Ethernet Frame Format Explanation

This is how an Ethernet frame is formatted and used.
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ALSO, when I mention in this video that the "Pre-amble" comes "before the actual frame" that DOES NOT mean the Pre-amble is not considered part of the frame. The Pre-amble IS considered part of the frame. When you take a quiz or certification test, be prepared to know the Pre-amble and know that it's also considered part of the frame (from most testing stand-points). See this related video for Preamble: • Ethernet Frame Preamble
Ethernet and Switching CCNA , CCIP, MCPIT, MCSA.MCSA ,Networking

[@Dusta_Rhymes]

It's always the lesser-viewed/known videos that have the most basic, simple and plain explanation of these types of things without making things overly complex, or glazing over important concepts. Stellar video.

[@AceNetworker]

Hey, thank you for that! And thanks for watching. That's my entire goal with this channel - to simplify it to the basics so anyone can "get" it 😎

[@nopehhhhh]

I agree with you 100%

[@adekunlestephentemitope4023]

I agree with you 100 percent. Short youtube videos has helped me understand some easy things made complex by my tutor.

[@lividlareb]

damn uploaded 6 years ago and im learning this today, you sure made a huge contribution, thanks bro

[@AceNetworker]

Thanks for watching! I'm just (personally) elated this still has validity in today's newer technology, and that Ethernet still uses these basics at its core that I can leave this video up and it still has significant relevance in networking. But again Thank you for watching! And if you'd like anything specific in the realm of networking, let me know on here 😎

[@YouSmokeChed]

Bro this was a fantastic explanation I was reading my CCNA /E stuff that they charge $50 for and u explained it so much better

[@AceNetworker]

Thank You! Appreciate that! Thanks for watching!

[@robsonnvula9285]

How this channel has this number of subscriber is beyond me.

[@adrianavargova]

Thank you, good job! Please, include 1. subtitles 2. graphics, because it is harder to understand for us, non-native English speakers and persons who are learning only. E.g. if you explain CRC, it would be fine to include examples and images.

[@AceNetworker]

Hey, thank you! I've already had a couple other requests for explanations of CRC, so I may make a specific video just for that. Appreciate your feedback!

[@7ma3loma]

Thank you, it was a very clear lesson and the Arabic translation was very clear and very useful - Your dear follower from Algeria😍🥰

[@tanvirahmed4710]

its disappointing u have only 113 subs...u shud hv more

[@SixAstron]

Exceptional structured video explanatio n. Just stumbled on this and I'm very glad I did. Tremendous help. Thank you!

[@AceNetworker]

You're very welcome! Thanks for watching!

[@arthurbenavides465]

great explanation thank you

[@AceNetworker]

You are welcome!

[@arianneedstostudy5506]

This was a wonderful explanation!

[@AceNetworker]

Thank you! And thank you for watching! Hope this simplifies it so anybody can understand, regardless of their experience, expertise or knowledge of networking

[@alihosseinipour5537]

Thanks a lot! Much clearer than my professor's lectures!!

[@AceNetworker]

You are welcome!

[@derroz3157]

@alihosseinipour5537

[@BaDman20051]

i have a networking and communication exam in 2 days..and how doi find this channel today

[@El_Narix]

Note : Preamble is 7 Bytes long (56bits) (64Bits if you include the SFD which is 8 bits long) is a series of alternating 1's and 0's. (10101010 * 7) And it allows devices to synchronize their receiver clocks to make sure they are ready to receive the frame and the data inside. The SFD or Start Frame Delimiter. Is 1 Byte (8bits) It marks the end of the preamble and the beginning of the rest of the frame.

[@AceNetworker]

@@El_Narix yes, I have an entirely different video talking about the preamble if anyone wants to know more about it.

[@iliasomerzai9800]

Thanks body! it helped me a lot to realize the concept of ethernet frame formation. I truly appreciate your hard work.

[@s.s.scriptties]

U mean buddy... People that correct this kinda stuff are dicks but I'm still gonna do it jus for the sake of bein a dick ( after this saying "Lmao" would be the perfect thing so people wouldn't feel hatred coming from the comment but I ain't gonna put it in jus to be even more of a dick ).

[@wightclaudia]

Wow im doing the google IT program and your explanation crushes theirs. So basically the FCS is like a final receiving invoice in a warehouse where the person in receiving checks to see if what they received matches what was written on the invoice by the people across the way at shipping? So Shipping says its 10 units, receiving checks and sees that it says 10 units but they only received 9 and that is where the determination that corruption has occured takes place?

[@AceNetworker]

Exactly!

