Option 43; Options 128 - Compaq t1000 - Terminal Thin Client PC Network Installation Manual

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Configuring Terminal Start-Up Resources
Files ending in a .txt name are treated as text files. Any other filename is treated
as an RFC-compliant file.
Use of this option requires a TFTP server. Since path names are included in the file,
the TFTP server must accept UNIX-style file separators, not DOS-style separators.
Likewise, the default transfer mode must be binary, and the file (either format) must
be capable of being read by the terminal without modifications (i.e., the terminal
does not accept carriage returns at the end of lines).
This provides the ability to give arbitrarily large option data to the terminal,
bypassing the limitations of the Maximum DHCP Message Size option and some
servers.

Option 43

Option 43 is the industry-standard method for providing vendor-specific option data
to network devices. The three disadvantages are: the total length of option 43 (i.e.
all vendor specific options) is 255 bytes; the option data is typically hard to enter;
and some servers do not maintain different scopes of option data based upon
Vendor ID, Client ID, or other device-defining tag. The Option ID for these options
are listed in an earlier table.

Options 128+

There is debate in the DHCP community about whether or not options 128 through
254 are for vendors' use. If your server is incapable of sending different option 43
values based upon an identifier, if you can not use TFTP, if you do not want to edit
binary data, or if the total set of T1500/T1510 options is greater than 255 bytes, all
T1500/T1510-specific options are available as text strings in this option space. All
T1500/T1510 options have the prefix 0080_ and are described in an earlier table.
By default (i.e., without configuring), the terminals request none of the 127 options
in this space. By running Setup, the set can be increased. Any T1500/T1510 option
can be placed anywhere in this option space, since the 0080_ tag is checked to
determine whether or not it is a valid option. If you know what option numbers are
going to be used, you can use Setup to define the requested set to just this set of
option numbers; if you do not know, you can expose the entire option space.