Quality of Service

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-'''Quality of Service''' ('''QoS''') is a method to guarantee a bandwidth relationship between individual applications or protocols. This is very handy when you max out your connection so that you can allow for each application to have some bandwidth and so that no single application can take down the internet connection. This allows, for example, a full speed download via FTP without causing jittering on a VOIP chat. The FTP will slow down slightly as bandwidth is needed for the VOIP, provided VOIP was given greater priority.+You are here: '''[[Main_Page|DD-WRT wiki mainpage]] / [[Web_Interface|Web-GUI]] / NAT/QoS / QoS '''
 +{{Languages|Quality of Service}}
-If you would like to set hard coded bandwidth limits (throttling), this can be done using the [[tc command]]+==Introduction==
 +<font color=red>Be using a build NO OLDER than r32170 before proceeding!</font>
-NOTE: Ethernet Port Priority only works on older, ADM based, chipsets. 
-That is, the Linksys WRT54G v1.0, 1.1, 2.0 and the WRT54GS v1.0. 
 +Quality of Service ('''QoS''') is a method to guarantee a bandwidth relationship between individual applications or protocols. This is very handy when you max out your connection so that you can allow for each application to have some bandwidth and so that no single application can take down the internet connection. This allows, for example, a full speed download via FTP without causing jittering on a VOIP chat. The FTP will slow down slightly as bandwidth is needed for the VOIP, provided VOIP was given greater priority.
 +
 +Please note, as of 336XX, if QoS is enabled, SFE (Shortcut Forwarding Engine) is disabled, even if it shows up as enabled in the GUI, it is disabled.
 +
 +'''If you plan on using QoS, please read [[Quality_of_Service#Priorities_explained|Priorities explained]] and [[Quality_of_Service#Precedence|Precedence]] before going any farther.'''
 +
 +==Priorities explained==
 +* Maximum - This class offers maximum priority and should be used sparingly.
 +* Premium - Second highest bandwidth class, by default handshaking and ICMP packets fall into this class. Most VoIP and video services will function good in this class if Express is insufficient.
 +* Express - The Express class is for interactive applications that require bandwidth above standard services so that interactive apps run smoothly.
 +* Standard - All services that are not specifically classed will fall under standard class.
 +* Bulk - The bulk class is only allocated remaining bandwidth when the remaining classes are idle. If the line is full of traffic from other classes, Bulk will only be allocated 1% of total set limit. Use this class for P2P and downloading services like FTP.
 +
 +
 +Bandwidth is allocated based on the following "minimum to maximum" percentages of downlink and uplink values for each class as of current builds:
 +
 +* Maximum: 75% - 100%
 +* Premium: 50% - 100%
 +* Express: 25% - 100%
 +* Standard: 15% - 100%
 +* Bulk: 5% - 100%
 +
 +
 +What this means is that if you have 10,000kbit of uplink traffic, "Standard" class traffic can be reduced and de-prioritized to 15% or 1,500kbit when a concurrent express or higher priority service requires the down/uplink pipe at the same time.
 +
 +Check which priorities are used with the command below:
 +<pre>
 +iptables -t mangle -vnL
 +</pre>
 +Then scroll down to the Chain SVQOS_SVCS section.
 +
 +
 +===TCP Packet Priority===
 +
 +Builds before r21061 will not have this option. Update your build if you dont have it, stay up to date.
 +
 +Prioritize small TCP-packets with the following flags: ACK/SYN/FIN/RST
 +
 +For detailed info on what these packets do see: http://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure
 +
 +It is highly recommended to have at least, SYN, FIN & RST checked, OR, none at all. ACK can go both ways as P2P intensive applications such as uTorrent etc involve a lot of ACKs, so theoretically prioritizing ACKs means you "prioritized P2P" though that is not entirely' accurate. Read up & do your own testing to find out whats best for your network. If you do not do large amounts of P2P activity on your network or none at all, then enable ACK prioritization.
 +
 +
 +==Precedence==
 +With all these ways of marking traffic its easy to get confused about how seemingly contradictory requirements are resolved. For example, what happens if you have an IP rule setting IP 192.168.1.2 to priority "maximum" and have a MAC rule setting AA:BB:CC:DD:EE:FF to priority "bulk"?
 +
 +The order the precedence is as follows:
 +
 +* (1st) MAC Priority
 +* (2nd) Netmask Priority
 +* (3rd) Interface Priority
 +* (4th) Services Priority
 +* (5th) Ethernet Port Priority
 +
 +
 +<font color="red">'''NOTE:''' Ethernet Port Priority only works on old 802.11g only models with ADMtek switch chips. If you don't have ethernet port priority listed, your router does not support it. Ethernet port priority is different than interface priority.</font>
 +
 +<font color="red">'''NOTE:''' Services can be used at the same time as netmask or MAC, such as limiting 192.168.1.2 to 6 Mbps down & 512 Kbps up while having http set to express, that device will have http packets prioritized within it's allocated bandwidth limit. This only applies to builds r21061 & newer</font>
 +
 +
