Service curves
Another way of looking at GPS: If connection i is backlogged during interval [t’, t), it is guaranteed that wi(t’,t) ? (t - t’) fi, where wi(t’,t) denotes the amount of service connection i receives over the interval [t’, t)
Packet-GPS algorithms make a weaker guarantee: If connection i is backlogged at time-instant t, it is guaranteed that wi(t’,t) ? (t - t’) fi where t’ is the start of some backlogged interval for connection i
Can alternatively state this as follows: Let Si(to) = fi to. Then, If connection i is backlogged at time-instant t, it is guaranteed that wi(t’,t) ? Si(t - t’) where t’ is the start of some backlogged interval for connection i