ISC DHCP supports an ASCII or binary option type
ISC DHCP has two "string" types:
- t - ASCII text
- X - either an ASCII string or binary data. On input, the option can be specified either as a quoted string or as a colon-separated hex list.
Kea has string and binary, t matches string but X can be either string or binary. Now only one standard option has a trailing X so the implementation converts X to string (option-def) and when building data (option-data) converts full binary input to binary with csv-format to false. For trailing X add a comment saying that the last type should be changed to binary.
Unfortunately mostly for documentation purpose.