Comment by hylaride

We're about half-way to exhausted, but a huge chunk of the ones assigned are long deprecated and/or proprietary technologies and could conceivably be reassigned. Assignment now is obviously a lot more conservative than it was in the 1980s.

There is sometimes drama with it, though. Awhile back, the OpenBSD guys created CARP as a fully open source router failover protocol, but couldn't get an official IP number and ended up using the same one as VRRP. There's also a lot of historical animosity that some companies got numbers for proprietary protocols (eg Cisco got one for its then-proprietary EIGRP).

https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers