UUCP protocol information

[Guy Harris]

> I have access only to level g and will document it as I begin to
> understand it.

In an issue of ";login:" a couple of years ago, there was a summary
of a talk given by Lauren Weinstein on UUCP at USENIX which gave some useful
information on the "g" protocol.

> (4) The slave sends a message that identifies all the protocols that
> 	it supports. It seems that BSD supports 'g' as the normal case.
> 	Some sites, such as Allegra, support 'e' and 'g', and a few
> 	sites support 'f' as well. I have no information about these
> 	protocols.

The "protocol" layer is actually two layers: the actual link-level protocol,
and a simple encapsulation of data.  The "e" protocol is, I believe, an
encapsulation intended to run on top of protocols like TCP/IP - it does
regular UNIX reads and writes to the descriptor, under the assumption that
the kernel is providing all the flow control and error recovery needed.
The 4.3BSD UUCP provides a "t" protocol for the same purpose (UUCP over
the ARPANET or over an Ethernet is kind of neat).  The "f" protocol assumes
a flow-controlled, mostly reliable, 7-bit data path - it was intended for
use over X.25 lines using PADs on both ends assembling 7-bit ASCII into
X.25 packets and disassembling them at the receiving end.  System V's UUCP
also has an "x" protocol that runs on top of the BX.25 code that they
"supply" in the form of zero-length source files with standard System V.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy