Re: [DNA] L2 link and L3 link

[JinHyeock Choi <athene@sait.samsung.co.kr>]

Bernard

Kindly find my in line comments. 

> > But if 802.11 APs and an Ethernet segment are bridged to form a link, it's
> > more complex. Assume there are two APs and a router on an Ethernet
> > segment as below.
> >
> >                                  +----+
> >                                  | AR |
> >                                  +----+
> >                                    |
> >                              +-----+--------+
> >                              |                       |
> >                           +----+         +----+
> >                           |AP 1|         |AP 2|
> >                           +----+         +----+
> >
> >                           +----+         +----+
> >                           | H 1|         |H 2 |
> >                           +----+         +----+
> >
> > Each AP forms a different BSS. And if a host moves from AP1 to AP2, it will
> > detect distinct link-layer change.
> 
> This case is not really different from the Ethernet case.  "Link down" and
> "Link up" events are observed, along with L2 authentication.

Let me be more precise. A host will detect the distinct difference between AP1 and AP2. 
It will receive a different BSS ID and observe it has attached to a different link-layer 
medium (AP). 

Roughly saying, it will notice Current Link/ Current AP Down and New Link/ New AP Up 
 
> > Also assume host 1 is attached to AP1 and host 2 is attached to AP2. I think
> > it's reasonable to say that they are at the different L2 link. But they are at the
> > same (L3) link.
> 
> Both hosts are within the same broadcast domain, so I'm not clear why you
> say that the L2 link is different.  Or do you mean that the "point of

O.K. the term 'L2 link' may not be proper. (Anyway that's one of reason why I 
raise this issue.  :-)) 

What I mean is that they are at the different BSS, which requires new association. 
In pure link-layer point of view, they are attached to the different entity (L2 link). 

RFC 2461 says 'link' is the layer immediately below IP. Hence I see more than 
one occasion (myself included. :-)) that people write AP change with the expression
'link change', though they are independent.  
 
> attachment" is different?  If so, then both cases exhibit a change in the
> point of attachment.
> 
> > We'd better clarify this lest there should be unnecessary confusion and arguments.
> 
> I'd suggest that the best way to eliminate confusion and unnecessary
> arguments is to use existing, standard terminology.  Creating new
> definitions of words like "link" or "subnet" will not help.

I agree to keep the term 'link' as it is. It will be more trouble to alter 
an entrenched term. 

But we'd better make it clear that, in 802.11, 
1) link and AP are different. 
2) An 'AP change' should not be automatically termed as a 'link change'  

And It would be nice if, in generic terms, we can describe the AP change without 
implying link change. 

We may define a new term corresponding to AP, for example L2 link :-).