Network Packets: Understanding How the Internet Works (Easy)

Network packets are small units of data that are sent from one network device to another.

When you send any information online – such as an email, file, or video stream – it is broken into packets, which travel separately to the destination. Once all the packets reach their destination, they are put back together to form the original message or file.

This guide explores network packets in detail: why they are necessary, their structure, and how they affect network performance and traffic.

Why network packets?

A computer network transfers digital data as network packets, a far more efficient and flexible method than traditional circuit-based transmission such as copper-wire phone networks.

Unlike archaic circuit switching, which required the establishment of a dedicated point-to-point connection before full-signal communication could occur, packet switching breaks data into smaller, standardized chunks.

These fragments (or packets) are self-contained bundles whose headers contain digital addressing information, directing them to the appropriate recipient. Then, intermediate network nodes such as routers and switches examine those headers to determine where to forward the packet during its journey on the global network mesh.

There are several reasons to use this method of delivery:

1. Flexible routing saves time

Since packets travel independently, physical routers can determine alternative routing paths as needed to avoid congested network links or nodes.

This agility allows packets to flow around digital barriers to find the least congested and fastest routes to their destinations at any time. Thus, packet-switching networks such as the Internet can better adapt to changing demands in real time than rigid legacy networks built on static paths.

2. Error resistance and effective retransmission

With traditional circuit switching, if any node on a fixed path between users fails, the entire connection will be shut down. Meanwhile, in packet-switching networks with freely routed packets, only the missing packets will need to be retransmitted after a failure, not the entire message.

Additionally, packet switching is also less wasteful when message data is lost or corrupted during its journey. With old-school networks, even one failure can disrupt the entire communication, forcing the endpoint to restart the entire transfer.

However, thanks to sequence numbers imprinted on each data packet, packet switching is more flexible. This means that devices can easily identify lost packets in the transmitted message stream. Then, rather than resending any error-free packets, devices request replacements only for specific lost or damaged packets.

This flexibility is particularly evident in VoIP (Voice over Internet Protocol) systems compared to the traditional PSTN (Public Switched Telephone Network). While the PSTN relies on circuit-switched technology, which establishes a dedicated line for the duration of a call, VoIP transmits voice data as packets over the Internet. If a packet is lost or damaged, VoIP systems can only request the missing pieces, unlike PSTN, where any network problem can disrupt the entire call.

See: PSTN is still in use, but there are better alternatives.

3. Sharing highly efficient infrastructure

In circuit-switched networks, dedicated connections between endpoints become idle whenever parties stop active communication, which is technically a waste of network capacity.

On the other hand, packet-switching networks are exceptionally efficient in using available communication capacity. Networks can combine multiple separate phone calls and Internet transmissions at the same time by first cutting the data into smaller packets.

By combining small pieces of flow together, the network ensures that no wire is idle if only one call stops. This process is called statistical multiplexing – but the important thing is that it makes the most of every bit of available capacity.

Packet switching is also helpful in maximizing the efficiency of things like fiber optic cables and LTE bands. When combined, these innovations enable more calls, videos, chats, posts and page views to be conducted simultaneously through shared lines.

4. Enhanced security through selective encryption

Small-sized encapsulation of session data into packets also provides many network security benefits. While packet headers must remain unencrypted for successful routing, packet payloads can use encryption to keep application-level data confidential.

Packet switching also enables more secure communications through public networks such as the Internet. Small data bundles can use special encryption that securely verifies the correct sender without decrypting the content.

Technologies such as VPN (Virtual Private Network) use these methods to create encrypted tunnels within public networks. Thus, when you connect to your office or home network via VPN, your packets remain safe from prying eyes. Of course, the destination knows the packets came from you, but potential hackers won’t be able to trace them back to their source.

Overall, packet-switching systems allow billions of devices to communicate at high speeds in a flexible, efficient, and secure manner. Today, these simple information packets power everything we do over today’s digital networks, from sending email to video chatting with friends around the world.

Three parts of a network packet

Each packet contains different parts that work together. The three essential components of a network packet are as follows:

1. Packet Header

The packet header contains metadata important for the transport, such as:

• Source and Destination: These are the sending and receiving IP addresses. Like postal addresses, they identify where packets come from and where they end up.
• Verification Field: This includes checksums and other data to confirm validity and accurate delivery.
• Priority flags: These mark packets that require preferential handling, such as video packets that are sensitive to latency.
• Sequence Numbering: It is a type of data that labels the sequence of packets so that the messages can be reassembled.

In short, the packet header provides the delivery instructions and handling flags necessary to keep the packet flowing smoothly.

2. Packet Payload

The payload section of a network packet carries the actual end-user data that is being transmitted from the sending application (like a web browser) to the receiving application at the destination.

This user data payload may include:

• A webpage contains text, images, video, and multimedia elements.
• Audio data of calls made through VoIP services.
• Video footage is being streamed from security cameras.
• Sensor measurements from an internet-connected weather station.
• Database entries are being synchronized to the cloud.

In other words, payload is like the cargo container of a transport truck – it holds the actual goods to be shipped from point A to point B. It is important to focus on maximizing payload size and delivery efficiency because sending user data is the entire purpose behind transmitting packets in the first place.

3. Packet Trailer (or Footer)

Defining clear beginnings and ends for variable-length packets helps network hardware parse transmission streams efficiently.

Trailers provide demarcation boundaries so that routers and switches processing at ultra-high speeds know when one packet ends and another begins. This allows them to handle, route, and deliver billions of packets at rapid speeds without the risk of fragmentation.

Trailers also include error-checking mechanisms such as Cyclic Redundancy Check (CRC) to validate payload integrity. This means that if the calculated trailer CRC does not match the previously calculated expected values, errors are detected, and the payload can be marked for re-transmission.

At the end of the day, packet trailers serve like safety barriers at the end of highways – because they are vital tools for preventing accidents. By neatly capping the packets, they prevent stray fragments from inadvertently merging and corrupting the transmission.

Network packets and network traffic

Network traffic is essentially a collection of packets traveling across the network. Understanding packet behavior helps diagnose congestion or identify inefficiencies.

Understanding the behavior of these packets is important for managing and optimizing network performance, especially for business phone services and other real-time communications applications.

Network traffic involves packets traveling throughout the network, and when congested, high packet loss can result in lag, buffering, and interruptions in services such as VoIP or video calls. Monitoring packet performance helps identify inefficiencies and maintain smooth operations.

Network monitoring tools play a vital role in analyzing packet flows to diagnose issues such as broken connections, slow speeds, or misconfigured devices. Packet sniffing, a method used to tap into network traffic, enables administrators to identify performance bottlenecks while encryption ensures that sensitive data remains safe from malicious actors.

Administrators can configure the network to prioritize specific types of traffic to ensure that critical applications perform reliably even under heavy load. For example, using QoS settings to prioritize voice packets is a common strategy for optimizing VoIP networks.

Continuous monitoring and optimization of packet performance allows businesses to maintain fast, secure and efficient networks that meet modern demands in both public and private environments.