What Is Packet Loss? Causes & How to Fix It

Packet loss occurs when data packets do not reach their destinations. This results in broken phone calls and meetings, and slow downloads even when your internet connection looks good. There are several causes, including congested and interference-prone networks, faulty cables, and overloaded equipment.

In this blog, we will explain how packet loss occurs and how different apps handle it. We will also discuss how to fix packet loss without randomly changing app settings.

Let us first understand what packet loss really is.

What Is Packet Loss?

Packets are small units of data carried by a network. Packet loss means a packet is sent by one node but never received by the destination node.

It is usually expressed as a percentage:

Packet loss (%) = (Packets lost ÷ Packets sent) × 100

If a test sends 1,000 packets and 20 do not arrive, the loss rate is 2%.

What Are the Main Causes of Packet Loss in Networking?

Some of the main causes of packet loss are:

Network Congestion

When traffic surges toward a bottleneck, queues form behind it. Packet loss occurs when the available queue space is exceeded. Backups, large file uploads, and simultaneous file transfers can all cause it.

Weak or Interfering Wi-Fi Signals

Packet loss may occur when signal strength is low due to distance, obstructions (such as walls), or interference. Wi-Fi can retransmit some data frames, but repeated failures still result in packet loss.

Faulty Cables, Ports, and Network Adapters

A faulty Ethernet cable or port may cause packet loss. Loose connections and network adapter problems can also cause it. Check physical connections before blaming the Internet Service Provider (ISP).

Overloaded Equipment and Software Faults

Routers, firewalls, and endpoint devices may drop packets due to overload and software or firmware faults. Equipment age alone does not prove it needs replacing.

Filtering, Routing, and Packet-Size Problems

An incorrect firewall rule may discard legitimate traffic. Routing faults can send packets toward an unusable path. Oversized packets can also be dropped when they exceed a link’s MTU and fragmentation is unavailable.

How Does Packet Loss Affect Applications?

Effects depend on application requirements:

• Voice or video calls can suffer clipped speech, missing words, robotic audio, or frozen and missing video frames.
• In games, characters may suddenly jump or change position when packets are lost and the application falls back on older information.
• File transfers and backups take longer because lost packets must be recovered.
• Remote desktop sessions can feel unresponsive because of recovery delays and data loss.

Do not confuse packet loss with latency (delay) or jitter (variation in delay). A connection can have low average latency and still lose many packets.

Packet loss affects network reliability, causing disruptions in calls, gaming, and data transfers. Learn to diagnose network issues with our CCNA Training Course.

How Does the Internet Handle Packet Loss?

IP alone does not ensure the delivery of datagrams. Recovery depends on the transport protocol and the application.

TCP Detects Missing Data and Retransmits It

TCP detects missing data using timers, acknowledgements, and sequence numbers. Once missing data is detected, TCP retransmits it and ensures bytes are delivered to the application in order.

Through congestion control and other mechanisms, TCP manages its sending rate. As a result, downloads can take noticeably longer when there is loss.

UDP Leaves Recovery to the Application

UDP does not guarantee delivery or offer automatic retransmission, so recovery of lost data is left to the application. An application using UDP may include its own retransmission.

Voice and video systems may use redundant data, selective retransmission, and techniques to mask missing data. If retransmitted data reaches the client in time for playback, media quality improves.

QUIC Adds Reliability over UDP

QUIC, the transport layer protocol of HTTP/3, provides reliable streams, loss recovery, and other features over UDP. Using UDP underneath does not mean an application cannot recover missing data.

How to Test for Packet Loss

You can follow these steps to troubleshoot packet loss.

Start with a Repeatable Ping Test

On Windows, open Command Prompt and run:

ping -n 100 1.1.1.1

This test sends 100 ICMP echo requests and provides a summary of sent, received, and lost packets. To compare local and external connectivity, run the test against your router’s default-gateway address and an external address.

Ping measures how many round-trip replies are missing. It cannot tell you whether the request or the reply was lost. Some devices also filter or rate-limit ICMP, so missing ping replies do not necessarily mean application traffic is being dropped.

Check the Traffic That Is Actually Affected

For calls and games, examine the application’s network statistics when available. Tools such as OpenPacketLoss and Packet Loss Test offer browser-based tests.

Repeat tests during the problem and when the connection is quiet. Keep the destination and settings consistent. A clean result to one test server does not prove every route is healthy.

Read Route Tests Carefully

MTR combines repeated probes with route information. An intermediate router showing loss while later hops and the destination respond normally may simply be limiting diagnostic replies.

Look for patterns that continue to the destination and match application symptoms before blaming a particular hop.

How to Fix Packet Loss

Troubleshooting packet loss focuses on finding the problem rather than changing configurations or hardware at random.

What you observe	Likely cause	Useful next step
Packet loss on Wi-Fi but not Ethernet	Wireless signal or interference	Improve access-point placement and review channel use.
Packet loss on only one wired device	Cable, port, adapter, or driver	Try a known-good cable and another port.
Packet loss only during heavy uploads	Upload congestion	Pause or limit backups and repeat the test.
Several devices losing external traffic	Router, WAN link, or provider path	Compare destinations and collect timed results.
Only one service affected	Service endpoint or its network route	Check service status and test another connection.

Check background traffic, cables, ports, and service-side problems first.

For persistent problems:

• Choose updates carefully. Install supported firmware or driver updates for the affected equipment.
• Check device counters. Error and queue drops on an interface can help determine whether a link is faulty or congested.
• Manage traffic on busy links. Use QoS or traffic shaping to protect critical traffic. (QoS cannot repair a damaged cable.)
• Document to escalate. Collect timestamps and wired test results. Give your provider the conditions that trigger the problem.

After every change, test the affected application task and check whether the problem stopped. Repeat this process to isolate the cause.

How Much Packet Loss Is Acceptable?

The short answer is that packet loss should be as low as possible. There is no magic percentage that guarantees good performance for all applications.

Short bursts of packet loss can be more problematic than the same number of losses spread out over time. Consider burst length together with latency, jitter, and the application’s ability to recover.

Conclusion

Packet loss is usually easy to fix, but only when you know the exact cause. To find it, understand the basic reasons that can affect packets moving across the internet. Start by comparing wired and wireless results. Next, test your connection during busy and idle hours. Finally, check the effect across all devices connected to the same router and see whether every device shows packet loss.

Frequently Asked Questions

Q1. How do you fix packet loss?

Packet loss has multiple possible causes, so first identify the root cause and then address it. This may involve replacing hardware such as cables or routers, installing software updates, or contacting your ISP if nothing else works.

Q2. What is packet loss?

Packet loss occurs when a packet sent from the source fails to reach its destination.

Q3. Is 2.7% packet loss bad?

Yes, 2.7% packet loss is bad for real-time internet activity. It can affect video calls, online gaming, and more.

Q4. Is 1% packet loss bad?

Any amount of packet loss is undesirable for real-time tasks, although very small amounts may go unnoticed.