Does it make sense to construct a WAN using Internet protocol?
Does it make sense to construct a WAN using Internet protocol? If so, how can this be implemented for a WAN covering less than three major cities in three different countries?
It is more and more common for businesses to interconnect offices using IP VPNs which run over the public Internet. In order to provide security in this type of environment, IP VPNs will often leverage IPsec tunnels. With respect to performance, one of the biggest challenges with IP VPNs comes from packet loss due to congestion in the Internet. This can be overcome using techniques like Forward Error Correction (FEC), where additional loss-recovery packets are sent for every "N" real packet. This additional loss-recovery packet enables network-layer equipment to reconstitute lost packets at the far end of a WAN link, before the packets are delivered to TCP or other transport layers. This avoids transport-layer retransmissions and, in the case of TCP, prevents TCP's congestion avoidance mechanism from stepping in and lowering the throughput available to the application. For the modest overhead of an additional loss-recovery packet, FEC reduces packet losses dramatically, enabling applications to benefit from the maximum throughput that the WAN link can support.
This was first published in March 2007