Talk:Web Science/Part1: Foundations of the web/Ethernet/Ethernet header

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Corrections/notes on the video

The video uses a graphic based on a Wikipedia SVG. It appends the 8 bytes long "Preambel (sic)", which should correctly be spelled "Preamble". This comment also affects all videos reusing this graphic. --81.17.28.58 (discuss) 10:00, 23 October 2013 (UTC) Personally speaking, I dislike the phrase "very unique". Things can't be more or less unique. By design, MAC-addresses are unique (at least in theory). --31.7.58.226 (discuss) 10:13, 23 October 2013 (UTC) I find the explanation of EtherType still confusing, because it mentions two different functionalities (type like IP vs. length) that cannot be conveyed at the same type. Consequently, EtherType (is this the correct name rather than Ethernet Type?) is also not picked up in the conclusion of the video (and it is the only element that is not picked up again) Trivial issue: "corrupted data" rather than "corrupt data" --SteffenStaab (discuss • contribs) 10:22, 25 October 2013 (UTC) --SteffenStaab (discuss • contribs) 10:22, 25 October 2013 (UTC)

we will correct this in the next version of the videos. Thanks a lot --Renepick (discuss • contribs) 12:10, 23 October 2013 (UTC)

does this still have to be done? --Renepick (discuss • contribs) 22:42, 10 September 2014 (UTC)

thanks a lot for this feedback. I also realized that phrase "very unique" is kind of weird. If we get another audio track in the next version we will omit this. --Renepick (discuss • contribs) 12:10, 23 October 2013 (UTC)

my proposal is, not only to omit the phrase, but to stress that (any amount of) uniqueness exists only in theory, whereas in practice naming-collisions in a vendor's scope do occur, and should be accounted for. --Gluteus (discuss • contribs) 11:16, 24 October 2013 (UTC)

That is an excelent point. I have a friend who is network admin at w:CERN who actually had problems due to the fact of naming collisions within a vendor's scope. We decided to omit this fact. but you are totally right that it might be worth while including it into the next version --Renepick (discuss • contribs) 11:31, 24 October 2013 (UTC)

This is actually how the protocol is defined. The EtherType in wikipedia (spelled correctly) can be used to define either a type of the inner protocol or the length of the data frame. I didn't invent this --Renepick (discuss • contribs) 13:43, 25 October 2013 (UTC)

Preamble

I did not get how preamble synchronize the clock between tow systems? --141.26.69.70 (discuss) 21:45, 25 October 2016 (UTC)

Preamble Synchronization

The first thing that the preamble does is that it puts a sequence of 1s and 0s in the network. This is made to find out how long one bit should be. Can you provide a practical view/understanding of the below explanation? When we say that Ethernet is 'Asynchrnous', why is there even concept of 'time/clk' involved?

So when you have 64 bits put into preamble and you always do 1,0,1,0 and so on, you do it with your own clock and time. The recipient interface might have another clock running with another time scope. But it can figure out how long one time interval of 1 bit is coming from the sender. So different computers will receive data and synchronize their clock even though one of these computers might find out that this data is not for him. --106.51.10.150 (discuss) 11:15, 22 September 2017 (UTC)

Corrupted data - @ 4.01

why the source mac address can not be used to inform the source about the corrupted data ? --2003:C5:5F20:A156:DD11:2F6A:9CE1:2E58 (discuss) 15:22, 26 October 2018 (UTC)

Corrupted data @4.01

why the source mac address can not be used to inform about the corrupted data? --Msaha.kob (discuss • contribs) 15:28, 26 October 2018 (UTC)

Preamble's feature

It can figure out how long one time interval of 1 bit is but how? --Fayme007 (discuss • contribs) 08:03, 29 October 2018 (UTC)

General question on Ethernet

In the script it says "though one of these computers might find out that this data is not for him" but how it can be possible since ethernet provides protocol which already knows sender and recipient? --Fayme007 (discuss • contribs) 08:08, 29 October 2018 (UTC)

@Fayme007: Sender is known. Recipient is almost never known initially. Consider sending a request to the Internet. The computer knows the IP address of the default gateway. It does not know the gateway's MAC address. The network stack has to broadcast an ARP request for that IP address. All hosts on the broadcast network will receive that broadcast. Most will find it is not for them and ignore it. The default gateway will respond to the ARP request and provide its MAC address. See ARP for more information. -- Dave Braunschweig (discuss • contribs) 12:49, 29 October 2018 (UTC)