18km link CM9 ws SR5, 40Mbit, but some packet loss.

RouterOS Wireless Networking
1

hi there,

i have a simple problem with a link, such as follows:
link works usually fine, but with some ping timeouts. several packets loss (once per 15-20 minutes and rearly ping loses sequence of several packets) and 1ms at the rest of the time. at hte same time link transfers 4-5Mbps of traffic. both sites does not contain connect/dosconnect messages in the log.

there is a link. 18km, MT boxes both sites. CM9 and SR5, 2.6GHz, 1.20m dishes with 1m low loss cable both sites, 2.9.11(not upgradeble yet). 5GHz-turbo, nstreme enabled. 36Mbits modulation limited. bandwith test shows 40Mbps at TCP, random data=no.

is there a known reason to loss packets.

regards,
C. G.

2

something else on the same/neighboring frequencies?

3

whats noise floor read on both radios?

4

channel is 5210. sr5 @ 5,8GHz is near but i think it’s not a problem.

5

You’re pushing a link 18KM, getting a packet dropped every 15-20 minutes and you think you’ve got a problem? I suspect most WISP’s pray to have as few problems as that. :slight_smile:

You get packet losses even on hardwire, don’t be surprised when an 18KM RF link looses packets also. That’s why TCP had retries. :slight_smile:

6

serious? in most our links there is packet loss approx. equal to 0. and if loosed, there is a single packet, not a sequence of packets.
here i talking about sequences of 5-6 loosed packets.

do you really mean that’s normal?

regards,
C. G.

7

Yes, I’m serious, loosing an occasional packet is normal, these aren’t perfect systems.

8

One packet dropped every 15 minutes is nothing to worry about. Are you using periodic calibration on the radios?

9

you mention 5ghz-turbo and 36 mbit modulation.
what’s your signal strength and signal to noise ratio?
do you run nstreme?

anything between 0% and 0.01% packet loss at 50% bandwidth is normal.
Loss up to 1% is normal when bandwidth usage is at around 90% (all depending on how you configure it of course)
most packetloss is caused by cables but probably not in your situation?

10

@sten: signal is usually -68/70dBm. Nstreme enabled. Export of "/interface wireless " listed bellow:

/ interface wireless
set wlan1 name=“wlan1” mtu=1500 mac-address=00:15:6D:51:02:99 arp=enabled
disable-running-check=no radio-name=“ZZZ-1” mode=station
ssid=“ZZZZZ” area=“” frequency-mode=superchannel country=no_country_set
antenna-gain=0 frequency=5250 band=5ghz-turbo scan-list=default
rate-set=configured
supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps
basic-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps
max-station-count=2007 ack-timeout=dynamic tx-power-mode=default
noise-floor-threshold=default periodic-calibration=default
burst-time=disabled dfs-mode=none antenna-mode=ant-a wds-mode=disabled
wds-default-bridge=none wds-ignore-ssid=no update-stats-interval=disabled
default-authentication=yes default-forwarding=yes default-ap-tx-limit=0
default-client-tx-limit=0 hide-ssid=no security-profile=default
disconnect-timeout=3s on-fail-retry-time=100ms preamble-mode=both
compression=no allow-sharedkey=no comment=“” disabled=no
/ interface wireless nstreme
set wlan1 enable-nstreme=yes enable-polling=yes framer-policy=none
framer-limit=3200
/ interface wireless manual-tx-power-table
set wlan1 manual-tx-powers=1Mbps:17,2Mbps:17,5.5Mbps:17,11Mbps:17,6Mbps:17,9Mbps:
17,12Mbps:17,18Mbps:17,24Mbps:17,36Mbps:17,48Mbps:17,54Mbps:17
/ interface wireless security-profiles



regards,
C. G.

11

That can be improved a little bit. What configuration is used on the ap-bridge side?

Calibration should be enabled, and anything that is dynamic should be made static.

12

what shuld it mean “anything that is dynamic should be made static”?

regards,
C. G.

