We have an SRX320 that uses a BT VDSL connection with an MTU of 1492. We have to use an all-tcp mss setting of 1350. In theory, this should be 1452, but I have also read somewhere in Juniper documentation a value of MTU-60 is recommended i.e. 1432. However, neither of these values allow for successful internet browsing. We have identical setups elsewhere which require no specific MSS setting. 1350 seems to the be the sweet spot on this router, but my question is why given the tried and tested calculations out there?