During the last few years, the research community has shown an increasing interest in the subject of inter-domain routing in optical networks, so new approaches like the optical extension of BGP, namely OBGP, have arisen. However, it is widely accepted now that a multi-domain routing model mostly centered on the exchange of reachability information – like the one we have today or the one provided by OBGP – is not going to be enough in the future. Routing domains must be able to exchange both, reachability, as well as aggregated Path State Information (PSI). Understanding that there is a missing piece in the routing models provided by BGP and OBGP is easy nowadays, but contributing with solutions capable of highly improving the performance of these routing protocols without increasing the number and frequency of the routing messages exchanged between domains is a challenging task. This study makes the following contributions. First, we propose a straightforward strategy to compute highly aggregated PSI between routing domains. Second, we propose OBGP+, an extended version of OBGP that exploits this PSI to compute inter-domain lightpaths in a highly efficient way. Third, in order to avoid the typical increase in the number of routing messages associated with the update of PSI, we propose to piggy-back these updates in non-dummy Keepalive messages exchanged between OBGP+ neighbors. Extensive simulations made with OPNET in the PAN European network topology reveal that: i) OBGP+ is able to drastically reduce the blocking experienced with OBGP; ii) while even needing less number of routing messages than OBGP to achieve this performance.