Middlebox has quite precise technical meaning: anything that works at higher layer than on which it is visible to neighboring network.
Usualy this refers to various "security" "solutions" which attempt to do deep packet inspection and generally break various things, but it also can mean NAT or L2 bridges that do filtering on L3/L4 headers (for example DOCSIS CMs and CMTSes are such middleboxes)
Usualy this refers to various "security" "solutions" which attempt to do deep packet inspection and generally break various things, but it also can mean NAT or L2 bridges that do filtering on L3/L4 headers (for example DOCSIS CMs and CMTSes are such middleboxes)