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What is happening with 3G?
Frogis's profile

Tutor

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3 Messages

Wednesday, May 14th, 2014 5:06 AM

HELP - 3G light is flashing, microcell was previously working fine

Hello,

 

   I figured it was worth posting here so I have yet to have success with anything else. 

 

Background

 

I live in an area almost exactly inbetween three AT&T cell phone towers, so subsequently my phone is constantly switching singnals from one tower to the other giving me very inconsistent service.  After diagnosing the problem with AT&T about six months ago they sent me a micro cell free of charge, and it worked absolutely fantastic until....

 

The Problem

 

About a week ago my microcell's 3g light started flashing, this had happened once or twice before so I performed a simple reset but it did not fix the problem like before.

 

  •   I tried resetting my modem, router, and microcell
  •   hard resetting my microcell for 30 seconds
  •   de-activing and re-activating my microcell twice
  •   checking my power cord to make sure it was the right voltage
  •   getting a replacement microcell sent to my house
  •   setting up my microcell in the alternate arrangement (modem-->microcell-->router)
  •   updating the firmware on my router

and none of these fixed the problems.

 

My current internet is about 30mbps DL and 10mbps upload so that isn't the problem

The ports on my router are all opened, and nothing has changed to effect that

 

After going extensively through the forums I am kind of at a loss of what to try next.  Any suggestions from people on the forums?

 

I am currently located in the East Bay of California (Alameda, CA)

 

Thanks very much.

 

-Frogis

 

 

Tutor

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11 Messages

9 years ago

I was able to do the de/ re-activation twice with no positive results. I will be contacting Cox and bumping the Mb up to 5 to see if that makes a difference.

 

Will post my finding once I do but that will be a day or two since I have to work.

 

Thanks for the help.

ACE - Expert

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24.2K Messages

9 years ago

Let us know what happens.

Professor

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2.2K Messages

9 years ago

Perhaps you've tried this but I can't see in your posts that you have.  Ethernet your Mcell directly to your modem and see if you can connect.

Mentor

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53 Messages

9 years ago

Look, for whatever it's worth, since you changed modems, etc,  I had a similar problem when changing DSL speeds, new modem, an "advanced" router from Netgear, etc.  I was running the DSL modem in bridge mode, and letting the Netgear router do everything (but the DSL modulation obviously).

 

Everything worked, except for the microcell.  Had the darn 3g blinking light.  Tried 10s of configurations, ideas from otto and avedis53, etc, couldn't get it to go.

 

You know what fixed it:  contrary to popular belief that the Microcell must run at 1492 MTU, reducing my router's MTU from 1492 to 1480.  And I discovered this by accident.  Yes, the specs outline 1492, however, a slightly lower MTU will not cause packets to fragment, whereas increasing does.  The performance impact is negligible and really unnoticeable at these speeds.  So I could only conclude that somewhere in the chain of equipment plus the ISP packets sized based on an MTU of 1492 were getting split up.  And that's a no no for the microcell.

(If you search for my post  partymonkey, you'll see the test I did to determine the max non-fragmentation MTU)

 

Bingo.   Now, your problem may be entirely different, but if all else fails its worth checking this little thing out.

 

Cheers.

Tutor

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11 Messages

9 years ago

Ran the VOIP check in the referenced site and got 5.45 Mb down and 1.1Mb up. I increased the bandwidth today and rebooted the Microcell with the same results.

When the VOIP test was running it showed

SIP blocked

RTP the same

T.38 the same

 

Consistency of Service was 68% which is considered OK

Unable to measure jitter or packet loss or MOS score.

 

Looked around the Belkin to see if I could see something blocked noted nothing that seemed to indicate that. I will go direct to the modem and connect to see the results but expect the same. Wondering if the modem is blocking?

 

Partymonkey thanks for the suggestion too...

Mentor

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51 Messages

9 years ago

The standard port used for SIP is 5060 UDP (some SIP provider's use others, just above and below this, but 5060 UDP is common) RIP is audio channel for VOIP portion of a VOIP phone normal area as I understand is around 7000 to 7300 UDP, but this can vary greatly depending on VOIP provider.

Not sure if this would really affect the Mcell as none of AT&T literature or information I've come across on Net indicates any port higher than 4500 UDP being used.....but maybe your provider has blocked SIP to "prevent unauthorized VOIP phones" on their network and they went wild with the UDP blocking and got into the 4500 range...............Run Gibson Research port scan, it would tell you if your blocked at either your ISP provider back towards you or your router end, it WON'T be able to scan back the other way. Not sure why partymonkey's fix worked, normal MTU is 1492....but glad it did. Wouldn't hurt to try it, if it doesn't help just set it back to 1492 and punt.

