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Traffic shaping lets you prioritize certain types of network traffic over others — ensuring latency-sensitive traffic (SSH, VoIP) stays responsive even when bulk operations (backups, large transfers) are consuming significant bandwidth.

When Traffic Shaping Helps

• A scheduled backup job saturates outbound bandwidth, making SSH sessions laggy during that window
• Multiple services on one VPS compete for limited bandwidth, and some are more latency-sensitive than others

Using tc (Traffic Control) for Basic Shaping

sudo apt install iproute2 -y

iproute2 (which includes tc) is pre-installed on most modern distributions.

Step 1 — Identify Your Network Interface

ip a

Step 2 — Apply a Simple Bandwidth Limit

sudo tc qdisc add dev eth0 root tbf rate 50mbit burst 32kbit latency 400ms

Limits total outbound bandwidth on eth0 to 50 Mbit/s — useful if you want to reserve headroom rather than let one process consume 100% of available capacity.

Step 3 — Prioritize Specific Traffic (More Advanced)

sudo tc qdisc add dev eth0 root handle 1: prio bands 3

sudo tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip dport 22 0xffff flowid 1:1

This example prioritizes SSH traffic (port 22) into the highest-priority band, ensuring it remains responsive even when other traffic is heavy.

Step 4 — Verify the Configuration

tc qdisc show dev eth0

Removing Traffic Shaping Rules

sudo tc qdisc del dev eth0 root

Making Rules Persistent Across Reboots

tc rules don't persist by default — add them to a startup script or a systemd service that runs at boot:

sudo nano /etc/systemd/system/tc-shaping.service

[Unit]
Description=Apply traffic shaping rules
After=network.target

[Service]
Type=oneshot
ExecStart=/usr/local/bin/apply-tc-rules.sh
RemainAfterExit=true

[Install]
WantedBy=multi-user.target

A Simpler Alternative: Rate-Limiting Specific Processes

For simpler needs (e.g. limiting a single backup script's bandwidth usage rather than system-wide shaping), tools like trickle or built-in rate limiting in specific applications (like rsync --bwlimit) are often simpler than full tc configuration:

rsync --bwlimit=5000 -avz /source/ user@remote:/dest/

When to Use Application-Level vs System-Level Shaping

Common Errors

Rules don't survive a reboot — expected; use a systemd service or startup script to reapply them automatically at boot.

Shaping seems to have no effect — verify you're applying rules to the correct interface (the one actually carrying the traffic you're trying to shape), and that the qdisc was applied without errors.

Best Practices

• Start with simple bandwidth limits before attempting complex multi-band prioritization
• Prefer application-level rate limiting (like rsync --bwlimit) when only one process needs control
• Always make shaping rules persistent via a startup script/service if needed long-term

Continue Reading

• How to Diagnose and Fix High Network Latency
• How to Monitor Network Traffic with vnStat and iftop
• How to Set Up Automated VPS Backups

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