13

@sten: ap's configuration listed bellow:

==========================
[admin@18999] > /interface wireless
[admin@18999] interface wireless> ex

sep/21/2006 20:03:22 by RouterOS 2.9.11

software id = DUV0-6Y0

/ interface wireless

…
…
set wlan1 name="wlan1" mtu=1500 mac-address=00:0B:6B:33:CB:7A arp=enabled
disable-running-check=no radio-name="000B6B33CB7A" mode=bridge ssid="ZZZZZ"
area="" frequency-mode=manual-txpower country=no_country_set antenna-gain=0
frequency=5290 band=5ghz-turbo scan-list=default rate-set=configured
supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps
supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps basic-rates-b=1Mbps
basic-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps max-station-count=2007
ack-timeout=dynamic tx-power-mode=default noise-floor-threshold=default
periodic-calibration=default burst-time=disabled dfs-mode=none antenna-mode=ant-a
wds-mode=disabled wds-default-bridge=none wds-ignore-ssid=no
update-stats-interval=disabled default-authentication=yes default-forwarding=yes
default-ap-tx-limit=0 default-client-tx-limit=0 hide-ssid=no security-profile=default
disconnect-timeout=3s on-fail-retry-time=100ms preamble-mode=both comment=""
disabled=no

/ interface wireless nstreme
set wlan1 manual-tx-powers=1Mbps:17,2Mbps:17,5.5Mbps:17,11Mbps:17,6Mbps:17,9Mbps:17,12Mbps
:17,18Mbps:17,24Mbps:17,36Mbps:17,48Mbps:17,54Mbps:17
[admin@18999] interface wireless>

kind regards,
C. G.

14

basic-rates a/g should be left to the default of 6Mb/s (unless you are experimenting). Most likely you should set all to default and start over and config only the basics.

15

i cannot set everything to default, because it’s an important router with several interfaces, routing 400 single users and more, eoip and vpn tunnels etc.

now basic rates are set to default.
there no a result, because the problem is sporadic.

regards,
C. G.

16

Then get dedicated machine for the wireless link.
MT is good router
MT is good AP
MT is good CPE
But things get worst, when you use it for everything !

?
/system resources print
?
/system resources irq print

17

[admin@1899999] > /system resource pr
uptime: 2d4h59m16s
free-memory: 213712kB
total-memory: 256728kB
cpu: "Intel(R)"
cpu-frequency: 2663MHz
cpu-load: 20
free-hdd-space: 86308kB
total-hdd-space: 121215kB
write-sect-since-reboot: 1240
write-sect-total: 120664
[admin@1899999] > /system resource pci pr

DEVICE VENDOR NAME IRQ

0 02:01.0 Atheros Communications, Inc. AR5212 802.11abg NIC (rev: 1) 11
1 02:02.0 Atheros Communications, Inc. AR5212 802.11abg NIC (rev: 1) 11
2 02:03.0 Atheros Communications, Inc. AR5212 802.11abg NIC (rev: 1) 5
3 02:00.0 Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev: 16) 5
4 02:05.0 Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev: 16) 11
5 01:00.0 nVidia Corporation NV18 [GeForce4 MX 440 AGP 8x] ... 10
6 00:1f.5 Intel Corporation 82801EB/ER (ICH5/ICH5R) AC'97 ... 5
7 00:1f.3 Intel Corporation 82801EB/ER (ICH5/ICH5R) SMBus ... 5
8 00:1f.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Co... 0
9 00:1f.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC In... 0
10 00:1e.0 Intel Corporation 82801 PCI Bridge (rev: 194) 0
11 00:1d.7 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 E... 11
12 00:1d.3 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UH... 10
13 00:1d.2 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UH... 5
14 00:1d.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UH... 3
15 00:1d.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UH... 10
16 00:01.0 Intel Corporation 82865G/PE/P PCI to AGP Control... 0
17 00:00.0 Intel Corporation 82865G/PE/P DRAM Controller/Ho... 0
[admin@1899999] > /system resource irq pr
IRQ OWNER
1 keyboard
2 APIC
3 [usb-uhci]
5 [a5212_pci]
5 [usb-uhci]
5 ether2
8 [rtc]
10 [usb-uhci]
10 [usb-uhci]
11 [a5212_pci]
11 [a5212_pci]
11 ether1
14 IDE 1


regards,
C. G.

18

Could this be a IRQ sharing problem?

Ekkehard

19

i don’t know is that a problem, usually cards works or not.
suddestions?

regards,
C. G.

20

Try this
Check in routeros Manual and change the ACK timeout to a static setting.
There is a lookup table.