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Briefly, the method used to assure successful IMP-Host
transfers is similar to that used for the inter-IMP channels.
Logical channels are used as described in section 2.3.1,
although in this case only two channels are employed and the
order of transmission is important.
Therefore, both the
Host and IMP software must be aware of packets.
For example,
assume packet A is transmitted from an IMP on channel 0, and
packet B is then transmitted on channel l. If an error were
detected in packet A, but not B, no ack would be returned for
A. ;rhe Host would retain Packet 1:3 until r.
A is retransmitted
to it and received successfully, thus insuring delivery of
the packets to its own processes in order A-B.
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