Question

question 1
what identifier is used at the data link layer to uniquely identify an ethernet device?
mac address
tcp port number
ip address
sequence number
udp port number

Explanation:

At the data - link layer, a Media Access Control (MAC) address is used to uniquely identify an Ethernet device. TCP and UDP port numbers are used at the transport layer for identifying applications. IP addresses are used at the network layer for identifying hosts on a network. A sequence number is used in TCP for sequencing data segments.

Answer:

A. MAC address