Http header or URL parameter to identify user in proxy

[digitalirony 22]

I want to capture a unique string from the HTTP header, or URL that is tied to a particular user that is making the call. Does this exist? If so, where is it, and what is the key?

I don't want to use sessions, because I want to use this to set a connection limit per user in my reverse proxy, not just per session. 

 

Basically what I am asking is, is there some sort of unique userID variable that I can capture in my gateway that I can act upon, that I can be sure is related only to user account that is making the request, and will always match that user across all sessions(so if they login from two devices at once, it would affect both)?

[Luke 37057]

Hi, yes, the Authorization header:

https://github.com/MediaBrowser/Emby/wiki/User-Authentication