 +For netmask, the IP address entries are applied in the order that they appear in your netmask table. Only the first match applies. Example, if you have an entry marking 192.168.1.10/32 as bulk, followed by an entry ABOVE IT, marking 192.168.1.0/24 (all 192.168.1.X) as premium, the traffic from 192.168.1.10 would be marked bulk because it was the first match.
 +
 +For services, The services entries are applied in the order that they appear in your services tables going from bottom to top. Again, only the first match will apply.
==Initial Setup== ==Initial Setup==
* Log into the [[Web Interface]] * Log into the [[Web Interface]]
 +
* Select the NAT/QoS tab and then the QoS sub-tab. * Select the NAT/QoS tab and then the QoS sub-tab.
-* Tick "Enable" 
-* Set Port to "WAN" or "LAN & WLAN". The term WAN here refers to the WAN connection on your router while the term "LAN & WLAN" refers to the combination of your local ports and Wifi connections. Normally the selection should not really matter since all traffic coming in the one end is going out the other. However, I recommend you select "LAN & WLAN" (See Application considerations below).  
-* Select HTB as your Packet Scheduler. (See Application considerations below)+* Click "Enable"
-* You can use a speed test like [http://www.dslreports.com/stest DSL Reports] to check your actual connection speed. The uplink/downlink setting in DD-WRT are with respect to the port selected above. Its a common error to get confused. When WAN is selected these match the uplink/downlink measured. When you select "LAN & WLAN" these are reversed. It is required that you enter 90% of the values you measure into the proper field. After you have everything set run the speed test again. If you geet 90% of your previous measurement in each direction of then things are cool. If you get results which are way off then chances are that you have reversed these values. +* Set Port to "WAN". This works for all QoS setups EXCEPT, when using QoS by interface on a BRIDGED interface under "interface priority", UNBRIDGED interfaces work fine with WAN port setting. If you want to use QoS on a BRIDGED interface you must select port as "LAN & WLAN", which also works for all other QoS setups, but with slightly more CPU usage.
-*Ignore Optimize for gaming. It does not do anything and hopefully will be deleted on day.+* Select HTB as your packet scheduler if you have "queuing discipline" listed below it, if not then use HFSC.
-You must enter a value for the downlink field but if you want you can enter 0 for the uplink field in which case no QoS will occur in that direction. I do not recommend setting you uplink field to zero.+* Select FQ_CODEL as your queuing discipline.
-I know it bugs you to set only 90% of your available bandwidth in these fields but this is required. There will be a bottleneck somewhere in the system and QoS can only work if the bottleneck is in your router where it has some control. The goal is to force the bottleneck to be in your router as opposed to some random location out on the wire over which you have no control.+* Set your download and upload speeds. You can use a speed test like [http://www.speedtest.net Speedtest.net] or [http://www.dslreports.com/speedtest dslreports.com/speedtest] to check your actual connection speed. Some ISPs also provide their own bandwidth testing service, which may be more reliable than the links provided. Enter no higher than 95% of the values you measured into the proper fields. After you have everything set run the speed test again. If you get near 90% of your previous measurement in each direction then things are cool. If you get results which are way off then chances are that you have reversed these values. You must enter a value for the uplink field but if you want you can enter 0 for the downlink field in which case no QoS will occur in that direction, setting your downlink field to 0 isn't recommended.
-==Optimize for Gaming==+ 
-This selection does not have any effect on the function of DD-WRT. Hopefully it will get removed from the QoS configuration page at some future date.+It probably bugs you to set less than 100% of your available bandwidth in these fields but this is required. There will be a bottleneck somewhere in the system and QoS can only work if the bottleneck is in your router where it has control. The goal is to force the bottleneck to be in your router as opposed to some random location out on the wire over which you have no control. Some ISP's even have bursting ("powerboost") which will temporarily give you extra bandwidth when you first start using your connection but will later throttle down to a sustained rate. Fortunately there is usually a minimum level that you receive on a consistent basis and you must set your QoS limits below this minimum. The problem is finding this minimum and you may have to repeat speed tests many times before determining it. For this reason start with 80% of your measured speed and try things for a couple of days. If the performance is acceptable you can start to inch your levels up. If you go even 2% higher than you should be, your QoS will totally stop working (just too high) or randomly stop working (when your ISP node/DSLAM is slow aka saturated). This can lead to a lot of confusion on your part so get it working first by conservatively setting these speeds and then optimize later.
==Prioritizing by Application (Skype, Http) or Port Range (P2P) == ==Prioritizing by Application (Skype, Http) or Port Range (P2P) ==
-* Choose an available Service or Port Range from the list, or create one.+* Choose an available Service or Port Range from the list or create one, and then press "Add" next to it.
