• On all previous pages about PPSK, a very important topic has hardly been addressed.
• Once we grant a user access to our network, we need a way to manage the bandwidth they consume.
• Both the Captive Portal and the PPPoE server are able to do this and have been developed with this functionality in mind.
• Giving someone access to a WiFi network does not automatically allow you to manage their bandwidth.
• Although we offer advanced features to change a user's assigned VLAN based on their usage during a certain period of time, we still need the ability to limit the speed of a VLAN.
• This is where Smart Queue Management (SQM) comes into play.
• With SQM, we can not only limit the bandwidth on an interface to the value we choose, but also manage the queues so that the user has a more pleasant online experience.

• The philosophy of RADIUSdesk is to offer a non-disruptive solution that can co-operate with other vendors.
• The following diagram shows a PPSK solution where the customer has chosen to use PFsense for NAT/DHCP and bandwidth limiting:

• We also offer the customer the option of using OpenWrt, which implements SQM.
• This can then be managed via APdesk.
• As OpenWrt can run on different architectures or even on a virtual machine, it offers us even more possibilities:
• Lets take a closer look at SQM on OpenWrt

The following sections are a brief summary of information from this wiki page (https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm) and from our own experiments.

• To make SQM available in OpenWrt, you need the package sqm-scripts.
• If you also have Luci on the OpenWrt device, it is recommended to install the additional package luci-app-sqm.
• This will install the Luci SQM package which is well developed and provides you with an intuitive way to apply SQM to selected interfaces via the Luci web interface.

• Essentially, the SQM application in Luci manipulates the UCI-based configuration file /etc/config/sqm and starts and stops the SQM service to apply these settings.
• Let's take a look at an excerpt from the sqm configuration file:

config queue 'br_ex_v104'
    option interface 'br-ex_v104'
    option enabled '1'
    option script 'piece_of_cake.qos'
    option linklayer 'none'
    option verbosity '5'
    option upload '4096'
    option download '4096'
    option debug_logging '0'
    option qdisc 'cake'

• Some notes on this snippet:
  • The queue discipline is CAKE. There are also other options like fq_codel that you can use if performance is an issue.
  • The upload and download values are in kbps, so this snippet limits the value to 4Mbps (4*1024)
  • The script to set up the SQM (based on the settings in the /etc/config/sqm file) is called piece_of_cake.qos.
  • The SQM section is applied to the br-ex_v104 interface, which is actually a bridge.
• Let us take a look at the /etc/config/network file to learn more about the br-ex_v104 interface.

config device                         
    option type 'bridge'          
    option name 'br-ex_v104'      
    option stp '0'                
    list ports 'eth1.104'         
                                      
config interface 'ex_v104'            
    option device 'br-ex_v104'    
    option proto 'static'         
    option ipaddr '10.200.105.1'  
    option netmask '255.255.255.0'

• Although the word interface is used intuitively in the /etc/config/sqm section, it can also be applied to a device such as a bridge.
• In our case, the br-ex_104 bridge has one port, eth1.104. This port receives traffic from VLAN 104 on eth1 (e.g. when a user connects to a private PSK and the dynamic VLAN assigned to it is 104)
• The data traffic that runs via this bridge is therefore throttled and managed with SQM.

Now that we have covered the configuration of SQM, we can take a look at some practical commands under the heading

• To start and stop SQM:

#You might first need to stop it before starting it:
/etc/init.d/sqm stop
SQM: Stopping SQM on br-ex_v104

#Start it
/etc/init.d/sqm start
SQM: Starting SQM script: piece_of_cake.qos on br-ex_v104, in: 4096 Kbps, out: 4096 Kbps
SQM: piece_of_cake.qos was started on br-ex_v104 successfully

• SQM creates a matching IFB interface with the convention ifb4-<interface>. In this way, you can easily determine whether the start was successful.

#Real interface
ifconfig br-ex_v104
br-ex_v104 Link encap:Ethernet  HWaddr 08:00:27:EA:B7:D5  
    inet addr:10.200.105.1  Bcast:10.200.105.255  Mask:255.255.255.0
    inet6 addr: fe80::a00:27ff:feea:b7d5/64 Scope:Link
    UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
    RX packets:0 errors:0 dropped:0 overruns:0 frame:0
    TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000 
    RX bytes:0 (0.0 B)  TX bytes:1088 (1.0 KiB)
#Matching IFB
ifconfig ifb4br-ex_v104
ifb4br-ex_v104 Link encap:Ethernet  HWaddr AA:93:EE:2A:4D:E6  
    inet6 addr: fe80::a893:eeff:fe2a:4de6/64 Scope:Link
    UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
    RX packets:0 errors:0 dropped:0 overruns:0 frame:0
    TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:32 
    RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B

• To get stats on SQM, you can use the tc command:

tc  -s qdisc show dev br-ex_v104

• This brings us to the end of SQM's section in OpenWrt.
• In RADIUSdesk we have taken this knowledge and created the SQM Profiles applet, which makes managing SQM in MESHdesk and APdesk a breeze.
• There is a special page for SQM Profiles that allows you to apply limits in no time at all.