[Nml-wg] Tube Terminology

[Freek Dijkstra]

Aaron Brown wrote:

> Both a network and a link connection seem to be 'connections between two 
> points'. You say that in one case it's terminated and in one case it's 
> not. Is 'terminated' a property of the link or is it a property of the 
> connection point

It's a 'property' of the connection point -- basically it says that
connection is terminated there (these connection points are end-points
for a certain layer and are called "termination connection points" or
"TCP").

> A tandem connection is a network or link connection that spans multiple 
> connections? How does it differ from a network connection which in 
> figure 1 also spans multiple connections?

A network connection is a special case of a tandem connection: it is a
tandem connection between termin

> What differentiates 
> a link whose contents gets demux'd to an higher layer vs. a link whose 
> contents get routed at the same layer?

I can't answer the question if I were to follow G.805 to the letter.

To be annoyingly precise (which G805 is):
First: in G805 the term "link" is only used for the physical wire/fibre.
What we are talking about is a "transport entity across a link", which
is called a "link connection".

Second: link connections are never routed or switched. Easiest is to
compare link connections and tandem connection with graph theory:
- link connection = single edge
- tandem connection = path (a sequence of edges)
you seem to talk about tandem connections (paths) rather than about link
connections (links).

So I take it that you mean to ask:

> What differentiates a tandem connection whose contents gets demux'd
> to an higher layer vs. a tandem connection whose contents get routed
> at the same layer?

The difference is that a tandem connection that gets demuxed to a higher
layer must thus be terminated at the lower layer. Thus, that is a
terminated tandem connection, which is called a "network connection".
(to be even more pedantically correct: the end-to-end connection before
termination is called a "network connection", while after termination it
is called a "trail")

> A subnetwork connection is a link or network connection that you view as 
> opaque, correct? I.e. I've got a connection between these two points, i 
> either don't know or don't care how it's constructed. If so, would 
> "opaque connection" be a more clear description?

Sure -- I'm certainly not saying that I'm a big fan of every word G805
come up with. However, there is a slight difference: a subnetwork
connection is a opaque connections *through a given network*.

To recap:
* link connection is a direct (or atomic) connection on a layer
   (think: link).
* tandem connection is a sequence of link connections
   (think: a path or a segment of a path)
* network connection is a tandem connection that will be terminated
   (think: a end-to-end path)

And for the real G.805-adepts:
* trail is a terminated network connection (think: end-to-end path)

Regards,
Freek


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