NSFD

What is NSFD?

NSFD (Network Service Failure Detector) is an academic project as a part of the course "Computer Networks". It is a simple monitoring system that verifies the connection with a server (via the ICMP protocol) and checks the availability of a network service running on a specific port by establishing a TCP connection.

Additionally NSFD measures and collects connection time for both protocols - ICMP and TCP.

NSFD runs two TCP servers that allows for defining health checks and reading metrics.

Building and running in docker container

docker build -t nsfd-server:latest .
docker run -it -p 8000:8000 -p 8001:8001 --name nsfd-server --privileged nsfd-server:latest

Using with netcat as a client

Define scheduling health checks for facebook:

echo -n "create;facebook.com;80" | nc localhost 8000

First column is an action, second is a domain or IP address and third is a port of a network service to monitor.

Reading metrics:

echo -n "facebook.com" | nc localhost 8001

It will return results of health checks and connection time in the following format:

1;17.8211;1;18.2539;1595454676038

• 1st column is 1 or 0 - connection between services is possible or not.
• 2nd column is a connection time for ICMP protocol.
• 3rd column is 1 or 0 - defined network service is health or not.
• 4th column is a connection time for TCP protocol.

Simulating ICMP connection failure

Run the command from the running container:

iptables -A OUTPUT -d facebook.com -j DROP

Now ICMP connections should fail. To restore the connection between servers execute command:

iptables -D OUTPUT -d facebook.com -j DROP

GUI

NSFD has also dedicated desktop client available here: https://github.com/jewertow/nsfd-client

It provides GUI to configure health checks and display metrics on charts.