High latency in Kubernetes can quickly become a serious pain point for DevOps engineers. It affects application responsiveness, increases request timeouts, and often leads to poor user experience. Fortunately, Kubernetes provides several tuning options and architectural improvements that can significantly reduce network and service latency.
Let's go through the key techniques that help optimize Kubernetes networking and speed up your cluster.
1. Tune kube-proxy: Switch from iptables to IPVS
By default, kube-proxy often runs in iptables mode, which can become inefficient as the number of services and rules grows. A better alternative is IPVS, which provides faster load balancing and more efficient packet processing.
To switch kube-proxy to IPVS mode:
kubectl edit configmap -n kube-system kube-proxySet the following value:
mode: "ipvs"Why IPVS helps
- More efficient load balancing
- Lower latency under high traffic
- Better scalability for large clusters
2. Use eBPF-Based Networking (Cilium)
Traditional iptables-based networking can become a bottleneck in high-throughput environments. Cilium, powered by eBPF, replaces iptables with kernel-level packet processing, significantly improving networking performance.
Install Cilium using Helm:
helm install cilium cilium/cilium --namespace kube-systemBenefits of eBPF
- Faster routing and filtering
- Reduced CPU overhead
- Improved observability and security
- Lower network latency for services and pods
3. Enable NodeLocal DNSCache
DNS resolution is a common hidden source of latency in Kubernetes. Every pod DNS request usually goes through CoreDNS, which can become overloaded.
NodeLocal DNSCache runs a local DNS cache on each node, dramatically reducing DNS lookup time.
Enable it with:
kubectl apply -f https://k8s.io/examples/admin/dns/nodelocaldns.yamlResults
As a result, DNS resolution becomes significantly faster, the load on CoreDNS is noticeably reduced, and overall performance improves, especially in microservice-heavy workloads where services frequently communicate with each other.
4. Tune TCP Settings with sysctl
Linux TCP defaults are not always optimal for high-performance Kubernetes workloads. Adjusting kernel parameters can reduce connection latency and improve throughput.
Recommended TCP tuning:
sysctl -w net.core.somaxconn=1024sysctl -w net.ipv4.tcp_tw_reuse=1sysctl -w net.ipv4.tcp_max_syn_backlog=8192What this improves
- Faster connection handling
- Better performance under high concurrency
- Reduced SYN queue drops
5. Use Multi-NIC Networking and Advanced CNI Plugins
In high-throughput or latency-sensitive environments, a single network interface can become a bottleneck. Using multiple network interfaces (Multi-NIC) allows traffic to be distributed more efficiently.
Multus CNI enables pods to attach to multiple network interfaces simultaneously.
When to use Multus
- High network bandwidth requirements
- Low-latency workloads (databases, streaming, telecom)
- Separation of control and data plane traffic
Conclusion
Reducing latency in Kubernetes is not about a single tweak—it’s about systematic optimization of networking, DNS, kernel settings, and cluster architecture. By switching kube-proxy to IPVS, adopting eBPF-based networking with Cilium, enabling NodeLocal DNSCache, tuning TCP parameters, and leveraging Multi-NIC setups, you can significantly improve cluster responsiveness and stability.
These optimizations are especially valuable for:
- Microservice architectures
- High-load production clusters
- Latency-sensitive applications
Start with the changes that provide the biggest impact for your environment, measure the results, and iterate carefully.
FAQ
- What causes high latency in Kubernetes clusters?
High latency is most commonly caused by inefficient service routing (iptables-based kube-proxy), overloaded DNS (CoreDNS), suboptimal Linux TCP settings, and network bottlenecks at the CNI or node level. In large or busy clusters, these issues become more noticeable and directly impact application response times. - Is switching kube-proxy to IPVS safe for production?
Yes. IPVS is widely used in production environments and is officially supported by Kubernetes. However, it should always be tested in a staging cluster first, especially if your environment relies on custom networking or firewall rules. - Do I need eBPF and Cilium to reduce latency?
Not necessarily. IPVS and NodeLocal DNSCache already provide significant improvements. Cilium with eBPF is recommended for high-performance or large-scale clusters where maximum efficiency and observability are required. - Will NodeLocal DNSCache work with existing CoreDNS setups?
Yes. NodeLocal DNSCache is designed to work alongside CoreDNS and acts as a local caching layer, reducing DNS request latency without requiring major changes to your existing configuration. - Are TCP sysctl optimizations universal for all workloads?
No. TCP tuning depends on workload characteristics and traffic patterns. Always benchmark and validate sysctl changes in a test environment before applying them to production clusters. - When should I consider Multi-NIC or Multus CNI?
Multi-NIC setups are most useful for latency-sensitive, high-throughput, or network-intensive workloads. For smaller clusters or low traffic scenarios, the added complexity may not be justified.
