Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

[Eric Gray <[e-mail]>]

Kiran,

              As we discussed last Friday, the wording here is dicey, because it is not “resources” that are connected by a network slice – it is endpoints that are connected using resources.

--
Eric

From: Kiran Makhijani <[e-mail]>
Sent: Friday, March 6, 2020 11:39 AM
To: Eric Gray <[e-mail]>om>; Dongjie (Jimmy) <[e-mail]>om>; Jeff Tantsura <[e-mail]>
Cc: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]>om>; Belotti, Sergio (Nokia - IT/Vimercate) <[e-mail]>om>; [e-mail]
Subject: Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual
Importance: High

+1 to your proposal, it reads better and captures the main aspects.

“A transport slice is a network topology connecting a set of shared or dedicated network resources and a number of endpoints,  which are used to satisfy specific Service Level Objectives (SLO).”
-Kiran

From: Eric Gray <[e-mail]<mailto:[e-mail]>>
Date: Friday, March 6, 2020 at 7:22 AM
To: Kiran Makhijani <[e-mail]<mailto:[e-mail]>>, "Dongjie (Jimmy)" <[e-mail]<mailto:[e-mail]>>, Jeff Tantsura <[e-mail]<mailto:[e-mail]>>
Cc: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]<mailto:[e-mail]>>, "Belotti, Sergio (Nokia - IT/Vimercate)" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: RE: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

So, when you were going through this yesterday, I noticed something a little bit off in the wording, but I agree with the use (or non-use) of “logical,” “virtual,” “abstract,” etc. as mostly interchangeable but with a tendency toward “better fit” depending on context, perspective, and so on.

If you use the one with the bracketed “description,” the brackets need to include “of” as well.  This is an unusual usage, because the phrase “description of” is somewhat parenthetical in that the sentence should be grammatically correct with or without the part in brackets – but (usually) parentheses would be used (hence “parenthetical”) rather than brackets.  But this is a stylistic observation and would likely be changed (if change is needed) by the RFC Editor.

The one issue that struck me earlier was that – with the current wording – the position of “and” (especially without punctuation) makes the statement claim two things:

  1.  The transport slice connects endpoints, and
  2.  The transport slice connects a set of shared or dedicated network resources.

While this may look okay at first glance, not all of the “resources” (whether shared or dedicated) are “connectable.”  For example, exactly what “resources” do you “connect” in an effort to achieve a maximum latency?

This could be addressed by rewording slightly as follows:

"A transport slice is a (description of) network topology connecting a number
   of endpoints, and using a set of shared or dedicated network resources, in a
   way that will satisfy specific Service Level Objectives (SLO)."

Another approach (significantly less preferable) would be to put a comma before “and.”

Without the comma, the phrases “a number of endpoints” and “a set of shared or dedicated resources” are grammatically co-equal and effectively commutable (i.e. – if the wording is correct, the sentence is equivalent to “A transport slice is a network topology connecting a set of shared or dedicated network resources and a number of endpoints,  which are used to satisfy specific Service Level Objectives (SLO).”

--
Eric

PS – I do have other comments, about other parts of the draft, but I thought I would bring this up as long as we’re talking about this part anyway.

From: Kiran Makhijani <[e-mail]<mailto:[e-mail]>>
Sent: Friday, March 6, 2020 12:50 AM
To: Dongjie (Jimmy) <[e-mail]<mailto:[e-mail]>>; Jeff Tantsura <[e-mail]<mailto:[e-mail]>>; Eric Gray <[e-mail]<mailto:[e-mail]>>
Cc: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]<mailto:[e-mail]>>; Belotti, Sergio (Nokia - IT/Vimercate) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual
Importance: High

There is one more way to see through this.
If you agree that all justifications on this thread are right,  then all or any of these terms (virtual, logical, real, etc.) are correct usage based on your perspective. What does not change is that it “is a network topology”,  “has end points” , “has network resources., and “connects with expected SLOs” – we all seem to converge on this much text.

Can we say:
"A transport slice is a [description] of network topology connecting a number
   of endpoints and a set of shared or dedicated network resources,
   which are used to satisfy specific Service Level Objectives (SLO)".
Or simply,
"A transport slice is a network topology….”

Would you accept just one word change from logical to some other noun or nothing [] at all? Words that come to my mind are depiction, representation, description…

-Kiran

From: Teas-ns-dt <[e-mail]<mailto:[e-mail]>> on behalf of "Dongjie (Jimmy)" <[e-mail]<mailto:[e-mail]>>
Date: Thursday, March 5, 2020 at 6:12 PM
To: Jeff Tantsura <[e-mail]<mailto:[e-mail]>>, Eric Gray <eric.gray=[e-mail]<mailto:eric.gray=[e-mail]>>
Cc: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]<mailto:[e-mail]>>, "Belotti, Sergio (Nokia - IT/Vimercate)" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

Hi all,

As mentioned on the conference call, my preference of the terms would be virtual >= logical > abstract.

