Performance and scalability are critically-important for on-chip interconnect in many-core chip-multiprocessor systems. Packet-switched interconnect fabric, widely viewed as the de facto on-chip data communication backplane in the many-core era, offers high throughput and excellent scalability. However, these benefits come at the price of router latency due to run-time multi-hop data buffering and resource arbitration. The network accounts for a majority of on-chip data transaction latency. In this work, we propose dynamic in-network resource reservation techniques to optimize run-time on-chip data transactions. This idea is motivated by the need to preserve existing abstraction and general-purpose network performance while optimizing for frequently-occurring network events such as data transactions. Experimental studies using multithreaded benchmarks demonstrate that the proposed techniques can reduce on-chip data access latency by 28.4% on average in a 16-node system and 29.2% on average in a 36-node system.