-* For P2P Applications, due to evolving protocols, encryption and obfuscation, it can be much better to define a Port Range [such as TCP/UDP, 60000-61000]. Set your P2P applications to operate within this range. This can significantly reduce the load on the router, avoid mis-identifying packets, and more efficiently shape your network traffic.+* For P2P Applications, due to evolving protocols, encryption and obfuscation, it can be much better to define a port range [such as TCP/UDP, 60000-61000]. Set your P2P applications to operate within this range. This can significantly reduce the load on the router, avoid mis-identifying packets, and more efficiently shape your network traffic.
-* For Service definitions [http://protocolinfo.org/wiki/List_of_protocols see here].+
* Add all your other selected Services and Port Ranges here * Add all your other selected Services and Port Ranges here
-* Prioritize to Express or Premium, or de-prioritize to Bulk. "Bulk" gives no guaranteed bandwidth, "Standard" ensures 10%, "Express" 15%, "Premium" 75% and "Exempt" 100% (values according to [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=3634 this post]).+* Choosing a Layer7 service based entry can work better than choosing a port range; though the router works harder as it has to dig into the packets beyond the header, to look at the data they contain.
-* Services not configured are always Standard priority.+
-* Choosing a Service (L7 Protocol) can work better than choosing a port range; though the router works harder.+
-* Tip: If you have trouble modifying the drop-down list, suggest using [http://www.opera.com/download Opera 9.x] and the BrainSlayer router GUI style (worked for me, firefox, safari, and IE don't)+
-==Prioritizing by IP Address (Netmask Priority)==+If you wish to add more than one priority then use the "Add" button to create more entries.
-These are entered in CIDR notation including the network prefix. +
-For example, to specify a single IP address enter xxx.xxx.xxx.xxx / 32. Be careful to enter netmask prefix as "32" because leaving it zero means something entirely different.  
-The network prefix is the number of bits of the IP address to use. For example, the entry 192.168.1.1/24 results in a match against all address on your 192.168.1.xx subnet. An entry of 192.168.1.1/16 results in all subnets beginning with 192.168.x.x being matched. So now you can see that 192.168.1.1/0 results in every IP address (x.x.x.x) being matched which is probably not what you want.+==Prioritizing by Interface==
 +Select your preferred interference, click add, then select the speed or priority you want. You can also limit ethernet ports this way as well (ethX or vlanX). Any limits or priorities set are shared for that interface regardless how many clients are connected to it. Excellent for running a guest network/hotspot on eg, ath1.1, applying QoS on the entire interface makes it impossible for a greedy user to bypass it by MAC cloning, changing IPs etc, short of connecting to a different interface. The same interface can also be entered multiple times with different speed limits or priorities for different services, example, ath0 512/512 with ssl & ath0 0/1024 with http would mean ssl traffic on ath0 is limited to 512kbps down & up, http is unlimited on down (up to global limits is used) & limited to 1024 (1mbps) on up, remaining entered services are not limited (up to global limits for both directions).
-After entering the IP address must press "Add" to get it appended to the list.+==Prioritizing by Netmask (IP address)==
 +These are entered in CIDR notation including the network prefix.
-==Prioritizing by MAC Address==+For example, to specify a single IP address enter xxx.xxx.xxx.xxx/32. Be careful to enter netmask as /32 because leaving it /0 means ALL IPs!.
-In the case you want to prioritize traffic from a particular device without a static IP address on your LAN, you can prioritize by MAC Address.+
-*Under 'MAC Priority', enter the MAC Address of the device+The netmask is the number of bits of the IP address to match. For example, the entry 192.168.1.0/24 matches 192.168.1.x addresses. An entry of 192.168.0.0/16 matches 192.168.x.x addresses. If you're unsure of how to create CIDR subnet masks and what they mean, then use a [http://www.subnet-calculator.com subnet calculator].
-*Click 'add'+
-*click 'Save changes'+
-This method works via the source MAC address only so traffic is only properly prioritized if the connection was initiated from this address. Traffic initiated from somewhere else will not be properly marked even if it is destined for one of the listed MAC addresses.+After you have filled it out, press "add" next to it. If you want to add multiple entries (make sure to have order correct!) click "save" before entering in another so any previous changes don't get deleted, only click "apply" when you want to start testing your current changes displayed.
-==Default Bandwidth Level== 
-*Bandwidth in Kbits is set to 5000 on ''DD-WRT v23 SP2 (09/13/06) special''. This entry is as yet unexplained and even googleing it does not enlighten. 
-*Default values are 0 in v24 SP2 and QoS is not applied when the particular interface is set to 0 
-==Priorities explained==+==Prioritizing by MAC Address==
