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* HTB scheduler, problem with blocking high priority traffic
@ 2016-04-12 13:17 Ewa Janczukowicz
  2016-04-15 14:34 ` Ewa Janczukowicz
                   ` (4 more replies)
  0 siblings, 5 replies; 6+ messages in thread
From: Ewa Janczukowicz @ 2016-04-12 13:17 UTC (permalink / raw)
  To: lartc

Hello,

I would like to ask a question about a weird (at least for me J) HTB
behavior that I get, while prioritizing one type of traffic.

I am working on assuring low delay for UDP traffic at the home gateway
level. At this home gateway I have two types of traffic, TCP and UDP,
and I assure differentiated treatment by using HTB.
The bandwidth I am testing equals 1Mbit/s.

 Thus, I have to types of leaf classes:
- UDP leaf class with:
    - the highest priority,
    - a short queue length (SFQ qdisc),
    - assured rate 200kbit/s and ceil rate 1Mbit/s,
     - quantum = 3 x MTU.

- TCP leaf class with:
    - lowest priority,
    - default queue length (pFIFO qdisc),
    - minimum assured rate (8bit/s – to force it to stay in yellow mode
most of the time)  and ceil rate 1Mbit/s,
    - quantum = MTU.

In order to see how the traffic interacts, for UDP I have a stairs
type of traffic, thus I start at 0bit/s and I increase the traffic
every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every
10s by 100kbit/s until I reach zero.

Alongside, I have TCP traffic, either a file upload, either a simple
iperf (without any influence on observed behavior).

Normally, most of the time, I get an expected behavior. Thus I can see
perfectly the traffic separation and the “stairs” trend of the UDP.
Additionally, UDP traffic takes over TCP (but TCP can still send – and
the trend is the opposite of UDP, thus first decreasing, later
increasing).

However when the UDP bitrate is already decreasing (about 30 seconds
before reaching 0), TCP traffic completely takes over for a couple of
seconds. I can’t really understand this behavior, because it seems
that UDP traffic cannot send, but it shouldn’t be in “red” mode since
its bitrate is already decreasing.

I think it has something to do with HTB scheduling and blocking UDP
traffic for some reason.

I hope my question is clear, but I can also provide wireshark bitrate graphs.

I will continue to test different configurations but I will appreciate
any suggestions.

Thank you in advance for your help.

Ewa

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: HTB scheduler, problem with blocking high priority traffic
  2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
@ 2016-04-15 14:34 ` Ewa Janczukowicz
  2016-04-15 15:51 ` Andy Furniss
                   ` (3 subsequent siblings)
  4 siblings, 0 replies; 6+ messages in thread
From: Ewa Janczukowicz @ 2016-04-15 14:34 UTC (permalink / raw)
  To: lartc

Hello again,
Just to give you an update.
I have tried different options, changing burst, cburst, ceil, rate and
quantums, but I could not see any improvement.
Different configurations only changes when and how many times my high
priority traffic gets starved by the low priority one (sometimes the
priority traffic is blocked up to three times in random moments
sometimes only once).

I am using the following configuration now:
tc qdisc add dev br0 handle 1: root htb default 15
tc class add dev br0 parent 1: classid 1:1 htb rate 1000kbit ceil 1000kbit
tc class add dev br0 parent 1:1 classid 1:14 htb rate 200kbit ceil
1000kbit prio 1
tc class add dev br0 parent 1:1 classid 1:15 htb rate 10bit ceil 1000kbit prio 2
tc filter add dev br0 parent 1: protocol ip u32 match ip tos 0xb8 0xff
flowid 1:14 (UDP)
tc filter add dev br0 parent 1: protocol ip u32 match ip tos 0x00 0xff
flowid 1:15 (TCP)
tc qdisc add dev br0 parent 1:14 handle 20: sfq limit 40
tc qdisc add dev br0 parent 1:15 handle 50: pfifo limit 1000

I still think it has something to do with HTB scheduling and blocking
high priority traffic for some reason. Thus when rate is calculated
for my high priority traffic, it somehow is higher than its ceil.
I have found some information that burst/cburst is used for rate
calculation, however leaving it to default seems the best option, thus
that way it is the lowest possible.

