1. Default TTL values in TCP/IP.
http://www.map.meteoswiss.ch/map-doc/ftp-probleme.htm
2. Functional requirements for broadband residential gateway devices.
https://www.broadband-forum.org/technical/download/TR-124.pdf
3. RIPE Atlas: Internet data collection system.
https://atlas.ripe.net/
4. RIPE Atlas: Statistics and network coverage.
https://atlas.ripe.net/results/maps/network-coverage/
5. Technical details behind a 400Gbps NTP amplification DDoS attack.
https://goo.gl/j7zWEp