The first router I ever worked on was one of these:
or rather, one of these boxes. The picture shows a "Torn-Tape Relay Center". Each of those rack-sized boxes contains two "Printing Reperforators" and three "Transmitting Distributors", plus power-supplies and a mess of relays. Messages came in on the two Re-perfs, being punched into chadless tape with printing along the top edge. Operators tore each message off individually, read the "headers", and placed the message in the TD (tape reader to computer-folks) corresponding to its next hop. The third TD on each box was fed from a prepared roll of sequence numbers. When the operator hit the "GO" button, that TD would send the next message-ID, which would end in a number. When the "letters-shift" code at the end of the number was detected (mechanically!), the selected "message" TD would start and send the message. Each "link" ran at a blazing 45.45 baud. Anybody want to figure out how many of these boxes would be needed to equal the bandwidth of a CRS-1?