Enable a compression algorithm.
The algorithm parameter may be "lzo", "lz4", or empty. LZO and LZ4 are different compression algorithms, with LZ4 generally offering the best performance with least CPU usage. For backwards compatibility with OpenVPN versions before v2.4, use "lzo" (which is identical to the older option "--comp-lzo yes").
If the algorithm parameter is empty, compression will be turned off, but the packet framing for compression will still be enabled, allowing a different setting to be pushed later.
DEPRECATED This option will be removed in a future OpenVPN release. Use the newer --compress instead.
Use LZO compression -- may add up to 1 byte per packet for incompressible data. mode may be "yes", "no", or "adaptive" (default).
In a server mode setup, it is possible to selectively turn compression on or off for individual clients.
First, make sure the client-side config file enables selective compression by having at least one --comp-lzo directive, such as --comp-lzo no. This will turn off compression by default, but allow a future directive push from the server to dynamically change the on/off/adaptive setting.
Next in a --client-config-dir file, specify the compression setting for the client, for example:
push "comp-lzo yes"
The first line sets the comp-lzo setting for the server side of the link, the second sets the client side.
I have the feeling that comp-lzo became compress lzo, for what I understood, it should be compatible. I suppose the setting became obsolete because you can use also LZ4