Chapter 02 Ethernet Networks in Review

CSMA/CD

• Carrier Sense Multiple Access with Collissiong Detection
• After a collission occurrs, each hosts waits for a while (the backoff period) before resending.

Ethernet frames

• Data link layer combines bits to bytes to frames.
• Preamble (7 bytes 1010 pattern)
• Start Frame Delimiter (SFD) (10101011)
• Destination Address (MAC 48 bit, LSD). Broadcast is all ones.
• Source Address (MAC)
• Length (802.3) or Type (Eth II, most common) -> IPv4 0x800, IPv6 0x86dd
• Data 46 - 1500 bytes
• Frame Check Sequence