Below is a discussion that John and I had that we inadvertently kept off the list. John Vollbrecht wrote:
On Jul 4, 2008, at 4:37 AM, Jeroen van der Ham wrote:
Hi John,
John Vollbrecht wrote:
On Jul 1, 2008, at 3:28 PM, Jeroen van der Ham wrote:
John Vollbrecht wrote:
Do you have the latest schema? I would like to understand how this all fits together. I have some questions about how multiple circuits can be carried over a Link. And how multiple paths can be carried over a sequence of links. Perhaps I can ask questions better after looking at the schema.
That is a multi-layer description, and that should be handled in the extension of the base schema.
Seems to me this is a single layer description, or a description of how a dcn "view" of a network can be incorporated with a global network description. I am not sure what makes it multi-layer. Is it that building circuits on top of a set of links and nodes? Sorry to be dense, but I don't understand the problem and would like to be able to talk about it in a way we both can understand.
In my opinion this is multi-layer: you are describing the topology, and how several paths are layered over that topology. And to be able to describe what a valid path is, you also need to know about adaptations, labels, et cetera.
So in my view, even if you describe the simple topology, and describe paths just as a list of nodes, ports and links, then you still need to know about the technology involved to be able to see if it can all work.
I think I agree with you. My confusion is that in other discusssions it seems that there is a single path over a Link - for example there can be only one adaptation per Link implies that there is only one path since there can be many paths and potentially a different adaptation per path.
In NDL an adaptation is a function, and is not tied to a single path. The same adaptation can be used many times in the same path. The label that is used with the adaptation will be different each time though.
I agree that one needs to include information about Links, and nodes to create a path. In particular one needs to know adaptations between link types, bandwidth, and possibly others like VLAN or color.
I think there is also a difference between describing what is possible to a pathfinder algorithm and what is actually reserved. What is reserved, including specific resources along the path, becomes a circuit. A circuit is a path with resources, including time.
I agree that there will be different purposes for network descriptions, and that each will have different requirements. However, a base part will always be the same. We should be aware of the different requirements. But I think that we can now focus on the base schema, and later create the extensions. Jeroen.