[RK_2014_0924] Ethernet II v. S. 802.3, rk_2014_0924802.3

[RK_2014_0924] Ethernet II v. S. 802.3, rk_2014_0924802.3

I. Ethernet Frame Types: Provan's Definitive Answer

Novell Frame Type Designation: Ethernet_II
Common name: Ethernet
Layout:

    6 bytes       6 bytes       2 bytes         Up to 1500 bytes+-------------+-------------+-------------+-------------------------+| Destination |   Source    |    E-type   | Network Protocol Packet || MAC Address | MAC Address | (IPX: 8137) |                         |+-------------+-------------+-------------+-------------------------+

Comments:

Novell Frame Type Designation: Ethernet_802.3
Common name: "Raw" 802.3
Layout:

    6 bytes       6 bytes       2 bytes         Up to 1500 bytes+-------------+-------------+--------------+------------------------+| Destination |   Source    | Total packet |       IPX Packet       || MAC Address | MAC Address |    length    | first two bytes: FF,FF |+-------------+-------------+--------------+------------------------+

Comments:

 

Ii. Some examples of values in the type/length field:

0 - 1500 length field (IEEE 802.3 and/or 802.2)0x0800 IP(v4), Internet Protocol version 40x0806 ARP, Address Resolution Protocol0x8137 IPX, Internet Packet eXchange (Novell)0x86dd IPv6, Internet Protocol version 6

 

Iii. Ethernet VS 802.3

0. [wireshark wiki: Ethernet]

Http://wiki.wireshark.org/Ethernet

1. [wikipedia: Jumbo frame]

Http://en.wikipedia.org/wiki/Jumbo_frame

 

2. Ethernet Frame Types

Http://telecom.tbi.net/frmlan.html

3. EtherType variable assignments

Http://telecom.tbi.net/etype.html

4. Ethernet Frame Types: Provan's Definitive Answer

Http://www.ee.siue.edu /~ Bnoble/comp/networks/frametypes.html

5. Ethernet frame

Http://en.wikipedia.org/wiki/Ethernet_frame

6. Ethernet

Http://en.wikipedia.org/wiki/Ethernet

 

7.802.3

Http://en.wikipedia.org/wiki/IEEE_802.3

 

8. IEEE Std 802.3-2012, IEEE Standard for Ethernet

Http://standards.ieee.org/about/get/802/802.3.html

Http://standards.ieee.org/getieee802/download/802.3-2012.zip

 

4. The website of this article [the original article was published on]

Http://www.cnblogs.com/tom-and-jerry/p/3989524.html

 

[End]

Analyzes the meaning of the frame header, indicating that it cannot be understood.

Ethernet frame format

I. Development of Ethernet frame formats

1980 DEC, Intel, and Xerox have developed Ethernet I standards
1982 DEC, Intel, and Xerox have developed standards for ew.net II
1982 IEEE started to study the International Ethernet standard 802.3
Novell 1983 can't wait to develop a dedicated Ethernet frame format based on the original version of IEEE 802.3
1985 IEEE introduced the IEEE 802.3 specification. Later, in order to solve the compatibility problem between EthernetII and the 802.3 frame format, the compromise Ethernet SNAP format was introduced.

(The early Ethernet I has been completely replaced by other frame formats, so now Ethernet can only see the following several Ethernet frame formats. Currently, most network devices support these Ethernet frame formats, such: when setting the Ethernet interface, the cisco router can specify different Ethernet frame formats: arpa, sap, snap, novell-ether)

Ii. Various frame formats
The following describes the formats of frames.
1. Ethernet II
DIX Ethernet Alliance launched .... It consists of 6 bytes of destination MAC address, 6 bytes of source MAC address, and 2 bytes of Type domain (used to indicate the Data Type encapsulated in this Frame) the above is the Frame Header, followed by-bytes of data, and 4-byte Frame Verification
2. Novell Ethernet
The Frame header is different from the Ethernet. The type field in the EthernetII Frame header is changed to the length field, and the next two bytes are 0 xFFFF, which indicates that the Frame is a Frame of the Novell Ether type, because the above 0xFFFF station drops two bytes, the data domain is reduced to 44-1498 bytes, and the frame verification remains unchanged.
3. IEEE 802.3/802.2
The Frame Header of 802.3 is different from the Frame Header of Ethernet II, and the EthernetII type domain is changed to the length domain. The 802.2 protocol (LLC) is introduced to add an LLC header after the 802.3 frame header. The DSAP (Destination Service Access Point) 1 byte, SSAP (Source SAP ), one control domain-1 byte! SAP is the upper layer protocol used to mark frames.

4. Ethernet SNAP
The biggest difference between SNAP Frame and 802.3/802.2 Frame is that a 5-Bytes snap id is added. The first three bytes are usually the same as the first three Bytes of the source mac address! Sometimes it can be set to 0, and the last 2 bytes is the same as the type domain of Ethernet II...

3. How to differentiate different frame formats

How do network devices of the four frames in Ethernet be identified? How to distinguish EthernetII from three other formats of Frame
If the 2 bytes value of the Frame header following the source mac address is greater than 1500, the Frame is in EthernetII format.

Then compare the two adjacent bytes. If 0xFFFF is used, it is a Frame of the Novell Ether TYPE. If 0xAAAA is used, it is a Frame in the Ethernet SNAP format. If not, it is a Frame in the Ethernet 802.3/802.2 format.

Several Ethernet frame formats

I haven't figured out a basic problem for a long time-the Encapsulation Format of Ethernet. I recently checked the relevant documents and summarized them as follows;

First, let's explain that Ethernet and 802.3 are not the same thing, although we often mix these two... the remaining full text>

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