Experimental Analysis of TCP Connection Memory Consumption in Different Socket States

The article investigates the actual memory footprint of a TCP connection in the Linux kernel, considering real‑world scenarios where connections send and receive data and transition through states like ESTABLISH, TIME_WAIT, and others.

Experiment 1: ESTABLISH (idle) connection – Images illustrate the memory usage of a newly established socket without data transfer.

Experiment 2: Client → Server data transmission – Measurements show memory consumption when the client sends data to the server.

Experiment 3: Server → Client data transmission – Similar measurements for data flowing from server to client.

Experiment 4: Non‑ESTABLISH states – Includes observations for sockets in states such as TIME_WAIT, highlighting additional memory reclamation.

The final summary consolidates the findings, noting that the kernel employs several strategies to reduce socket memory usage:

The kernel promptly recycles send and receive buffers, with newer kernel versions improving this behavior.

The minimum size of these buffers is not strictly tied to the rmem kernel parameter and can be smaller in practice.

In other states, for example TIME_WAIT, the kernel also frees unnecessary objects like socket_alloc .

Overall, the experiments demonstrate that kernel-level optimisations significantly affect the memory overhead of TCP connections.