bobkil@ibmpcug.co.uk (Bob Kilgore) (01/31/91)
Phil Blanchfield asks:
> Questions about 10BaseT concentrator.
First; There is NO such thing as a 'half repeater', all devices that
call themselves 802.3 repeaters are subject to conformance with the new
chapt. 9 as published in the 802.3 supplement. There is no provision
for a half-repeater in the chapter, and to the best of my knowledge
there has never been a half repeater. 802.3 defines a repeater set
which means just that, a set of 2 repeaters.
Second; What is a 10BaseT concentrator? Simply stated, a multi-port
repeater that is constructed to drive twisted pair wire. How many
10BaseT nodes may I have on a repeater (concentrator) port? One and
only one. If we make a small change to the definition of a 'Link-
segment', so it says it is a segment that connects two and only two
Medium Dependent Interfaces, then each 10BaseT connection is a link-
segment, and each original link-segment is still a link-segment.
Can anyone guess what a Medium Dependent Interface is?
Third; A possible point of confusion exists in the representation of a
multi-port repeater. How will this thing effect the timing of a network
and how many can I have. A multi-port counts as one repeater in all
possible cases. It can be visualized as a repeater with one input that
drives n outputs, where n is any possible number as determined by the
manufacturer. There are some esoteric arguments as to the practical
size of n, but 64 should be easily attainable. Confusion should be
avoided by stating that 'one and only one port can be a receiving port
at any point in time'. Or that' any port can be a receiving port as
long as no other port is receiving'.
fourth; reference my original posting as to how many repeaters you can
have in an 802.3 network. We still need to figure out how many standard
two port repeaters we can have in an 802.3 network. We can have the
same number if they are multi-port.
HINT 2; If anyone, not on the committee, has a copy of the 10BaseT
draft standard you will find the limiting factor in the first paragraph.
Good Luck;
BOB
bobkil@ibmpcug.co.uk
--
Automatic Disclaimer:
The views expressed above are those of the author alone and may not
represent the views of the IBM PC User Group.
-- pat@hprnd.rose.hp.com (Pat Thaler) (02/06/91)
> > > 802.3 defines a repeater set which means just that, a set of 2 repeaters. Actually, a repeater unit is the guts of the repeater, a repeater set is a repeater plus its accompanying MAUs (transceivers). In order to be able to be precise in writing specifications for repeaters, it was necessary to have terms which made it clear whether we were talking about the repeater function or the repeater plus MAUs. > > Second; What is a 10BaseT concentrator? Simply stated, a multi-port > repeater that is constructed to drive twisted pair wire. Or, you could say it was a repeater set with 10BASE-T MAUs internal to it. > Confusion should be > avoided by stating that 'one and only one port can be a receiving port > at any point in time'. Or that' any port can be a receiving port as > long as no other port is receiving'. Bob, you've gotten me confused now. What confusion were you trying to avoid? There are times when two or more ports receive simultaneously; that's called a collision. > fourth; reference my original posting as to how many repeaters you can > have in an 802.3 network. We still need to figure out how many standard > two port repeaters we can have in an 802.3 network. We can have the > same number if they are multi-port. > > HINT 2; If anyone, not on the committee, has a copy of the 10BaseT > draft standard you will find the limiting factor in the first paragraph. Bob, are you implying that those on the committee are incapable of reading the first paragraph or only that we don't get the prize for answering the question? Anyway, I spoiled the contest; I posted the answer in the earlier string before I read this. (BTW, I have a copy of the IEEE 802.3i, the _real_ 10BASE-T standard, published and everything. Available now from IEEE.) Pat Thaler