Subject: Re: Euro File Transfer Protocol
To: None <,>
From: Wolfgang Solfrank <>
List: tech-net
Date: 05/08/2000 19:47:41

> What they do looks (from a first glance) very much like how our in-kernel
> ppp interfaces and pppd work. The protocol seems to use X25 over an ISDN
> B channel (caveat: most time X25 is mentioned in ISDN context it's the slow
> variant over the D channel) and some command/login sequences outside of
> that (or a special virtual connection, not sure yet).
> The Linux guys do the X25 in kernel, just like our ppp interface attach to a
> tty device and pass IP up in kernel. *BUT* in this case there is nothing to
> pass up in kernel. There are no network packets coming out of the X25, but
> real "user data". They seem to create one socket per virtual circuit
> and then use that directly in userland.
> I agree that this is convenient to program from the userland point of view,
> but I'm not sure the X25 stuff needs to be inside the kernel. A userland
> implementation would not suffer any performance penalty, IMHO.
> I'm realy unfamiliar with our kernel networking internals outside of IPv4
> (I've only read [and understood] the Stevens "The Implementation" book), so
> maybe we already have stuff there that would allow to do something similar.
> If so, please give me a hint.
> If we don't have such a thing in kernel yet, would you put it into the kernel?
> I certainly wouldn't reuse it anywhere else, so for me implementing it as 
> a library or just plain inside that application would do (and probably will
> be easier to debug).

Hmm, assuming you are correct with needing X25 stuff for Euro File Transfer,
you probably should have a look at sys/netccitt.  While I haven't looked
how fully this implements X25, it seems to indicate that it is an
implementation of this protocol stack.

Hope it helps.

ws@TooLs.DE     Wolfgang Solfrank, TooLs GmbH 	+49-228-985800