>
User datagrams indeed are not useful for reliable communication, unless
you layer around them a reliable transport protocol. The intention of
datagrams is to provide a cheap service for applications where delivery
of messages need NOT be guaranteed. Most applications require a more
reliable message-passing mechanism.
Some possible datagram applications are:
Net information servers, such as the "rwho" daemon. It may not
be too important to get EVERY update for such information so
long as nobody trusts the absolute accuracy of the net status.
Sampling data acquisition. It may not be necessary to collect
EVERY datum if you are randomly sampling something.
System clock rate adjustments in a network. Generally some
slop in the relative clock rates must be permitted; it is okay
to miss a few packets from the master time server so long as
the rate is eventually tweaked on each host.
Junk mail. It is more important to have the transport done
cheaply than it is to ensure delivery.
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