Network Latency - Common Causes & How to Fix Them

Definition

Network latency is the time it takes for a data packet to travel from its source to its destination across a network. It's measured in milliseconds (ms) and is influenced by factors such as network congestion, distance between source and destination, and the quality of network connections. High latency can result in noticeable delays, affecting the performance of online applications and services.

What does it really mean?

Consider an orchestra where musicians are positioned far apart from each other in a large field, rather than in a traditional concert hall setting. In this scenario, the time it takes for the sound to travel from one musician to another represents network latency. If this time delay (latency) is significant, musicians will struggle to play in sync. The resulting misalignment in their playing is similar to the disruptions experienced in online activities due to high network latency, where delayed data transmission leads to out-of-sync video calls, lag in online gaming, or delays in real-time data updates.

What causes network latency?

Network latency is influenced by a variety of factors:

1. Propagation Delay: This is the time it takes for a signal to travel from the sender to the receiver. It is primarily determined by the physical distance between the two points and the speed of light in the medium (like fiber optics).
2. Transmission Medium: The type of medium used (like copper cables, fiber optics, or wireless) affects latency. For instance, fiber optic cables have lower latency compared to copper cables.
3. Router and Switch Processing Time: Every time data passes through a router or switch, there's a processing delay as these devices determine the data's next path. More hops mean more processing time, hence higher latency.
4. Traffic Congestion: Just like road traffic, data traffic can get congested. High network traffic can slow down data transmission, increasing latency.
5. Network Type: Different network types (like LAN, WAN, or wireless networks) have different inherent latencies. Wireless networks generally have higher latency compared to wired networks.
6. Bandwidth: Although bandwidth doesn't directly affect latency, low bandwidth can lead to network congestion, indirectly increasing latency.
7. Quality of Service (QoS) Settings: Network QoS can prioritize certain types of traffic over others, which can impact latency for lower-priority data.
8. Server/Host Processing Time: The time it takes for the receiving server or host to process the incoming data can also add to overall latency.

How can you measure network latency?

Measuring network latency involves assessing the time it takes for data to travel from its source to its destination and back again. Common methods include:

1. Ping: This is a basic network utility that sends an Internet Control Message Protocol (ICMP) echo request to a target host and waits for a reply. The time measured from sending the request to receiving the reply is the round-trip time (RTT), which is a direct indicator of network latency.
2. Traceroute (or Tracert): This tool traces the path that a packet takes to reach a destination and reports the time taken for each hop. It helps in identifying where delays are occurring in the network.
3. Network Monitoring Tools: These are more sophisticated solutions that provide real-time analytics on network performance, including latency. They can continuously monitor network latency and often provide additional insights into network health.
4. Application Performance Monitoring (APM) Tools: These are designed to monitor the performance of applications, including the network latency experienced by these applications.
5. Speed Test Websites: Websites like Speedtest.net measure the time it takes for your computer to download and upload data from a server, providing an estimation of the network latency along with bandwidth.
6. Synthetic Transactions: This involves creating and monitoring test traffic within your network to simulate and measure latency under controlled conditions.

How can you reduce the network latency?

Reducing network latency involves addressing the various factors that contribute to delays in data transmission. Here's how to mitigate these factors:

1. Propagation Delay:
   • Shorten the Distance: Use data centers or servers that are geographically closer to the end-users to minimize the distance data needs to travel.
   • Optimize Routing: Implement efficient routing protocols that find the shortest path for data packets.
2. Transmission Medium:
   • Upgrade to Fiber Optics: Replace slower transmission mediums like copper cables with faster ones like fiber optics.
   • Improve Wireless Technology: In wireless networks, use advanced wireless standards (like Wi-Fi 6) that offer lower latency.
3. Router and Switch Processing Time:
   • Upgrade Hardware: Use modern, high-speed routers and switches that can process data more quickly.
   • Simplify Network Topology: Reduce the number of hops (routers/switches) data must pass through.
4. Traffic Congestion:
   • Increase Bandwidth: Upgrading network bandwidth can alleviate congestion issues.
   • Traffic Shaping and QoS: Implement Quality of Service (QoS) and traffic shaping policies to prioritize critical traffic and manage bandwidth usage.
5. Network Type:
   • Wired vs Wireless: Prefer wired connections over wireless for critical applications, as they typically offer lower latency.
6. Bandwidth Limitations:
   • Bandwidth Upgrades: Increase the network's bandwidth capacity to reduce the chance of congestion, indirectly affecting latency.
7. Quality of Service Settings:
   • Optimize QoS: Fine-tune QoS settings to prioritize latency-sensitive applications like VoIP or gaming.
8. Server/Host Processing Time:
   • Server Optimization: Upgrade server hardware and optimize software configurations to process requests faster.
   • Load Balancing: Use load balancers to distribute traffic evenly across servers, preventing any single server from becoming a bottleneck.

By systematically addressing each of these areas, you can significantly reduce network latency and improve the overall efficiency and performance of your network.

Frequently Asked Questions

Difference between Network latency, throughput, and bandwidth

Network Latency: This refers to the time it takes for a packet of data to travel from its source to its destination across a network. It's usually measured in milliseconds (ms) and represents the delay in communication over the network. Factors like propagation delay, routing, and traffic congestion affect network latency.

Throughput: This is the actual rate at which data is successfully transferred over the network in a given period, usually measured in bits per second (bps). Throughput is influenced by the network's bandwidth, latency, and any packet loss or errors that occur during transmission. It's a measure of how much data is effectively transmitted, considering all network conditions and limitations.

Bandwidth: Bandwidth refers to the maximum rate at which data can be transferred over a network connection, also measured in bits per second (bps). It's like the width of a highway - the wider it is, the more traffic (data) it can handle at once. However, having high bandwidth does not necessarily mean high throughput, as other factors (like latency and packet loss) can constrain the effective data transfer rate.

What should my network latency be?

Ideal network latency varies based on the application, but for most online activities, a latency below 100 milliseconds (ms) is acceptable. For more latency-sensitive tasks like online gaming or video conferencing, a latency below 30 ms is often desirable.

What is the difference between ping and latency?

Ping measures the round-trip time for a message sent from the originating host to a destination computer and back, indicating network latency. Latency is the time it takes for a data packet to travel from source to destination, one-way.

References

• https://datatracker.ietf.org/doc/rfc9320/
• https://aws.amazon.com/what-is/latency/
• https://www.ir.com/guides/what-is-network-latency
• https://www.cloudflare.com/en-gb/learning/performance/glossary/what-is-latency/