Smartlink - Waterfall and Spectrum do not display from specific geographic location.

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  • Updated 2 years ago
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Have started a new post with the correct title.

I have a problem when trying to use smartlink from Gibraltar to the UK the waterfall and spectrum do not display.

Have done some further testing and the connection is fine when I use within the UK 3/4G and Wi-Fi/Ethernet on WAN. So getting out through router fine.

However trying to setup in Gibraltar with my son and the non display of waterfall and spectrum persists. The audio appears OK

Following tests have been completed and all showed the same problem.

1 - Tested two separate high speed fibre lines (and routers) into his house in Gib

2 - Two separate PC's (Desktop and MacBook running Win10). The desktop we had used before running SSDR via a VPN.

3 - 4G connection into Gib and across into Spain

4 - On his works network with laptop and works PC (extremely high download speed and behind no filters)


These tests smartlink worked OK.

5 - Tested the laptop from Croatia on Hotel Wifi and it was OK

6 - He did a VPN from Gibraltar home to DigitalOcean in London and smartlink worked ok. (but too slow for practical use)

It appears that this is something that affects the Gibraltar / Local Spanish area.

Anybody else had a similar experience.

Shall I raise a help ticket?

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Andy M5ZAP

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Posted 2 years ago

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Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

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Official Response

The Internet provider on the client end of the connection is blocking fragmented UDP packets which are dropping display data that is contained in the VITA-49 connection (stream) between the radio and the client.
The VITA-49 data sent for display data is greater than the 1500 byte payload of an Ethernet packet so the TCP/IP stack on the radio is fragmenting the data and the TCP/IP stack on the client is reassembling it.  This is a standard and customary way of handling large data streams over a packet network and a native feature in all TCP/IP protocol stacks.  

The problem is not with the radio, the radio end of the Internet connection, but with the router/firewall on the client end of the connection not allowing fragmented packets to pass. 

Not all Internet providers (ISPs and businesses providing WiFi) allow fragmented packets to pass. I suspect the reason they are blocking fragmented packets is due to the fear of an old type of DoS attack vector (Teardrop) or to prevent certain types of media streaming that utilize data quanta larger than the 1500 byte payload of a standard Ethernet Type II frame. 

You can raise a ticket with the Internet provider that is blocking the data from the radio reaching the client, but FlexRadio can not assist with this type of issue as the radio and SmartLink client are working correctly when the Internet connection is not blocking essential data.