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[Openvpn-users] dynamic header compression vs. lzo?

  • Subject: [Openvpn-users] dynamic header compression vs. lzo?
  • From: Dag Bakke <dag@xxxxxxxxx>
  • Date: Wed, 30 May 2007 23:05:25 +0200


I am currently reading some Cisco material on QoS and started to
think/wonder about how OpenVPN handles compression. Googling for
'openvpn "header compression"' didn't offer any obvious hits.

If I recall correctly, OpenVPN may employ LZO-compression in a dynamic
fashion, using lzo when it gains the tunnel throughput.
Cisco also does payload compression.

Cisco can also do header compression. The header compression algorithm
rips out interpacket redundant data and replaces it with a 'session
index'. (Hash of IPs/portnumbers/whatever) So instead of the original
headers, the packet is sent with a session index and whatever
non-constant data there was in the original headers.

This way, a 40 byte IP/UDP/RTP header can be reduced to 2 or 4 bytes.
(Without/with checksum)

Is anything like this implemented in OpenVPN? If not, would the effort
be worth it?

I wouldn't expect lzo to be able to utilize interpacket redundancy.
Unless openvpn wraps multiple packets into one?

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