 

The reason, as I understand it, that fragmented packets is a problem is the possible addition  (4 to 24 bytes is sometimes added to packet header's for various things, such as VLAN ID's, thus creating "Jumbo packets") of bytes to a packet. The Mcell is apparently Unable to reassemble these type packets and most (not all, but most) routers will just totally drop a packet if it is received fragmented, making no effort to reassemble it...

The T.38 is a particular VOIP protocol I believe..............one of many that I understand VOIP provider's use. This too is not mentioned anywhere in reference to the Mcell that I have ever come across.......Avedis53 is the guru on things VOIP, maybe he can throw more light on this subject.

 .

Now one thing I HAVE come across is that many people have various types of Problems with certain Belkin Router's, but as yours worked previously it doesn't APPEAR that it is problem.........................................unless your ISP or AT&T has changed something in their systems that might be incompatible with your model Belkin....a model number and some Googling might turn up something.

 

For those that have found Workarounds, it seems that the workaround fixes follow little set patterns and are hit and miss.

 

Your bandwidth is now quite decent....to the house... and will help in that area of troubleshooting (you've eliminated ONE area possible issue's), but not sure you will get the full advantage of it unless you are running a Gigabit system (ie a Gigabit modem and/or router)......Watching my WAN port in my Router System system logs I am averaging (with Roku streaming video and 2-3 add'l devices active) that I average 2.5 - 3 gigabit of average traffic, with occasional peaks to almost 6 gigabits.

 

But hooking the Mcell directly to you internet line before the Router would probably eliminate this issue.............unless.....it is possible that your older modem is only 10-100 mb (Avedis53 mentioned your modem is an older model....).......possibly your ISP upped their system trunks speeds/line amplifier's (and maybe some packet characteristic's, and your older modem and/or your Router is now "dropping packets" , as it may be unable to handle the added speeds/packets properly.........now. That's definitely a question for your ISP...........have they upgraded OR changed their distribution trunks equipment recently?

 

I'd hang with your new higher speeds awhile.......at least until you can definitely pin down the issue.....maybe you can talk your ISP into Loaning you a newer modem to try for a few days......Being as old as it is you MAY be sniffing the right tree...it's a logical move.

Professor

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2.2K Messages

9 years ago

@partymonkey - Having to lower your MTU setting in order to make your Mcell work properly is typically an indication of the presence of communication errors.  Perhaps the initial handshake to the Mcell from the AT&T servers on port 443 wasn't able to communicate properly at the recommended MTU setting of 1492 since that communication is occurring on a TCP port that requires packets to be retransmitted if they are not received in the proper order. 

 

If the retransmission rate is high enough due to issues with the quality of your internet connection, it could cause a communication error in the Mcell and the connection is not made to the servers.  The rest of the ports communicate using the UDP protocol which is more of a "fire and forget" method.  If the packets don't arrive or arrive out of order on a UDP port, no retransmission is requested.  If the packet loss/corruption is great enough, then the Mcell won't connect either. 

 

Changing your MTU setting from 1492 to 1480 isn't much of a change and I would agree that the data transfer rate wouldn't be appreciably affected.  If that worked for you then that is great.

 

@fun2drive - Based on my understanding of the Motorola SB5101U, that modem is not capable of blocking ports.  It's basically a dumb modem, therefore I don't think your modem is the problem.  I think your next step is to take the Belkin N600NB out of your LAN and try temporarily connecting the Mcell directly to your modem as previously suggested.  This should help narrow down where the problem may be.           

Tutor

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11 Messages

9 years ago

Direct connection to the modem didn't work at all. I will be investigating if something is blocking some of these ports but Cox states they don't block those ports but lower numbered ports in the hundreds to protect from getting attacks.

 

I have not run the GRC.com software but will be looking into that when I have time...

Thanks to all that are trying to help me out here.

ACE - Expert

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24.2K Messages

9 years ago

When you connected the MicroCell via the alternate connection (MicroCell -> modem, single ethernet cable, no switches) what did the light pattern look like on the MicroCell? If the power, ethernet, and GPS lights were solid green and only the 3G light was blinking, I'd try a hard reset and see if that works.

Tutor

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11 Messages

9 years ago

I unplugged the Microcell last night and plugged it in tonight and it is working. I have no idea why but it is working fine. I also have Magicjack and did some port forwarding for it 5060 and 5070 to improve what quality there is.

Wish I could tell you why it is working now but I can't but it is reaching the AT&T servers fine now. Tomorrow who knows. The Microcell was connected before I did the port forwarding by the way.

 

Fingers crossed...

 

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