| Value | Meaning |
|---|---|
| unspec0 | Unspecified. |
| local1 | Local to host (pipes and file-domain). |
| unixlocal | POSIX name for PF_LOCAL. |
| inet2 | IP protocol family. |
| ax253 | Amateur Radio AX.25. |
| ipx4 | Novell Internet Protocol. |
| appletalk5 | Appletalk DDP. |
| netrom6 | Amateur radio NetROM. |
| bridge7 | Multiprotocol bridge. |
| atmpvc8 | ATM PVCs. |
| x259 | Reserved for X.25 project. |
| inet610 | IP version 6. |
$(D_PSYMBOL AddressFamily) specifies a communication domain; this selects the protocol family which will be used for communication.