[nmrg] physical network / physical entity; RE: network digital twin vs. digital twin network

["Schwarz Albrecht (ETAS-DAP/XPC-Fe6)" <[e-mail]>]

I think that the notion of physical network and physical entity is misleading, if not incorrect at all.
The network types in scope of IRTF & IETF represent layered communication architectures, and only the lowest layer (as protocol layer, network layer, service layer or whatever layering paradigm is used) is tight to physics (transmission layer, physical protocol layer etc.) All layers above are non-physical entities.

A NDT might be used for twinning the e.g.,
- the physical layer network only,
- the entire network with all layers,
- a subset of layers (related to a specific protocol stack segment), or
- a single, non-physical network layer.

That said, I guess that you mean with the notion of physical entity rather the real technical entity, i.e., the real technical network (as the most abstract candidate for twinning).
The NDT as information model belongs to the category of virtual entities.

That term pair spelled out:
a) real (information and communication) technical entity (the "network") and
b) virtual (information) technical entity (the NDT).

Or shortened as real entity and virtual entity.

Proposal: replace predicate "physical" by "real". That would match all four basic use cases as outlined above.

Further:
you driving the specification of a NDT system / architecture in the technical viewpoint when using the notion of "physical".

However, you might engineer a NDT system also as functional or logical system (and there are not any technical terms in that two viewpoints).
The good news: the notion of real entity and virtual entity are also applicable in the functional and logical viewpoint.


Furthermore:
after twinning a particular layer network with a set of selected layers by a NDT information model, there might be further use cases for twinning dedicated communication services.
A NDT would be followed by CSDT (for communication service digital twin).
And a communication service (at whatever abstraction level selected for a particular CSDT information model) is definitely not a physical entity, but still a real entity.
So again, the term twin real and virtual entity match again.

Regards,
Albrecht



Dr. Albrecht Schwarz
Systems Engineer

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-----Original Message-----
From: nmrg <[e-mail]> On Behalf Of Pedro Martinez-Julia
Sent: 09 March 2023 05:52
To: Cheng Zhou <[e-mail]>
Cc: 'Christopher Janz' <christopher.janz=[e-mail]>; 'Jürgen Schönwälder' <[e-mail]>; 'Qin Wu' <bill.wu=[e-mail]>; [e-mail]
Subject: Re: [nmrg] network digital twin vs. digital twin network

On Thu, Mar 09, 2023 at 12:40:57PM +0800, Cheng Zhou wrote:
> No intention to bring more confusions here.
>
> - Digital twin network (DTN) in the draft means 'digital twin for 
> network', which can mean more than just building a twinning entity of 
> network. And from perspective of introducing Digital Twin in the 
> network field, DTN can be the whole interactive virtual-real mapping 
> system, building with the DT concept or techniques.
>
> - Network digital twin (NDT) means ' network's digital twin', the 
> twinning entity of the physical entity, focusing on all 
> functionalities in twin layer, including data, models, emulation, etc.
>
> This way, DTN and NDT is possible to co-exist in the draft with few 
> confusion.
>
> Surely, if this is acceptable, current draft needs update via 
> clarifying both terms.

The coexistence of two concepts whose names and meanings are so close will end in more confusion. In fact, while your definition of NDT is quite clear, your definition of DTN is not.

The virtual-real mapping you mention is a process required to build and maintain a NDT. It must not be separated. Let's say that the goal, NDT, is maintained by process "NDT construction" and this process is part of what is called DTN. This is confusing.

> Thanks and Regards,
> Cheng

Regards,
Pedro

--
Pedro Martinez-Julia
Network Architecture Laboratory, Network Research Institute National Institute of Information and Communications Technology (NICT) 4-2-1, Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan
Email: [e-mail]
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