Reordering of IP Packets in Internet

We have analyzed the measurements of the end-to-end packet reordering by tracing UDP packets between 12 testboxes of RIPE NCC. We showed that reordering quite often happens in Internet. For bursts of 50 100-byte UDP packets, there were about 56% of all the streams arrived at the destinations out-of-order. We studied the extent of the reordering in these streams, and observed that most reordered streams have a relative small number of reordered packets: about 14% of all the streams have more than 2 reordered packets in a bursts of 50 UDP packets. In addition, we showed that packet reordering has a significant impact on UDP performance since reordering adds a high cost of recovering from the reordering on the end host. On the other hand, packet reordering does not have a significant impact on the UDP delay. We also compared the reordered stream ratios in the different directions of Internet paths, and observed that reordered stream ratios are asymmetric, but they vary largely from testbox-to-testbox.