[Cerowrt-devel] VPN technology in a bufferbloated universe is doomed

david at lang.hm david at lang.hm
Tue Dec 6 14:29:51 EST 2011

On Tue, 6 Dec 2011, Dave Taht wrote:

> Last puppy to shoot today...
> I have adaquately proven to myself at least, that VPN technologies in
> a bufferbloated universe, are doomed.
> VPN streams over UDP cannot compete with GSO and TSO offloads without
> some form of fair queuing and AQM that works.
> Encapsulating TCP over TCP merely compounds the problem.
> I wouldn't mind writing a paper demonstrating this fully, but in the
> meantime I feel that pursuing vpn technologies as part of cerowrt is a
> waste of time.

I saw papers documenting this over a decade ago. they ween't academic 
papers, they were writups from VPN/tunneling tools explaining why 
tunneling across SSH wasn't a good idea. I am amazed at how many people 
find this a new idea, it needs a lot more publicity.

> Additionally, no matter how hard people try, things like ipsec have
> mysterious failure modes, and the additional protocols are frequently
> blocked by institutions and end user devices.
> Things like openvpn tend to work better than ipsec, but as I note
> above, fail to compete effectively.
> We have helped find and fix multiple problems in encapsulation over
> the past year, but until we achieve our primary goals as an
> organization - fixing bufferbloat - I strongly feel
> that vpns are a doomed technology.

I think this falls into the same category as IPv6.

Don't concentrate on this right now. Leave it as a supoorted function in 
Cerowrt, because people trying to use these devices may want to use it, 
but you can't solve the problems here, so don't try (at least until you 
have the basics working)

David Lang

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