LatScope: End-to-End Latency Decomposition Across the Cloud Network Stack

Abstract

Data centers are rapidly scaling and becoming more complex, making it critical to pinpoint where latency arises across the network protocol stack. Existing tools primarily measure RTT or single-layer delays, while multi-layer approaches are often invasive or limited. We present LatScope, a practical multi-layer latency analyzer that (i) matches packets across layers to compute accurate inter-layer delays despite retransmissions and out-of-order delivery, (ii) synchronizes server clocks using XDP to enable precise inter-server delay breakdowns, and (iii) controls overhead through selective data extraction. We validate LatScope across diverse environments and show how its insights can be applied effectively in cloud deployments.