Understanding Packet Errors, Packet Discards, and Packet Loss in Network Monitoring

More than likely, you’ve encountered the terms “packet loss”, “packet discards”, and other packet errors in networking monitoring before, but were confused about what each of them means. What are packets? How are they lost or discarded, or worse, encountering errors? And this often leads to most people (at least those not familiar with IT terms) lumping them together—believing that these terms mean the same thing.

They don’t. 

Each describes a different condition in the network, and misunderstanding those differences can send troubleshooting efforts in the wrong direction. For example, you may be unnecessarily replacing good hardware when your real issue is congestion or inadvertently increasing bandwidth when you really needed to fix cabling.

And these mishaps are not just frustrating; they’re costly, both in time and money. (Check out our guide on IT Cost Optimization: Best Practice Guide for 2026 for other tips and techniques to reduce poor spending!).

In this article, we clarify these differences so that you can reduce the risk of security vulnerabilities in your organization.

Short on time? Check out this table instead:

A quick glance at packet loss vs packet errors vs packet discard

What is a packet in IT?

Before we talk about packet errors, packet discards, or packet loss, it helps to understand what a packet actually is.

The easiest way to understand “packet” in the IT universe is to replace it with the term “package”. Stated simply: A packet is a small “package” of data that travels across a network. Whenever you send an email, load a website, join a video call, or download a file, that information is broken into many small pieces called packets.

Each packet contains:

• The actual data being sent
• Source and destination information
• Instructions that help devices route it correctly

Rather than sending data as one large block, networks break these large amounts of data into packets (or packages) so it can travel efficiently across different paths and be reassembled at the destination.

Think of it like receiving different parts of an IKEA set. Instead of shipping the entire assembled piece of furniture in one massive box, the company ships it in smaller pieces. Each box has labels that show where it’s going and what it contains. Once all the pieces arrive, you assemble them into the finished product.

Networks work the same way. Devices send data in smaller packets because it’s faster and easier to manage. If one packet gets lost or damaged, only that small piece needs to be resent, not the entire file or message.

So, when packets are lost, corrupted, or dropped along the way, communication slows down or fails. And this is where you can experience either a packet loss, a packet discard, or a packet error.

What is a packet loss?

Packet loss happens when data packets fail to reach their intended destination across a network. In our earlier metaphor, this would be like receiving a tracking number for your furniture, but one of the boxes never shows up, or shows up much later because it had to be reshipped.

In network management, a packet loss means that something along the path caused the packet to be lost before it reached its final destination. Typically, this happens when:

• Network congestion occurs: When there is too much traffic in the network, packets can be dropped because buffers fill up.
• Hardware is failing: Faulty network interfaces, aging switches, or unstable routers can drop packets unexpectedly.
• Routing instability exists: Incorrect routes or routing flaps can cause packets to be misdirected or discarded.
• Wireless interference is present: In Wi-Fi environments, signal interference or weak coverage can cause packets to be lost.
• ISP or upstream issues occur: Sometimes the loss happens outside your local network, within your provider’s infrastructure.

The impact of packet loss depends on the type of traffic involved. For example, TCP-based applications (like web browsing or file transfers) will retransmit lost packets. This usually results in slower performance rather than complete failure. On the other hand, real-time applications like VoIP or video conferencing often use UDP, which does not retransmit lost packets. In those cases, users may experience audio dropouts or a frozen video.

Even so, we must clarify that packet loss (especially in heavy-load environments) is completely normal. Small amounts of packet loss can occur in normal networks without causing noticeable issues. However, sustained or increasing packet loss is often a sign of congestion, instability, or infrastructure problems that require investigation.

Keep in mind as well that when most people talk about packet errors in networking, they are often referring to packet loss. This is because this type of error is the most visible metric, as users feel it directly.

What are packet errors?

If packet loss is like a box never arriving, packet errors are like receiving a damaged box that can’t be used. Imagine receiving your IKEA package only to see that it doesn’t have any screws.

Packet errors work similarly. They happen when data arrives, but something is wrong with it, usually corrupted during transmission. This typically happens when:

• Cabling is damaged or poorly terminated: Hardware failures, such as bent pins or low-quality cables, can corrupt signals.
• There is electrical interference: This happens more frequently in copper cabling environments.
• Speed or duplex mismatches exist: Interfaces configured incorrectly can cause collisions and corrupted frames.
• Network interface cards (NICs) are failing: Faulty hardware can introduce transmission errors.

Unlike packet loss, which may happen anywhere across the network path, packet errors often point to a physical layer or hardware problem close to the device reporting the error. If you’ve ever called your internet provider complaining about a slow connection and their first response is for you to check your cabling, this is why.

Left unresolved, packet errors increase the risk of infrastructure damage that can lead to severe outages worthy of any IT Horror Story.

What are packet discards?

Packet discards are anomalies in network management. Compared to an error or a loss, packet discards refer to a scenario where a packet is valid, but the device intentionally drops it.

Using our metaphor, packet discards are like a delivery center deciding it has too many boxes at once and choosing not to deliver them to prevent overload. And while these errors don’t happen as often as packet losses or packet errors, packet discards can still happen when:

• Buffers overflow due to congestion: The device simply cannot process packets fast enough.
• Interfaces exceed capacity: This occurs when traffic volume surpasses what the link can handle.
• QoS policies drop lower-priority traffic: Some packets are intentionally sacrificed to protect more important traffic.
• Rate limiting is enforced: Some organizations intentionally restrict their device traffic volume.

Occasional discards during peak usage may not be alarming. After all, networks are designed to handle bursts. However, sustained discards, especially when correlated with high utilization, may indicate that a link is oversubscribed or a device is underpowered for current traffic demands.

Why are these metrics often confused?

