I am using OpenVPN to handle voice traffic over Internet and I want to reduce my tunnel bandwidth usage.I use UDP tun mode and everythings seems to be working fine except huge bandwidth usage which is abnormal I think.
I used tcpdump to check my udp packet sizes through interface tun0 and the resault is all like this:
12:46:35.452412 IP xxx.xx.63.214.29014 > xxx.xx.99.11.24510: UDP, length 36
12:46:35.462336 IP xxx.xx.63.214.29010 > xxx.xx.99.11.24902: UDP, length 32
12:46:35.466547 IP xxx.xx.99.11.24364 > xxx.xx.63.214.29004: UDP, length 32
12:46:35.482370 IP xxx.xx.63.214.29014 > xxx.xx.99.11.24510: UDP, length 36
the I checked the same thing over interface eth0 which is tunneled udp packets including tunneling overhead I think and this is the resault:
12:51:46.302306 IP xxx.xxx.231.162.5002 > xxx.xxx.19.2.32771: UDP, length 101
12:51:46.302337 IP xxx.xxx.19.2.32771 > xxx.xxx.231.162.5002: UDP, length 77
12:51:46.304045 IP xxx.xxx.231.162.5002 > xxx.xxx.19.2.32771: UDP, length 101
12:51:46.311468 IP xxx.xxx.231.162.5002 > xxx.xxx.19.2.32771: UDP, length 101
12:51:46.312140 IP xxx.xxx.19.2.32771 > xxx.xxx.231.162.5002: UDP, length 101
So it seems that there is no MTU related problem because packet sizes are very small and not even anything near to 14xx/1500.
but why my tunneled packet sizes become 3 times larger than original ones?! and how can I reduce the overhead to its least possible to lower my requiered bandwidth usage.I searched your archive and could find nothing.
please help me and tell me what are my detailed udp packets overhead and how can I modify them?
I use TLS handshaking and this is one of my clients config file:
remote xxx.xxx.231.162 5002
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