ATT Hot Spot and SmartLink Not Exchanging all Necessary Information

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  • Updated 2 years ago
A hotspot is created on my phone with ATT as carrier; actually my carrier is Consumer Cellular using ATT. SmartLink on my MS Surface 3 Pro running Windows 10 connects through that hotspot to my Flex 6700 and brings up a screen with receiver slices. I can tune the slices. I can add bands. I can operate the ATU, and it reports success. In sum things seem to operate normally except there are no signals shown in the pan view; the usual receiver slices look normal and respond to mouse clicks in their windows and move up and down the band normally. And there is no audio coming through the computer speaker with the remote button activated. When that button is turned off audio comes through the external speakers attached to my Flex 6700 and confirm that tuning the slice receivers really does work. When I click Tune no signal is shown in the RF bar meter even with tune power increased. When I try to transmit using the MOX button I hear a relay click in the 6700 and the Level meter responds to my voice, but the RF meter show no signal. When I go to CW and send there's a good sidetone but a buzz also tracks the keying. Again there is no indication on the RF meter. Using WiFi at several locations around Austin I've had great success with everything operating as if I were in my shack connected by Ethernet cable. The network status reported by Flex on my tablet shows: Latency 138 to 1242; Remote Rx Rate 0; Remote Tx Rate 0; Dropped 0 out of 0. My hypothesis is ATT (or my phone, Huawei Ascend Mate 2) is not conveying one or more ports needed by SmartLink. The buzz may be another story or an additional result of some problem in the communication. Ideas? Suggestions? Additional tests? Thanks. --Jim, W5HFS
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Jim Bryce W5HFS

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  • Perplexed

Posted 2 years ago

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David Livingston

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My Verizon Hop Spot work flawlessly... I was shocked...
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NX6D Dave

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My guess would be that the cell service hotspot is blocking UDP packets, but allowing the TCP data to flow.
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Dan -- KC4GO

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AT&T work with all four slices/waterfalls here with no problem. 
Central Florida.  Get's a bit jerky, but works OK. Normally only use 2 or 1 Slice/Waterfall. 
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Bob - W7KWS -

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I've found that the AT&T MVNOs (Mobile Virtual Network Operator) that I've used, Straight Talk & Cricket Wireless, run my data through their own servers before it gets to the Internet. They probably do this to slow & measure the data but the longer path also increases ping times. It's also possible that they block certain data types or ports such as UDP or others in their effort to meet whatever economic criteria they have for providing cheap service.

I've gone directly with AT&T Prepaid for these reasons. 6-GB with teathering Hotspot and no contract is now down to $40/month plus tax. Ping times are often as low as 40 mSec. Speeds range all over the map but are almost always above 1Mb/Sec.

I use a ZTE Axon 7 which includes bands 2,4,17,29 & 30 among others. AT&T uses all these bands to accommodate ever increasing LTE traffic and their geographic licensing status. Using phones and/or MVNO services that don't support all of these bands may preclude services in some areas.

I actually got a band 30 cell site the other day in Bainbridge Island, WA. It tested at 60 Mb/Sec download.

Look at gsmarena.com for phone specs & get a factory unlocked phone that can do it all well for best performance. Some good ones with Snapdragon 820 processors are available for under $400 on Amazon Prime. Look for "like new" customer returns at Amazon Warehouse. Be sure it's "Prime" so you have easy, 30-day return if it isn't "like new".
(Edited)
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NX6D Dave

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I would imagine that AT&T requires MVNOs to provide a lesser quality of service.  I also use Consumer Cellular, which is OK for my needs, but not terrific (are any of them that good?).

As an example, CC didn't offer any service outside of the US until just recently.  I was just about to change carriers when I found that CC does offer this service now.

Thanks for all of the tips!
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Bob - W7KWS -

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Dave,

The AT&T Prepaid plan I mentioned includes roaming in Mexico & Canada, although I'm not familier with the extent of the coverage.
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Jim Bryce W5HFS

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Everyone, 

Thanks very much for all the suggestions. I'll ask CC about this, but I doubt they will provide a clear answer. It looks like I'll need to change carriers, probably to AT&T or Verizon, both facilities based. Bob's details and pricing and pricing information are quite helpful and confirm what I think has been going on. Stay tuned.

