Packets are lost even though links are up — why does network slow itself?
Per Wikipedia: “Congestion is overload when offered load exceeds capacity; queue builds, drops occur, goodput collapses without control.”
Like traffic jam — too many cars entering highway slows everyone, even those already on it.
- Load increases
- Buffers fill
- Drops increase
- Retransmits add load
- Collapse without backoff
- Distinct from flow control (receiver) vs congestion (network)
- Needs feedback — drops or ECN
- Backoff essential
TCP backs off on loss- Related: Circuit Switching — circuit avoids congestion via reservation
- Related: Packet Switching — packet suffers congestion
- Builds into: Datagram Network — datagram needs congestion control
- Related: Store-and-Forward — congestion lives in buffers
- Adding bandwidth alone — without control still collapses
- Confusing congestion with noise loss