(a) Distribution of best protocol responses across hosts across all nine snapshots (b) Variation of number of hosts responding to a protocol handshake with number of surveys.
Multiple systems actively monitor the IPv4 address space for outages, often through ICMP probing. In this work, we explore the potential benefits (in terms of increased coverage) of leveraging additional protocols for probing by analyzing Internet-wide scans conducted using transport layer (TCP/UDP) probes. Using several existing Internet-wide scan snapshots, we show that between 531k to 606k additional /24 blocks, which were originally too sparse to be monitored via ICMP probing alone, now have the potential to be monitored for outages. We also find that it is possible to improve the probing efficiency for 850k-970k blocks, of which, 106k-125k blocks were not observed in the previous two years of ICMP-based scans. We observe that the average percent of /24 blocks per AS that could potentially be reliably monitored for outages increases from 65% to 83%, spanning 28k ASes.