The TCP/IP transport service uses IP/IPv6 addresses for communication with a partner computer. However, instead of numeric IP/IPv6 addresses, important computers are often identified by names. These names can be stored in the Domain Name System (DNS) as Fully Qualified Domain Names (FQDNs). The DNS serves as a globally distributed naming system, structured hierarchically into different domain levels. An FQDN is a structured string that follows specific syntactic rules. It consists of multiple parts (subdomains/labels), separated by dots. The maximum length of a label is 63 characters (bytes), and the maximum length of an FQDN is 255 characters, including the dots. The number of labels within an FQDN is limited only by the maximum length of the FQDN. The structure of valid DNS names is described in RFC 1034 and RFC 1035, with further updates and improvements in later RFCs.
An FQDN can be associated with multiple IP/IPv6 addresses, which are returned as a list by the nameservers. Additionally, different FQDNs can lead to the same object, meaning that multiple DNS names can be assigned to one object in the DNS. FQDNs that identify the same object are known as alias names.
In BCAM, DNS names can be used to identify hosts (including virtual hosts) and processors. Both BCAM applications and SOCKETS applications can directly utilize DNS names, significantly simplifying diagnostics and identification.