Re: Several questions about LLC...

On 7 16 , 11 17 , Rich Seifert <use...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
In article <1184570371.538436.163...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,

lander <lostlander....@xxxxxxxxx> wrote:
After reading the 802.2 std, I've got several questions:

1, what does DL-REPLY-UPDATE.request exactly do? Does it mean that if
I pass an DL-reply.indication to LLC user, the user will have to use
"DL-REPLY-UPDATE.request" to pass response to the peer LLC entity?

First of all, the DL-REPLY-UPDATE primitive is associated only with the
"Acknowledged Connectionless-Mode" service of LLC (LLC Type 3). This
service was created specifically for use with MAP (Manufacturing
Automation Protocol) and MAP-like systems, typically using 802.4 Token
Bus technology. None of these systems or services has seen much
practical use in the last 20 years. I know of no commercial system today
that employs LLC Acknowleged-Connectionless service today. Thus, the
question you ask is purely of academic interest.

That said, the concept behind DL-REPLY-UPDATE was that an LLC entity
could "pre-load" the response (i.e., the contents of the reply) to a
future acknowledgment request into the MAC entity so that the MAC could
respond in real-time, without having to pass the request up the stack
and have the reply come back down while the entire network was "held up"
waiting for the exchange. Of course, none of this is really necessary,
since LLC primitives are simply an abstract way of defining the layer
interactions; there is no requirement (indeed, it is usually foolish to
do so) to actually *implement* a device in the manner described by the
LLC primitives.

2, As for the substatus field:CCCCRRRR, there are several values of
CCCC or RRRR, some of the meanings are the same, some of the meanings
are not clearly addressed, is there any specific or detailed document
describing how to set CCCC or RRRR field in the response?

3, the variable v(RB) is used to set CCCC field for duplicate command,
and there is also one value named as "Temp err", if the "temp err"
disappears, and the duplicate command comes in, should the CCCC is the
same as the previous one (v(RB))? why?

These are both issues related to the use of LLC Type 3. The standard
itself is the only place where you will find these fields and variables
explained. If the explanation given there is insufficient, I don't know
where else you would look. Again, it doesn't matter, since no one uses
LLC-3 (to my knowledge).

--
Rich Seifert Networks and Communications Consulting
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The DSRC protocol stack uses type3 service.

Type3 is the compromise of type1&type2, is that right?

And, in the real world , type2 service is more preferred than type3?

How about type4? Is it widely deployed as type2?

.