As usual Norm, you are absolutely dead-on!
I will try your suggestion below as I was "struggling" with exactly
the same issue ... how to draw on a "piece of paper"!
Cheers,
RR
From: Norman Finn
(nfinn) [mailto:nfinn@xxxxxxxxx]
Sent: Monday, March 28, 2016 2:08
PM
To:
STDS-802-11-TGAK@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-11-TGAK]
802.11 ARC teleconference announcement - March 30, 12:00 noon ET, 1 hour (Join
Me)
NOW I see where you’re
going with this, Richard!
Some 802.1 diagrams
use a diagonal line to place the bridge relay function adjacent to the MAC
layer, hence the “baggy pants” moniker for the diagrams. I’m guessing
that’s where you’re going with this. Without it, there is a bit of
confusion about whether the bridge (or DS) relay function is a peer of, or
below, the users of the stations’ MAC services.
I was tempted before
the last meeting to do that, myself, but didn’t think it was worth the effort.
If you want to give it a try, go ahead. But, because you only get
two legs on the “baggy pants”, I found it difficult to be 1) clear, 2)
accurate, and 3) hold the diagram down to 2 dimensions.
Another possibility is
to have a slide that shows this idea, and explains why it’s there, but we use
another convention in the rest of the diagrams. For instance, you could
put the relays right where they are now, and put a “T” with a dotted vertical
on the stations to elevate them above the relay functions, while keeping the
tops of the MACs all on one level.
Just a thought.
Good luck!
Thanks for taking the time to look over
the slide and comment ... I value and appreciate your input highly!
RR
I don’t know whether
I’ll be able to make the dial-in, but let me comment on the 11-16-0457
presentation.
The problem with the
picture on the last slide is not that it is wrong. It’s that it says
absolutely nothing, and therefore does not serve a purpose.
[RR>] Yes, you are right. What I posted was a
"work in progress" done "on the fly". The figure was
a last minute addition and not even close to being "complete",
however it was somewhat useful for the discussions at the time.
If that seems harsh,
[RR>] It's not harsh; it's CORRECT! :^)))
let me explain what
the purpose of the “complex” diagrams.
ISO defines a layering
model in which entities at one layer provide services to higher layers and make
use of services at lower layers. This enables one to model functions in a
way that makes it clear what happens when you connect them in various ways.
It is essential to understand that there are no “side doors”. You connect
with your peer by making use of a joint service (e.g. Two MACs talking down to
two PHYs linked by a wire). The ISO model is a consistent language.
You can feel free to draw boxes just anywhere, if you want to (e.g. off
the side of a MAC), but now you lose all meaning, because you’re operating
outside the language. A box on the side of a MAC has no semantics that
can be related to the other functions.
What the complex
diagrams show is exactly what connectivity you get in exactly what situations.
It points out why DSs that employ 802.1Q bridges (and many do!) work.
It points out exactly why the “one connection point to the bridged LAN”
rule is essential. It shows exactly where you have to put “magic” to avoid
silly packet flows caused by that rule. It does so in a language, like
mathematics, that is clear, precise, but not always trivial or obvious.
That is the price of accuracy. The “complex” diagrams show you
exactly where the issues are and are not, if you are worried about the
question, “Do these diagrams make my DS implementation non-conformant?”
(The answer is “NO!!”)
The suggested diagram
has the problem that, if I place a bridge on top,
[RR>] I would like to suggest that a bridge doesn't
"go on top", and I have new diagrams to show/explain why.
Furthermore, it is the placing of the bridge "on top" that in
some sense creates the problem. It doesn't belong there. To expand a bit,
bridges do NOT use services provided by the MAC, they are a service INSIDE THE
MAC sublayer. Putting a bridge on top of the MAC violates the ISO 7-layer
model. More to come ...
I have no idea whether
the packets will loop or not, or whether I will have connectivity or not,
because I don’t know what a side door on a MAC means.
[RR>] It's not really a "side-door"; its a
service in the MAC sublayer. The (.1Q) bridge functions will prevent
loops, provide connectivity, etc., because that's what they are designed to do.
THat's what I meant by "do the right thing".
(“It does the right
thing” is meaningless.) The “complex” diagrams tell me exactly what I
need to know. Replacing precision with ambiguity is not helpful.
[RR>] While that is certainly true, I hope that when I
finish the presentation, all ambiguity has disappeared and simple precision is
all that's left :^)))
Cheers,
RR
All,
This is notice that the
ARC SC will hold a teleconference on March 30, at 12pm (noon) ET, for 1 hour,
to continue review of a presentation on an alternate way to diagram 802.11
architectural concepts, especially APs, and by extension how TGak might be
viewed as fitting into the overall architecture.
The draft agenda and join.me meeting
information are below.
Mark
Draft agenda:
1. Call to order, patent policy, attendance
2. Review presentation on architectural descriptions – Dick Roy
(SRA): 11-16-0457-00-0arc-802-11ak-802-1ac-stas-aps-dses-and-convergence-functions.pptx
3. AOB
4. Adjourn
Note that teleconferences are subject to IEEE
policies and procedures, see:
–
IEEE
Patent Policy
–
Patent
FAQ
–
Letter of
Assurance Form
–
Affiliation
FAQ
–
Anti-Trust FAQ
–
Ethics
–
802 LMSC
P&P
–
802LMSC OM
–
802 WG P&P
–
IEEE802.11 WG OM
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