Re: Multi-protocol wide area networks


Harri Salminen (mcvax!enea!tut!santra!hks@uunet.uu.net)
19 Jul 88 19:35:20 GMT


X.25 isn't the only alternative for multiprotocol large WANs. Even
the X.25 equipment is expensive (not to mention public X.25) and
supports in most cases only 64Kbit/s host connections. In addition
you'll need routers. I know though that DCA X.25 switches should have
TCP/IP router for ethernet.

I've been much involved in planning a internordic (Denmark, Finland,
Iceland, Norway, Sweden) network to be called NORDUnet which will be
based on using extended Ethernet (ISO8802/3 if you like) as the
multiplexing WAN backbone (Translan bridges which have priority
queues, loops, filtering etc.) and connecting dedicated routers and X.25
switches (ISO CONS NS) to it. It gives the largest flexibility in
supported protocols and doesn't have low speed limits or "Virtual
Circosis". Supported protocols will include OSI CNLS and CONS (X.25
88), TCP/IP (everybody wants good SERVICE now), DECNET (we have quite
large ones being harmonized) and NJE (EARN/BITNET). Common lines to
rest of Europe and US are planned too.

We're going to use Cisco routers that already (or very soon) support
Dod IP, DECNET, ISO CNLS NS (ISO IP) (maybe chaos and XNS) and should
be, at least soon, behaving like bridges for others. Using just
Ciscos (or other multiprotocol routers like Proteon, WellFleet etc.)
might be enough for you since they probably can handle all protocols
you need. Cisco has also X.25 support for IP but I haven't found yet
anyone supporting ISO CONS (X.25 88) switch in the same box with all
the other protocols we need. Haven't seen a TP0/TP4 gateway either but
I hope somebody can design one. Our national network is currently a
LARGE (over 16 organizations) bridged ethernet but we are breaking it
up with these new multiprotocol router/bridges (brouters?).

If you like to run CONS OSI (X.25 88) on ethernet many switch and
software vendors are developing it so you can soon choose to use CONS
or CNLS as you wish. In Europe it at least seems to be huge
"religious" battle instead of technical one, so we're trying to support
both (at least internationally). If you choose to use X.25 as backbone
and 64Kbit/s is enough today be prepared to buy multiple routers and
expensive switches. If you happen to like SNA (like the Germans) you can
even set up a X.25 network (and telephone network for that matter) over
SNA backbone with XI and SNI. It's up to your preferences but
I wouldn't like to maintain that SNA/XI/SNI network.

Aren't standards fun. You can use them as building blocks as you wish and
not just as the manual says but have to know what you're doing ;-)

In case somebody is interested in our network project a draft report is
available from my listserv by sending a command "GET NORDUNET XEARN"
(or INFO GENINTRO first) to LISTSERV@FINHUTC.HUT.FI (FINHUTC.BITNET).
It misses the pictures and some appendixes but you'll get the picture :-)
We've also a list called NDNNET-I where we might sometimes announce
about something, to which you can subscribe with the command "SUB
NDNNET-I Your Name". Contact me when everything fails or you have
specific questions or comments about the report or project.

Harri



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