Understanding the latency differences between IPv4 and IPv6 is crucial for evaluating network performance in dual-stack environments. While theoretical discussions about protocol efficiency abound, actual measurements reveal how your network handles both protocols in real-world conditions. This comprehensive guide covers the tools, methodologies, and analysis techniques for accurately comparing IPv6 and IPv4 latency.
The fastest way to measure IPv4 vs IPv6 latency is to visit test-ipv6.run - a comprehensive testing tool that automatically measures and compares latency for both protocols:
The tool performs parallel tests across multiple endpoints and provides instant comparative results, making it ideal for quick checks and regular monitoring. For detailed technical analysis or scripting, use the command-line tools described below.
Latency (or Round-Trip Time - RTT) measures the time it takes for a packet to travel from your device to a destination server and back. It's measured in milliseconds (ms) and consists of several components:
Lower latency is better - it means faster response times for interactive applications, web browsing, gaming, and real-time communications.
IPv4 and IPv6 latency can differ due to:
Critical insight: In properly configured native dual-stack networks, IPv6 and IPv4 latency should be nearly identical. Significant differences indicate routing inefficiencies or misconfigurations.
For accurate comparison, you must test both protocols to the same destination host. This eliminates variables like geographic distance and server performance.
Identify servers that support both IPv4 and IPv6:
Popular dual-stack test targets:
# Google's public DNS servers
ipv4.google.com # 8.8.8.8
ipv6.google.com # 2001:4860:4860::8888
# Cloudflare DNS
one.one.one.one # 1.1.1.1 and 2606:4700:4700::1111
# Major services
google.com # Dual-stack
facebook.com # Dual-stack
cloudflare.com # Dual-stack
Confirm the host has both A (IPv4) and AAAA (IPv6) records:
Windows:
nslookup -type=A google.com
nslookup -type=AAAA google.com
macOS/Linux:
dig +short google.com A
dig +short google.com AAAA
Always collect multiple measurements - single pings are unreliable due to network variability. Aim for at least 20-50 samples for statistical validity.
Run tests simultaneously or in close succession to ensure network conditions remain consistent. Time-of-day variations can significantly affect latency.
Ping is the universal tool for measuring round-trip time. It sends ICMP Echo Request packets and measures reply time.
IPv4 Ping:
ping -n 50 google.com
IPv6 Ping:
ping -6 -n 50 google.com
Example output:
Pinging google.com [2607:f8b0:4004:c07::71] with 32 bytes of data:
Reply from 2607:f8b0:4004:c07::71: time=12ms
Reply from 2607:f8b0:4004:c07::71: time=11ms
Reply from 2607:f8b0:4004:c07::71: time=13ms
Ping statistics for 2607:f8b0:4004:c07::71:
Packets: Sent = 50, Received = 50, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 11ms, Maximum = 15ms, Average = 12ms
IPv4 Ping:
ping -c 50 google.com
IPv6 Ping:
ping6 -c 50 google.com
Or explicitly force IPv6 with modern ping:
ping -6 -c 50 google.com
Save as compare_latency.sh:
#!/bin/bash
HOST="${1:-google.com}"
COUNT=50
echo "Testing $HOST with $COUNT packets..."
echo ""
echo "IPv4 Results:"
ping -4 -c $COUNT $HOST | tail -1
echo ""
echo "IPv6 Results:"
ping -6 -c $COUNT $HOST | tail -1
Usage:
chmod +x compare_latency.sh
./compare_latency.sh google.com
Output:
Testing google.com with 50 packets...
IPv4 Results:
rtt min/avg/max/mdev = 10.234/12.456/18.123/1.892 ms
IPv6 Results:
rtt min/avg/max/mdev = 10.123/12.234/17.891/1.823 ms
Traceroute reveals the routing path and per-hop latency, helping identify where delays occur.
IPv4 Traceroute:
tracert google.com
IPv6 Traceroute:
tracert -6 google.com
IPv4 Traceroute:
traceroute google.com
IPv6 Traceroute:
traceroute6 google.com
# or
traceroute -6 google.com
Compare hop counts and latency at each hop to identify where protocols diverge. Different paths often explain latency differences.
iperf3 measures maximum throughput and provides latency statistics under load. It requires a server endpoint.
Ubuntu/Debian:
sudo apt install iperf3
macOS:
brew install iperf3
Windows: Download from iperf.fr
Server side:
iperf3 -s
Client side:
iperf3 -c server.example.com -t 30
Server side:
iperf3 -s -V
Client side (force IPv6):
iperf3 -c server.example.com -V -t 30
Key metrics from output:
MTR (My Traceroute) continuously monitors the route and provides real-time latency statistics for each hop.