So I still have some questions:
- Why could low priority traffic block the other one for several
seconds, even though its assured rate is close to zero? Probably
because priority rate used all its tokens, that leads to the next
question:
- Why would high priority traffic reach its ceil if the bitrate is
lower than 1Mbit/s?

Thank you in advance for any help.
Have a nice day,
Ewa


On Tue, Apr 12, 2016 at 3:17 PM, Ewa Janczukowicz
<janczukowicz.ewa@gmail.com> wrote:
> Hello,
>
> I would like to ask a question about a weird (at least for me J) HTB
> behavior that I get, while prioritizing one type of traffic.
>
> I am working on assuring low delay for UDP traffic at the home gateway
> level. At this home gateway I have two types of traffic, TCP and UDP,
> and I assure differentiated treatment by using HTB.
> The bandwidth I am testing equals 1Mbit/s.
>
>  Thus, I have to types of leaf classes:
> - UDP leaf class with:
>     - the highest priority,
>     - a short queue length (SFQ qdisc),
>     - assured rate 200kbit/s and ceil rate 1Mbit/s,
>      - quantum = 3 x MTU.
>
> - TCP leaf class with:
>     - lowest priority,
>     - default queue length (pFIFO qdisc),
>     - minimum assured rate (8bit/s – to force it to stay in yellow mode
> most of the time)  and ceil rate 1Mbit/s,
>     - quantum = MTU.
>
> In order to see how the traffic interacts, for UDP I have a stairs
> type of traffic, thus I start at 0bit/s and I increase the traffic
> every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every
> 10s by 100kbit/s until I reach zero.
>
> Alongside, I have TCP traffic, either a file upload, either a simple
> iperf (without any influence on observed behavior).
>
> Normally, most of the time, I get an expected behavior. Thus I can see
> perfectly the traffic separation and the “stairs” trend of the UDP.
> Additionally, UDP traffic takes over TCP (but TCP can still send – and
> the trend is the opposite of UDP, thus first decreasing, later
> increasing).
>
> However when the UDP bitrate is already decreasing (about 30 seconds
> before reaching 0), TCP traffic completely takes over for a couple of
> seconds. I can’t really understand this behavior, because it seems
> that UDP traffic cannot send, but it shouldn’t be in “red” mode since
> its bitrate is already decreasing.
>
> I think it has something to do with HTB scheduling and blocking UDP
> traffic for some reason.
>
> I hope my question is clear, but I can also provide wireshark bitrate graphs.
>
> I will continue to test different configurations but I will appreciate
> any suggestions.
>
> Thank you in advance for your help.
>
> Ewa

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: HTB scheduler, problem with blocking high priority traffic
  2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
  2016-04-15 14:34 ` Ewa Janczukowicz
@ 2016-04-15 15:51 ` Andy Furniss
  2016-04-15 16:14 ` Anton Danilov
                   ` (2 subsequent siblings)
  4 siblings, 0 replies; 6+ messages in thread
From: Andy Furniss @ 2016-04-15 15:51 UTC (permalink / raw)
  To: lartc

Ewa Janczukowicz wrote:
> Hello again,
> Just to give you an update.
> I have tried different options, changing burst, cburst, ceil, rate and
> quantums, but I could not see any improvement.
> Different configurations only changes when and how many times my high
> priority traffic gets starved by the low priority one (sometimes the
> priority traffic is blocked up to three times in random moments
> sometimes only once).
>
> I am using the following configuration now:
> tc qdisc add dev br0 handle 1: root htb default 15

> tc class add dev br0 parent 1:1 classid 1:15 htb rate 10bit ceil 1000kbit prio 2

> tc qdisc add dev br0 parent 1:15 handle 50: pfifo limit 1000

I don't know if it affects your test but using default catches arp
and it's not a good idea to send arp to a potentially "crap" class!


