NCPS - Network Connection Performance Stress Tool

Overview

NCPS is a cross-platform tool designed to stress test and measure TCP connection setup performance.
It runs on both Linux and Windows (x64 and ARM64), and supports generating TCP connections at a high rate.

Purpose

This repository contains the NCPS source code and associated binaries for performance testing in high-connection rate environments.
It is primarily used for validating TCP connection performance at scale and diagnosing networking bottlenecks.

Key Features

• Generates billions of unique TCP 4-tuples
• Multi-threaded for high scalability
• Works on Linux and Windows
• Command-line interface with flexible configuration

Building NCPS UPDATE

• Using make:

	make; make install

• Using CMake:

	cd src
	mkdir build && cd build
	cmake ..
	make && make install

Windows Prerequisites

• Windows 10 version 1703 or higher is required.
• Enable large ephemeral port range as described below.

Linux Prerequisites

• Increase file descriptor limits in /etc/security/limits.conf as described below.
• Adjust system parameters in /etc/rc.local to optimize TCP behavior and disable connection tracking as described below.

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Platform-Specific Configuration

Windows

Make sure to enable large ephemeral port range:

Set-NetTCPSetting -AutoReusePortRangeStartPort 10000 -AutoReusePortRangeNumberOfPorts 50000

Reboot the system after applying the setting.

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Linux

Boost your system for high connection throughput:

1. Increase file descriptor limits via /etc/security/limits.conf:

   * soft nofile 1048575
   * hard nofile 1048575
   

2. Add the following to /etc/rc.local (ensure rc.local has execution permission):

   #!/bin/sh
   sysctl -w net.ipv4.tcp_tw_reuse=1
   sysctl -w net.ipv4.ip_local_port_range="10000 60000"
   iptables -t raw -I OUTPUT -j NOTRACK
   iptables -t raw -I PREROUTING -j NOTRACK
   sysctl -w net.netfilter.nf_conntrack_max=0
   sysctl -w net.ipv4.tcp_syncookies=0
   sysctl -w net.ipv4.tcp_max_syn_backlog=2048
   sysctl -w net.ipv4.conf.all.rp_filter=0
   sysctl -w fs.file-max=1048576

3. Re-login or reboot for changes to take effect.

Note: If you encounter error 24 in NCPS, verify that the increased FD limits are applied (ulimit -n). Error 23 indicates OS-level limits may still be restrictive.

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Quick Start

On Server:

ncps -s

On Client:

ncps -c <serverIP> -wt 30 -t 330

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Output Reference

Periodic Output Columns

   T(sec)        N   Pend   Failed   IOFail   Conn/s  Close/s RXkbyte/s TXkbyte/s  RT/i    c0/i c0rtt/i    cR/i  cRrtt/i 
    1.002        7   1593        0        0  69065.9  69058.9   69062.9   69065.9     0   69204   12888       0        0 
    2.002       14   1586        0        0  69987.0  69980.0   69978.0   69984.0   606   69381   12962     606   161224 

Fields:

• T(sec): Elapsed time in seconds
• N: Number of currently active connections
• Pend: Number of in-progress connect operations
• Failed: Cumulative number of failed connect operations so far
• IOFail: Cumulative number of failed send/recv operations so far
• Conn/s: Rate of successful connect operations in the current interval
• Close/s: Rate of connection close operations in the current interval
• RXkbyte/s: TCP payload receive rate (bytes/1000 per second) in the current interval
• TXkbyte/s: TCP payload send rate (bytes/1000 per second) in the current interval
• RT/i: Number of SYN retransmits in the current interval
• c0/i: Number of connect operations completed with 0 SYN retransmits in the current interval
• c0rtt/i: Avg SYN-RTT (µs) for connections with 0 SYN retransmits in the current interval
• cR/i: Number of connect operations completed with one or more SYN retransmits in the current interval
• cRrtt/i: Avg SYN-RTT (µs) for connections with one or more SYN retransmits in the current interval

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Final Stats Example

	=== CMDLINE: ./ncps2 -c 10.1.0.5 -wt 5 -t 15
	 
	=== VERSION 1.5
	 
	###RXGBPS 0.45
	###TXGBPS 0.45
	 
	=== Time (ms) to Nth connection establishment for first 556947 connections:
	===       N   T(ms)     CPS
	===  100000    1678   59594
	===  200000    3467   57686
	===  300000    5248   57164
	===  400000    7093   56393
	===  500000    8919   56060
	===  556947   10002   55683
	 
	###ENDCPS 55683
	 
	###CPS,100000:1678,200000:3467,300000:5248,400000:7093,500000:8919,556947:10002
	 
	=== SYN RTT (us) stats for first 556947 connections:
	===      P25   Median     Mean      P75      P90      P95      P99    P99.9   P99.99
	===     2342     4441    15996    13249    24443    38198    79657  1038000  1057000
	 
	###SYNRTT,25:2342,Median:4441,Mean:15996,75:13249,90:24443,95:38198,99:79657,99.9:1038000,99.99:1057000
	 
	=== Percentage of connections with retransmits in the first 556947 connections: 1.7278%
	=== Average retransmit count per connection (excluding 0-retransmit cases): 1.0138
	 
###REXMIT,rtconnpercentage:1.7278,rtperconn:1.0138<img width="762" height="751" alt="image" src="https://github.com/user-attachments/assets/43061930-90c5-4780-90b6-173172f59ca4" />

Contents:

1. Command-line used
2. CPS summary over time
3. SYN-RTT distribution
4. Retransmit statistics

Parser-friendly lines prefixed with ### to simplify automation (e.g., grep for ###CPS).

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Troubleshooting

• Error 24: Limits from /etc/security/limits.conf not applied. Check ulimit -n.
• Error 23: System-wide FD limit insufficient. Set sysctl -w fs.file-max=1048576.

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Third-Party Code

This repository may contain third-party open-source libraries used for:

• Command-line parsing
• Cross-platform networking compatibility

All third-party components are listed with their licenses in the THIRD_PARTY_NOTICES.md file.

Trademark Notice

This project may contain trademarks or logos for projects, products, or services.
Authorized use of Microsoft trademarks or logos is subject to and must follow Microsoft’s Trademark & Brand Guidelines.
Use of Microsoft trademarks or logos in modified versions must not cause confusion or imply sponsorship.
Any use of third-party trademarks or logos is subject to those third parties’ policies.