Flow control
Many links do not have a fixed bandwidth that is known to the sender
- Link may be being shared (multiplexing)
- Receiver can’t always accept data.
Fixed bandwidth is bad when traffic is bursty
- It is either too small or too large
- Sender may not know the link bandwidth or can’t be trusted to stay below it
Flow control is necessary to match the flow of traffic to the link’s or the receiver’s capacity
A link can provide this in two ways, by contention or by scheduling -- these strategies take the form of backoff or backpressure