Re: [DNA] L2 link and L3 link

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

Dear Bernard

Kindly find my in line comments

> > 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
> 
> The host can also detect a difference between Ethernet Switch 1 and
> Ethernet Switch 2, since it will receive packets from a different switch
> MAC address.  For example, the source address for 802.1X packets will be
> different, as could the contents of the EAP-Request/Identity packet (e.g.
> the nas-id field will be different).
> 
> > What I mean is that they are at the different BSS, which requires new association.
> 
> The notion of "association" is not unique to 802.11.  This is required for
> any layer 2 protocol that allows multiple networks to be resident on the
> same media.  This is because, unlike classic IEEE 802 media,
> receipt of packets is not sufficient to conclude that the sender wishes to
> "join" the network.  An explicit association step is required.
> 
> PPP over Ethernet supports the notion of association, as will IEEE
> 802.1af.

Thanks for your elaborate and enlightening comments. It seems there is more of 
link-layer technology than I know. I am glad to learn that, in Ethernet, there also 
is difference between point of attachment/ L2 link and (L3) link. 

I presented Ethernet model to illuminate the issue. Because it rather clouds it, 
we'd better keep away from the difference between Ethernet and 802.11. 
 
> > 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'
> 
> I agree that there is a difference between 'link' and 'point of
> attachment'.  While the 'point of attachment' may change, this does not
> imply that the 'link' changes.

I guess roughly 'point of attachment' is what I meant by L2 link. But I wonder 
whether it is a widely understood and used term. 

And it may not be convenient to use the expression like 'When a host attaches 
to a new point of attachment,'  or 'When a host makes new connection to 
a point of attachment,'.  
 
> > We may define a new term corresponding to AP, for example L2 link :-).
> 
> I'd suggest that we continue to use the term 'link' to refer to L3
> links.  Otherwise, when VLANs are implemented, we will find ourselves
> drowning in confusion.

I agree. 

And what about Point of Attachment/ L2 link?