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: HTB scheduler, problem with blocking high priority traffic
  2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
  2016-04-15 14:34 ` Ewa Janczukowicz
  2016-04-15 15:51 ` Andy Furniss
@ 2016-04-15 16:14 ` Anton Danilov
  2016-04-18  9:31 ` Ewa Janczukowicz
  2016-04-21  9:33 ` Ewa Janczukowicz
  4 siblings, 0 replies; 6+ messages in thread
From: Anton Danilov @ 2016-04-15 16:14 UTC (permalink / raw)
  To: lartc

Hello, Ewa.

Can you catch the traffic with NFLOG target and tcpdump before
enqueueing into device to investigate the original order of packets?
Also, it will be useful to check the statistics of classes (tc -s -s
-d class ls..). Can you share the some part of this data?

2016-04-12 16:17 GMT+03:00 Ewa Janczukowicz <janczukowicz.ewa@gmail.com>:
> Hello,
>
> I would like to ask a question about a weird (at least for me J) HTB
> behavior that I get, while prioritizing one type of traffic.
>
> I am working on assuring low delay for UDP traffic at the home gateway
> level. At this home gateway I have two types of traffic, TCP and UDP,
> and I assure differentiated treatment by using HTB.
> The bandwidth I am testing equals 1Mbit/s.
>
>  Thus, I have to types of leaf classes:
> - UDP leaf class with:
>     - the highest priority,
>     - a short queue length (SFQ qdisc),
>     - assured rate 200kbit/s and ceil rate 1Mbit/s,
>      - quantum = 3 x MTU.
>
> - TCP leaf class with:
>     - lowest priority,
>     - default queue length (pFIFO qdisc),
>     - minimum assured rate (8bit/s – to force it to stay in yellow mode
> most of the time)  and ceil rate 1Mbit/s,
>     - quantum = MTU.
>
> In order to see how the traffic interacts, for UDP I have a stairs
> type of traffic, thus I start at 0bit/s and I increase the traffic
> every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every
> 10s by 100kbit/s until I reach zero.
>
> Alongside, I have TCP traffic, either a file upload, either a simple
> iperf (without any influence on observed behavior).
>
> Normally, most of the time, I get an expected behavior. Thus I can see
> perfectly the traffic separation and the “stairs” trend of the UDP.
> Additionally, UDP traffic takes over TCP (but TCP can still send – and
> the trend is the opposite of UDP, thus first decreasing, later
> increasing).
>
> However when the UDP bitrate is already decreasing (about 30 seconds
> before reaching 0), TCP traffic completely takes over for a couple of
> seconds. I can’t really understand this behavior, because it seems
> that UDP traffic cannot send, but it shouldn’t be in “red” mode since
> its bitrate is already decreasing.
>
> I think it has something to do with HTB scheduling and blocking UDP
> traffic for some reason.
>
> I hope my question is clear, but I can also provide wireshark bitrate graphs.
>
> I will continue to test different configurations but I will appreciate
> any suggestions.
>
> Thank you in advance for your help.
>
> Ewa
> --
> To unsubscribe from this list: send the line "unsubscribe lartc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Anton.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: HTB scheduler, problem with blocking high priority traffic
  2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
                   ` (2 preceding siblings ...)
  2016-04-15 16:14 ` Anton Danilov
@ 2016-04-18  9:31 ` Ewa Janczukowicz
  2016-04-21  9:33 ` Ewa Janczukowicz
  4 siblings, 0 replies; 6+ messages in thread
From: Ewa Janczukowicz @ 2016-04-18  9:31 UTC (permalink / raw)
  To: lartc

Hello,
Thank you for your suggestions.
@Andy
I do not know if arp has anything to do here. Especially that the
behaviour that I observe seems quite random. Sometimes it even works
as expected.

