[ale] VPN Protocol Question

[Pat Regan]

Michael B. Trausch wrote:
> While I hadn't really thought of that, I was thinking of something
> more-or-less easily doable with user-level privileges that is
> reasonably portable.  Configuring PPP is pretty easy, and usually (at
> least, if memory serves) you can create PPP links as a normal user for
> dialup, so doing the same over something like SSH would (again, if
> memory serves) work in a similar fashion.  The only difference is that
> you're using PPP over a terminal running over the Internet instead of
> over a modem.

PPP is very useful if you don't have the means to use anything else.  I
imagine not having admin rights but being a member of the correct group
to allow you to run the copy of pppd that is already installed setuid.

Unfortunately, pppd isn't as likely to be installed on a server as it
used to be (at least on Debian and Ubuntu).  :)

> That said, wouldn't PPP over an error-correcting modem suffer similar
> problems?

In theory, maybe.  In practice, probably never.  The modem immediately
corrects errors right after they are detected.  TCP does its
retransmissions for dropped packets after a delay.

The ssh TCP connection and the TCP stream running over PPP will both be
likely to have attempt retransmission at the same time.

Pat

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