![ethernet mac address format ethernet mac address format](https://webeduclick.com/wp-content/uploads/2020/03/IEEE-802.3-MAC-Frame-Format.jpg)
Hex 'C8' - HPR (High Performance Routing) Hex 'AA' - SNAP (Sub-Network Access Protocol) Hex '04' - IBM SNA (Systems Network Architecture) The DSAP/SSAP provide information on what network protocol is embedded within the data field. IEEE 802.2 is not part of the definition of IEEE 802.3 however, it is always bound together with an IEEE 802.3 header.Ī 1-byte Destination Service Access Point (DSAP)Ī 1-byte Source Service Access Point (SSAP) If the field is greater than '05DC', the frame is an EtherType field and is an Ethernet Version 2 frame. If the field is less than '05DC', it represents a length field, and the frame is an IEEE 802.3 Ethernet frame. NIC cards look at this field to determine which Ethernet standard is being used. This corresponds to 1500 bytes which is the maximum frame size for Ethernet. The length field in IEEE 802.3 Ethernet frames is always less than hex '05DC'. Combined, these fields are no different than the 8-byte preamble used by Ethernet Version 2.įollowing the address fields, IEEE 802.3 Ethernet uses a 2-byte "length" field that includes the IEEE 802.2 Logical Link Control (LLC) bytes and the data bytes. The frame begins with a 1-byte preamble followed by a 7-byte start frame delimiter. The receiving system then passes the frame up to higher levels (provided the FCS check is accurate) not knowing that the data has been corrupted.Ī typical Ethernet Version 2 frame looks like this: However, if, along the path of transmission, other network equipment strips the FCS and regenerates it, it is still possible that an error has occurred but that the regenerated FCS is accurate, based on the corrupted data. If they match, the frame is assumed to have been received with no errors. The receiving system generates the same CRC and compares that value to the value in the FCS. This is an algorithm that is generated over the address, type, and data fields based on the number of 1s and 0s (bits) in each. The field 46 to 1500 bytes.įinally, the frame ends with a 4-byte Frame Check Sequence (FCS) that uses a 32-bit cyclical redundancy check (CRC) for error detection. The data unit follows the EtherType field. Hex '80D5' - IBM SNA Service over Ethernet The following EtherTypes are examples used in this field: Each field is 6 bytes.įollowing the address fields, Ethernet Version 2 uses a 2-byte "type" (or EtherType) field that identifies the unique network protocol type embedded within the data field. The next two fields are the Destination MAC Address and the Source MAC Address. The frame begins with an 8-byte preamble that is used to alert and synchronize the Ethernet Network Interface Card (NIC) to the incoming data. The primary difference between Ethernet Version 2 and IEEE 802.3 Ethernet standards is the frame layout. The reason for its development was to attempt to standardize the protocol across all pieces of networking equipment, regardless of the manufacturer. In 1983, the IEEE (Institute of Electrical and Electronics Engineers, Inc.) introduced the 802.3 Ethernet standard, named after the committee responsible for its development.
![ethernet mac address format ethernet mac address format](https://i0.wp.com/howdoesinternetwork.com/wp-content/uploads/2011/11/Screen-Shot-2011-12-29-at-12.19.49.png)
The standard was superseded in 1982, by DIX 2.0, the current Ethernet standard, also known as Ethernet II (or Ethernet Version 2). This standard is called DIX 1.0, sometimes referred to as Ethernet I.
![ethernet mac address format ethernet mac address format](https://forum.huawei.com/enterprise/en/data/attachment/forum/202012/21/091619j4ueu4p5t0efq6fp.png)
In 1980-81, the first Ethernet standard was developed by Digital (DEC-Digital Equipment Corporation), Intel, and Xerox, and combined the first letter of all of their names. This document provides information to network users to assist them in decisions regarding which Ethernet standard to use.