Congestion control with ICMP
Having solved the small-packet congestion problem and with it the
problem of excessive small-packet congestion within our own network, we turned our attention to the problem of general congestion control. Since our own network is pure datagram with no
node-to-node flow control, the only mechanism available to us
under the IP standard was the ICMP Source Quench message. With
careful handling, we find this adequate to prevent serious
congestion problems. We do find it necessary to be careful about
the behavior of our hosts and switching nodes regarding Source
Quench messages.