What is network latency?
Network latency, also called lag, is the time it takes for a data packet to travel from its source to its destination across a network, measured in milliseconds (ms). The lower the latency the higher the quality of user experience.
The most common signs of high latency include:
- Emails with large attachments take a long time to send.
- Accessing servers or web-based applications feels sluggish.
- Websites load slowly, especially elements like images or scripts.
- VoIP calls are choppy, or video conferencing lags.
The 6 common causes of high network latency
1. Long physical distance
Data takes time to travel between endpoints. If your users are in India but your application servers are hosted in the U.S., packets have to traverse multiple network hops and thousands of miles, naturally increasing latency. The greater the distance between the user and the server, the higher the round-trip time (RTT).
2. Hardware faults or overloaded devices
Faulty network cables, damaged ports, or failing NICs can cause retransmissions and signal degradation. Similarly, routers, switches, or firewalls running at high CPU or memory utilization may struggle to process packets efficiently. This processing delay, even in milliseconds per hop, adds up across multiple devices and increases latency.
3. Network congestion
When too many users or applications share limited bandwidth, data packets queue up or get dropped. This congestion is common during peak office hours, large file transfers, or bandwidth-heavy activities like video streaming. As a result, packets must be retransmitted, increasing both latency and jitter.
4. Seasonal or event-based data center overloads
During high-demand periods like festive season sales, product launches, or marketing campaigns servers in data centers often experience traffic spikes. If the resources aren’t scaled up to meet the growing demand, servers and network links become saturated, leading to longer processing times and higher latency for end users.
5. Lack of a Content Delivery Network (CDN)
Without a CDN, every user request is routed to the origin server, regardless of where the user is located. This increases physical distance and response time. A CDN stores cached content in edge servers closer to users based on the region, reducing the number of network hops and significantly improving latency and load times.
6. Suboptimal routing or configuration issues
- Inefficient Routing/Peering: Data takes unnecessary detours due to poor ISP peering or suboptimal routing configurations.
- MTU Mismatches: Inconsistent Maximum Transmission Unit sizes between devices cause packet fragmentation and retransmissions.
- Duplex Mismatches: One device set to full-duplex and another to half-duplex leads to collisions and severe performance degradation.
- Outdated Firmware/Configs: Inconsistent or buggy configurations on network devices can introduce unexpected latency.
How to troubleshoot network latency issues? - A six step process
Step 1: Perform basic checks
Rule out the obvious first:
- User Device: Is the user's Wi-Fi signal strong? Are they running background updates or large downloads? Are cables securely plugged in?
- Local Network: Reboot the user's modem and router. Check physical connections between switches and devices.
Step 2: Measure Latency & Packet Loss (Ping & Traceroute)
Use basic command-line tools to get initial measurements:
- Ping: Checks RTT and packet loss to a specific destination (
ping \<hostname\\\_or\\\_IP\>). High RTT or lost packets confirm a latency issue. - Traceroute (Tracert/Pathping on Windows): Maps the hop-by-hop path packets take, showing the latency added at each device. This helps identify where the delay is occurring – is it on your internal network, your ISP's network, or the destination server's network?
OpManager includes built-in Ping and Traceroute tools accessible directly from any device's snapshot page. You can run these checks instantly without switching consoles. With Zia Chatbot, the AI assistant, you can also perform these checks via chat using pre-defined commands.
Step 3: Analyze the Network Path in detail
While Traceroute shows the hops, Network Path Analysis tools provide much deeper visibility.
- How it works: These tools visualize the entire route, showing performance metrics (latency, loss) for each hop and link, often overlaying this on a map.
- The Benefit: They quickly pinpoint the exact link or device causing degradation (e.g., a congested router at an ISP peering point) which Traceroute alone might not reveal clearly.
OpManager includes Network Path Analysis, providing a hop-by-hop visualization of traffic flow and performance, making it easy to identify the source of latency.
Step 4: Correlate Performance Metrics
Latency rarely happens in isolation. Use a monitoring tool to see the bigger picture:
- Compare latency with: Throughput, response time, packet loss, and device CPU/memory utilization.
