🚀 go-pugleaf

I have a question about how one would go about running the OSI
ConnectionLess Network Protocol on X.25.  In particular I'm interested
in how X.25 virtual circuits are managed, and how routing and
addressing is done.  I would very much like to hear about actual
router products and how their vendors accomplished this task.  As I
understand the problem, there are two different ways to go about it.

1) The first way is to open up X.25 Permanent Virtual Circuits (PVC)
between your various OSI Intermediate Systems (IS).  Under this scheme
when ever that IS has packets to send to some other IS it just puts
them out on the already open X.25 virtual circuit.  The routing could
be just a matter of mapping the OSI IS address to the proper X.121
addresses and determining which X.25 PVC goes to that X.121 address.
The primary problem I see with this method is that it is very
expensive to have a bunch of X.25 PVC's open.

2) The second method I see is for there to be some sort of protocol
that allows OSI TP4 to open and close X.25 virtual circuits on the
fly.  To keep things simple, I'll assume that routing and addressing
are done the same way as in 1).  The big advantage with this method is
that X.25 PVC's aren't needed, and thus your X.25 bill should be
lower.  In fact, it may even be possible to, as needed, open up more
then one X.25 virtual circuit to improve your performance under peak
load conditions.

The primary problem I see with this method is the delay needed to open
X.25 circuits, and how to determine when to close them.  Maybe someone
who knows more about X.25 can comment on how long it takes to open a
virtual circuit on a typical X.25 network.  I have heard that cisco
does have a OSI-X.25 router that operates CLNP.  I wasn't able to
determine though which of the above methods is used.  If they use
method 2) how does their router determines when to close the X.25
circuit?  

If anyone has any product/vendor information they would like to send
to me I will summarize and post to this news group.  I will also
summarize any comments on methods/protocols I receive.   

Thank you for your help.  

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Steven Myers                        | Internet: smyers@luna.dpl.scg.hac.com
Hughes                              |    Phone: 213-414-6261
Space and Communications Group      |      FAX: 213-414-6699
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