-Jim
W5HFS
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Jim Bryce W5HFS

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NX6C Dave suggests the problem may be CC does not allow UDP packets. Can anyone advise me what protocols are required to carry SmartLink, and what appears to be failing based on my description in my original post. I need this information to speak with CC. 
(Edited)
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Tim - W4TME, Customer Experience Manager

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If an Internet provider blocked UDP, the Internet would break.  I suspect that the issue is related to the provider / router not allowing fragmented packets to pass and this is eliminating the display data.  BTW, fragmented packets are normal in a packet based network (Ethernet) since not all data fits conveniently into 1500 byte chunks.

I suspect this is a setting they have set due to the fear of a very old type of DoS attack vector (Teardrop).
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Jim Bryce W5HFS

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Thanks Tim. That's interesting because some are reporting here that SmartLink is working through their cellular services. It will be interesting to find out what's happening here. I gather the DoS attack vector problem has been solved by other means that some cellular carriers are using and thereby allowing fragmented packets. Stay tuned. I'll let everyone know what I find out. I suspect I'll not be the only one to run into this problem.
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Tim - W4TME, Customer Experience Manager

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In a previous life, I used to consult for a telecom SS7 services vendor.  I have been to a lot of telcos, both domestic and international and I can tell you that there isn't a lot of consistency in services configuration from one location/region to another.

The fragmented packet type attacks have a specific attack signature and more modern stateful firewalls that employ ID/IP (intrusion detection/ intrusion prevention) systems can identify this and block it from the source IP (stream) rather than dropping frames with the fragment flag set.  More rudimentary protection measures block all fragmented packets, which is not ideal, since you end up throwing out the baby with the bath water, as they say.
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Eric - KE5DTO, Official Rep

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Jim,

To test the fragmented packet theory, you can shrink down the display width to the minimum which will use smaller display packets (and thus not fragment).  If this works, it confirms that fragmented packets are not making it across the link.
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Andy M5ZAP

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The sending of fragmented packets is creating a lot of problems. The only solution from Gibraltar was to setup a VPN. Would it not be a good idea to have smartlink encapsulate the packets to alleviate the problem
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Phil - WG5D

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I have tried to remote to my radio from a variety of networks, some work fine and some don't. I have a Verizon cell phone what has data tethering and I have yet to be able to get that to work at all despite SmartLink seeing the radio and giving me a green light. I think that in this case that Verizon is dropping the packets as I never see the traffic hit the public interface on my firewall. 
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Bob - W7KWS -

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I wish that I knew enough about these various networks and what they will pass and what they won't pass.  We need much more input on these things from those that really know the details. 

What I can state is that I've tried both AT&T and Verizon directly and used many of their MVNOs over the years.  This has been done with Remote Desktop, SIP VOIP audio and RemoteRig up until know.  I'm just getting going with SmartLink. 

With every one of these cellular companies, my Remote Desktop SIP and RemoteRig packets have gone through to and from my cell phone or a tethered computer, be it Windows or Android.  Sorry, I have no experience with Apple..

What this brings to my mind is the character of the SmartLink Packets.  Mine are getting through just fine but it's clear that others are having difficulty.

Attached is a picture of my Maestro in the RV.  It is connected to a 6300 at my house via an AT&T Post-Paid Hotspot.  Hopefully Post-Paid directly with AT&T has the fewest restrictions, if any, and the minimum latency.

Again, I wish I knew more about these networks, why Microsoft Remote Desktop, SIP and RemoteRig always work but but others are having difficulty with SmartLink .

Best regards!

(Edited)
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Jim Bryce W5HFS

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LOSING GROUND?  Recently I've tried connecting through the same phone and service. Whereas in the past I'd get a complete screen but it lacked signals now I cannot even get that far. I click on the Smart SDR v2.1.33 icon and receive the expected return:



Then I click on Connect or Low BW Connect and receive:



This is happening both on the phone hotspot and at public WiFi locations that previously worked. I guess the changes in Flex releases made since my original post have caused this result. In the past I could get into the screen, but couldn't do anything. I tried the suggestion of reducing the screen size to the minimum possible, but I'm still receiving the same unable to connect response. Ideas please. Thanks.