Ultra-densification is a key approach aimed at satisfying high data traffic in next-generation 5G networks. However, the high number of small cell eNB deployments in such ultra-dense networks (UDNs) may result in unnecessary, frequent, and back-and-forth handovers, with additional problems related to increased delay and total failure of the handoff process. Additionally, due to the separation of control and data signaling in 5G technology, the handover operation must be executed in both tiers. In this article, we propose an SDN-based mobility and available resource estimation strategy to solve the handover delay problem. Here, we estimate the neighbor eNB transition probabilities of the mobile node and their available resource probabilities by using a Markov chain formulation. This allows a mathematically elegant framework to select the optimal eNBs and then assign these to mobile nodes virtually, with all connections completed through the use of OpenFlow tables. Finally, we compare the conventional LTE and our proposed handover strategies by analyzing the observed delays according to the densification ratio parameter. Also, we analyze the handover failure ratios of both strategies according to the user number. Results reveal that the proposed strategy reduces the handover delay and failures by 52 and 21 percent compared to the conventional approach.