SSH Performance Optimization: Tips and Tricks

Posted on by Lee Painter

Optimizing SSH performance is essential for ensuring smooth and efficient remote connections, especially in high-latency networks or environments with multiple users. This article provides tips and tricks to optimize SSH performance, covering various configurations and best practices.

1. Use Faster Ciphers

Certain ciphers are faster and more efficient than others. Switching to faster ciphers can improve SSH performance.

Edit the SSH Configuration File:

sudo nano /etc/ssh/sshd_config

Specify Faster Ciphers:

Ciphers aes128-ctr,aes192-ctr,aes256-ctr

Restart SSH Service:

sudo systemctl restart ssh

2. Enable Compression

Enabling compression can reduce the amount of data transmitted over the network, improving performance, especially on slower connections.

Enable Compression in SSH Config:

sudo nano /etc/ssh/sshd_config

Add the Following Line:

Compression yes

Restart SSH Service:

sudo systemctl restart ssh

3. Adjust TCP KeepAlive Settings

TCP keepalive settings help maintain the SSH connection by sending periodic messages. Tuning these settings can prevent connection drops and improve stability.

Edit the SSH Configuration File:

sudo nano /etc/ssh/sshd_config

Adjust KeepAlive Settings:

ClientAliveInterval 60
ClientAliveCountMax 3

Restart SSH Service:

sudo systemctl restart ssh

4. Use Multiplexing

SSH multiplexing allows multiple SSH sessions to share a single connection, reducing the overhead of establishing new connections.

Enable Multiplexing in Local SSH Config:

nano ~/.ssh/config

Add the Following Configuration:

Host *
    ControlMaster auto
    ControlPath ~/.ssh/sockets/%r@%h-%p
    ControlPersist 600

Create the Sockets Directory:

mkdir -p ~/.ssh/sockets

5. Optimize DNS Resolution

Disabling DNS resolution for SSH can speed up connection times, especially in environments with slow or unreliable DNS.

Disable DNS Resolution in SSH Config:

sudo nano /etc/ssh/sshd_config

Add the Following Line:

UseDNS no

Restart SSH Service:

sudo systemctl restart ssh

6. Increase Network Throughput

Adjusting TCP window size and other network parameters can improve SSH performance over high-latency networks.

Edit the SSH Configuration File:

sudo nano /etc/ssh/sshd_config

Increase Network Throughput:

TCPRcvBufPollInterval 200
MaxSessions 10

Restart SSH Service:

sudo systemctl restart ssh

Conclusion

By implementing these tips and tricks, you can optimize SSH performance for smoother and more efficient remote connections. Faster ciphers, compression, multiplexing, and tuning TCP keepalive settings are just a few of the ways to enhance your SSH experience. Regularly reviewing and adjusting these settings can ensure your SSH environment remains optimal for your needs.