MSS or maximum segment size is the total number of data transferred minus the TCP and IP header. The total number of transmitted frames in a switch network is between 64 bytes to 1518 bytes with a header and trailer. The MSS does not exclude this data-link layer effect but only the transport layer like TCP and UDP, and IP address header, unlike the mtu (maximum transfer unit) which involves all headers.
Sandbox testing is used to test the new changes which is not their in your production server. Sandbox refers to a test server where we can deploy untested changes so that tester can test those changes separately
