Hi John,

For, reference, we have updated the terminology spreadsheet here:

http://forge.gridforum.org/sf/go/doc15512?nav=1

I left out the cases that were OK.

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This is a link at a level. This seems a fine name. For NSI the question is if the link can carry links at a different level. I think so - I think there is a relation which says a link at one layer can support multiple links at a different layer. Examples would be multiple VLANS over ethernet or multiple VCGs over SONET, or multiple waves over a fiber.

This is definitely part of the model. As noted in later notes the concept of layer and level are close. I

This is good discussion. It would be good to have some goals for the two groups so that we can have standards that are in sync. I try to list a few inline below -- On May 11, 2009, at 2:30 PM, Martin Swany wrote: think for NSI we need a definition of what links over other links are called. Does the over refer to level or layer? What exactly is a level or layer. Some discussion of this has gone on informally that I know of, but noting written down. This may be the major concept to hopefully be define between us at Chapel Hill.

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<pastedGraphic.pdf> logical port (per layer) - G.805 calls this a connection point, NML and NMwg call it a port. In NSI we started discussion calling it a Port but switched to edge point to avoid the physical connotations of port. The groups should agree on this name or include an alias for different names if we can't agree.

I think that the NML has agreed to call this a port. Our naming was changed a while ago (due to ITU naming!) in perfSONAR and I believe the NDL group has agreed. Certainly any term carries connotations, but the pervasive opinion is that they are more similar than they are different and it is useful (for pathfinding) to use the same underlying term, but specialize it for different purposes.

I personally have no concern about what it is called as long as everyone agrees. However it is a group decision, so both groups need to agree. In my opinion since the G.805 doc calls it a point - I personally like having point rather than port in the name. This is a discussion also for Chapel Hill, but lower priority than the above.

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<pastedGraphic.pdf> concatenated series of links - Path in NML and NMwg, concatenated series of links in G.805. It seems to me that this should be a link not a path. I am not sure when some thing is a path rather than a link. I also think a concated series of links is a link (maybe it needs a name to become a link?)

In my mind, there is often a one-to-one relationship between paths and links and the only question as to which you use is whether you need to see the internals or not. I think this addresses and issue below as well.

This is confusing to me. What internals does a path see or not see vs a link? Is a path resourceless?

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<pastedGraphic.pdf> Network Layer (topology on a single layer) - This seems an important concept - topology on a layer. A couple parts of this that I think may need definition: 1) how to tie together administrative domains with topology - for example one administrative domain may know about a subset of what another administrative domain knows; and 2) How do layers interact - is one layer carried by or used by another?

<pastedGraphic.pdf> aggregated device -- called topology in NML. this might be a network in NSI, but I am not sure that fits well.

I don't know that there's agreement that an aggregated device is a topology, but it sounds like this isn't an issue

I don't think this is an issue unless someone wants to use it instead of topology

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<pastedGraphic.pdf> domain - this seems like a network in NSI terms. Certainly it has a lot of the same characteristics. But it does not have all the characteristics - see discussion on "what is missing" below

The easiest answer is that we can add characteristics and plan to do just that as the base elements are "subclassed" into specific uses.

But I do understand that there is a little gray-ness between Networks and Domains. My own take is basically this: Networks are addressing scoped, and Domains are administratively scoped. I take that largely from Internet terminology and I know there are counter- examples. So, the more complicated answer is that there are a number of different kinds of groups and we need to see which ones fit.

I think this is the other very high priority thing to agree on at Chapel Hill. NSI has the concept of a network which can be controlled by an NS agent. This network has a topology which to the outside world looks like a set of edgepoints (or ports). I am not sure what corresponds to in NML. Also, NSI has the concept of a link which has resource which may be an independent administrative domain from networks to which it connects. I am not sure how these all fit the definitions.

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What seems missing --

1) The description of adapatation in general: for example in a concatenated series of links, each concatenated link may be carried on a different sort of higer layer link. A VLAN might be carried on an Ethernet link (as a VLAN), on a SONET link as GFP encoded VLAN. In this case the underlying link with its coding is carried over different higher layer links with their coding.

I believe that this is a good example of where the Link/ Path dichotomy helps. If we need to know that details of of the different sorts of constituents, we need to access the path object, otherwise it's just a link. Also note that I don't really think we have any fixed notion of "higher" and "lower" layers now. I know that we did in perfSONAR but there were so many special cases of relationships (L2TP, q in q, ip in ip) that we pretty much gave up. So, I don't think there are any problems with representing what you're talking about above, so maybe we should try to look at specific examples?

I think we should look at examples. One such example is the one described briefly above. It might be interesting to include perfSONAR examples.

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2) The concept of connection oriented network: A NSI network is something that can create segments (aka links a lower layer) between edge points (aka ports). A network participates with other networks in a topology where the elements are networks that connected with links. In graph theory network would be node, and link an edge.

I think that a Link represents a network connection pretty well. Maybe the Path/Link discussion is convincing, but I should say that's more of the perfSONAR/DCN perspective and not that of NDL (necessarily -- I think it's close, but I won't speak for them.)

I am not sure what the Path/Link discussion is ---

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3) Names for the elements within a layer that are concatenated. NSI calls these segments for now. The NSI topology elements are links and networks. Each of these elements can provide segments and the segments can be concatenated to create a ete segment. I believe that segments and links at a level are identical concepts, so perhaps we can come up with an alias for how to describe NSI segments and ete concatenated segments.

Again, hopefully, the Path/Link concept describes this for the complicated case. (And a simple relation works when 4K VLAN links are carried over the same Link....)

I think examples and then a specific agreement on naming - perhaps aliasing - is needed

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I suggest that we might want to have a call to start discussions on this before OGF and to try to resolve issues at OGF. There is a NSI call every Wed at 9ET - we could have a joint call on Wed May 20 if that seems reasonable.

I can't make this slot (or would have to join late at the very least.)

best, martin

John Vollbrecht Senior Network Engineer, Internet2 office 734 352 4960 cell 734 395 7890