How does ethernet work when disconnected and reconnected

On 10/9/2023 3:31 PM, Klaus Vestergaard Kragelund wrote:
> On 09-10-2023 01:45, Don Y wrote:
>> On 10/7/2023 10:26 AM, Don Y wrote:
>>>> But, can an ethernet connection work like this?
>>>
>>> The connection can work but the protocol may give you complaints.
>>> Especially if you are shutting off the i/f without regard to
>>> what is happening on the wire.
>>>
>>> And, as this inevitably alters throughput, any higher levels in the protocols
>>> that expect a particular level of performance may complain.  E.g., if you
>>> were expected to complete some transaction in a certain timeframe (or,
>>> with a certain maximum latency), you'd have to carefully reevaluate those
>>> constraints.
>>
>> By way of example, I transferred a few TB onto a new NAS I had
>> assembled.  When done, I checked the number of objects present
>> on the NAS vs. the original server -- identical.  BUT, was
>> surprised that the total storage usage was a fair bit LESS
>> than the originals!
>>
>> Looking at the logs, I noticed that the connection had
>> dropped -- many times (a bug in the Gbe NIC's driver on the
>> new NAS)!  As the protocol kept partial transfers, each dropped
>> connection still produced AN object... just not a COMPLETE
>> object.  (The Windows client that I was using as an intermediary
>> didn't throw any errors so it was only the NAS that knew something
>> had failed)
>>
> Sounds from your experiment that it might be possible to have some kind of 
> working connection, maybe with some added encapsulation to retransmit missed 
> packets

A lot will depend on how much control you can exert over the other
hosts in the network -- and, the level of performance that you
will consider acceptable.

If you are "off" when some host initiates a transaction, then
you obviously won't "see" those packets (assuming the switch
discards them because "you" don't currently exist -- something
really worth checking!).  So, you are then at the mercy of that
host's retransmission policy -- will it try to reinitiate
the transaction?  Or, will it just give up?  If it *does* make
another attempt, will it's retry algorithm's timing "fit"
into your "up" time?  Or, will Murphy reign supreme?

Remember, not all protocols build on TCP.