Packet loss explained

Datadiode hardware setups
Extra: €25 euro functional data-diode demonstrator

In this example we will show how to send one or multiple files trough a data-diode using UDPCAST on Linux. UDPcast is also available for Windows. For more information about UDPcast see http://www.udpcast.linux.lu/

For this example we used 2 proxies with a gigabit data-diode in the middle.
Configure the senders network interface connected to the data-diode to 10.0.0.1, subnet 255.255.255.0 and gateway.
Configure the receivers network interface connected to the data-diode to 10.0.0.2, subnet 255.255.255.0 and gateway.

Create random file of 5Gb

head -c 5120M /dev/urandom > 5gb-testfile.tmp

UDPCAST sends data using UDP and has the possibility to send the data over unidirectional connections like radio. It also adds the possibility to add FEC (Forward Error Correction) and to limit the transfer speed. This makes UDPcast an ideal tool to send data trough a data-diode.

all items between <<variable>> are variables and can be found in the application man pages.

Receiver:

udp-receiver --nosync --interface <<enp0s3>> --file 5gb-testfile.tmp

Sender:

udp-sender --interface <<enp0s8>> --async --fec <<8x8/64>> --max-bitrate <<600Mbps>> --file 5gb-testfile.tmp --broadcast --rexmit-hello-interval 1000 --autostart 3

On both proxies the outcome should be identical:

sha256sum 5gb-testfile.tmp

Sending large and multiple files trough a data-diode / unidirectional network connection using udpcast and tar.

Receiver:

udp-receiver --nosync --interface enp0s3 | tar –x

Sender:

tar -c <</data/>> | udp-sender --interface <<enp0s8>> --async --fec 8x8/64 --max-bitrate <<600Mbps>> --broadcast --autostart 3 --rexmit-hello-interval 1000 --nokbd

For sending data directly to an IP address first we need to add an arp entry at the sender. To simplify this we use a layer 2 broadcast address. Please note that sending data to fast can cause packet loss and netcat will crash.

sudo arp -i <<enp0s8>> -s <<10.0.0.2>> ff:ff:ff:ff:ff:ff

Receiver:

nc -l -u -p 9999 >> /tmp/netcat.log

Sender

tail -F /var/log/syslog | nc -u <<10.0.0.2>> 9999

Receiver:

Open VLC media player and go to

Media-> open network stream -> network url rtp://@:5004

Sender:

First make sure your sender knowns the correct interface to send the data with an ARP inject.

sudo arp -i <<enp0s8>> -s <<10.0.0.2>> ff:ff:ff:ff:ff:ff

Open VLC media player and go to

Media -> stream -> <<choose source: example http://icecast.omroep.nl/radio4-bb-mp3>> -> Stream button-> next -> new destination -> RTP / MPEG transport stream -> add -> address <<10.0.0.2>> base Port 5004 stream name <<OSDD>> -> next -> profile Video - H264 + mp3 (mp4) -> next -> stream

It takes a few seconds to start the video on the receiver because of caching.

For more Dutch sources: https://mediamagazine.nl/live-links-nederland/livestreams-nederland-landelijk/

UDP buffers to 32Mb.

sudo sysctl -w net.core.rmem_max=32777216
sudo sysctl -w net.core.rmem_default=32777216
sudo sysctl -w net.core.wmem_max=32777216 
sudo sysctl -w net.core.wmem_default=32777216

Set MTU on all to the OSDD connected interfaces to jumbo frames. No impact on UDPCAST due to fixed maximum packet size but will be useful for other applications.

ifconfig <<enp0s3>> mtu 9000

https://github.com/azzid/pmddft