Community discussions

MikroTik App
 
wingolo
just joined
Topic Author
Posts: 13
Joined: Thu Nov 28, 2013 4:36 pm

PTP SXTsq-5-ac excelent status but terrible throughput

Thu Aug 26, 2021 11:47 pm

Hello everyone!

I've been searching for this situation and I've found some related posts but without any help... so I try to discuss here my problem, hoping for some solution.

We made a ptp link between our main site and the werehouse (200-300m away) using two RBSXTsqG-5acD, no obstacles between, just a plain field.

Here the configuration:
ptp-config.png
And this are the statistics of the link:
ptp-statistics.png
and signal
ptp-signal.png
So, all looks very good and we was excited to have a ~700Mbps link (based on the rates) but then we tried to strasfer a file from the fileserver to a laptop (connectet to the remote point with a 1G eth port) end here the very bad news... the trasfer is terribly slow, 5 to 6MB/s so ~48Mbps (as indicated in the interface menu in winbox).
Both devices have cpu usage close to 0%, so it's not this the limit... With the builtin speed test we can reach 200Mbps but then the cpu reach the maximum capacity so I think it's not a usefull test.
Just for information, the same test done in the main site (same laptop, cable, file etc) reach the maximum speed possible in a 1G eth link.

I'm asking to you if you have some suggestions on how to create a good link, so we could use the other building for work, since I've spent three days without any improvements.
Almost forget... I've been able to reach 10MB/s changing the wireless protocollo from nv2 to 802.11... and this looks odd to me :?

Thanks to all in advant!
You do not have the required permissions to view the files attached to this post.
 
User avatar
bpwl
Forum Guru
Forum Guru
Posts: 2979
Joined: Mon Apr 08, 2019 1:16 am

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Fri Aug 27, 2021 12:44 am

Well the wireless link seems to be OK. Great numbers. The thing that MT is not showing is the free air-time in that wide channel. But nv2 should not care about the 802.11 politely wait for transmission. And if there was adjacent channel interference the interface rate would have stepped down. Much more information is in the registration table (detailed view), but again there is probably nothing that can explain the low data rate (you measured 200Mbps, with UDP you should get something like 390Mbps if only one direction is used.)

If it is not the wireless link, what is it then? There are some known pitfalls ... unlikely but that's all what we have here.

- ethernet interface negotiation , do they agree on 1000Mbps/full duplex on all sides ? Well known issue as 100Mbps half/full mismatch gives 40kbps as throughput
- ethernet - wireless transition, is just bridged I hope.
- another, less known, is the TCP congestion avoidance algoritmes throttling way too much at the endpoints (viewtopic.php?f=2&t=174113#p851770)
- and the different MTU sizes could trigger the "120ms delay for ACK, if the transfer was in blocks with a now odd number of packets, and is waiting for the ack to continue with the next block" (I Had this with NFS between a UNIX server and Windows client, over ethernet cable)

Unstable TCP congestion control (Reno, Tahoe, compound, Cubic ....) is for me the prime suspect here. (Easily spotted on sawthooth graphs, or in detail with Packet Sniffer, while looking at the packet timing.)
 
wingolo
just joined
Topic Author
Posts: 13
Joined: Thu Nov 28, 2013 4:36 pm

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Mon Aug 30, 2021 12:25 pm

Thanks @bpwl, I had to wait until today to be on site and make some more tests
- ethernet interface negotiation , do they agree on 1000Mbps/full duplex on all sides ? Well known issue as 100Mbps half/full mismatch gives 40kbps as throughput
- ethernet - wireless transition, is just bridged I hope.
- another, less known, is the TCP congestion avoidance algoritmes throttling way too much at the endpoints (viewtopic.php?f=2&t=174113#p851770)
- and the different MTU sizes could trigger the "120ms delay for ACK, if the transfer was in blocks with a now odd number of packets, and is waiting for the ack to continue with the next block" (I Had this with NFS between a UNIX server and Windows client, over ethernet cable)

Unstable TCP congestion control (Reno, Tahoe, compound, Cubic ....) is for me the prime suspect here. (Easily spotted on sawthooth graphs, or in detail with Packet Sniffer, while looking at the packet timing.)
I've followed your suggestions and...
- all auto negotiate on 1000Mbps/full duplex (also tried to set directly on 1G eth)
- yes, just one bridge between eth and wireless, nothing else, no firewall rules, nat, etc.
- every interfaces have the same MTU (1500)
- Also tried to make some changes in the tcp congestion etc, but after all the tuning I'm able to reach 11MB/s nothing more...

I've also tried downloading a file from an internal webserver (on linux server) but, same speed.

