Example of OSI package/data structure?

[Vincent Smeets <VSmeets@meppen.sema.slb.com>]

Hallo,

Can someone point me to an example of an implementation for the ISO/OSI
protocol stack?

I have a description of a protocol that has to be coded in Ada95. I it
now coded (hacked) in a bad form in Ada83 and I want to redesign it for
Ada95.

First I need a package structure. I want to decopple every layer as much
as possible and was thinking of a tagged type for the device and extend
it in every next layer. I have three ideas from which I think the first
is the best (your opinion please?):

OSI
OSI.Physical
OSI.Physical.Data_Link
OSI.Physical.Data_Link.Network
OSI.Physical.Data_Link.Network.Transport
OSI.Physical.Data_Link.Network.Transport.Session
OSI.Physical.Data_Link.Network.Transport.Session.Presentation
OSI.Physical.Data_Link.Network.Transport.Session.Presentation.Application

OSI
OSI.Application
OSI.Application.Presentation
OSI.Application.Presentation.Session
OSI.Application.Presentation.Session.Transport
OSI.Application.Presentation.Session.Transport.Network
OSI.Application.Presentation.Session.Transport.Network.Data_Link
OSI.Application.Presentation.Session.Transport.Network.Data_Link.Physical

OSI
OSI.Physical
OSI.Data_Link
OSI.Network
OSI.Transport
OSI.Session
OSI.Presentation
OSI.Application

Next; what type definition can I use for my device. As I only have two
physical devices, I would like to define only two variables in the
package Physical that has to be used for the operations and not allow
the user to define extra variables. Something like:
	type Device (<>) is tagged limited private;
	Device_1 : Device;
	Device_2 : Device;
The problem is that this doesn't work and if the type is extended, the
variables has to be redefined to contain the extension.

I hope you have enough information. Can you give me some help or point
me to an example?

Thanks,
Vincent

-- 
Vincent Smeets
SchlumbergerSema -
Competence Center Informatik GmbH 
Lohberg 10 - 49716 Meppen - Germany
tel:  +49 5931-805-461
fax:  +49 5931-805-175
mail: VSmeets@slb.com
web:  www.cci.de