Hour 4. The Internet Layer

What You'll Learn in This Hour:

• IP addresses

• The IP header

• ARP

• ICMP

As you learned in the preceding hour, the computers on a single network segment such as an ethernet LAN can communicate with each other using the physical addresses available at the Network Access layer. How, then, does an email message get from Carolina to California and arrive precisely at its destination? As you'll learn in this hour, the protocols at the Internet layer provide for delivery beyond the subnet. This hour discusses the important Internet layer protocols IP, ARP, and ICMP.

At the completion of this hour, you will be able to

• Explain the purpose of IP, ARP, and ICMP

• Explain what a network ID and host ID are

• Explain what an octet is

• Convert a dotted decimal address to its binary equivalent

• Convert a 32-bit binary IP address into dotted decimal notation

• Describe the contents of an IP header

• Explain the purpose of the IP address

• Identify the network ID and host ID fields for Class A, B, and C addresses