What Is Network Latency and How to Minimize It?

Network latency is an important measure of network performance. It affects everything from everyday web browsing and video conferencing to industrial automation, cloud applications, and high-performance computing.

Although network bandwidth determines how much data a connection can carry, latency measures how long data takes to travel between two points. A network can offer high bandwidth yet still feel slow if latency is excessive.

Ethernet switches play a role in determining network latency, but the total delay also depends on the transmission medium, network congestion, routing, endpoint processing, and the applications communicating across the network.

This article explains what network latency is, what causes it, why it matters, and how to reduce unnecessary delays in Ethernet networks.

Understanding Network Latency in Ethernet Switches

Network latency is the time required for data to travel from a source to a destination. In an Ethernet network, switch latency refers more specifically to the time a packet or frame spends being processed and forwarded through a switch.

Two common latency measurements are:

• One-way latency: The time it takes for data to travel from a source to a destination.
• Round-trip time (RTT): The time it takes for data to travel to a destination and for a response to return to the source.

Round-trip time is commonly used when testing network responsiveness with tools such as ping. However, it is not the same as switch latency: RTT includes delays across the entire path in both directions, as well as any response-processing time.

Several factors contribute to total network latency, including transmission delay, propagation delay, queuing delay, and processing delay.

For example, a packet may experience a small delay as a switch examines its destination address and forwards it to the appropriate port. If the outgoing port is busy, the packet may also wait in a queue.

In applications that rely on frequent exchanges between devices, such as interactive services and distributed computing, even modest delays can affect responsiveness and overall performance.

What Causes Network Latency?

Network latency can originate from several parts of a network. Identifying the source of the delay is the first step toward reducing it.

1. Transmission Medium and Physical Distance

Data takes time to travel through copper and fiber optic cables. Fiber supports long-distance communication and is resistant to electromagnetic interference, but it does not eliminate propagation delay.

Longer physical routes generally introduce more propagation delay. Network paths that pass through multiple locations or service-provider networks can add further delays.

2. Switch and Router Processing

Switches and routers process incoming traffic before forwarding it. The time required depends on the device architecture, forwarding method, configuration, and workload.

In a well-designed network, switching delays are often small. However, overloaded equipment, complex processing, or insufficient hardware capacity can contribute to higher latency.

3. Network Congestion and Queuing

When packets arrive faster than a network link can transmit them, they may have to wait in a queue. This queuing delay can increase significantly during periods of congestion.

If queues fill up, packets may also be dropped, resulting in retransmissions or interruptions for applications that require reliable delivery.

4. Endpoint and Application Processing

Latency is not limited to switches and routers. Computers, servers, storage systems, and applications all require time to process requests and responses.

For example, a slow server response may make a website appear unresponsive even when the network itself is functioning normally. Security inspection, encryption, and other processing tasks can also contribute to end-to-end delay.

5. Network Configuration and Routing

Inefficient routing, unnecessary network hops, poorly configured links, and inappropriate traffic-handling policies can increase latency.

Software defects and device configuration problems may also contribute to delays. Diagnosing these issues requires examining the network path and the behavior of the affected devices.

How to Minimize Network Latency with Ethernet Switches

Reducing network latency requires identifying the actual cause of the delay. The following approaches can help improve performance.

1. Provide Sufficient Network Capacity

Ensure that switches, uplinks, and network interfaces have enough capacity for the traffic they carry. Congested links can cause packets to queue, increasing latency and jitter.

Upgrading an overloaded link or adding capacity where needed may reduce congestion. Link aggregation can also combine multiple compatible physical links into one logical link, using protocols such as the Link Aggregation Control Protocol (LACP).

However, link aggregation does not automatically make every individual connection faster. The distribution of traffic across links depends on the switch's hashing method and configuration, and a single traffic flow may remain limited to one physical link.

2. Use VLANs to Organize Network Traffic

Virtual local area networks (VLANs) logically separate devices into distinct Layer 2 broadcast domains. They can help organize traffic, improve network administration, and limit unnecessary broadcast traffic within each segment.

For example, an organization may place security cameras, office computers, and management devices on separate VLANs.

VLANs do not automatically reduce latency. Their benefit depends on the network design and traffic patterns. Communication between VLANs generally requires Layer 3 routing, which must be configured appropriately.

