Why datagram service is unreliable

[jdd at allegra.UUCP]

    The design decision that datagram service is unreliable was made by
    DOD, in the TCP/IP protocol. This is what 4.2 implements.  Over
    (say) a local network, the chances of a datagram being garbled or
    lost are very slim. The virtual circuit service (TCP) is implemented
    by using the datagram service (IP) with sequence numbers and
    acknowledgements; there is, of course, a speed penalty for this.

Another off-the-wall reply.  The 4.2BSD \Internet/ domain implements TCP/IP;
I'm talking about the \UNIX/ domain.

Cheers,
John ("Can Anybody Here Read?") DeTreville
Bell Labs, Murray Hill