0. Recall

Network layer: host-to-host delivery
Primary role of network layer: move packets from a sending host to a receiving host
Each device can have different IPs
IP address is associated with the interface
- interface is between network layer and physical link
each interface has one IP address

	Layer	Function	Communication Scope
IP	Network Layer	Identify devices across different networks and facilitate routing between them.	Used to determine the path for data to travel across multiple networks when two devices are not directly connected
MAC	Link Layer	Identify devices within the same local network (LAN) based on their hardware address	Used when two devices are directly connected within the same network

1. IPv4 Address

Two notations:

dotted decimal: 128.11.3.31 
binary:         10000000 00001011 00000011 00011111

Address block: the range of IP addresses that are grouped together to form a "block.”

Each block can be allocated to different networks or organizations based on the number of devices (hosts) they need to support
Host: individual devices that can connect to a network and require a unique IP address