Re: [vnrg] Logical vs. virtual

[Didier Colle <[e-mail]>]

Dear Joe, all,

> I tend to think of a logical device as not really adding to the 
> capabilities of a physical one, though, whereas a virtual one seems to 
> (at least to me).

Please explain. What capabilities are you referring to?
So far, I think most people on the list have expressed a virtual network 
having the same or a subset of the capabilities of the network. Do you 
agree with that? And remains that statement true for a virtual device 
rather than virtual network?

 From your previous post today, these capabilities are not apparent.
> 1.c. what is the characteristic behavior/capability of the
>     resulting system?
>
> I think that the defining characteristic of a VN is that it allows an 
> existing network to concurrently emulate another, distinct and 
> separate network. 
Is that a characteristic/capability of the virtual network (VN) or of 
the underlying existing network?

>
> Maybe these are really just two aspects of a single thing, i.e., I 
> would differentiate between:
>
> - a device which does not map 1:1 to a physical entity
> (could be a part of one, a group of many, or a group of parts)
>
> - a device which provides supports virtual networking
>
> Since we call the latter "virtual networking" (the name of this RG), I 
> would propose that the latter would be the virtual device, and the 
> former be the logical one.

Hmm... so the resulting question is: What is virtual networking? ;-)

> I don't think of it as a 'specialized form', but rather the fact that 
> a single virtual router CANNOT be mapped onto a single physical device 
> with no other logical components.
>
> I.e., a virtual router needs a base router to connect to the links of 
> the tunnel. A virtual host needs a base router (as well) for the same 
> reason.
Really? In your previous post  you said: "A virtual link is the easiest 
to define - it is a tunnel over some existing network path, i.e., with 
an additional layer of encapsulation that is used solely for the VN, but 
which is otherwise not needed. A virtual router forwards packets between 
virtual links. " So, virtual link is encapsulated (e.g., by tagging with 
a VLAN-ID?) to allow multiplexing: is this something the virtual router 
cannot do (although invisible to the user/owner of the virtual router)? 
Do you need for that another "base" router?

Kind regards,

Didier

-- 
Didier Colle
Ghent University - IMEC - IBBT
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