On May 12, 2009, at 9:24 AM, Martin Swany wrote:
Hi Jeroen,
I'm (re-?) adding Jason to the cc list as he's right in the middle of this discussion as well.
I would add that I think that we are all very close on the way in which things are related, which gives rise to layers/levels of the network. I think that the "Relation" element that we're using in UNIS (perfSONAR/DCN) land really makes the expressions there start to look like the RDF 3-tuples in a way. While that problem is hard, I think that we've been inching closer to having a common solution framework.
I think the relation might work for this if it is defined -- but still it is complicated and important to agree on. See comment below.
best, martin
On May 12, 2009, at 4:13 AM, Jeroen van der Ham wrote:
Hi,
I think Martin's analysis of your description is correct. I only want to add that you seem to be contradicting yourself regarding layering, and I think it is very important that we clear that up.
Before I begin, I want to clear something up: Networks transport data by encapsulating it in different layers. I think we can all agree on that analysis, and we all know what layers are in general. Therefore I don't want to complicate this (already complex) discussion by introducing yet another term (i.e. "level").
Then on to your analysis: in the beginning you say that NSI wants to describe links at a certain layer going over links at a lower layer. Then later on you say that NSI operates at a single layer for a particular request.
Current networks operate at multiple layers (Ethernet, SONET, Lambda, etc.). Therefore, if the NSI wants to be able to provision services across these networks, then it will have to handle multiple layers.
Please realise that the NML is currently describing a layer-less model. Layers are not part of the model and we are only describing the general things that are part of every layer. So NML is currently not able to describe that links at one layer run over a link at a lower layer.
As Martin said, describing layers, and the adaptations between them is a very very hard problem. One that the NML group will be taking on soon though. I agree this is hard. I think levels and layers are different. Layers apply to protocol layers. I may misuse the term. Levels for me apply to what can be switched for a given topology. I.e. A given topology allows VLANS to be created ete, by concatenating VLANS at each edge point. The VLANS to be switched are carried on something else - SONET trunks, GOLEs, Ethernet trunks, etc. Level in this case refers to VLANs on one level and what carries them on the other.
Jeroen.
John Vollbrecht Senior Network Engineer, Internet2 office 734 352 4960 cell 734 395 7890