-Bandwidth classification based on the four categories will be enabled first on the hardware ports, then on MAC addresses, then netmasks and finally services. If prioritizing by MAC addresses, highest priority should be express (exempt is NOT a priority) - up-prioritize programs via the ports (sidenote: regular internet activities are already top prioritized via inherent software). *A higher class does not necessarily mean better performance - match the priority to the needs of the MAC address.+In the case you want to prioritize traffic from a particular device without a static IP address on your LAN, you can prioritize by MAC Address. Enter the MAC Address of the device and press "Add" next to it.
-* Exempt - This class tries to keep the bandwith and packet flow untouched. Use for gaming. 
-* Premium - The top bandwidth class. By default handshaking and icmp packets fall into this class. This class should be used sparingly. Occasionally VoIP service may be placed in this class so that voice receives top priority. Use per program requirement only. 
-* Express - The Express class is for interactive applications that require bandwidth above standard services so that interactive apps run smoothly. Use for computers who have interactive data. 
-* Standard - All services that are not specifically classed will fall under the standard class. 
-* Bulk - The bulk class is only allocated bandwidth when the remaining classes are idle. Use this class for P2P services and downloading services like FTP. 
-===Detailed breakdown of traffic=== 
-If you'll like to know the specifics, traffic are allocated based on the following percentages of uplink and downlink values on each class: 
-* Exempt: untouched 
-* Premium: 75% - 100% 
-* Express: 15% - 100% 
-* Standard: 10% - 100% 
-* Bulk: 1.5% - 100% 
- 
-What this really means is that if you have 10,000kbit of uplink traffic, "Standard" class traffic can be reduced and de-prioritized to 10% or 1,000kbit when a concurrent Express service requires the uplink pipe at the same time.  
- 
-You can run the following tc command to check breakdown of traffic applied to each interface. Uplink limits are applied on the WAN interface while Downlink limits are applied on the LAN interface. The interface names are device specific so you might have to check by running "ifconfig" to list all interfaces on your router. The following command will check QoS uplink limits applied on a Broadcom device's WAN interface (vlan2): 
-<pre> 
-tc class show dev vlan2 
-</pre> 
==How Do You Check What QoS Priorities Were Applied== ==How Do You Check What QoS Priorities Were Applied==
The DDWRT web UI doesn't display any live traffic. Short of doing a practical test, you can get your hands dirty by checking the conntrack entries via telnet or ssh access in the router. When you're logged in run: The DDWRT web UI doesn't display any live traffic. Short of doing a practical test, you can get your hands dirty by checking the conntrack entries via telnet or ssh access in the router. When you're logged in run:
<pre> <pre>
-cat /proc/net/ip_conntrack+iptables -t mangle -vnL
</pre> </pre>
 +Then scroll down to the Chain SVQOS_SVCS section.
 +
 +With the above iptables mangle command you can see the inbound/outbound chains, entered IPs/MACs/services & whats being matched where.
 +
It will list out all currently open connection and protocol that is currently being routed by the router. This is what it would look like: It will list out all currently open connection and protocol that is currently being routed by the router. This is what it would look like:
<pre> <pre>
Line 94: Line 131:
</pre> </pre>
What you'll be interested to look at will be the first set of source and destination IP, including the port numbers. Next the presence of l7proto and the "mark" field. The entries indicate the current live connection QoS priority applied on them based on the "mark" field. The "mark" values corresponds to the following: What you'll be interested to look at will be the first set of source and destination IP, including the port numbers. Next the presence of l7proto and the "mark" field. The entries indicate the current live connection QoS priority applied on them based on the "mark" field. The "mark" values corresponds to the following:
-* Exempt: 100+* Maximum: 100
* Premium: 10 * Premium: 10
* Express: 20 * Express: 20
Line 100: Line 137:
* Bulk: 40 * Bulk: 40
* (no QoS matched): 0 * (no QoS matched): 0
-I have "ftp" set to bulk, and "dns" set to premium priority. Thus the conntrack output confirmed that the right QoS rules were applied. Using this method requires that you know the destination IP, and port number of the service, and this must be checked while the connection is active. You may see "mark=0" for some l7proto service even though they are in configured in the list of QoS rules. This may mean that the layer 7 pattern matching system didn't match a new or changed header for that protocol. Custom service on port matches will usually take care of these. 
-Alternatively, you can also check applied QoS on active connections using the following command (pipe to more if output is huge): 
-<pre> 
-cat /proc/net/ip_conntrack | awk '{print $1 " " $5 ":" $7 " " $6 ":" $8 " " $16}' | sed -e 's/sport=//' -e 's/dport=//' -e 's/mark=100/Exempt/' -e 's/mark=10/Premium/' -e 's/mark=20/Express/' -e 's/mark=30/Standard/' -e 's/mark=40/Bulk/' -e 's/mark=0/Default-Standard/' 
-</pre> 
-==Precedence==+You may see "mark=0" for some l7proto service even though they are in configured in the list of QoS rules. This may mean that the layer 7 pattern matching system didn't match a new or changed header for that protocol. Custom service on port matches will usually take care of these.