[@ashokantony694]

You haven't covered the Start of Frame Delimiter . Please include it. Thanks

[@DONTLAUGH]

he explained the preamble and the SFD as one part, which is why he said its 64 bits ending with "11".

[@James_Knott]

The preamble and SFD, as described here only applies at 10 Mb. With 100 Mb and above, a different coding method is used, which eliminates the need for the preamble.

[@dunner079]

Good explanation but it would be great if there were subtitles. Thumbs up.

[@MustafaMzr]

a life saving video , thanks papa

[@fedisalhi6320]

Good explanation, thank you :)

[@max_snowtr]

Thanks man, helped me a lot

[@AceNetworker]

You are welcome! Thanks for watching

[@malikamirshabazz7032]

Thank you for your video! It really helped allot.

[@AceNetworker]

Glad it helped!

[@himmyneutron5769]

Great explanation 👍👍👍

[@yassineesspg]

Very good explanation, thanks

[@derroz3157]

I got an error called the system cant receive the entropical input from the sending system derrived from BlackHole

[@ianokay]

The pieces (frames) are like, way too small though in the perspective of modern computing (5kb), for the dialog about being useful for "only having to retransmit a piece and not the whole file"

[@logio7663]

Thanks, waiting for more :D

[@jackojagan8600]

Sir, How does the sender know if a frame is received by the receiver as a corrupted frame / frame dropped in transit to re-transmit the frame. Is there a acknowledgement sent by the receiver for each frame received correctly. Also how does the receiver knows the frames are received in correct order. Because sequence number comes only in layer 4 correct me if i am wrong.

[@AceNetworker]

Hey, thank you for the feedback and the question. Essentially, the Transport Layer is what confirms if all packets (and the frames they were transported in) arrived correctly to the receiving device/computer. If a frame is corrupted and dropped by the receiver, and TCP is being used, there will be no confirmation that the packet information IN that frame was ever received, so the sender will have to resend. I'll try to make a video explaining this in more detail shortly, but hope that helps.

[@jackojagan8600]

@@AceNetworker Thank you very much for the quick response

[@dietwaffles5907]

Start frame delimiter?

[@압둘하미드이드리스]

can I get this ppt slide sir?

[@boolve]

Is this FCS include first three part of the frame including SRC Mac destination Mac and type or just the data part and also FCS part?

[@AceNetworker]

So, this is a long explanation, but here goes... The IEEE 802.3 standard that defines the basic Ethernet framing defines the FCS field in Section 3.2.9 as follows: A cyclic redundancy check (CRC) is used by the transmit and receive algorithms to generate a CRC value for the FCS field. The FCS field contains a 4-octet (32-bit) CRC value. This value is computed as a function of the contents of the protected fields of the MAC frame: the Destination Address, Source Address, Length/ Type field, MAC Client Data, and Pad (that is, all fields except FCS). So specifically the Preamble and Start-of-Frame Delimiter are not covered by the FCS field. This is logical, considering the fact that these fields were used in 10Mbps Ethernet versions to provide synchronization function between the sender and receiver, and thus a (varying) couple of starting bits from the Preamble could have been lost or incorrectly recovered. That did not invalidate the whole frame, however. (Hope that helps clarify it somewhat.) Thank you for watching!

[@ironmanlifts]

Thanks

[@usamafazal3661]

@Ace Networker there is series of 56 bits in preamble, correct me if i am wrong

[@AceNetworker]

Correct! Thank you for pointing that out. 56 bits followed by the 8 bit SFD

[@AceNetworker]

The SFD at the end of the preamble warns when “real” data is about to start since the receiver may lose bits of the preamble while syncing the receive clock.

[@usamafazal3661]

@@AceNetworker thanks sir you cleared me confusion

[@olafgunther9401]

10/10

[@AceNetworker]

Thank you! And thanks for watching!

[@nicksmith3026]

Is a NIC the same thing as TCP/IP Protocol or is it more the general term for any card (network interface card) that uses the 7 layer OSI model

[@AceNetworker]

The NIC is the actual network interface card (NIC) that connects to either an ethernet cable or coaxial or other cable. The NIC can also be a wireless NIC with an antenna that connects to a wireless Access Point (AP). TCP/IP defines a set of standardized rules that allow computers to communicate on a network such as the internet. (Hope that helps clarify a bit)

[@nicksmith3026]

@@AceNetworker Yes it does thank you very much and what a quick response! Thanks so much for the videos they are incredibly useful and the information is all communicated in a way that is easy to understand and retain. Best of luck with the channel! : )

[@jaydenritchie1992]

i have a question, if higher level tcp for example layer 7 realises a frame has been dropped how would it do this over a layer 2 gpon lan? also is the preamble like a syn syn ack?

