Enabling Source Hosts to Precisely Select Paths via ECMP Hash Linearity in Data Center Networks

In data center networks (DCNs) with high-density computing power, the path selection managed by the equal-cost multi-path (ECMP) hashing function often causes path overlap and overuse of switch ports, undermining performance. While recent approaches allow hosts to influence egress port selection via single-bit changes in packet headers, they offer limited port coverage and are restricted to determining a single hop’s egress port. To address this, we propose a host-based path selector (HPS) that enables source hosts to precisely select paths via multiple hops by making targeted multi-bit header changes. HPS is based on two key principles: (a) exploiting the predictable relationship between the relative changes to hash values to select switch egress ports effectively, and (b) applying the criteria for ensuring modified headers accurately direct packets along the desired path. HPS iteratively adjusts packet headers at each switch along the path, ensuring efficient path selection with polynomial time and constant space complexity, making it scalable for large networks. We evaluated HPS in two and three-layer DCN topologies, testing up to 1,000 paths. The results show that HPS enables precise path selection, greatly reducing path overlap compared to traditional ECMP and state-of-the-art RePaC port influence method, resulting in substantial performance improvements.