Data-link layer

Data-link layer

1. Collision domain

   • One collision domain
     • CSMA/CD
       • listen before send, listen while sending, stop sending due to collision, and resend after random delay.
   • Separating collision domain
     • Switch

2. Broadcast domain

   • One broadcast domain
     • Ethernet
       • -> An all-1 MAC address (FF-FF-FF-FF-FF-FF) is a broadcast address -> Note that a MAC address uniquely identifies a network interface card (NIC). Each network adapter requires a unique MAC address.
     • Switch

3. Ethernet frames

   • Frame
     • -> Is the unit of data that is transmitted between network nodes on an Ethernet network. -> The total length of a data frame ranges from 64 bytes to 1518 bytes.
     • Ethernet II
       • Type field
         • 0x0800
           • Internet Protocol Version 4 (IPv4)
         • 0x0806
           • Address Resolution Protocol (ARP)
     • IEEE 802.3 LLC Ethernet
       • Type field
         • 0x0800
         • 0x0806

4. MAC Address

   • -> Uniquely identifies a NIC on a network. -> Each NIC has a number, that is, a MAC address, to identify itself, just as each person has an ID card number to identify himself/herself.