[@James_Knott]

That depends. With TCP, it determines a packet is missing and there is a mechanism where the missing data will be retransmitted. With UDP, it's up to the application to determine if a packet is missing and what to do about it.

[@jaydenritchie1992]

@@James_Knott cheers

[@wally19]

NICs are L1 but works at L2 right? I'm confused now...

[@AceNetworker]

The NIC (the physical NIC, the hardware) is considered Layer 1 (Physical Layer). The other Layers are all assembled or unassembled on the NIC circuitry and on the NIC's microchip. Hope that clears it up a little bit.

[@NaniS-w2n]

❤ thanks

[@Bozzigmupp]

What are frames. How do I learn all these basic fundamentals, because I can't understand these "simple" videos

[@AceNetworker]

@Bozzigmupp Frames are the structure for 1's and 0's sent at Layer 2 on a computer network. They are how ethernet networks communicate data across the network. Think of a frame like a conversation between 2 humans: One says "Hi, how are you today?" and the other person responds with "Great! How are you?" Those intro phrases are like a frame for a conversation to begin

[@guillecobo_]

Great video.

[@AceNetworker]

Thanks for the visit

[@sudokoder59]

thanks for the video! sorry if this is annoying but in some other videos i saw when the preamble ends in '11' then its an indication that its an ethernet 802.3 frame which means that the 'type' field is actually a 'length' field. just wondering if thats just a generalization or if all frames preceded by a preamble ending in '11' have to be 802.3? im trying (and failing) to find clarification on google so figured id ask in the comments.

[@James_Knott]

The preamble is only used at 10 Mb. As for 802.3, the only difference is that last bit is actually defined. Nothing more. The value of the Ethertype/length field is what is used to determine whether 802.3 or DIX ll. If it's 1500 or less, it's 802.3. If 1536 or more, it's DIX ll. If you want to see what the original, pre 802.3 DIX looked like, you can search on "ethernet blue book" and download the PDF from Gordon Bell. DIX ll came in with 802.3, with very minor changes from the original DIX, the most significant being the Type field became Ethertype/length.

[@ProfessorProkopski]

Is FCS calculated for preamble and frame (destMac, sourceMac, type, data) or only for frame?

[@AceNetworker]

So, this is a long explanation, but here goes... The IEEE 802.3 standard that defines the basic Ethernet framing defines the FCS field in Section 3.2.9 as follows: A cyclic redundancy check (CRC) is used by the transmit and receive algorithms to generate a CRC value for the FCS field. The FCS field contains a 4-octet (32-bit) CRC value. This value is computed as a function of the contents of the protected fields of the MAC frame: the Destination Address, Source Address, Length/ Type field, MAC Client Data, and Pad (that is, all fields except FCS). So specifically the Preamble and Start-of-Frame Delimiter are not covered by the FCS field. This is logical, considering the fact that these fields were used in 10Mbps Ethernet versions to provide synchronization function between the sender and receiver, and thus a (varying) couple of starting bits from the Preamble could have been lost or incorrectly recovered. That did not invalidate the whole frame, however. (Hope that helps clarify it somewhat.) Thank you for watching!

[@ProfessorProkopski]

@@AceNetworker thanks!

[@James_Knott]

The preamble is not included in the FCS. Also, the preamble is used only at 10 Mb. A different coding method is used at 100 Mb and faster that eliminates the need for the preamble.

[@PratikPati]

Now all modern communication protocols use CRC check. E.g CAN, CAN FD.. etc

[@AceNetworker]

Yes! Thank you! That's a very good point. I'm glad you pointed that out. CRC seems to have proven itself so well that it's been implemented in multiple other communication protocols and systems.

[@PratikPati]

@@AceNetworker Yes, I am working with CAN now a days, CRC is a failsafe, it is saving life. Every embedded engineer should right their own logic of CRC to improve the logic and to understand CRC better. The video is very informative and cool, thanks.

[@exceltutorial2714]

forgot to put the SFD after the Preamble....anyway, great explanation. student here.

[@AceNetworker]

Yeah, just trying to keep things simple and un-complicated. I talk about it in this separate video on the Preamble: kzbin.info/www/bejne/gJuTeXWdjKl2fsU

[@anah7249]

thank you

[@AceNetworker]

You're absolutely welcome! Hope this helped. And thanks for watching!

[@NoDestenyMV]

This is super.

[@Sultan-xd6zg]

Nice video

[@vijaygubbala6137]

Fantastic sir

[@AceNetworker]

Thank you!

[@derroz3157]

Goog explination lot better than indian peeps

[@zhir6465]

Thanks