code: func (s *Server) HandleRequest(r *ssh.Request) {
  	switch r.Type {
  	case teleport.KeepAliveReqType:
  		s.handleKeepAlive(r)
  	case teleport.RecordingProxyReqType:
  		s.handleRecordingProxy(r)
  	default:
  		if r.WantReply {
  			r.Reply(false, nil)
  		}
  		log.Debugf("Discarding %q global request: %+v", r.Type, r)
  	}
  }
docs: // HandleRequest processes global out-of-band requests. Global out-of-band
  // requests are processed in order (this way the originator knows which
  // request we are responding to). If Teleport does not support the request
  // type or an error occurs while processing that request Teleport will reply
  // req.Reply(false, nil).
  //
  // For more details: https://tools.ietf.org/html/rfc4254.html#page-4