-With all these ways of marking traffic its easy to get confused about how seemingly contradictory requirements are resolved. For example, what happens if you have an IP rule setting IP 192.168.1.2 to priority "exempt" and have a MAC rule setting MAC AA:BB:CC:DD:EE:FF to priority "bulk"? +
-The order the precendence is as follows:+==Time Based QoS==
-MAC - If you have specified a MAC address priority then it takes precedence over all others+As described in [http://www.dd-wrt.com/phpBB2/viewtopic.php?p=438664#438664 this thread] you can use [[CRON]] jobs to enable/disable QoS. This is just a simplistic approach but more complex things could be done if you put your mind to it. These commands will enable HTB QoS on the WAN port from 5PM to 1AM but you will still need to configure everything else in the GUI. If you want to use LAN&WLAN then change "`get_wanface`" to "imq1". To change the times, see the [[CRON]] page for information.
-Netmask - The IP address entries are applied in the order that they appear in your netmask table. Interestingly only the first match applies. For example if you have an entry marking 192.168.1.10/32 as bulk followed by an entry marking 192.168.1.0/24 (all 192.168.1 addresses) as premium the traffic from 192.168.1.10 would be marked bulk because it was the first match. Also if a match is found in this table it does not matter what you put in the services table.+ 1 17 * * * root /usr/sbin/svqos `nvram get wshaper_downlink` `nvram get wshaper_uplink` `get_wanface` `nvram get wan_mtu` 0
 + */6 1-17 * * * root /usr/sbin/svqos stop 0 `get_wanface` 0 0
-Services - The services entries are applied in the order that they appear in your services tables. Again, only the first match will apply.+If you use HFSC then you would do something like this instead.
-Ports - Be careful with port priorities. On many routers these have no effect at all. This is the case on my router (WRT54G-TM) so I cannot tell you how to verify that yours works or not. The note at the top of this page indicates specific models and versions. + 1 17 * * * root /usr/sbin/svqos2 `nvram get wshaper_uplink` `nvram get wshaper_downlink` `get_wanface` `nvram get wan_mtu` 0
 + */6 1-17 * * * root /usr/sbin/svqos2 stop 0 `get_wanface` 0 0
-'''Note for PPTP Users''':+As described in [http://www.dd-wrt.com/forum/viewtopic.php?p=512889#512889 this thread] you can also set different rates at different times by doing something like this which changes the HTB rates.
-There seems to be a problem by using PPTP and QoS at the same time. If you use DD-WRT with enabled PPTP server and want to activate QoS for the WAN interface then you are no longer able to connect to the PPTP server from your LAN.+ 1 23 * * * root /usr/sbin/svqos '''[downlink rate]''' '''[uplink rate]''' `get_wanface` `nvram get wan_mtu` 0; nvram set wshaper_downlink='''[downlink rate]'''; nvram set wshaper_uplink='''[uplink rate]''';
-PPTP, L2TP and IPSec Passthrough also doesn't work.+ 1 10 * * * root /usr/sbin/svqos '''[downlink rate]''' '''[uplink rate]''' `get_wanface` `nvram get wan_mtu` 0; nvram set wshaper_downlink='''[downlink rate]'''; nvram set wshaper_uplink='''[uplink rate]''';
 + 
 +<font color="red">Edit: This will cause trouble on current firmware releases greater than r21061. Use the predefined service handler to stop/start QoS instead. Even if needed, use imq1 instead of br0 for internal traffic shaping.
 +</font>
 +<pre>stopservice wshaper
 +startservice wshaper</pre>
 + 
 +<font color="red">If you need to alter down/up rates edit the nvram variables before restarting wshaper</font>
 +<pre>
 +nvram set wshaper_downlink=20000
 +nvram set wshaper_uplink=800
 +startservice wshaper
 +</pre>
-The problem is reproducible on a WRT54GL 1.1 with DD-WRT v24-sp1. 
-==Books== 
-Xipeng Xiao, "Technical, Commercial and Regulatory Challenges of QoS: An Internet Service Model Perspective", Morgan Kaufmann/Elsevier, 2008 
-Tim Szigeti and Christina Hattingh, "End-to-End QoS Network Design: Quality of Service in LANs, WANs, and VPNs", Cisco Press, 2004 
=External Links= =External Links=
* [http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm HTB Manual] * [http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm HTB Manual]
* [http://linux.die.net/man/8/iptables iptables man page] * [http://linux.die.net/man/8/iptables iptables man page]
-* [http://protocolinfo.org/wiki/List_of_protocols Look up the DD-WRT pre-defined QoS Service definitions] 
-* [http://www.solosoft.org/projects/qos A more detailed QoS Setup Page] 
-* [http://www.csc.fi/english/funet/calc/laskin2.html Netmask Calculator] 
* [http://l7-filter.sourceforge.net/ L7-Filter] * [http://l7-filter.sourceforge.net/ L7-Filter]
* [http://frottle.sourceforge.net/ Frottle sourceforge] * [http://frottle.sourceforge.net/ Frottle sourceforge]
-* [http://patraswireless.net/software.html Petra's wireless homepage]+* [http://www.gargoyle-router.com/wiki/doku.php?id=qos Lots of QoS myths explained, what QoS can & can't do & much more info.]
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=3100 Another way of doing it for experienced users]+
-* [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=28816 TCP Vegas makes QoS unnecessary?]+
-* [http://www.linksysinfo.org/forums/showthread.php?t=60304 Using QoS - Tomato firmware (same guidelines will apply to DD-WRT)]+
- +
-[[Category:English documentation]]+[[Category:Traffic moderation]]
[[Category:Basic tutorials]] [[Category:Basic tutorials]]

