Notes on data communication and network-wired LAN: Ethernet

Wired LAN: Ethernet classification Ethernet has gone through four generations of development: the minimum length of a standard Ethernet frame: 64 bytes. Maximum length: 1518 bytes. Addressing Ethernet uses a 6-byte physical address provided by the NIC, which is usually expressed in hexadecimal notation. For example: 06: 01: 02: 01: 2C: 4B Unicast address. The multicast address and broadcast address source address are always one Unicast address (because the frame only comes from one site ), the destination address can be a unicast address, multicast address, or broadcast address. If the delimiter of the first byte of the target address field is 0, this address is a unicast address; otherwise, it is a multicast address. A broadcast address is a special case of multicast addresses. The receiver address is all the sites in the LAN. A Broadcast Destination Address 48 is 1, that is, FF: FF is also associated with unicast, multicast, and broadcast addresses in the IP address at the network layer? Yes. In fact, the IP addresses at the network layer must be mapped to the addresses at the data link layer before being sent out. The specific ing will be explained later. Access Method: standard Ethernet access using CSMA/CD. I wrote an article about CSMA/CD: http://www.bkjia.com/net/201307/226574.html Physical Layer Implementation Standard changes fast Ethernet IEEE creates Fast Ethernet under the name of 802.3u, Fast Ethernet is backward compatible with standard Ethernet, but its transmission speed is 100 Mbps. The goal of Fast Ethernet is: 1. upgrade the data speed to 100 Mbps. 2. Make it compatible with standard Ethernet. 3. Retain the 48-bit address. 4. retain the same frame format. 5. Retain the maximum and minimum values of the frame length. In the mac Sub-layer, the bus topology is abandoned in Fast Ethernet and only the star topology is retained. In a star topology, half duplex and Full Duplex are available. Use a Hub Connection in half duplex and a switch connection in full duplex. The half-duplex access method is CSMA/CD. In full-duplex mode, CSMA/CD is unnecessary and CSMA/CD is retained so as to be compatible with standard Ethernet. Automatic negotiation Fast Ethernet adds a new feature: Automatic negotiation, which allows two devices to negotiate their operating mode and transmission speed. The physical layer achieves Gigabit Ethernet. IEEE creates a Gigabit Ethernet under the name of 802.3z. The design goal of Gigabit Ethernet is as follows: 1. upgrade the data rate to 1 Gigabit 2. make it compatible with standard or fast Ethernet 3. use the same 48-bit address. 4. Use the same frame format. 5. Retain the maximum and minimum values of the frame length. 6. Supports automatic negotiation defined in Fast Ethernet. Working mode full duplex and half duplex (rarely used) Physical Layer achieve 10 Gigabit Ethernet EEE create Gigabit Ethernet under the name of 802.3ae. The design goal of Gigabit Ethernet is as follows: 1. the data rate is upgraded to 10Gbps2. make it compatible with standard Ethernet, fast Ethernet, and Gigabit Ethernet. use the same 48-bit address. 4. Use the same frame format. 5. Retain the maximum and minimum values of the frame length. 6. Allow interconnection between existing LAN and man or WAN 7. Make Ethernet compatible with technologies such as frame relay and ATM. Work mode can only work in full duplex mode.