The confusion generally starts with monitoring dashboards. In most cases, packet errors, discards, or losses are displayed together under “interface statistics” or “performance metrics”. And since packet losses are the easiest to detect, many people believe that all three terms are the same.

However, as we’ve seen, the underlying causes of each type of metric are different and distinct and require specific types of troubleshooting. For example, A cable fault (errors), congestion (discards), and routing instability (loss) can all degrade performance, but they require completely different remediation approaches.

How to find the likely root cause of a packet-related error

While every network environment is different, some general troubleshooting patterns consistently hold true. Now that you understand what each packet metric represents, you can start narrowing your investigation much faster. Here are our short recommendations (keep in mind that these are only general tips! Make sure that you apply the best method for your specific use case.):

Packet Loss

• What to look for: Rising packet loss percentages across interfaces, user complaints about slow applications or choppy VoIP/video, and monitoring alerts tied to retransmissions or latency spikes.
• Easiest thing to check first: Verify interface utilization and look for congestion. High bandwidth usage is one of the most common contributors to packet loss.
• Fast troubleshooting tip: Run a simple ping or traceroute test to identify where the loss begins along the path. If loss appears at the first hop, it’s likely local; if it starts further downstream, the issue may exist beyond your network.

Expert tip: Read this guide, How to Troubleshoot and Fix Packet Loss for more info.

Packet errors

• What to look for: Increasing input or output error counts on a specific interface, especially when tied to one switch port, server NIC, or uplink.
• Easiest thing to check first: Inspect the physical layer, and check cabling, reseat connectors, verify speed and duplex settings match on both ends of the link.
• Fast troubleshooting tip: Swap the cable or move the connection to a different port temporarily. If the errors follow the cable, it’s likely cabling; if they stay with the port, the interface may be faulty.

Packet Discards

• What to look for: Rising discard counts during peak usage, often accompanied by high interface utilization or performance slowdowns.
• Easiest thing to check first: Review bandwidth usage and interface capacity to see whether traffic volume is exceeding what the link or device can handle.
• Fast troubleshooting tip: Compare discard spikes with traffic graphs. If discards increase during high utilization, congestion is likely the cause rather than hardware failure.

Why context matters in network packet metrics

To be clear: Network packets can be lost, discarded, or encounter errors all the time. These events are completely normal, and IT teams usually develop fail-safes to compensate for this inevitability.

So, seeing a number greater than zero in raw packet counts does not automatically mean an IT emergency. Small bursts of traffic, configuration changes, or even normal device behavior can temporarily increase packet counters without indicating a serious issue.

That is why packet metrics matter in context. All metrics must be evaluated alongside other performance indicators, such as:

• Interface utilization: If packet discards occur when utilization is low, congestion may not be the root cause. If utilization is consistently near capacity, oversubscription may be likely.
• Latency and jitter: Rising packet loss combined with increased latency or jitter often points to congestion or path instability affecting real-time traffic.
• Historical trends: Are the metrics steadily increasing over days or weeks? Or was this a single short-lived event? Trend data provides far more insight than isolated readings.
• Application performance metrics: If users are not experiencing degradation, minor packet counts may not be operationally significant. Conversely, if applications are slow and packet metrics are rising, the correlation strengthens the case for investigation.

This is where network monitoring and management tools such as NinjaOne shine. These tools analyze trends over time and allow you to see patterns and respond appropriately.

When packet metrics indicate a real problem

Packet metrics become actionable when they are sustained or correlated.

If packet loss aligns with user complaints, VoIP degradation, or performance monitoring alerts, the signal is meaningful. If packet errors steadily increase on a specific interface, hardware inspection is warranted. If discards rise in parallel with high utilization, capacity planning may be needed.

Your IT team should take special care to record all packet-related incidents (even those that may seem trivial) to determine any pattern. If they note any consistent complaints, this would signal the need for further investigation.

Limitations and scope considerations

1. They don’t reveal root causes

Network packet metrics are valuable indicators, but they do not necessarily reveal a root cause. They only tell you that something is happening, not necessarily why it’s happening.

For example, packet loss could be caused by congestion, routing instability, firewall processing limits, ISP issues, or even upstream peering problems. The metric alone doesn’t tell you which of those is responsible. It simply signals that packets are failing to arrive at their destination.

2. Packet metrics are not standardized across vendors

Another important limitation is that packet metrics often vary in definition and format, which makes comparisons tricky. This is why we always recommend conducting a vendor risk assessment before deciding on any tool for your organization.

Different network manufacturers may define, calculate, or report discards differently. Some devices separate input and output discards. Others combine them. Some count buffer drops differently depending on the queue type. Even terminology may vary between platforms.

This means you must interpret packet metrics within the context of:

• The specific vendor and device model
• The role of the interface (such as access port, uplink, WAN link, and firewall edge)
• The traffic type passing through that interface
• The broader network topology

3. Require layer-by-layer analysis

Because of the first two limitations, effective troubleshooting requires a layer-by-layer analysis approach. Here is an example of one:

• Starting at the physical layer (cabling, interfaces, signal integrity)
• Move up to the data link layer (duplex, VLANs, switching), then
• Evaluating routing, queuing, and application behavior.

Each layer can introduce conditions that affect packet delivery differently.

Managing network packet drops

Packet errors, packet discards, and packet loss are related but distinct indicators of network health. Each metric represents a different failure condition and often points to a different troubleshooting path.

Using an NMS tool like NinjaOne gives you single-pane visibility across all your SNMP devices so you can easily troubleshoot your network when needed.

NinjaOne’s IT management software has no forced commitments and no hidden fees. You can request a free quote, schedule a 14-day free trial, or watch a demo.

Related topics:

• How to Diagnose and Eliminate Network Congestion
• 8 Common Network Issues & How to Address Them
• 6 Network Monitoring Best Practices