Installation:
# Linux
sudo apt install mtr
# macOS
brew install mtr
IPv4 test:
mtr -c 100 google.com
IPv6 test:
mtr -6 -c 100 google.com
MTR output shows:
Look for: Hops with high packet loss or latency spikes indicate problem areas.
curl can measure connection time and total request time, reflecting real-world web performance.
IPv4 timing:
curl -4 -o /dev/null -s -w "Time: %{time_total}s\n" https://google.com
IPv6 timing:
curl -6 -o /dev/null -s -w "Time: %{time_total}s\n" https://google.com
Detailed timing breakdown:
curl -6 -o /dev/null -s -w "\
DNS: %{time_namelookup}s\n\
Connect: %{time_connect}s\n\
TLS: %{time_appconnect}s\n\
Start: %{time_starttransfer}s\n\
Total: %{time_total}s\n" https://google.com
This reveals where time is spent: DNS resolution, TCP handshake, TLS negotiation, or data transfer.
Raw measurements need statistical analysis to account for network variability.
Save ping results to files for analysis:
Linux/Mac:
ping -4 -c 100 google.com | grep "time=" | awk -F'time=' '{print $2}' | awk '{print $1}' > ipv4_times.txt
ping -6 -c 100 google.com | grep "time=" | awk -F'time=' '{print $2}' | awk '{print $1}' > ipv6_times.txt
Save as analyze_latency.py:
#!/usr/bin/env python3
import statistics
import sys
def analyze_latency(filename, protocol):
with open(filename, 'r') as f:
times = [float(line.strip()) for line in f if line.strip()]
times.sort()
mean = statistics.mean(times)
median = statistics.median(times)
stdev = statistics.stdev(times)
p95_idx = int(len(times) * 0.95)
p99_idx = int(len(times) * 0.99)
p95 = times[p95_idx]
p99 = times[p99_idx]
print(f"\n{protocol} Latency Statistics:")
print(f" Samples: {len(times)}")
print(f" Mean: {mean:.2f} ms")
print(f" Median: {median:.2f} ms")
print(f" Std Dev: {stdev:.2f} ms")
print(f" Min: {min(times):.2f} ms")
print(f" Max: {max(times):.2f} ms")
print(f" P95: {p95:.2f} ms")
print(f" P99: {p99:.2f} ms")
return mean, median, stdev
if __name__ == "__main__":
ipv4_mean, ipv4_median, ipv4_stdev = analyze_latency('ipv4_times.txt', 'IPv4')
ipv6_mean, ipv6_median, ipv6_stdev = analyze_latency('ipv6_times.txt', 'IPv6')
print(f"\n{'='*50}")
print("Comparison:")
diff_mean = ipv6_mean - ipv4_mean
diff_median = ipv6_median - ipv4_median
print(f" Mean difference: {diff_mean:+.2f} ms ({diff_mean/ipv4_mean*100:+.1f}%)")
print(f" Median difference: {diff_median:+.2f} ms ({diff_median/ipv4_median*100:+.1f}%)")
if abs(diff_mean) < 2:
print(" → Latency is essentially identical")
elif ipv6_mean < ipv4_mean:
print(" → IPv6 is faster")
else:
print(" → IPv4 is faster")
Usage:
chmod +x analyze_latency.py
python3 analyze_latency.py
Latency difference guidelines:
Standard deviation interpretation:
Understanding what causes latency differences helps diagnose performance issues.
Most common cause of IPv6/IPv4 latency disparity. The internet uses separate routing tables for each protocol, meaning packets can take completely different physical paths.
Diagnosis:
# Compare hop counts and paths
traceroute google.com # IPv4 path
traceroute -6 google.com # IPv6 path
Common scenarios:
Tunneling IPv6 over IPv4 (or vice versa) adds latency:
Tunnel types:
Detection:
# Look for IPv4 addresses in IPv6 traceroute
traceroute -6 google.com
If you see IPv4 addresses like 2002:c0a8:0101:: (6to4) or 2001:0::/32 (Teredo), you're tunneling.
Impact: Tunnels add encapsulation/decapsulation processing time plus an extra network hop. Native dual-stack is always faster.
IPv4 typically requires Network Address Translation at the home router or ISP level. NAT processing adds latency:
IPv6 eliminates NAT entirely, providing direct end-to-end connectivity with lower processing overhead.
