TCPsessioner

TCPsessioner is a software framework designed to observe, analyze, and manage Transmission Control Protocol (TCP) sessions across computing hosts and networks. It provides instrumentation, state tracking, and analytics to monitor the lifecycle and performance of TCP connections in real time and historically. The primary goal is to help operators, developers, and researchers understand how TCP sessions behave under varying loads, networks, and configurations, and to diagnose performance or reliability issues.

The architecture typically consists of a lightweight session core, a data collection layer, and a presentation or integration layer. The session core assigns a per-session identity using the standard four-tuple (source IP, source port, destination IP, destination port) and optionally associates the session with a process. It tracks the TCP state transitions (SYN, SYN-ACK, ESTABLISHED, FIN, RST) and records metrics such as round-trip time, retransmissions, congestion window estimates, and bytes transferred. Depending on deployment, TCPsessioner can operate in-kernel, in user space, or as a hybrid agent, often leveraging technologies such as eBPF, kernel probes, or packet capture libraries to collect data with minimal overhead.

Key features include fine-grained session lifecycles, RTT and retransmission analysis, congestion control behavior monitoring, loss and delay metrics, and event logging. It supports multiple TCP variants and negotiates options such as SACK and path MTU where available. Data can be exported to dashboards, monitoring systems, or analytics platforms for correlation with application performance and network conditions.

Common use cases are performance tuning, troubleshooting latency and loss, validating congestion control behavior during load testing, and security monitoring for anomalous resets or reset storms. Privacy and performance implications must be managed, and proper privileges are usually required.