IDP | DSP | |||
AFI | IDI | Subnet-ID | System-ID | N-Selektor |
Format of an OSI network address
The Internet address (network address) comprises the components IDP (AFI, IDI) and DSP. IDP (Initial Domain Part) describes the type and structure of the address, where AFI (Authority and Format Identifier) defines the structure and length of the address itself. IDI (Initial Domain Identifier) describes the addressing area, as well as the institution responsible for assigning the DSP.
Finally, the DSP (Domain Specific Part) contains the network address itself, divided into subnet ID, host ID, and N-selector. The Internet address is up to 20 bytes in length. Routing information can be obtained from the RIB (Routing Information Base). The RIB contains the assignment of network and subnetwork address. The RIB is set up and updated either dynamically or administratively.
Since Ethernet addresses are used within a subnetwork, the ISO protocols ISO9542 and ISO8473 are available for the assignment of Ethernet addresses to OSI addresses and vice versa. Both these protocols periodically update the Routing Information Base (RIB) with the appropriate address entries.