Maximum Transmission Unit size affects latency, especially for larger packets:
IPv4:
IPv6:
PMTUD issues: If ICMP "Packet Too Big" messages are blocked by firewalls, IPv6 connections may blackhole, appearing as extreme latency or timeouts. See our Path MTU Discovery guide for more details.
Test PMTUD:
# Send large packet to test fragmentation handling
ping -6 -s 1400 -c 10 google.com
ping -6 -s 1500 -c 10 google.com
If larger packets fail or have much higher latency, you have an MTU problem.
DNS lookups add latency to the first connection:
IPv4: A record lookup IPv6: AAAA record lookup
Some DNS resolvers have slower IPv6 connectivity, adding delays to AAAA lookups.
Test DNS latency:
time dig google.com A
time dig google.com AAAA
IPv4: Decades of optimization, mature peering, optimized routing IPv6: Still maturing in many networks
Some ISPs and networks have:
This explains why some networks show systematically slower IPv6 despite no tunneling.
Research and monitoring data provide context for your measurements:
Google's IPv6 Statistics:
Akamai CDN Data (2023):
IEEE Study (2024):
T-Mobile US:
IPv6 Matrix Project (46 countries):
There is no inherent latency advantage to either protocol. Performance depends entirely on:
In well-configured native dual-stack environments, IPv6 and IPv4 latency should be virtually identical (within 1-5ms). Significant differences indicate infrastructure or routing issues, not protocol limitations. For more on protocol differences, see our IPv4 vs IPv6 comparison.
What it means: Your network has mature dual-stack implementation with optimized routing for both protocols.
Action: No action needed - your network is performing optimally.
Likely causes:
Action: Generally acceptable. Most users won't notice this difference. If consistently > 15ms, contact ISP about IPv6 routing optimization.
Likely causes:
Diagnosis:
traceroute -6 google.com
Look for:
Action: If tunneling, disable tunnel and use IPv4-only until ISP offers native IPv6. If routing issue, report to ISP.
Likely causes:
Diagnosis:
# Test basic connectivity
ping -6 google.com
# Test MTU
ping -6 -s 1400 google.com
# Check IPv6 address
ip -6 addr show # Linux
ifconfig | grep inet6 # macOS
ipconfig # Windows
Action: This is the worst scenario - broken IPv6 causes dual-stack sites to timeout (60+ seconds) before falling back to IPv4. Either fix IPv6 properly or disable it completely.
Likely causes:
Action: Enjoy the performance benefit! This increasingly common scenario shows IPv6's advantages in modern networks.
Step 1: Verify native vs tunneled IPv6
# Check your [IPv6 address](ipv6-address-types)
ip addr show # Linux
ifconfig # macOS
ipconfig # Windows
Tunnel indicators:
2002: = 6to4 tunnel2001:0: = Teredo tunnelfd00::/8 or fc00::/8 = Unique Local (not routable)Step 2: Trace the route
traceroute -6 google.com
Count hops and look for:
Step 3: Test MTU/PMTUD
# Small packet (should work)
ping -6 -s 1200 google.com
# Large packet (tests PMTUD)
ping -6 -s 1450 google.com
If large packets fail, you have MTU/PMTUD issues - likely firewall blocking ICMPv6 Packet Too Big messages.
Step 4: Check DNS resolver
time dig @8.8.8.8 google.com AAAA
time dig @2001:4860:4860::8888 google.com AAAA
If IPv6 DNS is much slower, your DNS resolver may have poor IPv6 connectivity.
Step 1: Check for Carrier-Grade NAT
curl -4 ifconfig.me
If your public IPv4 is in CGNAT range (100.64.0.0/10), you're behind Carrier-Grade NAT which adds latency.
Step 2: Verify no double NAT
Check if both your router and ISP are doing NAT - this compounds latency.
Step 3: Test without VPN
VPNs add latency. Disable VPN and retest.
For thorough latency comparison:
The test-ipv6.run tool is particularly valuable because it:
Measuring IPv6 versus IPv4 latency requires:
In properly configured networks, IPv6 and IPv4 latency should be nearly identical (within 1-5ms). Significant differences indicate routing inefficiencies, tunneling overhead, NAT processing delays, or infrastructure maturity issues - not inherent protocol limitations.
For most users, test-ipv6.run provides comprehensive latency comparison with zero configuration. For network engineers and advanced users, command-line tools like ping, traceroute, MTR, and iperf3 enable detailed analysis and troubleshooting.
As IPv6 deployment matures and networks optimize routing and peering, the performance gap continues to narrow. In many modern networks - particularly mobile carriers with IPv6-native infrastructure - IPv6 now demonstrates lower latency than IPv4 due to elimination of NAT processing and more direct routing paths.