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Can anyone explain to me what is the difference between Ethernet, Ethernet-II and 802.3 Ethernet.

I referred to a lot of books, they are in high level language. Can anyone explain to me in a simple manner?

  • wireshark.org sample captures seems like a good place to figure it out – Mike Pennington Dec 3 '13 at 13:35
  • @MikePennington : Hi , I am not not taking regarding the packet format . I Just Want to know the theoritical explanation . – user2720323 Dec 3 '13 at 13:37
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    ...a few seconds of google yields useful links too, notably this home run "Ethernet II and IEEE 802.3". – Craig Constantine Dec 3 '13 at 14:30
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    Daniel has a great write up here explaining the differences in detail: lostintransit.se/2012/06/06/… – mellowd Dec 3 '13 at 16:08
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 8 '17 at 15:26
18

802.3 (which uses 802.2 LLC format) has a Length field in the same place that Ethernet II has a Type field.

  • IEEE 802.3 with 802.2 LLC (used by Spanning-Tree, ISIS) use the highlighted bytes for a Length field. 802.3 Upper-layer protocols are decoded via the 802.2 LLC Header / SNAP bytes. The SNAP bytes are used to decode protocols using traditional ethertype values; SNAP is only included when the 802.2 LLC DSAP / SSAP = 0xAAAA.

       +----+----+------+------+------+------+-----+
       | DA | SA | Len  | LLC  | SNAP | Data | FCS |
       +----+----+------+------+------+------+-----+
                 ^^^^^^^^
    
       DA      Destination MAC Address (6 bytes)
       SA      Source MAC Address      (6 bytes)
       Len     Length of Data field    (2 bytes: <= 0x05DC or 1500 decimal)  <---
       LLC     802.2 LLC Header        (3 bytes)
       SNAP                            (5 bytes)
       Data    Protocol Data           (46 - 1500 bytes)
       FCS     Frame Checksum          (4 bytes)
    
  • RFC 894 (commonly known as Ethernet II frames) use these bytes for Type. Upper-layer protocols are decoded via the Type field

       +----+----+------+------+-----+
       | DA | SA | Type | Data | FCS |
       +----+----+------+------+-----+
                 ^^^^^^^^
    
       DA      Destination MAC Address (6 bytes)
       SA      Source MAC Address      (6 bytes)
       Type    Protocol Type           (2 bytes: >= 0x0600 or 1536 decimal)  <---
       Data    Protocol Data           (46 - 1500 bytes)
       FCS     Frame Checksum          (4 bytes)
    

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