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Turning an Ethernet into a WAN
Date: Mon, 15 Apr 91 18:02 EDT
From: bill@ATHENA.PANGARO.dialnet.symbolics.com (Bill Wilkinson)
I am looking for hardware and/or service recommendations in connecting
Lispms and/or other machines on different Ethernets via telephone and/or
other service. I want low cost point-to-point service, across town or
maybe between different cities. I want the connection at the Ethernet
level so I can route Chaos packets, IP packets, etc. Between Lispms, I
want mail service and file service and a single namespace for both
Given than I don't want to pay for a T1 or chunck thereof, or wait for
ISDN to show up at my door, I figure that a 9600 bps (V.32) modem and
the public telephone network are acceptable.
I've looked at a few routing Ethernet bridges in the $2000 and up range.
These are high performance devices that are made for higher speed comm
media. Thus the total hardware cost for bridges and modems for 2 sites
is in the $6000 range. Are there any cheaper boxes out there that I
should know about?
Bargain basement solution: we have successfully connected MacIvories into our
building LAN via 9600 baud SLIP connections. All IP based services work as
expected (including namespace queries and updates). Chaos, as you might guess, is
not supported, but this is not a problem. We (initially) used nothing more than
stock PC/AT's as Ether-to-SLIP gateways. The AT's ran Phil Karn's NET code. We
successfully used Telebit T2500 modems in v.32 mode. We also had some success
with Microcom QX/v.32's in this configuration.
Higher-priced spread: we have since tested a configuration with a Telebit
NetBlazer as the gateway to the building LAN and a PS/2 Mod 70 running NOS (Phil's
latest) via buffered async at 19.2KB/s at the remote site. Many variations on
this theme are possible.
While we tested this all out for MacIvories, it should work well with other
(Symbolics, at least) LISPMs. With the MacIvory, using thin Ethernet makes the
physical connection to the AT a snap. For LISPMs which only use the DB15
transceiver style of Ether connection, the interface will be (physically) more
awkward, but workable nonetheless.
Even higher-priced spread: call your local TELCO and ask if "switched 56" service
is available to you. This provides 56 KB/s digital service over a dialup
connection. It is more expensive than basic telephone service (both monthly and
per-connect-minute), but it can be cheaper than a leased line in some
applications, depending on usage. If you implement one of the above two
connections initially, switched 56 is a natural growth alternative.
Has anyone out there successfully connected multiple Lispms on separate
Ethernets via routing bridges (locally or remotely)?
This style of connection is completely general in the sense that it provides no
less IP functionality than what one expects from "in-building" LAN
Can Genera software deal with slow data rates gracefully or am I going
to find myself timing out at inconvenient times? What else do I need to
know or what questions should I be asking?
Genera works just fine over this connection. Timeouts are not a problem.
Interactive IP traffic can be slow, especially if you have background activity
(e.g., file transfer) in process. There are ways to optimize this. Be prepared
for some slightly contorted world-building for the remote machine(s). I can
provide details if/when you try this.
Has anyone implemented SLIP (serial line IP) for Lispms? I understand
that there are commercial services out there providing IP data services
at costs competitive with leased telephone lines.
Obviously, a better solution than using the AT (or PS/2) would be a LISP-native
SLIP (or better yet, on the MacIvory, a SLIP driver on the Mac side that provides
a packet-level interface to LISP). I do not know of one, but would appreciate
details if anyone else does.
Thank you very much.