- Ethernet Frames Format
- MAC address Each NIC has a unique, 48-bit MAC address; The first 24 bits identify the manufacture while the 2nd half is assigned by the manufacture.
- Ethernet Access Before Gigabit Ethernet, CSMA/CD is designed to allow fair access on shared media: Listen to avoid collision before transmitting. If collision occurs, retransmission is necessary. In 1997 IEEE 802.3x introduces full-duplex Ethernet, MAC control protocol and PAUSE.
- Ethernet Equipment
|Field||DIX Frame||IEEE 802.3 Frame|
|Preamble||8 bytes||7 bytes|
|Start Frame Delimiter||1 bytes|
|Destination Address||6 bytes||6 bytes|
|Source Address||6 bytes||6 bytes|
|CRC/FCS||4 bytes||4 bytes|
- Hubs/Repeaters Hubs/Repeaters are the central devices in a star topology and enhance the incoming signals to avoid degradation before transmitting them out. Hubs/Repeaters also support SNMP.
- Bridges Bridges transfer MAC layer packets from one network to another; and help prevent collisions by creating separate collision domain. To control the traffic, bridges need to build MAC tables and prevent loops using Spanning Tree Protocol
- Switches Switches link multiple networks compared to Bridges. Two categories of switches are commonly in use today: Cut through and Store-and-forward. Cut through provide lower latency while store-and-forward provides more intelligent processing of MAC layer packets.
- Routers Routers filter out unnecessary traffic by looking up IP address instead of MAC address in bridges/switches. Routers works like firewall to some extent and provide security functionality.