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VSAT technology and installation >> iDirect Forum: hubs and terminals >> Very weird problem with iDirect 3000

Message started by alalim00 on Aug 2nd, 2010 at 4:31pm

Title: Very weird problem with iDirect 3000
Post by alalim00 on Aug 2nd, 2010 at 4:31pm
Hello Guys:
I had very strange problem with my iDirect 3000 series satellite router
We use this system to provide us with internet connectivity. before 4 months we decide
to change the location of the dish and the installation goes very well. and I manage to get very good signal
And the modem hook to the network very fast but after about one hour the internet is hangs up and we had to restart the modem again
And every thing works fine but after one hour we had to restart the modem again.
We consult our service provider and they tell us that we had to check the cables and they say every thing looks very fine
I double check the cables 100 times I and re point the dish several time but without any success .finally I come to conclusion that the problem is
The modem it self. So I decide to log to the modem using Isite and see what is going on. I got 12 dB downstream SNR and -17.5 dBm as TX Power which Cleary indicate
There is no problem with the pointing.
Also I take look at the Ethernet statistics (error section)I found something interesting
There no error (value = 0) in the following fields TX frames, TX bytes, heartbeats, late collision, carrier sense errors
But the retry limit exhausted it start from zero but it increase steadily with time until it reach like 23333333 and then the internet hangs and we had to restart the modem again so does any body come across such problem before. And what could be the solution for this

Title: Re: Very weird problem with iDirect 3000
Post by Eric Johnston on Aug 2nd, 2010 at 7:34pm
Examine the ethernet cable.  Are the plastic ridges between the gold contacts undamaged and uncrushed ?  A crushed ridge can overlay the gold and stop the spring wire making contact.

Examine inside the sockets at each end. Are the six spring wires visible or is one stuck down ?

Try a different ethernet cable.

Does that stop the symptom ?

Try a different PC on the end of the ethernet cable ?

If you are using a CISCO router then try replacing it with a PC directly connected.  iSite program works with directly connected PC.

A CISCO router may have facility for 10 Mbit/s 100 Mbit/s, AUTO, half/full duplex etc.  Try different settings.

If you have a passive hub try removing it.

Maybe someone from iDirect can help.  I thought retry limit went up to 16 max ?

Best regards, Eric.

Title: Re: Very weird problem with iDirect 3000
Post by alalim00 on Aug 3rd, 2010 at 8:09am
Dear Eric:
i already try all that but without no success
and i am really frustrated of this situation
you mention that i should contact idirect
so how can i get access to them

Title: Re: Very weird problem with iDirect 3000
Post by dot on Aug 3rd, 2010 at 11:32am
It sounds like you have are running out of TCP sessions on your modem. Each internet connection (browser) uses multiple sessions. You either have too many computers connected behind your modem or you have a virus infection creating all these sessions. You may want to start by disconnecting all but one of the computers and making sure it is virus free. If this works then clean and add one machine at a time.

Title: Re: Very weird problem with iDirect 3000
Post by alalim00 on Aug 4th, 2010 at 2:16pm

i am 100%sure the our network is virus free but i do exactly as Dot say but this not improve the situation.
So i pushed the service provider and they told i had to readjust my polarization becuase they that probably the cause of the problem . so i re adjust the plarization and now the internet become painfully slow below is the Email letter i recieve from the service provider

(it looks like your VSAT is having re-transmission problems.

From the set-up point of view you are right: everything is working properly.

Can you pls. try to adjust a little bit the polarization value on your antenna in order to optimise the Upstream C/N, because at the moment you get
7.02 dB instead of the standard value of 8.5 dB.

This is probably the problem affecting your connection, that every time is re-transmitting bursts to the hub is creating the interruption on the connection.


bear in mind that i adjust the polarization and they say i have 5.6 dB right now which is what do you think

Title: Re: Very weird problem with iDirect 3000
Post by Scout on Aug 4th, 2010 at 2:31pm
there are a couple of issues with the email from the service provider.
1. it sounds like you have adjusted the polarisation and lost performance.....not good, I would work with them and do a full line up one ast time to get it optimum.
2.  they are telling you to adjust your set up as you only had 7 db C/N in the upstream, the system should be adjusting you to the optimum, if the system is not able to they should be telling you exactly what to do to correct it.

