[Nml-wg] OGF 23 discussions: pictures

[Freek Dijkstra]

Hi all,

OGF was very useful, at least to me, and a LOT of papers notes were 
scribbled scribbled in discussions after the session.

I took the liberty of recreating an electronic copy of a few of these 
pictures. You will find them attached.

Slide 1: Node Virtualization
----------------------------
During the session, we had a discussion about physical versus virtual 
nodes. Later, it turned out we had to distinguish two different concepts:
a) partitioning of devices into multiple logical devices. Typically, 
control of each logical part will be given to another party.
b) abstraction of multiple device and expose it as one single device 
(for example, Raptor switches and multi-chassis routers do this).

In the picture, the green boxes are physical devices -- real hardware, a 
chassis. The blue boxes in the physical devices represent logical 
partitionings, referred to as "virtual nodes".

Note: We first used the terms "nodes" for logical nodes and "device" for 
physical devices. Later we agreed that "node" and "device" should be 
interchangeable, and we should refer to "physical nodes" and "virtual 
nodes" (or "physical device" and "virtual device"). The parent concept 
is called "node".

A group of nodes (either virtual nodes or physical nodes) can be exposed 
as an abstracted thing that behaves as if it was a device (with 
interfaces, capabilities, etc.). This is a "network", or "graph", since 
it must behave as a connected graph (thus there is a implicit assumption 
  that data can be transported between any two interfaces of the same 
graph/network.

Slides 2+3: Node Relations
--------------------------
This slide gives the relationship between node and network, and between 
virtual and physical nodes. Each node has an attributed "implemented". 
If this is undefined, it is a physical device. If it is set, it means 
that this is a virtual node, which is a partition of the referred instance.

Note: this schema only gives the relations between classes (one to many, 
many to one). In this example, the "implemented" attributed is a many to 
one attribute; the others are one to many. To convert this to a 
relational database, it is much more convenient to use many to one than 
one to many attributes. I suggest we follow that practice in the final 
schema.

Slides 3 is a variant of slides 2. In here, virtual node and physical 
node are subclasses of the base node class. This is useful if one of 
them has attributes that the other does not. I put location in there, 
but that may be a bad example.

The network/graph abstraction has interfaces, just like regular nodes. 
These can be inferred (derived) from the original nodes in the network. 
Therefor, this is not an attribute, but a function that calculate the 
edge interfaces of the network. Of course, in (XML or RDF) messages, 
this relation is explicit -- it just is implied in a database (to avoid 
internal inconsistencies).

Slide 4: Networks
-----------------
There are two concepts of the term "network". Martin Swany noted that in 
the IP world, the word "network" has a very well defined meaning, the 
"link local" network between routers.

The definition which was proposed in the session by Pascale Primet was 
that of a connected graph. This is what is meant by "network" when 
people talk about e.g. the "Internet2 network" or "the SURFnet network".

John Vollbrecht proposed to use the term "multi-point link" for a 
IP-terminology "network", and use the term "network" for the graph-like 
"network".

This image attempts to show the two terms in a single picture. While the 
definition was agreed upon, the term was not. We may use "G-Network" 
(for graph-like network) and "I-Network" (for IP-term network) until we 
decide on this.

Slide 5+6+7: G.805 Functional Elements
-----------==-------------------------
We had a discussion on the terms "link", "path" and "connection". In 
particular, it should be noted that a path on a lower layer is a link on 
a higher layer. For example, an IP "link" may in fact cross a while DWDM 
network, or Ethernet network. G.805 defines exactly this. This slide 
re-iterates the terminology of G.805.

Slide 6 relates this to "our" terminology:
- link = G.805 link connection
- path = G.805 network connection
- circuit = G.805 trail

A  trail is a terminated network connections (thus with error 
correction, retransmission, etc.). John Vollbrecht likes the distinction 
between these two terms, but there was no consensus for that.

Slide 7 is a picture I added to explain G.805 for those really 
interested (including subnetworks and multiplexing adaptation).
Ask me if you are interested.

Groups
------
(not in the slide pictures)

We agreed that we should keep the concept of group, and that path and 
domain, and perhaps also network are specific types of groups.

Function/Service
----------------

Martin Swany argued that adaptations and cross connects are functions or 
services in a node. This was not extensively discussed in the group 
itself, but in general the idea was met in favour.

Note: it is not clearly defined yet what a service or function is. For 
example, if it is a transport function between ports, this includes 
adaptations, cross connects and link connections. An alternative is to 
reserve the term only for operations within a node (thus excluding link 
connections).



Regards,
Freek Dijkstra
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