Flow control: Backpressure
Link tells the sender explicitly how much it can send without suffering losses
- Let b be the bandwidth at which sender can send
- r be the time for the link to respond to new traffic
Start and stop signals
- Allow r b units of traffic between a start and a stop
- Link that has to buffer this traffic will overrun and lose traffic if r is too large
- Autonet and RS-232
'Credits’
- Allow a certain amount of traffic to be sent
- The number of unused credits is called 'window’
- A credit scheme needs r b credits when the link is idle to keep running at full bandwidth
- Link will underrun and waste bandwidth if r is too large
- TCP
- also uses backoff to deal with congestion within the link (the underlying packet network)