Drift Tracer

Network utility to trace clock drift between two peers.

Build the Project

This project uses the following tools:

CMake v3,
Conan C/C++ package manager,
GCC v5 or higher (for Linux),
libatomic (for CentOS).

Building on Linux

To build the project on Linux you need to create a C++11 compliant Conan profile:

mkdir build && cd build

# Create new Conan profile
conan profile new cxx11 --detect

# Switch compiler to C++11 (libstdc++11)
conan profile update settings.compiler.libcxx=libstdc++11 cxx11

# If required, switch GCC compiler version to the one installed in a system
conan profile update settings.compiler.version=8 cxx11

# To view the profile run
conan profile show cxx11

# Install dependencies with the C++11 profile
conan install .. --profile cxx11 --build fmt --build spdlog

cmake .. -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release
cmake --build ./

Building on Mac

mkdir build && cd build

# To build the fmt library from sources
conan install .. --build=fmt

cmake .. -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release
cmake --build .

Debug Build On Windows

Debug build on Windows will fail, because spdlog library is built in release configuration by default. Follow the steps provided below to build a debug version of the application:

Create Conan debug profile like this

[settings]
os=Windows
os_build=Windows
arch=x86_64
arch_build=x86_64
compiler=Visual Studio
compiler.version=16
build_type=Debug
[options]
[build_requires]
[env]

Build spdlog package

conan install .. --build=spdlog --profile debug

Build the project

cmake .. -G "Visual Studio 16"
cmake --build . --config Release

Usage

Collecting drift tracer logs on two machines A and B:

(A)
drift-tracer start udp://192.168.0.7:4200?bind=192.168.0.10:4200 --tracefile drift-trace-a.csv
(B)
drift-tracer start udp://192.168.0.10:4200?bind=192.168.0.7:4200 --tracefile drift-trace-b.csv

The URI should provide remote IP and port, and local IP and port to bind UDP socket to:

udp://remote_ip:remote_port?bind=local_ip:local_port

One of the peers can listen for an incoming connection so that there is no need to specify remote IP on a listener side:

drift-tracer start udp://:4200 --tracefile drift-trace-a.csv
drift-tracer start udp://192.168.2.2:4200 --tracefile drift-trace-b.csv

Binding is also optional.

Reading Logs

The transmission between peers is bidirectional. Both peers send acknowledgement (ACK) packets and receive acknowledment of acknowledgment (ACKACK) packets back.

Statistics are measured at the time of ACKACK packet reception. The following statistics are available:

Timepoint - Timestamp of collecting statistics;
usElapsed - Time elapsed since the start of connection;
usAckAckTimestamp - Timestamp extracted from the ACKACK packet (the time ACKACK has been sent);
usRTT - RTT sample calculated by ACK/ACKACK pair;
usSmoothedRTT - Smoothed RTT (an exponentially weighted moving average) of RTT samples;
RTTVar - Variance in RTT samples;
The latest 4 fields usDriftSample, usDrift, usOverdrift, TsbpdTimeBase are the values of Drift Sample, Drift, Overdrift and TSBPD Time Base as per SRT drift tracer model. By default, there is no compensation for RTT variance in drift samples. However, there is a possibility to enable this compensation by means of --compensatertt option, start sub-command. See PR #1965 - Drift Tracer: taking RTT into account for details.

Some statistics are measured using both system (Sys postfix) and monotonic or steady clock (Std postfix).