In enterprise router configuration, we often encounter IP QoS feature setup. To help you better understand the configuration process, we’ll use the TL-R480T as an example. After upgrading the R480T software, the new “QoS” feature is added as described below:
QoS Set Interface Description:
The QoS Set page has two parameters: “Upstream Bandwidth” and “Downstream Bandwidth.” Click the “Help” button to see the following information:
You can think of “Upstream Bandwidth” and “Downstream Bandwidth” as the actual upstream and downstream bandwidth of the broadband line subscribed by the user. For example, if an ADSL line has 512 Kbps upstream and 2 Mbps downstream, you would fill in those values here accordingly.
As noted above, it’s crucial to emphasize: you must first enable the “Enable QoS” switch here and enter the actual upstream and downstream bandwidth of the line before you can continue configuration on the IP QoS page. Otherwise, an error will be prompted.
Example of IP QoS Configuration:
1) “Address Range” 鈥?This includes 11 IP addresses from .10 to .20. Additionally, the address range here allows entering IP addresses that are not on the same subnet as the router’s LAN IP address. This means that even if your internal network uses Layer 3 switches to plan different subnets, our router can still support bandwidth limiting for IP addresses across different network segments.
2) “Mode” 鈥?Independent Bandwidth. As the name implies, the “Max Bandwidth” and “Min Bandwidth” below apply to each individual IP within this address range. If “Shared Bandwidth” mode is selected, then the entire IP range shares the parameters below.
3) “Upstream/Downstream” 鈥?As we all know, data flows transmitted over the network have direction. For instance, with a BT download, data can be downloaded from servers on the Internet, while the host itself also acts as a server uploading data. Our router’s IP QoS restricts traffic based on these “directional data flows.”
The router accurately restricts upstream and downstream data flows separately. Based on the parameters filled in the figure, suppose a host configured with the IP address 192.168.1.10 is performing a BT download. This host’s data traffic will be relatively large, and its data flow is divided into two parts: one part is downloading data from other servers, and the other part is uploading data to other hosts. The router’s IP QoS will restrict and regulate the download and upload data traffic of this .10 host in both directions.
According to the parameters filled in above, for the .10 host, the upstream data traffic (uploading data) is guaranteed a minimum of 50 Kbps and capped at a maximum of 100 Kbps, while the downstream data traffic (downloading data) is guaranteed a minimum of 100 Kbps and capped at a maximum of 200 Kbps. The available bandwidth for upstream and downstream data here is referenced against the actual upstream/downstream bandwidth of the line.
If all 11 hosts from .10 to .20 are downloading data simultaneously, and the line’s actual downstream bandwidth is limited to 2 Mbps, bandwidth contention may occur. According to the parameters we set above, the router first guarantees that each IP address can use at least 100 Kbps of downstream bandwidth. So, the 11 hosts use a total of 1100 Kbps of bandwidth resources, leaving approximately 900 Kbps remaining from the total 2000 Kbps downstream bandwidth. How is this remaining 900 Kbps allocated? We can understand the router’s allocation of the remaining 900 Kbps line bandwidth as follows: At a certain moment, if all 11 hosts are contending for the remaining 900 Kbps, then “in the first round of contention, the 11 hosts equally share the 900 Kbps.” After this first round, suppose 2 of the 11 hosts find their guaranteed minimum 100 Kbps is just enough for their transfers and don’t need extra bandwidth; these 2 hosts exit the contention, leaving 9 hosts to continue. Then, in the second round of contention, the 9 hosts equally share the 900 Kbps.
As highlighted in red in the figure, now assume the line’s downstream bandwidth is 10 Mbps. Two hosts, 192.168.1.10 and 192.168.1.11, are configured with a minimum “Downstream Bandwidth” of 100 Kbps each, but different maximums of 1000 Kbps and 2000 Kbps respectively. During bandwidth allocation:
The router first guarantees both hosts can use their minimum “Downstream Bandwidth” of 100 Kbps. After the minimum bandwidth guarantee, if both hosts still require more downstream bandwidth, for traffic exceeding 100 Kbps, the router uses a “round-robin” method to increase the effective bandwidth occupied by each host. When the downstream data flow occupied by 192.168.1.10 reaches the maximum of 1000 Kbps, the router will no longer forward data packets exceeding 1000 Kbps. However, if 192.168.1.11 still requires more bandwidth after reaching 1000 Kbps during contention, the router will keep increasing its occupied effective downstream bandwidth up to 2000 Kbps, after which it will stop forwarding packets beyond this range. The remaining 7 Mbps of downstream bandwidth resources will be idle and not allocated to .10 or .11. Unless their maximum available “Downstream Bandwidth” is changed to a larger value, they cannot use the remaining bandwidth. When configuring IP QoS, if “Mode” is selected as “Shared Bandwidth,” then all IP addresses included in the address range share the configured maximum and minimum upstream and downstream bandwidths.
We’ve spent considerable time describing the usage of the new IP QoS feature on enterprise routers. Does it seem complex? Even if you don’t fully understand it, don’t worry. Just follow the steps below to set up your network:
鈶?Manually assign static IP addresses to the computers on your internal network, ensuring they are consecutive, e.g., 192.168.1.2 to 192.168.1.100. This makes subsequent configuration easier.
鈶?On the IP QoS settings switch page, configure your line’s bandwidth: set the upstream and downstream bandwidth respectively. For example, for a 10 Mbps fiber line, enter 10000. Then, enable the QoS master switch.
鈶?Go to the IP QoS rule settings page, add a new entry, and configure:
IP Address Range: e.g., 192.168.1.2 to 192.168.1.100;
Mode: Select “Independent”;
Minimum Upstream Bandwidth: Real line upstream bandwidth / number of internal computers. In this example, 10000/99 =