QoS - Queue Tree - unexpected drops

Bernhard · Tue Jan 25, 2022 5:46 pm

Dear community,
I have a pair of CCR1016 as routers to the internet and some Cisco Catalyst 3650 in the back for Client and AccessPoint (cAP ac) connectivity.
As this is a redundant solution I have the internet connection not directly on an interface but on a vlan (id 600) on the bridge.
On the access points I provide also a guest SSID and I want to limit guest traffic to 20Mbps up- and downstream - the total bandwidth is 300Mbps up- and downstream.
So I did mangle rules and a queue tree according to what I found in the manual and examples in the internet.
The upstream I bound to vlan600, but where to bind the downstream? If I choose bridge1, there is also vlan600 included (which is upstream). So I decided to already distinguish up and down traffic with mangle rules - see attached config

conf.rsc

What makes me wonder is that there are a lot of drops in the downstream default traffic. I already defined it with a max limit of 320M and the internet connection is not more than 300M.

[router] > queue tree print stats 
Flags: X - disabled, I - invalid 
 0   name="Total_downstream" parent=bridge1 packet-mark="" rate=6044416 packet-rate=1271 queued-bytes=0 queued-packets=0 bytes=18340724263 packets=25820140 dropped=0 
 1   name="down_Guest" parent=Total_downstream packet-mark=Guests_down rate=0 packet-rate=0 queued-bytes=0 queued-packets=0 bytes=523087367 packets=379152 dropped=17950 
 2   name="Total_upstream" parent=vlan600_Telekom packet-mark="" rate=2876976 packet-rate=1022 queued-bytes=0 queued-packets=0 bytes=3585789801 packets=16326126 dropped=0 
 3   name="up_Guest" parent=Total_upstream packet-mark=Guests_up rate=0 packet-rate=0 queued-bytes=0 queued-packets=0 bytes=18116339 packets=214953 dropped=208 
 4   name="up_default" parent=Total_upstream packet-mark=no-mark rate=2876976 packet-rate=1022 queued-bytes=0 queued-packets=0 bytes=3567673462 packets=16111173 dropped=17497 
 5   name="down_default" parent=Total_downstream packet-mark=default_down rate=6044416 packet-rate=1271 queued-bytes=0 queued-packets=0 bytes=17817636896 packets=25440988 dropped=62213

Questions:
* is my config OK?
* where does these drops in the down_default come from (even when the max limit is more than ever can come in from the internet)?

Tue Jan 25, 2022 10:04 pm

sometimes a queue type too small can lead to drops if there is too much traffic

try tuning up your queue sizes in respective queue types you are using in your queue tree until you dont see drops with normal traffic

keep in mind this consumes RAM memory, if you establish too big queue size in some scenarios this can lead to a excesive RAM memory consumption

Bernhard · Wed Jan 26, 2022 11:45 am

sometimes a queue type too small can lead to drops if there is too much traffic

try tuning up your queue sizes in respective queue types you are using in your queue tree until you dont see drops with normal traffic

keep in mind this consumes RAM memory, if you establish too big queue size in some scenarios this can lead to a excesive RAM memory consumption

I raised the queue size from 10 to 50 packets in the down_default queue -> still packet drops.
* is my config OK?
* is it OK to have a vlan-interface as a parent of a queue?
* is there a possibility to debug dropped packets?

Assuming that vlan-interfaces are allowed as parents of a queue, I changed the config for downstream to:

/ip firewall mangle
add action=mark-connection chain=forward connection-state=new new-connection-mark=Guests passthrough=yes src-address-list=local_Guests
add action=mark-packet chain=forward connection-mark=Guests new-packet-mark=Guests passthrough=yes
/queue tree
add max-limit=20M name=Total_down_Guest parent=vlan401_Guest
add max-limit=20M name=down_Guest packet-mark=Guests parent=Total_down_Guest

Wed Jan 26, 2022 10:52 pm

sometimes a queue type too small can lead to drops if there is too much traffic

try tuning up your queue sizes in respective queue types you are using in your queue tree until you dont see drops with normal traffic

keep in mind this consumes RAM memory, if you establish too big queue size in some scenarios this can lead to a excesive RAM memory consumption
I raised the queue size from 10 to 50 packets in the down_default queue -> still packet drops.
* is my config OK?
* is it OK to have a vlan-interface as a parent of a queue?
* is there a possibility to debug dropped packets?

Assuming that vlan-interfaces are allowed as parents of a queue, I changed the config for downstream to:
Code: Select all
/ip firewall mangle
add action=mark-connection chain=forward connection-state=new new-connection-mark=Guests passthrough=yes src-address-list=local_Guests
add action=mark-packet chain=forward connection-mark=Guests new-packet-mark=Guests passthrough=yes
/queue tree
add max-limit=20M name=Total_down_Guest parent=vlan401_Guest
add max-limit=20M name=down_Guest packet-mark=Guests parent=Total_down_Guest

check if changing queue size reduce or not the amount of drops

if there is not any change then your problem can be other

QoS - Queue Tree - unexpected drops

QoS - Queue Tree - unexpected drops

Re: QoS - Queue Tree - unexpected drops

Re: QoS - Queue Tree - unexpected drops

Re: QoS - Queue Tree - unexpected drops

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