@Anton
I have run the test again, and collected the statistics with tshark
also before the enqueueing.
So I do see a different behaviour than for outoing interface. Thus for
incoming traffic TCP is close to zero for more than 40s, and later it
increases.
Whereas incoming udp traffic behaves as expected. Thus I observe the
"stairs" trend.

What suprises me is that I do not see any packet losses for udp on the
outgoing interface.
I share with you tc -s -d class show. However I do not know how to
share tshark info on this mailing list.

class htb 1:15 parent 1:1 leaf 50: prio 2 quantum 1000 rate 8bit ceil
1Mbit linklayer ethernet burst 225b/1 mpu 0b overhead 0b cburst
1600b/1 mpu 0b overhead 0b level 0
 Sent 11912330 bytes 8133 pkt (dropped 749, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0
 lended: 8 borrowed: 8125 giants: 0
 tokens: -738824047 ctokens: 179250

class htb 1:14 parent 1:1 leaf 20: prio 1 quantum 2550 rate 204Kbit
ceil 1Mbit linklayer ethernet burst 1599b/1 mpu 0b overhead 0b cburst
1600b/1 mpu 0b overhead 0b level 0
 Sent 11521440 bytes 7620 pkt (dropped 0, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0
 lended: 2845 borrowed: 4775 giants: 0
 tokens: 53919 ctokens: 11000

class htb 1:1 root rate 1Mbit ceil 1Mbit linklayer ethernet burst
1600b/1 mpu 0b overhead 0b cburst 1600b/1 mpu 0b overhead 0b level 7
 Sent 23433770 bytes 15753 pkt (dropped 0, overlimits 0 requeues 0)
 rate 0bit 0pps backlog 0b 0p requeues 0
 lended: 12900 borrowed: 0 giants: 0
 tokens: 179250 ctokens: 179250

Thank you in advance.
Ewa





On Fri, Apr 15, 2016 at 6:14 PM, Anton Danilov
<littlesmilingcloud@gmail.com> wrote:
> Hello, Ewa.
>
> Can you catch the traffic with NFLOG target and tcpdump before
> enqueueing into device to investigate the original order of packets?
> Also, it will be useful to check the statistics of classes (tc -s -s
> -d class ls..). Can you share the some part of this data?
>
> 2016-04-12 16:17 GMT+03:00 Ewa Janczukowicz <janczukowicz.ewa@gmail.com>:
>> Hello,
>>
>> I would like to ask a question about a weird (at least for me J) HTB
>> behavior that I get, while prioritizing one type of traffic.
>>
>> I am working on assuring low delay for UDP traffic at the home gateway
>> level. At this home gateway I have two types of traffic, TCP and UDP,
>> and I assure differentiated treatment by using HTB.
>> The bandwidth I am testing equals 1Mbit/s.
>>
>>  Thus, I have to types of leaf classes:
>> - UDP leaf class with:
>>     - the highest priority,
>>     - a short queue length (SFQ qdisc),
>>     - assured rate 200kbit/s and ceil rate 1Mbit/s,
>>      - quantum = 3 x MTU.
>>
>> - TCP leaf class with:
>>     - lowest priority,
>>     - default queue length (pFIFO qdisc),
>>     - minimum assured rate (8bit/s – to force it to stay in yellow mode
>> most of the time)  and ceil rate 1Mbit/s,
>>     - quantum = MTU.
>>
>> In order to see how the traffic interacts, for UDP I have a stairs
>> type of traffic, thus I start at 0bit/s and I increase the traffic
>> every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every
>> 10s by 100kbit/s until I reach zero.
>>
>> Alongside, I have TCP traffic, either a file upload, either a simple
>> iperf (without any influence on observed behavior).
>>
>> Normally, most of the time, I get an expected behavior. Thus I can see
>> perfectly the traffic separation and the “stairs” trend of the UDP.
>> Additionally, UDP traffic takes over TCP (but TCP can still send – and
>> the trend is the opposite of UDP, thus first decreasing, later
>> increasing).
>>
>> However when the UDP bitrate is already decreasing (about 30 seconds
>> before reaching 0), TCP traffic completely takes over for a couple of
>> seconds. I can’t really understand this behavior, because it seems
>> that UDP traffic cannot send, but it shouldn’t be in “red” mode since
>> its bitrate is already decreasing.
>>
>> I think it has something to do with HTB scheduling and blocking UDP
>> traffic for some reason.
>>
>> I hope my question is clear, but I can also provide wireshark bitrate graphs.
>>
>> I will continue to test different configurations but I will appreciate
>> any suggestions.
>>
>> Thank you in advance for your help.
>>
>> Ewa
>> --
>> To unsubscribe from this list: send the line "unsubscribe lartc" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
> --
> Anton.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: HTB scheduler, problem with blocking high priority traffic
  2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
                   ` (3 preceding siblings ...)
  2016-04-18  9:31 ` Ewa Janczukowicz
@ 2016-04-21  9:33 ` Ewa Janczukowicz
  4 siblings, 0 replies; 6+ messages in thread
From: Ewa Janczukowicz @ 2016-04-21  9:33 UTC (permalink / raw)
  To: lartc

