| Value | Meaning |
|---|---|
| IPPROTO_IP0 | default internet protocol (probably 4 for compatibility) |
| IPPROTO_IPV44 | internet protocol version 4 |
| IPPROTO_IPV641 | internet protocol version 6 |
| IPPROTO_ICMP1 | internet control message protocol |
| IPPROTO_IGMP2 | internet group management protocol |
| IPPROTO_TCP6 | transmission control protocol |
| IPPROTO_PUP12 | PARC universal packet protocol |
| IPPROTO_UDP17 | user datagram protocol |
| IPPROTO_IDP22 | Xerox NS protocol |