3. Select Switches with Suitable Forwarding Performance

Switch architecture and forwarding behavior can influence latency. Some switches use cut-through switching, beginning to forward a frame after reading enough of its header to determine the destination port.

By contrast, store-and-forward switching receives the complete frame before forwarding it and can check the frame's integrity using its frame check sequence (FCS).

Cut-through switching can reduce forwarding delay in suitable environments, but its benefits depend on the switch, traffic conditions, and link speeds. It is not limited to ports operating at the same speed, although speed differences can affect forwarding behavior and performance.

When selecting a switch for a latency-sensitive application, evaluate its documented forwarding latency, throughput, port speeds, and traffic-management capabilities rather than relying on the switching method alone.

4. Configure Quality of Service (QoS)

Quality of Service allows switches to prioritize selected traffic when network resources are shared. For example, latency-sensitive voice, video, or control traffic may receive higher priority than less time-sensitive transfers.

QoS can help manage congestion and reduce delays for important traffic. It cannot create additional bandwidth, however, and poorly designed priorities may negatively affect other traffic classes.

5. Reduce Unnecessary Network Hops

Every device and link along a network path can contribute some delay. Review routing and switching paths to identify unnecessary hops, inefficient routes, or bottlenecks.

Simplifying the path where practical can help reduce end-to-end latency, particularly for applications that exchange data frequently between endpoints.

6. Monitor Network Performance

Use network monitoring and diagnostic tools to measure latency, packet loss, jitter, interface utilization, and errors.

Tools such as ping can help measure round-trip time, while traceroute can help identify the route taken by traffic. Switch management interfaces and network monitoring systems may provide additional information about port utilization, dropped packets, and interface errors.

Measure performance under realistic operating conditions. Comparing results during normal operation and peak traffic can help determine whether congestion, equipment, or another part of the network is responsible.

Why Does Network Latency Matter?

Network latency affects how quickly applications respond to user requests and how efficiently connected systems communicate.

User Experience

High latency can make websites, remote desktops, video calls, and interactive applications feel slow. Even when sufficient bandwidth is available, delayed responses can make an application less responsive.

Productivity

Employees may experience delays when accessing remote files, business applications, or cloud-based systems. In environments that rely on real-time data exchange, latency can also affect the responsiveness of monitoring and control systems.

Business Performance

Slow application responses can affect customer experience, operational efficiency, and online transactions. The business impact depends on the application and how sensitive it is to delay.

Real-Time Communication

Voice, video, and interactive applications are sensitive to latency and jitter, which is the variation in packet delay. Excessive delay or jitter can disrupt conversations, video playback, and other time-sensitive activities.

Network Reliability and Throughput

High latency does not necessarily mean a network is congested, and it does not automatically cause packet loss. However, congestion can increase queuing delay and cause packet drops, which may reduce effective throughput and trigger retransmissions.

How to Choose an Ethernet Switch for Low-Latency Applications

When evaluating Ethernet switches for applications that require responsive communication, consider the following:

• Forwarding latency: Review the manufacturer's specifications and determine how latency is measured, including the packet size and switching conditions.
• Port speeds and uplinks: Ensure that connected devices and uplinks provide sufficient capacity to avoid bottlenecks.
• Traffic management: Look for appropriate QoS, VLAN, and monitoring capabilities when the application requires them.
• Network environment: For industrial or outdoor installations, verify the switch's operating-temperature range, power requirements, and environmental ratings.
• Copper and fiber connectivity: Consider fiber for longer links or environments with significant electromagnetic interference, and verify that the selected optical interfaces are compatible.
• Monitoring and troubleshooting: Choose equipment with the management and diagnostic features needed to identify congestion, errors, and performance problems.

A switch with a high advertised switching capacity is not necessarily the best choice for every application. The complete network design, traffic load, endpoint performance, and required latency all matter.

Conclusion

Network latency measures the delay involved in transferring data across a network. It can be influenced by physical distance, transmission media, switch and router processing, congestion, routing, and endpoint performance.

To reduce unnecessary delay, provide sufficient network capacity, configure VLANs and QoS appropriately, select switches with suitable forwarding performance, and monitor the network for congestion and errors.

VERSITRON offers a range of fiber optic network switches for different network environments and connectivity requirements. Review the specifications of individual models to determine whether their port speeds, management features, and operating characteristics meet the needs of your application.