IMO all of these terms refer to something not totally physical or “real”. Actually this is what is expected from network slicing, multiple network slices are built on a shared physical network infrastructure, and each network slice is provided with a subset of the characteristics of the underlying network.

To me virtual and logical can be seen as similar terms and sometimes interchangeable. Virtual has been used widely in IETF and industry, which makes it easier for people to associate “virtual” with specific implementations, although it can be a technology-agnostic term. Logical can be considered more comprehensive, the other side of which may be is more vague.  That said, both would be OK for the definition.

As for abstract, as explained in my previous mails, “abstract” is more related to the policy used to provide the consumer with a selective view of the network, which is mainly about the NBI, while in the definition we may also want to cover the characteristics of the transport slice itself.

Best regards,
Jie

From: Teas-ns-dt [mailto:[e-mail]] On Behalf Of Jeff Tantsura
Sent: Friday, March 6, 2020 3:03 AM
To: Eric Gray <eric.gray=[e-mail]<mailto:eric.gray=[e-mail]>>
Cc: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]<mailto:[e-mail]>>; Belotti, Sergio (Nokia - IT/Vimercate) <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

+1 to “logical”
Regards,
Jeff


On Mar 5, 2020, at 10:06, Eric Gray <eric.gray=[e-mail]<mailto:eric.gray=[e-mail]>> wrote:
Yes, the separation of virtual and real is a big part of the “freight” that “virtual” carries.

At a “Disruptive Technologies” class given at AT&T decades ago, the teacher told us “Whenever you hear ‘virtual’ – you should interpret this as ‘I am lying.’”

This is only a perception thing, but that does not mean it is not just as real as if it were real.  In way too many cases, virtual is used explicitly to distinguish it from reality.  For example, “virtual reality” is pretty much never considered to include “real reality.”  😊

I tend to prefer “logical” in this context, over either “virtual” or “abstract” – in no small part because “abstract” also has “freight.” “Abstract” is often considered to be similar in meaning to “surreal” – which is very unlikely to be what we mean by an “abstract topology” for example.  I cannot wrap my head around the notion of a network designed (for instance) by either Salvador Dali, or M.C. Escher.

But these are minor preferences.  With the exception of context-related cases (where we need to use the terminology that fits best in a given context), I think we should try to be consistent and I am fine with any term everyone can live with.

From: Teas-ns-dt <[e-mail]<mailto:[e-mail]>> On Behalf Of Belotti, Sergio (Nokia - IT/Vimercate)
Sent: Thursday, March 5, 2020 12:35 PM
To: LUIS MIGUEL CONTRERAS MURILLO <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

I think that logical (or even abstract) is more comprehensive since virtual reminds to some kind of virtualization of the underlying resources, but a slice could naturally involve (dedicated) physical resources. So that is why I'm inclined to use logical as a more generic term.

Virtualization has nothing to do with “select” only physical resources but instead is related to select underlying resources (physical or abstract) in the prospective to a particular customer, application or service.
If this was your problem with virtual , it is not a problem.

Regards
SErgio

From: Teas-ns-dt <[e-mail]<mailto:[e-mail]>> On Behalf Of LUIS MIGUEL CONTRERAS MURILLO
Sent: Thursday, March 5, 2020 6:12 PM
To: [e-mail]<mailto:[e-mail]>
Subject: [Teas-ns-dt] Comment to definitions draft in today's call -- logical vs abstract vs virtual

Hi all,

Apologies, I experienced problems in the call today, not being able for me to speak up (even I lost part of the discussions, apologies again).

I wrote my preference in the chat, I think you couldn’t echoed.

So respect to the discussion of preference for logical  vs abstract vs virtual, I think that logical (or even abstract) is more comprehensive since virtual reminds to some kind of virtualization of the underlying resources, but a slice could naturally involve (dedicated) physical resources. So that is why I'm inclined to use logical as a more generic term.

Note that in the operators’ vocabulary today “virtual” has further connotations (exceeding the transport part), so can be an overloaded term in some end-to-end scenarios.

Best regards

Luis


__________________________________
Luis M. Contreras

Technology and Planning
Transport, IP and Interconnection Networks
Telefónica I+D / Global CTIO unit / Telefónica

Distrito Telefónica, Edificio Sur 3, Planta 3
28050 Madrid
España / Spain

Skype (Lync): [phone]
Mobile: [phone]
[e-mail]<mailto:[e-mail]>



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