IANA assigns 256 registered Internet Protocol numbers (0-255). The protocols assigned to each number vary widely in capability, purpose, and function. What protocols do you route on your network? For sure TCP, UDP, and ICMP. Perhaps a few others as well for one reason or another. Are you sure that you only route the protocols you think you do? Looking at the data is the only way to find out for sure.
A colleague of mine was looking at a client network and discovered that the client was routing some pretty unusual protocols. The client was not aware of this and became quite concerned. Just another reason we should all be vigilant in monitoring our networks and studying what the data are telling us.