How fast is ISDN over Inmarsat Fleet F77 and Fleet 55?

Inmarsat Fleet F77 ISDN provides a 64Kbps link (‘Euro ISDN’). N.B. As with any such connection, the actual speed of delivery depends on the slowest link between the user and the distant end, and the application used, which may deliver less than 64Kbps. AND, for Fleet 77 users, there is an upgrade to 128Kbps service available.