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montare
02-05-2008, 10:21 PM
We're getting a lot of dropped packets (particular inbound) during calls. I have tried a number of things to no avail. I am wondering if reducing the MTU size in the internet connection wizard from 1500 down to something lower like 800 could possibly help?

AramK
02-06-2008, 01:11 AM
Probably reducing the MTU size of Quadro will not solve your problem. First, you need to understand why the packets are getting lost. You can use network analizer or sniffer programms like Ethereal, to make some captures in your network in order to find at what point you are losing the packets.
Another assumption is your network bandwidth. The default (max) values of Quadro's WAN Upstream/Downstream are 10000/10000 kbit/s. If this does not match with your real bandwidth, then configure the actual values from Internet Configuration Wizard.

montare
02-06-2008, 06:23 PM
Another assumption is your network bandwidth. The default (max) values of Quadro's WAN Upstream/Downstream are 10000/10000 kbit/s. If this does not match with your real bandwidth, then configure the actual values from Internet Configuration Wizard.

Yeah I had these at 10000 down, 1000 up. When I actually tested my line speed my downloads were around 4500 down and 720 up. So I adjusted these to 4000 down and 700 up in the quadro and call quality appears to have improved (touch wood).

Am I correct in understanding that by having these values too high, the QoS in the router would not have been limiting bandwidth to other non-voice data, thus when calls were in progress they would have been competing for bandwidth?

Also, are these max values enforced by the router? Ie. If my download speeds went up to say 10Mbps (due to some change at the ISP) and my Max download is set to 4Mbps in the Quadro2x, will the Quadro still allow a download (data file or something) to proceed at faster than 4Mbps, or will it be limited?

AramK
02-07-2008, 02:50 AM
Yeah I had these at 10000 down, 1000 up. When I actually tested my line speed my downloads were around 4500 down and 720 up. So I adjusted these to 4000 down and 700 up in the quadro and call quality appears to have improved (touch wood).

That's good :) So defining the limits solved your problem.


Am I correct in understanding that by having these values too high, the QoS in the router would not have been limiting bandwidth to other non-voice data, thus when calls were in progress they would have been competing for bandwidth?

Correct.


Also, are these max values enforced by the router? Ie. If my download speeds went up to say 10Mbps (due to some change at the ISP) and my Max download is set to 4Mbps in the Quadro2x, will the Quadro still allow a download (data file or something) to proceed at faster than 4Mbps, or will it be limited?

Quadro upstream/downsrteam capabilities will be limited by the values configured in Internet Config Wizard, regardless of your router's bandwidth.

montare
03-31-2008, 08:25 AM
I don't seem to get much packet loss anymore, but I now often seem to have calls with poor quality and the Quadro stats are showing high levels of jitter.

I thought maybe reducing the MTU would help resolve this (or at least I figured it is worth a try), so I've reduced it to 536 for the time being.

The interesting thing here is that after reducing the MTU I ran a ping -f -l 1024 sip.epygi.com and got successful replies. Since I had reduced the MTU to 536 I would have expected these ping requests to fail since I had passed the -f (set don't fragment flag in packet) and -l (set packet size to 1024) arguments.

This tends to suggest to me that the MTU setting in the internet config wizard isn't being effected. I have tried rebooting the device and this has made no difference.

Any thoughts?

Regards,
Michael.

AramK
04-01-2008, 12:54 AM
Quadro does modify the MTU setting when you change it from internet config wizard. That is tested in our lab and there is no any problem with it. No reboot is needed to apply that changes. I assume you've ran a ping from the PC located in Quadro LAN side. Your assumption is quite correct, that the "ping -f -l 1024 sip.epygi.com" must fail and it does fails here in our lab. Find below the ping from my PC that is placed in the Quadro LAN with MTU size 536.

C:\>ping -f -l 1024 sip.epygi.com

Pinging sip.epygi.com [74.54.85.200] with 1024 bytes of data:

Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.

Ping statistics for 74.54.85.200:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

C:\>ping -f -l 500 sip.epygi.com

Pinging sip.epygi.com [74.54.85.200] with 500 bytes of data:

Reply from 74.54.85.200: bytes=500 time=743ms TTL=42
Reply from 74.54.85.200: bytes=500 time=743ms TTL=42
Reply from 74.54.85.200: bytes=500 time=745ms TTL=42
Reply from 74.54.85.200: bytes=500 time=744ms TTL=42

Ping statistics for 74.54.85.200:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 743ms, Maximum = 745ms, Average = 743ms

C:\>

I would suggest again to check your network to understand the reason of poor quality.

montare
04-01-2008, 05:08 AM
I've confirmed that I have the MTU set to 536 in the Quadro and I can still ping out from a LAN side PC using the previously stated command.

I'm using the Quadro in PPPoE mode so I'm wondering if this is having some impact on that setting? I've read in some situations overriding the MTU doesn't always stick when using PPPoE (not a Quadro, but other devices in PPPoE mode). Is it possible that the ADSL modem is ignoring the MTU setting?

I'm going to try disabling PPPoE and just using the modem as a router through to the Quadro and see what impact this has.

AramK
04-01-2008, 06:54 AM
No, PPPoE mode on Quadro cannot be a reason for not applying MTU setting.