| George-
What you say is true. It is not guaranteed not to work. OTOH it should not be expected to work. Cat 3 is pretty bad stuff. In general, you can't buy it any more 'cause everybody's machinery is set up for Cat5e or better. If you buy "Cat3" the days it will very likely pass Cat5 specs. You just can't believe labels any more.
Having said that, it remains true: - BASE-T Autonegotiation does not test cable quality or sufficiency - BASE-T Autonegotiation uses event lower bandwidth than 10BASE-T
Geoff
Actually Geoff, it may or may not operate. Remember - link segment specs say that a phy must operate over a link segment that meets the specs, and the cable specs say a cable must meet certain specs. Neither says that the phy won't operate over worse or
even that the cable doesn't perform.
Cabling specs and link segment specs in phy clauses are sufficient conditions, not necessary.
Remember the demos over barbed wire? What category was that?
George A. Zimmerman, Ph.D.
CME Consulting, Inc.
Experts in PHYsical Layer Communications
310-920-3860
Natalie-
For whatever it is worth,
the traditional 802.3 BASE-T Auto-Negotiation does not do anything in the way of cable testing.
If you put 1000BASE-T transceivers at each end of a Category 3 link it will AutoNegotiate to 1000BASE-T successfully but will not operate
(solely because of the insufficient cabling).
Geoff
All,
my opinion is that „Auto-Neg“ always should cover on type of channel.
So all 1-pair solutions should autoneg (100M/1G/2.5G ?)
If e.g. the 10G solution uses a different media (2-pairs, coax, or any other choice different to 1-pair) autoneg to another media (1-pair) does not
make sense.
So the autoneg requirement should somehow reflect that if different media is choosen, autoneg is not needed.
Regards,
Stefan
Stefan Buntz
Mercedes-Benz Cars Development, Daimler AG
Group Research & Advanced Engineering
Safeguarding Hard & Software
HPC: U059 – Dep.: RD/FEQ
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All,
As we discuss auto-negotiation and multiple speeds, is it necessary for all of the speeds to use twisted pair to do this? If coax or twinax is chosen for 10 Gbps is it possible for this phy to operate
at and communicate with PHYs at lower speeds that use a form of twisted pair? If auto-negotiation is truly needed by some parties between these speeds we need to ensure that we don't select a cable type that makes this impossible.
It would be helpful if PHY vendors could provide contributions on whether this is possible and if end users could provide information on their needs for auto-negotiation.
Thanks,
Natalie Wienckowski
Colleagues
What I would like to see is some technical presentations on the impact
of HIGHLY ASSYMETRICAL data rates on:
- Relative implementation complexity (e.g. gate count, die size)
- Operational power dissipation
and (therefore presumably)lower relative cost.
It seems from the discussions that in this particular case,
we have high enough prospective volume and
enough cost sensitivity
and enough sensitivity to power dissipation
that this case is unusual enough in our history to be worth extra attention
In particular, the back channel requirements seem low enough that they
could be satisfied by what exists in other standards as an auxiliary
or management channel.
Geoff Thompson
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