So IP networks are robust. If there is enough redundancy built into the system, then communication is maintained. In 1975 when SNA was designed, such redundancy would be prohibitively expensive, or it might have been argued that only the Defense Department could afford it. One could imagine an IP router in Atlanta routing messages for smaller cities throughout the Southeast. The problem is that data arrives without a reservation.
Airline companies experience the problem around major events, like the Super Bowl.
Just before the game, everyone wants to fly into the city. After the game, everyone wants to fly out. Imbalance occurs on the network when something new gets advertised. Occasionally a snow storm cancels flights and airports fill up with stranded passengers. Many go off to hotels in town.