The bandwidth-intensive applications on Smart-Mobile-Devices (SMDs) are increasing with SMD's colossal growth. The overlapped cellular and non-cellular networks, in hot-spot-places, and SMDs capabilities are significant reasons for this growth. SMD's interfaces-RAT (Radio-Access-Technology) can have complementary link characteristics. The end-users can avail always-best-connectivity (ABC) on their SMDs with complementary RAT characteristics. This paper proposes an Integrated-multi-RAT-utilization (Im-Ru) framework for multipathcomputing support to realize ABC for the end-users. The Im-Ru framework has two approaches. The First is a hybrid-RATdiscovery model based on SMD's interfaces, current-location, and identification using ANDSF and MIIS servers. The second is the user's preference-based RAT-selection using weighted-RATparameters. We observe that the Im-Ru framework for multipathcomputing is useful in future 5G-NR networks. We analyzed the Im-Ru's performance related to average-throughput improvement over the existing approaches for SMD's different speeds and observed a significant improvement. The experimental results show that Im-Ru is more reliable by realizing lower packet-loss and delay than existing work.