Current revision

You are here: DD-WRT wiki mainpage / Web-GUI / NAT/QoS / QoS


Contents

[edit] Introduction

Be using a build NO OLDER than r32170 before proceeding!


Quality of Service (QoS) is a method to guarantee a bandwidth relationship between individual applications or protocols. This is very handy when you max out your connection so that you can allow for each application to have some bandwidth and so that no single application can take down the internet connection. This allows, for example, a full speed download via FTP without causing jittering on a VOIP chat. The FTP will slow down slightly as bandwidth is needed for the VOIP, provided VOIP was given greater priority.

Please note, as of 336XX, if QoS is enabled, SFE (Shortcut Forwarding Engine) is disabled, even if it shows up as enabled in the GUI, it is disabled.

If you plan on using QoS, please read Priorities explained and Precedence before going any farther.

[edit] Priorities explained

  • Maximum - This class offers maximum priority and should be used sparingly.
  • Premium - Second highest bandwidth class, by default handshaking and ICMP packets fall into this class. Most VoIP and video services will function good in this class if Express is insufficient.
  • Express - The Express class is for interactive applications that require bandwidth above standard services so that interactive apps run smoothly.
  • Standard - All services that are not specifically classed will fall under standard class.
  • Bulk - The bulk class is only allocated remaining bandwidth when the remaining classes are idle. If the line is full of traffic from other classes, Bulk will only be allocated 1% of total set limit. Use this class for P2P and downloading services like FTP.


Bandwidth is allocated based on the following "minimum to maximum" percentages of downlink and uplink values for each class as of current builds:

  • Maximum: 75% - 100%
  • Premium: 50% - 100%
  • Express: 25% - 100%
  • Standard: 15% - 100%
  • Bulk: 5% - 100%


What this means is that if you have 10,000kbit of uplink traffic, "Standard" class traffic can be reduced and de-prioritized to 15% or 1,500kbit when a concurrent express or higher priority service requires the down/uplink pipe at the same time.

Check which priorities are used with the command below:

iptables -t mangle -vnL

Then scroll down to the Chain SVQOS_SVCS section.


[edit] TCP Packet Priority

Builds before r21061 will not have this option. Update your build if you dont have it, stay up to date.

Prioritize small TCP-packets with the following flags: ACK/SYN/FIN/RST

For detailed info on what these packets do see: http://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure

It is highly recommended to have at least, SYN, FIN & RST checked, OR, none at all. ACK can go both ways as P2P intensive applications such as uTorrent etc involve a lot of ACKs, so theoretically prioritizing ACKs means you "prioritized P2P" though that is not entirely' accurate. Read up & do your own testing to find out whats best for your network. If you do not do large amounts of P2P activity on your network or none at all, then enable ACK prioritization.


[edit] Precedence

With all these ways of marking traffic its easy to get confused about how seemingly contradictory requirements are resolved. For example, what happens if you have an IP rule setting IP 192.168.1.2 to priority "maximum" and have a MAC rule setting AA:BB:CC:DD:EE:FF to priority "bulk"?