- Example: If latency spikes correlate perfectly with high CPU on a specific router, you've likely found an overloaded device bottleneck. If latency is high but device health is fine, suspect network congestion or path issues.
OpManager’s Root Cause Analysis (RCA) feature simplifies this process by bringing all critical metrics such as latency, throughput, packet loss, CPU, memory, and interface metrics as well into a single correlated view. Instead of switching between multiple dashboards, you can instantly compare performance parameters side by side to identify what’s driving the slowdown.
Step 5: Check Device Health & Configurations
Dive deeper into the network devices identified in previous steps:
- Performance: Log in to routers, switches, and firewalls along the path. Check CPU, memory usage, and look for interface errors/discards.
- Configuration: Review configurations for potential issues like duplex mismatches, incorrect MTU settings, or buggy firmware versions.
- QoS Settings: Ensure Quality of Service policies are correctly prioritizing latency-sensitive traffic like VoIP and video conferencing.
Step 6: Monitor Bandwidth & Traffic Trends
Identify what's consuming your bandwidth:
- Identify Top Talkers: Use flow analysis (NetFlow, sFlow) to see which users, applications, or conversations are using the most bandwidth.
- Spot Anomalies: Detect unexpected traffic spikes that might indicate large file transfers, backups, or even security incidents causing congestion.
- Optimize Usage: Throttle non-critical traffic or schedule heavy transfers during off-peak hours.
OpManager: Your unified latency troubleshooting platform
Manually performing all these steps across a complex network is inefficient. ManageEngine OpManager provides a unified platform with the integrated tools needed to quickly identify and resolve latency issues.
- End-to-End Visibility: OpManager monitors latency, packet loss, bandwidth, device health (CPU/Memory), and interface errors across your entire hybrid network from a single console.
- WAN Performance Monitoring: Leverages Cisco IP SLA to provide deep insights into WAN link availability, RTT, and bottlenecks between sites.
- VoIP Quality Monitoring:Tracks key VoIP metrics like jitter, packet loss, and MOS scores to pinpoint issues affecting call quality.
- Integrated Troubleshooting Tools: Includes built-in Ping, Traceroute, and advanced troubleshooting features like Network Path Analysis (which helps visualize the entire path between the source and destination, enabling faster issue detection).
- Bandwidth Analysis (NetFlow Add-on): Provides detailed traffic analysis to identify bandwidth hogs and application-specific congestion.
- Configuration Management (NCM Add-on): Tracks configuration changes and helps identify misconfigurations that might be causing latency.
Conclusion
ManageEngine OpManager is a comprehensive network monitoring and network troubleshooting software. The solution effectively performs network latency testing by tracking the total RTT taken by data packets to reach the destination and return, and troubleshoots network latency. The tool enables you accurately diagnose issues to implement corrective actions to mitigate the effect of network issues and resolve them quickly.
FAQs on network monitoring:
1. What is considered "high" latency?
It depends on the application:
- < 50ms: Excellent for most applications, including gaming and VoIP.
- 50ms - 100ms: Generally acceptable for web browsing and most business apps.
- 100ms - 200ms: Noticeable lag, may impact real-time interactions.
- > 200ms: Poor performance, significant lag in applications, choppy VoIP/video.
2. How can I differentiate between latency caused by my network vs. the application server?
Use Traceroute or Path Analysis . If high latency appears at hops within your network or at your ISP connection, the issue is likely network-related. If latency is low until the very last hop (the server itself), the issue might be server processing delay or an application bottleneck. Correlating with server CPU/memory monitoring is also key.
3. What is jitter and how does it relate to latency?
Latency is the delay itself. Jitter is the variation in that delay over time. Consistent latency is often manageable, but high jitter (rapidly changing delay) severely impacts real-time applications like VoIP and video, causing dropouts and garbled audio/video.
4. Can latency be caused by Wi-Fi?
Yes. Wi-Fi inherently has slightly higher latency than a wired connection.More importantly, Wi-Fi interference, poor signal strength, or an overloaded access point can significantly increase latency and packet loss for wireless users. Always test with a wired connection if possible to rule out Wi-Fi issues.
By Allan Joshua,
Product Marketer, ManageEngine
