Library /sys$common/syshlp/ncphelp.hlb SET, LINE, ECHO LENGTH number  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Applies only to FDDI lines.  Specifies the number of bytes used in an
 echo request frame.  The hexadecimal bytes are specified by the ECHO
 DATA parameter. The frame is sent to the address specified by the ECHO
 TARGET parameter.

 The number must be a decimal value from 0 to 4478.  The default ECHO
 LENGTH  is 1.  ECHO LENGTH can be set in the volatile database, but it
 cannot be defined in the permanent database.