Traffic Shaping Calculator
Size SQM, CAKE, fq_codel, or router QoS rates from real WAN speed, overhead, active traffic, and latency goals.
| Traffic Class | Typical Apps | Download Rule | Upload Rule |
|---|---|---|---|
| Realtime | VoIP, gaming, video meetings | 10-25% reserved, low delay | 10-25% reserved, highest priority |
| Interactive | DNS, SSH, browsing, smart home | Shared fair queue | Shared fair queue |
| Streaming | 4K video, IPTV, media boxes | 25 Mbps per 4K stream | Low upload, normal priority |
| Bulk | Backups, torrents, OS updates | 15-50% cap after priority traffic | Cap tightly to protect calls |
| Link Type | Starting Shaper | Overhead | Practical Note |
|---|---|---|---|
| Fiber ONT | 95-98% of measured rate | 1% | Often stable enough for a smaller margin |
| DOCSIS Cable | 85-92% of measured rate | 3% | Retest during evening congestion |
| PPPoE DSL | 85-90% of sync or test rate | 5% | Upload shaping is usually critical |
| LTE or 5G | 70-85% of low-period rate | 7% | Use conservative values for failover |
| Project | Devices | WAN Example | Shaping Focus |
|---|---|---|---|
| Small apartment Wi-Fi | 8-15 | 300/20 Mbps | Protect upload for calls |
| Family streaming home | 20-35 | 500/50 Mbps | Separate streaming and bulk |
| Home lab with NAS | 25-50 | 1000/1000 Mbps | Cap cloud sync and backups |
| Remote work household | 12-25 | 100/20 Mbps | Prioritize video meetings |
Bufferbloat can occur when the router tries to send more data through an internet connection than the internet connection can handle. When the router sends more data through the connection than the internet connection can manage, it causes a traffic jam in the network. As a result, the latency between the router and the internet become high.
High latency causes problems for individuals when performing latency-dependent tasks like video calls and online gaming. Even with a higher amount of bandwidth provided by the internet connection, bufferbloat can still occur because the router isnt managing the bandwidth proper. Traffic shaping can be used to fix the problems caused by bufferbloat.
Fix Slow Internet and Lag with Traffic Shaping
Traffic shaping works by instructing the router to work at a speed that is slightly slower than the maximum speed that the internet connection can reach. Although limiting the speed at which data from the internet connection travels through the network may seem like a bad idea, it is actualy necessary to ensure proper management of data at the router. By managing the bottleneck created by the internet connection, the router can manage data by prioritizing small packet, such as gaming data, over large packets, such as movie download data.
However, if the bottleneck is at the ISP modem, not the router, then the router will not have control over the data traveling through the network, causing all tasks to lag. The correct setting for traffic shaping will be difficult to find because internet connection speed will fluctuate. The speeds that the ISP advertises are not the same as the actual speed at which data will travel through the connection.
Some type of connections is more stable than others. For instance, fiber connections are much more stable than cable or LTE connections. The speed settings will have to include a safety margin to account for these difference.
By setting the speed of traffic shaping to slightly less than the speed of the internet connection, there will be a buffer that will prevent the modem from becoming overwhelmed by the data that arrives at the router. Not all digital tasks require the same amount of bandwidth and require the same amount of precision in data arrival times. For instance, a 4K streaming service requires a considerable amount of bandwidth, but a VoIP call require very little bandwidth.
A late gaming packet can cause lag in the game, but the individual watching the movie will not notice late movie data. By being able to distinguish between tasks that have high requirements as compared to those with low requirements, a buffer can be created for data that has high requirement for precision and bandwidth availability. By creating a buffer for these high-demand tasks, packets for critical tasks will always have a path to take through the network.
Queue disciplines, such as CAKE and fq_codel, determine the task of the router in choosing which data packet will be sent through the network next. Some queue discipline will focus on giving each device an equal share of the internet connection. This ensures that one device cannot slow the internet for others on the same network.
Other queue disciplines will focus on ensuring that data packets are sent at a rate that keeps the latency between devices in the network and the router low. A calculator can be used to determine the ideal traffic shaping rate based off the choice of the queue discipline. Using this calculator will save people the trouble of having to use guess and try to determine the ideal setting.
The upload speed for the internet connection is just as critical as the download speed, but many person tend to ignore the upload speed. For most internet connection, the upload speed is much slower than the download speed. This is because when a device downloads something from the internet, that device must also send acknowledgment packets back to the server to acknowledge the data that was downloaded.
Thus, if a device is using the upload bandwidth to perform cloud backups, it will take up all of the available upload bandwidth, and the device will not send any acknowledgment packet. Consequently, the download speed will drop. Ensuring that the upload speed is prioritized is a fast way of improving the function of the network.
Traffic shaping settings will not be permanent settings for any network. Thus, it is important to periodically retest the connection speed. The ISP may have changed the routing of the internet connection, or there may have been an increase in the number of device on the network.
During the busiest part of the day, the network will be under the highest amount of strain on the internet connection. Thus, it is important to test the speeds during this time. Additionally, if the latency between devices and the router is still high, the safety margin will have to be increased.
This adjustment to the safety margin is a way of further refining the management of the network.
