🚀 Speeding Up SSH Transfers on Arch Linux with IPQoS

I recently ran into a frustrating issue on Arch Linux: SSH file transfers between two computers (each behind their own Livebox, using Orange as the ISP in France) were painfully slow — barely reaching 1 MB/s.

After some digging, I found out the cause was IPQoS (IP Quality of Service) default settings in OpenSSH.

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🐢 The Default Behavior

By default on Arch Linux, ssh and sshd use:

• af21 for interactive sessions
• cs1 for bulk transfers

These QoS classes can be deprioritized by some ISPs (including Orange), resulting in terrible throughput.

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💡 The Fix

We can override IPQoS in both server and client configs.

On the server (/etc/ssh/sshd_config):

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1IPQoS lowdelay throughput

On the client (/etc/ssh/ssh_config or ~/.ssh/config):

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1Host *
2    IPQoS lowdelay throughput

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🔄 Apply the Change

Restart SSHD on the server:

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1sudo systemctl restart sshd

Reconnect, and enjoy the speed boost — I went from 1 MB/s to ~50 MB/s 🚀.

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🔍 Checking the Current Settings

From the client:

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1ssh -G user@host | grep -i ipqos

From the server (if you have shell access):

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1sshd -T | grep -i ipqos

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📌 Conclusion

If you’re on Arch Linux (or any Linux) and notice unusually slow SSH file transfers, especially with certain ISPs like Orange France, tweaking IPQoS can make a huge difference.

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