Hello,
I have worked more on analyzing my problem.

So I have captured TCP packets that are sent from the TCP user. And
thus the behavior is different than at the exit of home gateway (that
was quite misleading).

There is no ‘stairs’ trend, when the packets enter the home gateway.
However at some point(s) the TCP bitrate decreases or even stops and
later sends a huge burst of bytes. I believe it is cause by a packet
loss somewhere on the way and since congestion window is big (the
congestion window is big since TCP queue is very long so actually
packet loss is not that big). This burst of traffic probably takes
over the prioritized UDP traffic (it lasts about 13ms and sends 346 of
1516B packets).

However TCP takes over UDP for a good couple of seconds (3-4 seconds),
which seems to me a little longer than expected.

Do you have any suggestions why would HTB act like that in case of
such a big burst? Thus I thought it would be managed by burst/cburst
parameter.

Thanks in advance for any help.
Ewa

On Mon, Apr 18, 2016 at 11:31 AM, Ewa Janczukowicz
<janczukowicz.ewa@gmail.com> wrote:
> Hello,
> Thank you for your suggestions.
> @Andy
> I do not know if arp has anything to do here. Especially that the
> behaviour that I observe seems quite random. Sometimes it even works
> as expected.
>
> @Anton
> I have run the test again, and collected the statistics with tshark
> also before the enqueueing.
> So I do see a different behaviour than for outoing interface. Thus for
> incoming traffic TCP is close to zero for more than 40s, and later it
> increases.
> Whereas incoming udp traffic behaves as expected. Thus I observe the
> "stairs" trend.
>
> What suprises me is that I do not see any packet losses for udp on the
> outgoing interface.
> I share with you tc -s -d class show. However I do not know how to
> share tshark info on this mailing list.
>
> class htb 1:15 parent 1:1 leaf 50: prio 2 quantum 1000 rate 8bit ceil
> 1Mbit linklayer ethernet burst 225b/1 mpu 0b overhead 0b cburst
> 1600b/1 mpu 0b overhead 0b level 0
>  Sent 11912330 bytes 8133 pkt (dropped 749, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
>  lended: 8 borrowed: 8125 giants: 0
>  tokens: -738824047 ctokens: 179250
>
> class htb 1:14 parent 1:1 leaf 20: prio 1 quantum 2550 rate 204Kbit
> ceil 1Mbit linklayer ethernet burst 1599b/1 mpu 0b overhead 0b cburst
> 1600b/1 mpu 0b overhead 0b level 0
>  Sent 11521440 bytes 7620 pkt (dropped 0, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
>  lended: 2845 borrowed: 4775 giants: 0
>  tokens: 53919 ctokens: 11000
>
> class htb 1:1 root rate 1Mbit ceil 1Mbit linklayer ethernet burst
> 1600b/1 mpu 0b overhead 0b cburst 1600b/1 mpu 0b overhead 0b level 7
>  Sent 23433770 bytes 15753 pkt (dropped 0, overlimits 0 requeues 0)
>  rate 0bit 0pps backlog 0b 0p requeues 0
>  lended: 12900 borrowed: 0 giants: 0
>  tokens: 179250 ctokens: 179250
>
> Thank you in advance.
> Ewa
>
>
>
>
>
> On Fri, Apr 15, 2016 at 6:14 PM, Anton Danilov
> <littlesmilingcloud@gmail.com> wrote:
>> Hello, Ewa.
>>
>> Can you catch the traffic with NFLOG target and tcpdump before
