Overhead Characteristics

Figure 10: Overhead Characteristics in the wide-area testbed: Compares overhead of FEC+ARQ with FEC and Average loss rate across the links, $p_{avg}$.

Figure 10 shows the cumulative distribution of the overhead for an FEC+ARQ based CLVL across the $83$ overlay links over which we performed our measurements. For each link, we ran an $N-$TCP pipe for $N = 10$ and measured the overhead required to achieve a target loss rate of $q=0.1\%$. We notice that the overhead of FEC+ARQ is very close to the average loss-rate along the overlay links. The difference between the two is the amount of FEC used in the second round to protect the retransmitted packets. In comparison, a pure FEC based CLVL construction far higher bandwidth. This is primarily due to the network loss characteristics: the burstier the background traffic (i.e., the longer the tail of the loss-rate distribution), the higher the amount of FEC required to recover from these losses [22].