smart@ditmela.UUCP (07/12/88)
When creating a wide area network for the academic and research
community it seems desirable to be able to run a variety of middle
level protocols: TCP/IP, DECNET, OSI, UUCP, ACSnet. The only
choice I know of that can do this is X.25. The trouble with an
X.25 network for TCP/IP and DECNET is that you have to have a
host to gateway between each local ethernet and the wide area
network. What I would like is an X.25 switch which knows how to
do TCP/IP and DECNET and OSI/CLN gatewaying to a local ethernet.
Something like this:
host-------X.25-switch---------wide area network
| |
----------------------------
ethernet
Hosts that want to be connected to the X.25 network could be, but
most would get their network access from their LAN connection.
Is there anything like this around? Or planned? Or does somebody
have a better idea?
Bob Smartperry@MCL.UNISYS.COM (Dennis Perry) (07/15/88)
Bob, there are gateways around which support ethernet interfaces which do what you want. Unisys makes a gateway which supports ethernet and x.25 interfaces, along with other types of interfaces. dennis
hks@santra.HUT.FI (Harri Salminen) (07/20/88)
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
smart@ditmela.oz (Robert Smart) (07/23/88)
We are in learning mode about creating wide area networks. The
shortage of good solutions is shown by the NORDUNET plan. They are
going to create a wide area ethernet (via mac-level bridges) with no
hosts on it, only routers for mid-level protocols like IP and DECNET
plus funny boxes for connecting serial lines through an ethernet!
Let me say what I think is available today, and why it is deficient
for what we would like to do.
Cisco and Proteon provide boxes which will route IP and DECNET (and
other protocols of no interest to us) between ethernets. They claim
they will soon support OSI Connectionless Network routing as well.
I know a little about Proteon P4200s, and assume Ciscos are the same:
the boxes can have ethernet boards and serial line boards. However the
serial lines can only speak the secret Proteon protocol: so they have
to lead to another Proteon box.
The first problem with this is that not all points on your network can
justify a proteon box. If you have a small site with just a few Suns
or VMS Vaxes then you will want to connect them to the world by just
running slip out of one of the Suns or Asynch or Synch decnet out of
one of the VAXes. It would be nice to be able to run these serial
lines into a Proteon box serial port instead of having to run them
into some host on your ethernet. The whole point of getting Proteon
boxes is to avoid having hosts doing packet routing.
Another protocol we would like to support is X.25. It would be nice
to allow two Proteon boxes to be able to talk to each other over X.25.
Presumably this would be used as a backup mechanism for connection
when a leased line malfunctions. But it could also be used as the
normal method of moving packets between networks that don't have a lot
to say to each other. Once again there are standards for running IP
and DECNET over X.25. It would be nice to be able to run connections
from isolated IP or DECNET nodes into a Proteon box via an X.25
virtual circuit instead of having to run them through another host.
However we would also like to be able to have our router network act
as an X.25 network. I.e. host1 can talk X.25 to host2 in:
X.25 connection private protocol X.25
host1---------------router----------------router-------host2
Why would you want to do this? Well firstly there are plenty of
implementations now that will run OSI over X.25, so it is a natural
way to get OSI protocols now. Conversely it is not obvious when there
will be host implementations of Connectionless, or routing software
that will allow implementations of X.400 (say) over CLN to talk to
implementations connected to X.25 networks around the world. Also
there is a lot of software around that runs over raw X.25 (or via
non-standard mid-level protocols): such as the Coloured Book suite.
There are now protocols for running X.25 packets over ethernet
(pinkbook), and over DECNET (PSI-access) and now also over TCP/IP. We
would, of course, like our X.25 implementation to talk happily with
these.
Another thing that would be useful would be to have our routers
connect arbitrary synchronous lines.
sync line----router------------router----sync line continues
This would allow for connecting IBM and other things through the
network. Obviously a sync packet entering one end should not be unduly
delayed before emerging from the other: these packets would have to
have priority. For longish packets it might well be important to
arrange for them to start emerging from the far end before they have
even finished arriving at the receiving end. In which case you better
arrange to get the rest to the far end in time!
It would also be nice if the router would act as a mac level bridge
for some or all protocols it doesn't really know about. I gather from
the nordunet proposal that this is coming.
Well, while we're at it. It would be nice to be able to use the serial
ports as a serial line concentrator. Users logging in to these ports
could be connected to their destination in many ways: telnet, rlogin,
X.29, OSI VT, or just by connecting to another port somewhere. And if
it was done nicely the user need not even be aware of how the
connection is being made. Protocol transparency: never quite comes off
in real life.
Would any of the router makers like to comment on these proposals. All
pie-in-the-sky? Is the NORDUNET wide area ethernet really the only
way?
Bob Smart <smart@ditmelb.oz.au> or <smart%ditmelb.oz.au@uunet.uu.net>