Re: tcp-ip terminal servers


Keith Mitchell (mcvax!tarantula.spider.co.uk!keith@uunet.UU.NET)
Fri, 21 Oct 88 11:53:45 -0100


I am surprised to hear that the provision/non-provision of rlogin on
terminal servers is a major issue. It seems to me that while rlogin does have
some advantages over telnet, it is a protocol designed specifically for use
between Unix systems. Terminal servers are usually not Unix systems, and so
some of the assumptions which rlogin makes tend to break down.

The two main advantages of rlogin over telnet are probably that of
authentication and passing across of terminal type. For client use it is
possibly reasonable to build these into a non-Unix system. However, when
using the server as a milking machine, these advantages are lost, there
being no defined mechanism for passing authentication and terminal type
information across the serial lines.

In any case, I have yet to see a Unix system with rlogin which does not
support telnet too. Telnet also has the advantage of being an officially
defined and well-documented protocol, which is more than can be said for
rlogin.

One approach is of course to have a terminal server which runs Unix, but
I suspect supporting Unix (hardware, licensing etc) puts the per-box cost
up enough that rather more lines are needed to keep the per-line cost down.
Having to fit all these lines onto one server has the side-effect of
restricting the number of control signals provided on each line.

With SpiderPort, we go for a small, cheap unit with a smaller number (10) of
lines, but with full bi-directional hardware flow and modem control signals
on each line. We did not go for rlogin support, largely for the reasons
detailed above. On the other hand, if rlogin's a big issue with users, and
we've missed something, then I'd be interested to hear what.

Keith Mitchell

Spider Systems Ltd. Spider Systems Inc.
65 Bonnington Road 12 New England Executive Park
Edinburgh, Scotland Burlington, MA 01803
+44 31-554 9424 +1 (617) 270-3510

keith@spider.co.uk keith%spider.co.uk@uunet.uu.net
keith@uk.co.spider ...!uunet!ukc!spider!keith



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