The order the precedence is as follows:

  • (1st) MAC Priority
  • (2nd) Netmask Priority
  • (3rd) Interface Priority
  • (4th) Services Priority
  • (5th) Ethernet Port Priority


NOTE: Ethernet Port Priority only works on old 802.11g only models with ADMtek switch chips. If you don't have ethernet port priority listed, your router does not support it. Ethernet port priority is different than interface priority.

NOTE: Services can be used at the same time as netmask or MAC, such as limiting 192.168.1.2 to 6 Mbps down & 512 Kbps up while having http set to express, that device will have http packets prioritized within it's allocated bandwidth limit. This only applies to builds r21061 & newer


For netmask, the IP address entries are applied in the order that they appear in your netmask table. Only the first match applies. Example, if you have an entry marking 192.168.1.10/32 as bulk, followed by an entry ABOVE IT, marking 192.168.1.0/24 (all 192.168.1.X) as premium, the traffic from 192.168.1.10 would be marked bulk because it was the first match.

For services, The services entries are applied in the order that they appear in your services tables going from bottom to top. Again, only the first match will apply.

[edit] Initial Setup

  • Select the NAT/QoS tab and then the QoS sub-tab.
  • Click "Enable"
  • Set Port to "WAN". This works for all QoS setups EXCEPT, when using QoS by interface on a BRIDGED interface under "interface priority", UNBRIDGED interfaces work fine with WAN port setting. If you want to use QoS on a BRIDGED interface you must select port as "LAN & WLAN", which also works for all other QoS setups, but with slightly more CPU usage.
  • Select HTB as your packet scheduler if you have "queuing discipline" listed below it, if not then use HFSC.
  • Select FQ_CODEL as your queuing discipline.
  • Set your download and upload speeds. You can use a speed test like Speedtest.net or dslreports.com/speedtest to check your actual connection speed. Some ISPs also provide their own bandwidth testing service, which may be more reliable than the links provided. Enter no higher than 95% of the values you measured into the proper fields. After you have everything set run the speed test again. If you get near 90% of your previous measurement in each direction then things are cool. If you get results which are way off then chances are that you have reversed these values. You must enter a value for the uplink field but if you want you can enter 0 for the downlink field in which case no QoS will occur in that direction, setting your downlink field to 0 isn't recommended.


It probably bugs you to set less than 100% of your available bandwidth in these fields but this is required. There will be a bottleneck somewhere in the system and QoS can only work if the bottleneck is in your router where it has control. The goal is to force the bottleneck to be in your router as opposed to some random location out on the wire over which you have no control. Some ISP's even have bursting ("powerboost") which will temporarily give you extra bandwidth when you first start using your connection but will later throttle down to a sustained rate. Fortunately there is usually a minimum level that you receive on a consistent basis and you must set your QoS limits below this minimum. The problem is finding this minimum and you may have to repeat speed tests many times before determining it. For this reason start with 80% of your measured speed and try things for a couple of days. If the performance is acceptable you can start to inch your levels up. If you go even 2% higher than you should be, your QoS will totally stop working (just too high) or randomly stop working (when your ISP node/DSLAM is slow aka saturated). This can lead to a lot of confusion on your part so get it working first by conservatively setting these speeds and then optimize later.

[edit] Prioritizing by Application (Skype, Http) or Port Range (P2P)

  • Choose an available Service or Port Range from the list or create one, and then press "Add" next to it.
  • For P2P Applications, due to evolving protocols, encryption and obfuscation, it can be much better to define a port range [such as TCP/UDP, 60000-61000]. Set your P2P applications to operate within this range. This can significantly reduce the load on the router, avoid mis-identifying packets, and more efficiently shape your network traffic.
  • Add all your other selected Services and Port Ranges here
  • Choosing a Layer7 service based entry can work better than choosing a port range; though the router works harder as it has to dig into the packets beyond the header, to look at the data they contain.

If you wish to add more than one priority then use the "Add" button to create more entries.


[edit] Prioritizing by Interface

Select your preferred interference, click add, then select the speed or priority you want. You can also limit ethernet ports this way as well (ethX or vlanX). Any limits or priorities set are shared for that interface regardless how many clients are connected to it. Excellent for running a guest network/hotspot on eg, ath1.1, applying QoS on the entire interface makes it impossible for a greedy user to bypass it by MAC cloning, changing IPs etc, short of connecting to a different interface. The same interface can also be entered multiple times with different speed limits or priorities for different services, example, ath0 512/512 with ssl & ath0 0/1024 with http would mean ssl traffic on ath0 is limited to 512kbps down & up, http is unlimited on down (up to global limits is used) & limited to 1024 (1mbps) on up, remaining entered services are not limited (up to global limits for both directions).

[edit] Prioritizing by Netmask (IP address)

These are entered in CIDR notation including the network prefix.

For example, to specify a single IP address enter xxx.xxx.xxx.xxx/32. Be careful to enter netmask as /32 because leaving it /0 means ALL IPs!.

The netmask is the number of bits of the IP address to match. For example, the entry 192.168.1.0/24 matches 192.168.1.x addresses. An entry of 192.168.0.0/16 matches 192.168.x.x addresses. If you're unsure of how to create CIDR subnet masks and what they mean, then use a subnet calculator.

After you have filled it out, press "add" next to it. If you want to add multiple entries (make sure to have order correct!) click "save" before entering in another so any previous changes don't get deleted, only click "apply" when you want to start testing your current changes displayed.


[edit] Prioritizing by MAC Address

In the case you want to prioritize traffic from a particular device without a static IP address on your LAN, you can prioritize by MAC Address. Enter the MAC Address of the device and press "Add" next to it.



[edit] How Do You Check What QoS Priorities Were Applied

The DDWRT web UI doesn't display any live traffic. Short of doing a practical test, you can get your hands dirty by checking the conntrack entries via telnet or ssh access in the router. When you're logged in run:

iptables -t mangle -vnL

Then scroll down to the Chain SVQOS_SVCS section.

With the above iptables mangle command you can see the inbound/outbound chains, entered IPs/MACs/services & whats being matched where.

It will list out all currently open connection and protocol that is currently being routed by the router. This is what it would look like:

tcp      6 113 ESTABLISHED src=192.168.1.5 dst=83.141.4.210 sport=48959 dport=21 src=83.141.4.210 dst=216.239.61.104 sport=21 dport=48959 [ASSURED] use=1 rate=73 l7proto=ftp mark=40
udp      17 29 src=192.168.1.5 dst=128.63.2.53 sport=56105 dport=53 src=128.63.2.53 dst=216.239.61.104 sport=53 dport=56105 use=1 rate=157 l7proto=dns mark=10

What you'll be interested to look at will be the first set of source and destination IP, including the port numbers. Next the presence of l7proto and the "mark" field. The entries indicate the current live connection QoS priority applied on them based on the "mark" field. The "mark" values corresponds to the following:

  • Maximum: 100
  • Premium: 10
  • Express: 20
  • Standard: 30
  • Bulk: 40
  • (no QoS matched): 0


You may see "mark=0" for some l7proto service even though they are in configured in the list of QoS rules. This may mean that the layer 7 pattern matching system didn't match a new or changed header for that protocol. Custom service on port matches will usually take care of these.

[edit] Time Based QoS

As described in this thread you can use CRON jobs to enable/disable QoS. This is just a simplistic approach but more complex things could be done if you put your mind to it. These commands will enable HTB QoS on the WAN port from 5PM to 1AM but you will still need to configure everything else in the GUI. If you want to use LAN&WLAN then change "`get_wanface`" to "imq1". To change the times, see the CRON page for information.

1 17 * * * root /usr/sbin/svqos `nvram get wshaper_downlink` `nvram get wshaper_uplink` `get_wanface` `nvram get wan_mtu` 0
*/6 1-17 * * * root /usr/sbin/svqos stop 0 `get_wanface` 0 0

If you use HFSC then you would do something like this instead.

1 17 * * * root /usr/sbin/svqos2 `nvram get wshaper_uplink` `nvram get wshaper_downlink` `get_wanface` `nvram get wan_mtu` 0
*/6 1-17 * * * root /usr/sbin/svqos2 stop 0 `get_wanface` 0 0 

As described in this thread you can also set different rates at different times by doing something like this which changes the HTB rates.

1 23 * * * root /usr/sbin/svqos [downlink rate] [uplink rate] `get_wanface` `nvram get wan_mtu` 0; nvram set wshaper_downlink=[downlink rate]; nvram set wshaper_uplink=[uplink rate];
1 10 * * * root /usr/sbin/svqos [downlink rate] [uplink rate] `get_wanface` `nvram get wan_mtu` 0; nvram set wshaper_downlink=[downlink rate]; nvram set wshaper_uplink=[uplink rate];

Edit: This will cause trouble on current firmware releases greater than r21061. Use the predefined service handler to stop/start QoS instead. Even if needed, use imq1 instead of br0 for internal traffic shaping.

stopservice wshaper
startservice wshaper

If you need to alter down/up rates edit the nvram variables before restarting wshaper

nvram set wshaper_downlink=20000
nvram set wshaper_uplink=800
startservice wshaper



[edit] External Links