Then I've found this thread viewtopic.php?f=7&t=177925, where he can transafare 420Mpbs... maybe I can ask him the configuration.

btw here my config on the AP:
/interface bridge
add admin-mac=00:00:5E:AA:BB:01 auto-mac=no name=br-lan protocol-mode=none
/interface ethernet
set [ find default-name=ether1 ] auto-negotiation=no
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/interface wireless
set [ find default-name=wlan1 ] band=5ghz-onlyac channel-width=20/40/80mhz-Ceee country="etsi 5.5-5.7 outdoor" disabled=no distance=1 \
    frequency=5520 mode=bridge nv2-cell-radius=10 nv2-preshared-key=XXXXX nv2-security=enabled ssid=TEST station-roaming=enabled tdma-period-size=1 wireless-protocol=nv2
/queue interface
set ether1 queue=ethernet-default
/user group
set full policy=local,telnet,ssh,ftp,reboot,read,write,policy,test,winbox,password,web,sniff,sensitive,api,romon,dude,tikapp
/interface bridge port
add bridge=br-lan interface=ether1
add bridge=br-lan interface=wlan1
/ip neighbor discovery-settings
set discover-interface-list=!dynamic
/ip settings
set tcp-syncookies=yes
/ip address
add address=10.10.10.48/24 interface=br-lan network=10.10.10.0
/ip route
add distance=1 gateway=10.10.10.1
Any suggestions?
 
User avatar
bpwl
Forum Guru
Forum Guru
Posts: 2979
Joined: Mon Apr 08, 2019 1:16 am

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Mon Aug 30, 2021 1:17 pm

I don't know if it is important in your area for adjacent channel interference , but there is a way (convention?) people divide the spectrum for 20, 40, 80 MHz wide channels.
802.11ac is able to just transmit if the C channel is free, but still ...

5520 Ceee is channel 104-108-112-116 , compare this to . http://bowdennetworks.co.uk/downloads/5 ... -%20v1.pdf

Other thing to consider is disabling (R)STP on the bridge, set to "none", you don't want to have a spanning tree transition or root-bridge election interfere with you transmissions.

I did not experiment with the TDMA period size .... viewtopic.php?t=104271
Can you try without the TCP-syncookies ? ... viewtopic.php?t=8178
 
wingolo
just joined
Topic Author
Posts: 13
Joined: Thu Nov 28, 2013 4:36 pm

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Mon Aug 30, 2021 5:26 pm

I changed TCP-syncookies and TDMA period size just to see, but nothing changed...

In lab we have two SXT G-2HnD r2 so I tried to create a new ptp on 2.4GHz using same parameters, with slightly better performance ~140Mbps with a distance af 7-8m... but considering the max datarate of 300 Mbit/s, seems to be a nice value.

Does anyone have ever used a ptp to transfer files between remote sites or similar?
 
User avatar
bpwl
Forum Guru
Forum Guru
Posts: 2979
Joined: Mon Apr 08, 2019 1:16 am

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Mon Aug 30, 2021 6:25 pm

Ok Syncookies probably not involved as you don't pass the firewall.

So you say 5 -6 MBps, or 48Mbps with 5 GHz nv2 (interface rate 870Mbps), but 200 Mbps with router based Btest.
and 140Mbps with 2.4GHz (protocol ?) (interface rate 300Mbps)

Doesn't feel right. The only remaining way to find out, is like in that other "Slow TCP" discussion: use twice the Packet Sniffer and compare what gets through, what is dropped, what is delayed
viewtopic.php?f=2&t=174113#p875445
 
wingolo
just joined
Topic Author
Posts: 13
Joined: Thu Nov 28, 2013 4:36 pm

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Thu Sep 02, 2021 11:16 am

Doesn't feel right. The only remaining way to find out, is like in that other "Slow TCP" discussion: use twice the Packet Sniffer and compare what gets through, what is dropped, what is delayed
viewtopic.php?f=2&t=174113#p875445
I'm starting to thinking that too, since the wireless connection seems to be perfect looking the numbers.

Need few days more to be able to sniff traffic and see what's going on on tcp connections. Thanks for the link, I'll reply with (hope) more details.
 
User avatar
loloski
Member Candidate
Member Candidate
Posts: 277
Joined: Mon Mar 15, 2021 9:10 pm

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Thu Sep 02, 2021 5:21 pm

hi,

looking on the numbers, i think the problem is elsewhere. On the client PC are you using sata OR ssd? this could be a disk bottleneck issue, since you have already a linux server in-place, can you put an iperf3 server there and on the other end put an iperf client and re-test please post the result here, just my 0.2$
 
wingolo
just joined
Topic Author
Posts: 13
Joined: Thu Nov 28, 2013 4:36 pm

Re: PTP SXTsq-5-ac excelent status but terrible throughput

Tue Sep 07, 2021 5:09 pm

Unfortunatly I haven't jet had the time to dig into tcp sessions with wireshark, but since we need a more reliable solution to move some desks to the warehouse, we decided for a 60GHz solution, by using an nray pair (https://mikrotik.com/product/wireless_wire_nray) and... here the results
test.jpg
I think it's quite amazing! :D
You do not have the required permissions to view the files attached to this post.

Who is online

Users browsing this forum: Amazon [Bot], sybadi and 32 guests