Efficient topology discovery for African NRENs

Abstract

The proliferation of under-sea and terrestrial fibre optic cables in Africa is leading to an evolution of the interconnection among Africa's National Research and Education Networks (NRENs). To fully monitor and track this evolution, NREN stakeholders and researchers need to continuously run active network measurements to map the inter-NREN topology. However, active topology measurement tools, such as Traceroute, introduce additional traffic in the network, which maybe undesirable for networks that have limited bandwidth. Furthermore, many network routers are configured to block/drop network probing packets, thereby making the task of topology discovery a lot more difficult. The paper aims to show that by carefully analysing Internet path overlaps, significant reductions can be made on the number of packets required to probe the topology. Furthermore, by using multiple probing protocols and vantage points, it is possible to alleviate the impact of blocked packets. The paper reports on a Traceroute study carried out on African NRENs, which shows that by jointly using different probing protocols, and taking into consideration path overlaps, it is possible to map all probe destinations, while achieving a 65% reduction in the number of probe packets sent.