Re: Connecting to Ethernet

[Toby Reiter <str4552@OBERLIN.EDU>]

On Thu, 21 Nov 1996, David Empson wrote:
> Yes they could - machines capable of running TCP/IP could run SLIP or
> PPP over a direct serial connection (SLIP is "Serial Line Internet
> Protocol", after all).

Well, in this case, people with no ethernet capabilities cannot use 
TCP/IP capabilities.  I.e. people with a modem can only dial into the VMS 
server, and then use pine, ftp, telnet, gopher, etc. but not Netscape, 
Fetch, IRC, etc.

> If you can plug a dumb terminal into the port, then it is not an
> Ethernet port.
I think perhaps the ones I saw were not ethernet, but I would think the 
rest of them were. It did really mess with my mind that the ports and 
cables were identical, but as people have posted, it's more likely that 
these specific connections are serial, and not the entire network. 

> All that would be needed to support this is an intelligent terminal
> server that can be configured to run SLIP or PPP over some ports and
> ASCII-only sessions over other ports.
> 
> However, if the machine has a built-in 10Base-T or AAUI port, it makes
> more sense to hook directly into Ethernet.
This is true for most of the computer on campus. All student computers 
are connected through ethernet (if they are part of the network. 
Otherwise they can only access the shell server using a modem).

> (An aside: the Mac SE has a slot, so one possibility is that 
these
> machines might have an Ethernet card installed.  If so, there is no
> problem plugging them into a 10Base-T connector.)
>
> I then said:
> > The email host is a VMS Alpha server. The majority of the ethernet capable
> > computers use telnet to connect to the network, so I distinctly doubt it
> > is sent only be Kermit. (However, access to TCP/IP is only available 
> > through ethernet, and _not_ by modem connection.)
> 
> I think this is what is happening:
> 
> 1. The machines which have TCP/IP access simply use a Telnet connection
> to the E-Mail server.  The individual machines may be connected to a
> 10Base-T hub, or over a serial connection to a hub or terminal server.
I doubt it. The machines which have TCP/IP access must use ethernet, and 
each have their own specific IP number.  There is no serial access to 
TCP/IP.
 
> 2. Dumb terminals (or computers emulating them) must be connected via a
> serial line to a terminal server, which provides the Telnet connection
> to the E-Mail server.  (Alternatively, they may be connected directly to
> a serial port in the E-Mail server or another host.)  Some facility is
> provided to allow file transfer via Kermit for these machines.
Probably this is true. The terminal server, I guess, is the alpha server 
itself.  So that would mean a dumb terminal simply has a direct serial 
connection to the server, and ethernet capable computer access it through 
a telnet program using TCP/IP.

> From one of your earlier messages, I got the impression that a menu of
> some kind was involved, which implies BBS-type access to a host machine.
This is categorically untrue. ;) No, there is no menu at all.

> > Actually, we have a large number of IIci's, IIcx's (or whatever), and
> > assorted PowerMacs attached to the network on both ethernet and localtalk
> > (depending upon where on campus they are). I am currently typing this on
> > a Power Macintosh 5260/100 in another dorm room, which is attached to the
> > ethernet network by means of a blue ethernet cable which is identical to the
> > one used to attach the Mac SE's to the network. All of these normally
> > ethernet attached computers are able to access all of the Mac servers
> > over EtherTalk.
> 
> The type of cable isn't conclusive - 10Base-T cables have enough wires
> to run a serial connection, though it would be rather confusing to use
> the same wiring for two physically incompatible connections.
This would explain my confusion. Silly me, thinking that an ethernet 
cable is an ethernet cable <grin>.
 
> Your mention of EtherTalk brings up another issue: if a machine is
> connected directly to Ethernet, it should be able to run TCP/IP and
> AppleTalk simultaneously over the network.  If it is connected via a
> LocalTalk port, TCP/IP data would have to be encapsulated in AppleTalk
> packets and extracted by a router before being fed onto Ethernet.
There is no access to the AppleShare volumes without ethernet, so I 
assume it is connected using EtherTalk. There may be some exceptions on 
campus (i.e. LocalTalk on computer center computers), but very few.
 
> If there are some serially connected Macs, then they might be able to
> run AppleTalk encapsulated in TCP/IP over SLIP or PPP (I'm not sure if
> this is possible), or TCP/IP encapsulated in AppleTalk over a simulated
> LocalTalk connection (RS-422 point-to-point connection to some kind of
> terminal server).
No serial connected Mac on campus, I assume, can use TCP/IP, so 
neither SLIRP nor PPP is in use.
> I'd be interested to hear if your computer centre can explain this
> conclusively.
I've been meaning to get back to them, I just haven't had the chance, 
yet. Hopefully someone will be able to explain it. :-)

Thanks for all the ideas (this should become a FAQ somewhere),

Toby Reiter