the DHCP sets other networking information, of which the most important are the IP addresses of the DNS servers because without access to a DNS server a given host cannot resolve domain names into IP addresses, which is necessary for Internet-based communication. Therefore DHCP is also standardized for dynamic assignment of IPv6 addresses, called DHCPv6 [13]. From the QoS point of view, proper functioning of the DHCP server in the IP network to which a given host is attached is crucial in order for a host to obtain an IP address on its network interface in a plug-and-play manner and to have Internet connectivity. 2.1.4 Domain Name System - DNS While in traditional telephone networks the main naming and addressing space was (and it still is) the telephone numbering space, standardized and governed on a global scale by the ITU (defined with ITU-T E.164 telecommunication numbering plan [14]), on the Internet there are exactly two name spaces, which are governed on a global scale by ICANN and its department IANA. These two name spaces are: IP addresses, including: IPv4 addresses, e.g. 194.149.144.1 (typically given in decimal-dot notation, with a length of 32 bits) IPv6 addresses, e.g. 2001:0000:0000:0000:0008:0800:200C:417A (typically given in a hexadecimal notation, with a length of 128 bits); domain names [15], e.g. "www.itu.int," "www.ietf.org." DNS was created to provide a means for using names (domains) instead of IP addresses to access certain machines on the network as people more easily use names than long 2.1 Overview of Internet Technology Protocols numbers. However, machines communicate over the Internet only via IP addresses, SO the domain name must be resolved to an IP address (which corresponds to the given domain name according to the DNS system records). For that purpose, DNS is a dis- tributed hierarchically-based system which translates a domain name to an IP address associated with that domain. DNS is a fundamental Internet technology which provides translation between the two name spaces on the I