Elastic optical networking (EON) has the constraint that all flows must have contiguous allocated frequency slots across all fiber links end-to-end, hence, the routing, modulation and spectrum assignment (RMSA) is one of the most important considerations in EON. This paper proposes and demonstrates a design of a generalized multiprotocol label switching (GMPLS) control plane for EON with distributed RMSA. The proposed approach uses an extended RSVP-TE to find multipath by broadcasting PATH message, using tentative reservation to avoid setting up multipath for one request. The proposed method also overcomes challenges faced by the previously pursued GMPLS-EON methods which relied on dynamic OSPF-TE where control plane overhead and the collision among lightpath requests caused by signaling latency. Simulation results based on the proposed GMPLS-EON method on different network scenarios reveal that our proposed design reduces the blocking probability by 4.56 and 3.86 when compared with the conventional GMPLS and GMPLS/PCE approaches, respectively, in the NSF topology at the network offered load of 60 Erlang. It also reduces signaling time by a factor of 1.84 compared with conventional GMPLS/PCE approach in the same network condition.