Network Service Access Point (NSAP) address is the networklayer address for CLNS packets. An NSAP describes an attachment to a particular service at the network layer of a node, similar to the combination of IP destination address and IP protocol number in an IP packet. NSAP encoding and format are specified by ISO 8348/Ad2. NSAP address has two major parts: the initial domain part (IDP) and the domain specific part (DSP). The IDP consists of a 1-byte authority and format identifier (AFI) and a variable-length initial domain identifier (IDI), and the DSP is a string of digits identifying a particular transport implementation of a specified AFI authority. Everything to the left of the system ID can be thought of as the area address of a network node. See also NSAP.