B. Effect of link parameters on reordering
Our next set of simulations study the effect of reordering on the application layer buffer requirements at the client.
We study three key parameters which can affect reordering,namely, edge link data rate, link latency and number of hops from the striping router to the end host. The basic topology remains the same as before, but this time the client is equipped
with two Wi-Fi interfaces and is kept static.
For the baseline scenario, the number of hops from the striping router to the end host is kept at 2, the end-to-end link delay is kept at 10ms and the Wi-Fi edge data-rate for each of the interfaces is set to 36Mbps.
Each parameter is then changed, such that they are in ratios of 1:1, 1:2 to 1:5, keeping the others constant.
The buffer size at the application is measured, from which the average buffer occupancy is calculated in each case.
As seen in Fig. 5, the dominant factor in reordering is the disparity
in the data rate of the edge links.
Note that increase in the number of hops from the striping router to end-host increases
the delay for the ack-withholding to set in and therefore increases the reordering. However, even with a hop ratio of 1:5, the reordering requirements are minimal.
Fig. 6 shows the improvements in terms of reduction of buffer requirements,when we employ out-of-order chunk delivery, as proposed in Sec.
III-B. This optimization does not affect the reordering due to number of hops, however, the scheme brings down the reordering due to both link delay and data rate disparities. Note that this would not in any way reduce the raw throughput at the client, as the striping router only sends chunks out-of-order,if available, and does not wait idle for chunks to arrive at the back of the queue if it already has pending chunks to send.