Re: [Supa] Network Topology Data Model and Network Configration Data Model

[Juergen Schoenwaelder <[e-mail]>]

On Tue, Nov 11, 2014 at 09:21:01PM +0000, Wunan (Eric) wrote:
> Hi Juergen,
> 
> Reply in line.
> 
> Regards
> Eric
> 
> ________________________________________
> 发件人: Juergen Schoenwaelder [[e-mail]]
> 发送时间: 2014年11月12日 4:15
> 收件人: Wunan (Eric)
> 抄送: [e-mail]; Tina TSOU
> 主题: Re: [Supa] Network Topology Data Model and Network Configration Data Model
> 
> On Tue, Nov 11, 2014 at 08:04:33PM +0000, Wunan (Eric) wrote:
> >
> >
> > In the IP world, we usually talk about nodes, links, and interfaces.
> > And interfaces have been generalized to cover multiple layers. Is
> > there a specific reason why you prefer the term 'TerminationPoint'?
> > How is a 'TerminationPoint' different from an interface (and what
> > is the relationship between them)?
> >
> > [Eric]: As the draft said, network topology DM is supposed to be defined in a hierachy manner.
> >
> > When "IP world" is the concern, we are acutally talking about the topology DM for IP.
> >
> > You are right that people are more familar with "interface", I am.
> >
> > Actually in the IP Topology DM, "TerminationPoint" is interface.
> >
> > Per my understanding, this word may be prefered because network topology is not only focusing on IP.
> >
> > As you know some protocols don't have to depend on "interface", they got their own vacabulary.
> >
> > For example, IS-IS was using "circuit" and VLAN got "port".
> >
> > When speaking "interface", i feel it will be more proper when CLI is used.
> 
> A VLAN port is just another interface. See the IF-MIB or the
> ietf-interfaces YANG model or the IANA interface registry. If a
> TerminationPoint is just a different name for 'interface', then I
> clearly prefer to stick to terms we are all familiar with.
> 
> [Eric]: I think VLAN port's definition use IF-MIB's defined type, but port is not the interface directly in VLAN MIB.
> 
> I think this is what you are talking about:
> 
> 
> 
>    Dot1dBasePortEntry ::=
>        SEQUENCE {
>            dot1dBasePort
>                Integer32,
>            dot1dBasePortIfIndex
>                InterfaceIndex,                               -----------------interface
>            dot1dBasePortCircuit
>                OBJECT IDENTIFIER,
>            dot1dBasePortDelayExceededDiscards
>                Counter32,
>            dot1dBasePortMtuExceededDiscards
>                Counter32
>        }

This proves my point. A bridge port maps to an interface since an
interface is the generic way to refer to an an 'endpoint' of a 'link'.

So again, what is the difference between a TerminationPoint and an
interface?

> > What is the difference of this topology data model from other
> > proposals on the table, such as draft-clemm-i2rs-yang-network-topo-01
> > and draft-hares-i2rs-info-model-service-topo-01 (there there might
> > be more)?
> >
> > [Eric]: I would say both of them are talking about topology data model.
> >
> > One difference may be the position they are used in the architecture.
> >
> > For draft-hares-i2rs-info-model-service-topo-01,
> >
> > I think it is the topology for service, another layer in the hierarchy.
> 
> I was hoping for a more technical answer. Why do we need N topology
> data models? If I look at the YANG snippets, I do not see what makes
> them specific to a 'position in the architecture'.
> 
> [Eric]: Of course it is not because the "position" only. Actually not at all.
> 
> For the I2RS model you mentioned, i think it mainly focus on the IP/IGP topology.
> 
> While the conception i got from the draft-contreras-supa-yang-network-topo-01,
> 
> it tried to define one hierarchy for topology.
> 
> Plus it contains some extXXX definition in the model, which don't catched in I2RS topo.
> 
> I think it may have some consideration behind this. Maybe the authors can talk more about this.
> 
> Based on that currently I won't suggest to reuse I2RS YANG model directly in the SUPA scenario.

Hm. I am still puzzled. I do not know what extlinks are since there
are only empty description clauses. It is not clear why this is not
just a property of a link or why it is a good idea to replicate lots
leafs. While there are differences (no wonder) in the YANG fragments,
I like to know more precisely why topology model A is limited to layer
B and why model C is limited to layer D and why model E is 'more'
generic than model A or B.

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1, 28759 Bremen, Germany
Fax:   [phone]         <http://www.jacobs-university.de/>