Notes

Physical Layer
The Physical layer encodes and decodes the bits found in a frame and includes the transceiver that drives and receives the signals on the network.

Data Link Layer
The Data Link layer creates the frames that move across the network. These frames encapsulate the packets and use MAC addresses to identify the source and destination.

Network Layer
The Network layer creates the packets that move across the network. It uses IP addresses to identify the packet’s source and destination.

Transport Layer
The Transport layer adds the TCP or UDP header which includes the source and destination port addresses. Additional information like the packet sequence number used for TCP will also be added to the header.

MAC address
A media access control address is a unique identifier assigned to a network interface controller for use as a network address in communications within a network segment

IP address
An Internet Protocol address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.

Port
In computer networking, a port is a communication endpoint. At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service.

Checksum
A checksum is a small-sized datum derived from a block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify data integrity but are not relied upon to verify data authenticity.

Routing table
In computer networking a routing table, or routing information base, is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics associated with those routes

TTL
Time to live or hop limit is a mechanism that limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data.