OpenVPN TCP vs UDP

[Derek Atkins]

"Thomas Charron" <twaffle at gmail.com> writes:

>  But from a practical standpoint, it only *really* makes a difference
> when you have massive packet loss on a link.  This is why most people
> who DO use it don't see the huge deal, because the majority of the
> time, packet loss isn't a problem.

Well, if by "massive" you mean "5%", then sure.  Packet loss as little
as 5% can set off the cascading TCP congestion control problem.
Granted, it's not as bad as it COULD be -- the network just stops
working completely when you get up to 20% loss.

>  There is, however, also the issue of TCP connections requiring more
> overhead to provide a connection then UDP.  On the other hand, passing
> TCP connections thru a NAT is much easier then getting inbound UDP
> packets to get thru.

All depends on your NAT gateway.  There are ways to make it work.
Most NAT gateways work just fine with bi-directional UDP protocols.
You just need to make sure you have NAT keepalives in order to keep
the mappings open.  It's really not much of a problem if you plan for
it, and the added value of running this technology over UDP vastly
outweighs the issues you can get running it over TCP.

Just my $0.02, but it was a very hard-earned $0.02!  ;)

> -- Thomas

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
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