SCTP, DCCP are special case. Ideally those protocols supposed to be handled only by the endpoints, but over time the support of those protocols leaked to the ne

SCTP, DCCP are special case. Ideally those protocols supposed to be handled only by the endpoints, but over time the support of those protocols leaked to the network as well. Mainly because of wasteful allocation of IPv4 addresses we had to use NAT. A lot of that equipment makes other protocols impractical because they are not supporting them, even though initially they shouldn't have anything to do with them. I suppose HTTPs equivalent of that would be various http proxies, but in that case barely anyone uses them.