Please call them and have them go through a full line up with you, make sure you ask for a fresh compression test, make sure you do a full polarisation test.

The lack of sessions Dot mentioned can be caused by things other than a virus  skype is a notorious session killer if not configured properly on someones system skype will set itself as a supernode killing session counts, but you should work on making sure the alignment is perfect, then you can check other things out.

post again how you get on

Title: Re: Very weird problem with iDirect 3000
Post by Eric Johnston on Aug 4th, 2010 at 4:41pm
Regarding the retry limit.  Does the count increase with nothing connected to the modem ethernet port ?
Record the count. Unplug for 10 minutes, reconnect and record the count ?

Try a PC with Wireshark and see if the increasing count corresponds to the number of packets of a particular type ?  What packet causes the problem.

A full polarisation test involves making the remote site transmit a steady unmodulated CW carrier for several minutes on a carefully selected frequency which won't interfere with other people. The hub measures your transmit cross-pol isolation using a spectrum anlalyser set to a narrow resolution bandwidth (so the C/N is higher than 35 dB). A cross-pol isolation result like 10dB is awful, 15 dB is bad, 20 dB fair, 25 dB acceptable, 30 dB good. If the measurement is poor then you need to make a small change in your polarisation (e.g. 1 deg) while the hub observes the change. It may take them one whole minute to make a measurement, so be patient. If an improvement, continue in the same direction. You need to be on the phone to the hub while making the adjustments. The idea is to get you into the narrow >30 dB deep cross-pol null, which is only a couple of degrees wide.

Getting your cross pol right protects your receive performance from cross pol carriers operating on the other polarisation.  Getting your cross pol right also stops your transmissions causing interference to other people's service. If you have poor cross pol alignment you potentially knock out someone else's transmission every time you send burst. It is in everyone's interest that all sites should be set up accurately.

Note that large polarisation errors (say +/- 10deg) make no significant difference to the reception of your tx signals at the hub, but it causes loss of service to people using the same frequency on the opposite polarisation.  A 45 deg error reduces your signal by 3 dB (and it may still be receivable at the hub), but your signal will completely wipe out the opposite polarisation user who will have C/N=0.

My comment: The Hotbird Tooway system unfortunately uses linear polarisation, which requires careful skilled adjustment at every site. Wildblue, on the other hand, uses circular polarisation, which simply requires that the correct hardware option is used at each site, with no adjustment possible or skill needed.  Wildblue has its polarisation either perfect or is totally non-functional (i.e. the wrong way round polariser hardware assembly).

Compression test:  In normal service the transmit power from a site will be automatically adjusted to try and maintain a stable C/N into the hub. If it is raining at the hub or at the remote the hub will tell the remote to increase its power or chnage its transmit modulation to assure continuing service.  The problem is that the hub does not know what upper limit on the output level from the modem will cause the BUC to saturate, since this depends on the cable type and cable length used at the site and the exact gain of the BUC. During a compression test the hub will progressivly increase the transmit power from the remote modem and observe the output power from the BUC. Once the BUC goes into compression the quality of the signal deteriorates and interference is caused to adjacent return link frequencies. The hub determines the -1dB gain compression point and make sure that the hub never tells the remote modem to try above this level.  Under clear sky operating point should be well below the -1dB gain compression point. This gives a significant (e.g. 6dB) uplink power control margin.  If the margin is negligible the customer is either mispointed or should be using a large dish size. Note that pointing is really important as the transmit beam is much narrower than the receive beam (29/19 GHz).

Best regards, Eric.  

Title: Re: Very weird problem with iDirect 3000
Post by alalim00 on Aug 4th, 2010 at 9:15pm
Thank you Guys for this useful information.
I will try to follow your instructions and let you know the results.
There some points that really caught my eye:
1-Use of Skype it happen that every computer in our network had skype on it and people are using it all the time and scout mention some thing about configure it correctly so do you have more information about that.
2-Regarding the point that Eric made I disconnect the ethernet net port after writing the Retry limit count and connect it back after few minutes I notice there no signifcant change in the retry limit. So I open one web page and noticed that the count increase slightly. But when I start my skype the number retry limit increase drastically.
So is there any comment on that?
Tomorrow I will call the service provider to run a full polarisation test and Compression test.

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