RE: [EFM] Half-duplex - definition of a repeater
General question:
Is the 802.3 definition of a repeater explicitly limited to half duplex
only?
I am only asking this here for the sake of expediency. I could go through
the CDROM but that would take me a day and I still wouldn't be sure of the
negative answer.
I guess there is a supplementary question that members of this group may
ask, which is 'why would anybody want a full duplex repeater?'. The answer
being 'as a full duplex media converter, with management'. If there isn't a
definition for this within 802.3 then would anybody be interested in
supporting a proposal to create a standard definition for one?
Please respond to this directly rather than busy the reflector.
Thanks
Bob
> -----Original Message-----
> From: owner-stds-802-3-efm@majordomo.ieee.org
> [mailto:owner-stds-802-3-efm@majordomo.ieee.org]On Behalf Of Rich
> Seifert
> Sent: 10 December 2001 17:25
> To: Behrooz Rezvani; 'Arthur Marris'; 'Shimon Muller';
> stds-802-3-efm@ieee.org
> Subject: RE: [EFM] Half-duplex deferral for MAC-PHY rate matching and
> comp atibility with existing silicon
>
>
>
> At 7:17 AM -0800 12/10/01, Behrooz Rezvani wrote:
> >Arthur,
> >
> >As I mentioned in our conference call we need to support data
> rate greater
> >than 100 Mbps in total. As I have been listening to you, Rich
> and Shimon, I
> >gather that there is a way to operate the MAC such that we can exceed the
> >half duplex rate.
>
> Operating at data rates in excess of 50 Mb/s (full duplex) would be
> problematic with the system being proposed so far. Since it is
> predicated on a single, 100 Mb/s MAC operating in half-duplex mode,
> the combined transmit+receive rate cannot exceed 100 Mb/s; this is
> the equivalent of a 50 Mb/s symmetrical full-duplex PHY.
>
> In order to operate at greater data rates, one would need to use a
> Gigabit MAC operating in half-duplex mode. Such MACs are relatively
> rare; indeed, even if they exist, the use of half-duplex GbE is more
> theoretical than practical--there are no GbE repeaters in commercial
> use. It is not even clear that such MACs work properly in half-duplex
> mode.
>
> In addition, it is not possible to aggregate multiple 100 Mb/s MACs
> when operating in half-duplex mode. The current Link Aggregation
> standard restricts aggregation to full-duplex links only.
>
> >Note that VDSL PHY is full duplex system, and it can transmit and receive
> >independently.
> >
>
> I suspect that EFM will want to operate over a variety of PHY types
> and speeds. Rather than trying to cobble all of these systems to some
> pre-existing MAC chips (which I agree may provide some short-term
> benefit), perhaps it would be wiser in the long run to define a
> full-duplex MAC with a variable (quasi-static) data rate.
> --
>
> --
> Rich Seifert Networks and Communications Consulting
> rich@xxxxxxxxxxxxxxx 21885 Bear Creek Way
> (408) 395-5700 Los Gatos, CA 95033
> (408) 395-1966 FAX