Re: [lwip-users] elegant way to detect network connection

[Noam Weissman]

Hi Sergio,

Thanks for the reply. Let me explain it better.

HDBaseT is a protocol developed by Valens LTD. This protocol is used mainly for 
extenders. There is 
an RX chip and a TX chip. The protocol is transferring video, audio, USB, 
RS232, IR and ETH over CAT5/6 cables !. 

As HDMI or other video connections are limited in cable length. If you go above 
5-10m cables are very
expensive and without active cables you have a problem getting longer cables. 
HDBT is designed for 100M :-)

Anyway, HDBT devices use a regular CAT5/6 ETH cable to transfer all the above 
with one cable and with minimum 
loos in video quality.

What is my problem?. I am working on systems that have one or more HDBT TX or 
RX. An average system
has an embedded ETH switch that has one or more outputs that are connected to 
an HDBT chip (local). 

This chip is transferring the ETH data to the remote chip over CAT5 cable.

There is indication for HDBT link (between HDBT TX <> RX) but there is no 
indication on remote side ETH link.

The local system with the embedded ETH switch has an internal micro that runs 
HTTP server etc... Normally
the device will be connected to the network. That means that the system itself 
has an ETH connector connected
to the network and on the other end (internal) it is connected to one of the 
embedded ETH switch ports. The 
micro has access to this port and to the local ETH switch.
 
Our client is asking that if we connect the remote ETH side (over HDBT) to a 
router or network to be able
get a dynamic address and operate the same as if we connected the local ETH 
system port to the network.

Without some indication if there is an ETH link on remote side I cannot do 
that. 

What we did in one system is that we added code to the micro on the remote HDBT 
end to detect ETH link.
ETH link status was sent as a command over the serial connection that the HDBT 
transfers as well. 

I am wondering if there is an elegant way of doing it without sending an 
explicit status to the local system 
>From the remote side.

I hope now it is clear :-)

BR,
Noam.


-----Original Message-----
From: lwip-users [mailto:address@hidden On Behalf Of Sergio R. Caprile
Sent: Wednesday, November 09, 2016 4:32 PM
To: address@hidden
Subject: Re: [lwip-users] elegant way to detect network connection

Hi Noam,
I was about to say you could sniff how windows 7+ does it; but I don't think 
they would do it in an elegant, not even standard, way... ;^)

I don't know if I get the whole picture, but I bet your problem is an 
"application ping". Do you actually need to know link is present or another 
device like yours or server or @ access or ?

Yes, ICMP Echo Requests might be discarded by the router, I think it is a bad 
idea on an internal network, but some admins think otherwise.
That is why I suggest "application ping", as long as your devices can see each 
other, you know you have a link. It is usually done on a separate UDP port, but 
some guys like to dedicate in-band commands to that purpose, like a keep-alive 
message. What I suggest is sort of a discovery protocol on UDP broadcasts, or a 
directed app ping if you know your neighbors addresses.

Toying with your DHCP server every half a second might pester some net admins 
and get you enemies for free... I wouldn't go that way, I think your 
application's problems have to be solved by your application. Just my 2 cents.

Regards!

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