MSS (maximum segment size) is the term at the TCP layer. Each end of a connection can (and usually does) declare its MSS in a TCP option in the first packet it

MSS (maximum segment size) is the term at the TCP layer. Each end of a connection can (and usually does) declare its MSS in a TCP option in the first packet it sends. Advertised MSS, interface MTU, and route MTU can all constrain packet sizing. Using large-MTU routes for internal destinations can work well.