Kabelová, Alena and Libor Dostálek, Libor. DNS in Action. Birmingham, UK and Mumbai, India: Packt Publishing, 2006.
Understanding DNS – Beginner's Guide to DNS. Steve's Internet Guide's DNS tutorial: http://www.steves-internet-guide.com/dns-guide-beginners/
RFC 1034 – Domain Names – Concepts and Facilities. This is an introduction to DNS: https://www.ietf.org/rfc/rfc1034.txt
RFC 1035 – Domain Names – Implementation and Specification. The official DNS specification: https://www.ietf.org/rfc/rfc1035.txt
RFC 5905 – Network Time Protocol Version 4 Protocol and Algorithms Specification. The RFC for NTP: https://tools.ietf.org/html/rfc5905
What Is NTP? A more concise overview of NTP than you will find in RFC 5905: http://www.ntp.org/ntpfaq/NTP-s-def.htm
RFC 1157 – A Simple Network Management Protocol. The SNMP specification: https://tools.ietf.org/html/rfc1157
SNMP Basics: What is SNMP and How Do I Use It? This is a good overview of SNMP: https://www.networkmanagementsoftware.com/snmp-tutorial/