Network Packets and Frames

Packets: The Units of the Network Layer

• Definition: Packets are self-contained units of data that are routed across networks (like the internet). They carry the actual information you're sending.

• Components: A packet includes:

  • Payload: The actual data being transmitted (part of an image, a web page, an email, etc.)

  • Header: Contains control information like source and destination IP addresses, protocol type, and other metadata to help it reach its destination.

Frames: The Units of the Data Link Layer

• Definition: Frames are used to transmit data over a physical network medium (like Ethernet or Wi-Fi). They are the "envelopes" that carry packets.

• Components: A frame includes:

  • Header: Contains source and destination MAC addresses (hardware addresses of network devices), error detection codes, and other information for transmission over the physical network.

  • Payload: This is the packet received from the network layer.

  • Trailer: May contain error checking information.

How Packets and Frames Work Together

1. Encapsulation: Your computer creates a packet containing data. This packet is encapsulated within a frame at the data link layer.

2. Transmission: The frame with its payload (the packet) is sent over the physical network (like an Ethernet cable).

3. Reception: The receiving device strips off the frame headers and trailers. The remaining packet is passed up to the network layer.

4. De-encapsulation: The packet is further processed to eventually bring you the data you requested.

Key Points

• Packets are about logical routing across networks.

• Frames are about physical transmission of data.