So, at 30 and 40 milliseconds we'll say again that we increase the window size accordingly and now at 50 milliseconds we'll say okay, we'll, the fifth packet is acknowledged and the current RTT is 50.8 milliseconds. So, the congestion window sized then went, it increased to eight and now it's at nine, so the window size is now at nine. So we have an RTT or a window size of 9, so we take 9 for the ideal case, and we divide that by 50 milliseconds. And we get 177 packets per second. And then we take for the non ideal case, we take 9 packets and we divide it by 50.8 milliseconds, and we get 180 packets per second. [SOUND]. Now, this is, this difference is exactly three when you subtract. You do 180 minus 177, and you get 3. So that means that we keep the window size the same. So the end, the end results here is that the congestion window size is going to stay right at nine. And we can show that in the diagram here. basically what happens is if we slide over, right and since the difference was equal to thresholds, we just send one new packet, right. because, so there's no increase. There's no additive increase. It's just a sliding window effect whereas before we saw the sliding window effect in the additive increase simultaneously. Now, at 60 milliseconds the six packet gets an acknowledgement. And the current RTT is 51.8 milliseconds that we observed for that packet, so let's see what happens here. So now we have 9 milliseconds again, we divide it by 50 milliseconds, just like before we get roughly 177 packets per second. And for the non ideal case. We have 9, and we have 51.8 milliseconds. And doing that division gives us 173.7 packets per second. So, and subtracting these out, we get 180 minus 173.7. And that gives us 6.3 packets per second. [SOUND] And that is greater than 3. So what happens is then, we decrease the congestion window size. So now the congestion window size goes down, to 8. So now to see that in a diagram, since the difference is greater than the threshold, we slide but we also decrease the window size by one, so that means that we're we only have window four so we don't send any packets at all. So, once the window size decreases now, we're still sliding but we're decreasing at the same time and they counteract each other out. So, remember there's three different cases here. The first case is that. We just slide and we have it greater than, or we have it less than the threshold, in which case we also increase. That causes us to send two packets. if the difference is the same as the threshold then we slide and we send one packet, because there's no additive increase. And if the difference is less than threshold we slide, but at the same time congestion windows decrease by one, so we don't send any packets. So, at 70 and 80 milliseconds we decrease the congestion window size again, so we can say that it goes down to seven and then to six and then we can look at a plot over time, just to see where we might be going from here. Again, all these you know, this is just a made-up example, so just to plot the. Congestion window over time instead we're increasing every ten milliseeconds we basically are seeing something else happen. So, every 10 milliseconds something is coming in, then we actually hold steady for awhile, for two, then we start decreasing and then we hold steady, then we start increasing again. And, as we see this whole pattern of increase, hold steady, decrease. And increase hold steady. decrease then hold steady and so on, that would keep happening. And the objective is to get the congestion to a reasonable window. so everyone has to accept a certain amount below a threshold because you might be wondering why, why if we why, why when we hit the threshold don't we keep increasing or ramping up. Well the idea is you, you can never get to the ideal scenario right? You can never get to the ideal RTT/g. Right, so why don't you want to drive it under 0, it's because you don't want to ever, you're never going to be operating in ideal conditions. so everyone has to accept a certain amount below a threshold a to be operating the network efficiently and b so that no one is achieving higher rate, really than anyone else. So it has to be allocated fairly among all of the users. [BLANK_AUDIO]