>> enqueueing into device to investigate the original order of packets?
>> Also, it will be useful to check the statistics of classes (tc -s -s
>> -d class ls..). Can you share the some part of this data?
>>
>> 2016-04-12 16:17 GMT+03:00 Ewa Janczukowicz <janczukowicz.ewa@gmail.com>:
>>> Hello,
>>>
>>> I would like to ask a question about a weird (at least for me J) HTB
>>> behavior that I get, while prioritizing one type of traffic.
>>>
>>> I am working on assuring low delay for UDP traffic at the home gateway
>>> level. At this home gateway I have two types of traffic, TCP and UDP,
>>> and I assure differentiated treatment by using HTB.
>>> The bandwidth I am testing equals 1Mbit/s.
>>>
>>>  Thus, I have to types of leaf classes:
>>> - UDP leaf class with:
>>>     - the highest priority,
>>>     - a short queue length (SFQ qdisc),
>>>     - assured rate 200kbit/s and ceil rate 1Mbit/s,
>>>      - quantum = 3 x MTU.
>>>
>>> - TCP leaf class with:
>>>     - lowest priority,
>>>     - default queue length (pFIFO qdisc),
>>>     - minimum assured rate (8bit/s – to force it to stay in yellow mode
>>> most of the time)  and ceil rate 1Mbit/s,
>>>     - quantum = MTU.
>>>
>>> In order to see how the traffic interacts, for UDP I have a stairs
>>> type of traffic, thus I start at 0bit/s and I increase the traffic
>>> every ten seconds by 100kbit/s. When I reach 1Mbit/s I decrease every
>>> 10s by 100kbit/s until I reach zero.
>>>
>>> Alongside, I have TCP traffic, either a file upload, either a simple
>>> iperf (without any influence on observed behavior).
>>>
>>> Normally, most of the time, I get an expected behavior. Thus I can see
>>> perfectly the traffic separation and the “stairs” trend of the UDP.
>>> Additionally, UDP traffic takes over TCP (but TCP can still send – and
>>> the trend is the opposite of UDP, thus first decreasing, later
>>> increasing).
>>>
>>> However when the UDP bitrate is already decreasing (about 30 seconds
>>> before reaching 0), TCP traffic completely takes over for a couple of
>>> seconds. I can’t really understand this behavior, because it seems
>>> that UDP traffic cannot send, but it shouldn’t be in “red” mode since
>>> its bitrate is already decreasing.
>>>
>>> I think it has something to do with HTB scheduling and blocking UDP
>>> traffic for some reason.
>>>
>>> I hope my question is clear, but I can also provide wireshark bitrate graphs.
>>>
>>> I will continue to test different configurations but I will appreciate
>>> any suggestions.
>>>
>>> Thank you in advance for your help.
>>>
>>> Ewa
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe lartc" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>>
>>
>> --
>> Anton.

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2016-04-21  9:33 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-04-12 13:17 HTB scheduler, problem with blocking high priority traffic Ewa Janczukowicz
2016-04-15 14:34 ` Ewa Janczukowicz
2016-04-15 15:51 ` Andy Furniss
2016-04-15 16:14 ` Anton Danilov
2016-04-18  9:31 ` Ewa Janczukowicz
2016-04-21  9:33 ` Ewa Janczukowicz

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