A number of protocols/services expose product tags describing the vendor implementation for a variety purposes. These tags generally include the "vendor" and some "version" information and are often used by protocol peers to alter behavior. In some cases, like HTTP (RFC 2616), they may include vendor/version information of subsystems. I am looking for references to technical specifications, considerations, and discussions concerning the use of product tags in Internet protocols. I would also be interested in any published materials describing operational experience using (or abusing) such information. Please note that this message is not intended to start a discussion or debate concerning the use ( or abuse) of product tags, we've likely "been there, done that". So, please, just references to existing works. Regards, Kurt