On Sun, 03 Jun 2018 18:27:26 -0400, J. Clarke
wrote:

On Sun, 03 Jun 2018 17:10:28 -0400, Clare Snyder
wrote:

On Sun, 03 Jun 2018 03:36:52 -0400, J. Clarke
wrote:

SNIPP
Then you don't get what noisy lines are all about, and what can create
them. Interference. Also just pulling too hard on Ethernet cabling can
stretch the wire messing things up.

So tells us of a documented case in which "pulling too hard on the
cable" or "interference" reduced the transfer rate for 1000BaseTX to 2
mb/sec. You're saying "can happen". So show us when it _did_ happen
or you're just spreading FUD.

If you pull too hard on a gigabit cable and damage the cable it will
NOT autonegotiate down.

Maybe it will, maybe it won't. Depends on the damage. I just
replaced a network cable that was consistently resulting in
autonegotiation from 1 gig to 100 meg and then sometimes failing the
100 meg. It had a lot more problems than "being pulled too hard"
though.

100/10 autonegotiates. Gigabit by definition does not.

I have seen it slow the network down SIGNIFICANTLY due to dropped
packets and retries - to well below a 2mb equivalent. Any one
conductor suffering damage in Gb ethernet WILL slow the network down.
Or kill it DEAD (at least the one segment)

Ok, so you have numbers to present that show this? Please show the
actual numbers.

Gigabit uses all 8 wires in a cat5 /6/7 cable for full duplex mode
10/100 does not - so with 10-100 you COULD damage 2 pairs without
affecting the ethernet.

A bad connection in ANY pair will affect data transmission on gigabit
ethernet.

I don't have numbers - just years of experience troubleshooting
network cabling.

A kinked Cat5E cable will fail the quality test for GB ethernet.
Running the cables parallel to a high current AC conductor will do the
same.

I have tried experiments in this regard and Fluke does not seem to be
able to detect the high current conductor.

It might just be a fluke???

All I know is we had a network speed issue and it was solved when we
moved the vertical network cable run about 18 inches away from the
electrical service sub-panel instead of running them behind the panel

It won't slow down the bit-rate - but it will definitely cause
deterioration in the service via lost packets and retries, which
translates to a slower EFFECTIVE bit-rate.
SNIPPPPP

How much slower, based on actual evidence?

Enough for the database program to fail out on data requests and
transfers. Off hand I'd say it cut the speed to about 1/10 when the AC
was on, about half speed at other times.

When talking 10BT /100BT, the troublesome auto-negotiation protocols
COULD downgrade a 100BT to 10BT, and often provided better throughput
on a reliable 10BT connection than on a flakey 100BT - but 10BT is "so
nineties"

So you say that the autonegotiation protocols for 100baseT can reduce
to 10 but somehow the autonegotiation protocols for gigabit can't
reduce to 100. Why would that be?
It is my understanding autonegotiation in gigabit ethernet is based
on each device reporting (signaling) it's capability (using the base
link code word) and the devices choosing the fastest mutually
supported speed/configuration - and then it either works or doesn't.
If both ends of the segment report giga capability, they ONLY attempt
connection at giga speeds and can NOT down-switch to 100, unlike the
somewhat problematic earlier 10/100 protocol that COULD (sometimes, if
the stars were properly aligned) switch two 100Mbs devices ro 10Mbs if
the cabling could not support 10Mbs without errors.

I MAY be wrong, but that is my understanding, and how it was described
to me back when gigabit ethernet came on the scene way back about
1998?





The base link code word (from WIKI)

Every fast link pulse burst transmits a word of 16 bits known as a
link code word. The first such word is known as a base link code word,
and its bits are used as follows:
0–4: selector field: it indicates which standard is used between IEEE
802.3 and IEEE 802.9;
5–12: technology ability field: this is a sequence of bits that encode
the possible modes of operations among the 100BASE-T and 10BASE-T
modes;
13: remote fault: this is set to one when the device is detecting a
link failure;
14: acknowledgement: the device sets this to one to indicate the
correct reception of the base link code word from the other party;
this is detected by the reception of at least three identical base
code words;
15: next page: this bit is used to indicate the intention of sending
other link code words after the base link code word;

The technology ability field is composed of eight bits. For IEEE
802.3, these are as follows:
bit 0: device supports 10BASE-T
bit 1: device supports 10BASE-T in full duplex
bit 2: device supports 100BASE-TX
bit 3: device supports 100BASE-TX in full duplex
bit 4: device supports 100BASE-T4
bit 5: pause
bit 6: asymmetric pause for full duplex
bit 7: reserved

The acknowledgement bit is used to signal the correct reception of the
base code word. This corresponds to having received three identical
copies of the base code word. Upon receiving these three identical
copies, the device sends a link code word with the acknowledge bit set
to one from six times to eight times.

The link code words are also called pages. The base link code word is
therefore called a base page. The next page bit of the base page is 1
when the device intends to send other pages, which can be used to
communicate other abilities. These additional pages are sent only if
both devices have sent base pages with a next page bit set to 1. The
additional pages are still encoded as link code words (using 17 clock
pulses and up to 16 bit pulses