All –
Let me clarify some things that seem to have gotten lost, or perhaps mis-stated.
The compatibility criterion in clause 1.1.3.2 is specified for the physical media signals. Regardless of the connector used, the signals at the interface plane meet the criteria specified in the draft (PMA electricals are specified at
that interface plane) and link segment meets the transmission parameters from the interface plane to the interface plane at the link partner.
IEEE Std 802.3-2018 contains PHYs with minimal description or requirements on the specifics on the mechanical connector, which leads me to the understanding that calling out a specific mechanical connector is not the requirement. However,
electrical specification of the signal parameters at the interface point is provided, at least for the examples I have looked at. 802.3cg follows this practice, whether there is one IEC mechanical connector specification called out with a ‘shall’, two with
a ‘may’, or none at all.
The electrical performance of the MDI, as an interface, is specified, uniquely, in the 802.3cg draft, and has been for some time, as well as specific statements about the mechanical interface pins, similar to those found in IEEE Std 802.3-2018
clause 96 and elsewhere.
Mr. Kim, as a champion of 802.3bw 100BASE-T1, should be aware of this, as the resulting clause 96 specifies an MDI, but not a specific MDI connector.
96.8.1 offers no more on the mechanicals than the number of pins that are used – not even whether the connector only has that number of pins – but 96.8.2 specifies the electrical characteristics of the MDI at the interface plane, which
is what is needed for compatibility and testing.
I will stay out of the debate about the desirability to have a single connector specified. However, I would note that the balance of utility vs. pain for requiring a single connector is generally associated with how dominant a singular
application environment is. The expansion of Ethernet beyond the IT space has brought with it many different operational environments. The automotive world and the industrial world both use application-specific connectors, often for good reasons. Even when
using existing BASE-T ethernet, they may not be using the specified RJ-45 connector, but still use the MDI electrical specifications, and may test with an adapter to RJ-45.
-george
From: Geoff Thompson <thompson@xxxxxxxx>
Sent: Wednesday, August 28, 2019 11:10 AM
To: STDS-802-3-10SPE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_10SPE] [EXTERNAL] Re: [802.3_10SPE] Proposed response to MDI connector comment r02-14
Yong-
I have not missed your point.
I think my point is being missed WRT to THE MDI.
It's not a matter of how many connector test head you are using.
Hypothetically, what would you do if your test fails with one connector head but passes with another connector head on what seems to be equivalent units (or the same unit with different connector).
Perhaps -- later -- someone could explain away some parasitic XYZ (crosstalk, capacitance, etc whatever) or previously not known factors.
Having what we have had in 802.3 -- THE MDI spec -- helps to avoid issues while increasing the probably of interoperability that for which we do standards.
Yong Kim, affiliation: NIO
Theo-
Thanks for your input and experience.
Anecdotally, it is obvious that you never worked for Bud Blitz as I did.
He was the tool Czar at the leasing company that I worked for many years ago.
Designing tools was part of my job.
Bud's position was that the tools suitcase was already too heavy,
so you didn't get to add a tool unless you took one out.
His "guidance" (far too soft a word) drives my thinking here.
All great rants. Thank you.
Speaking as one who has had the good fortune to produce more than a few portable field testers, I find agreement with at least one point. A single test interface is always preferable.
However, when multiple connection interfaces present themselves, (and they always do), there are numerous techniques to offer users an efficient and cost effective means to adapt. So far, at least in my 20+ years of experience this has
not presented a barrier to broad market adoption.
I would like to add one comment in particular that you didn't cover.
That is test equipment, in particular field test equipment, even more so portable field test equipment.
Field test equipment is built in far, far smaller quantity than DTE ports.
Therefore, having a single port type (i.e. single MDI connector type) has a far larger impact on field test equipment development cost, device cost, device portability and of course device broad applicability in the field. Cheap, light,
portable test equipment is a key element in broad market adoption.
My addition to your excellent points.
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