iPhone 17 Cellular Network performance is getting worse than the previous device models

Recent our APP performance online has revealed significant degradation in cellular network SRTT (Smoothed Round-Trip Time) on the latest iPhone models (iPhone 18.1, 18.2, and 18.3) relative to previous generation devices. IDC network transmission SRTT P50 increased by 10.64%, P95 increased by 103.41%; CDN network transmission SRTT P50 increased by 12.66%, P95 increased by 81.08%.

Detailed Performance Metrics:

1. Network Transmission SRTT Degradation

Following optimization of our APP's network library, iOS network transmission SRTT showed improvement from mid-August through mid-September. However, starting September 16, cellular network SRTT metrics began to degrade (SRTT increased). This degradation affects both IDC and CDN routes. WiFi network performance remains unaffected.

2. Excluding iOS 26.x Version Data

After data filtering, we discovered that the increase in iOS cellular network transmission SRTT was caused by data samples from iOS 26.x versions. When excluding iOS 26.x version data, network transmission SRTT shows no growth.

3. Comparative Analysis: iOS 26.x vs. iOS < 26.0

network transmission SRTT shows：

IDC (Internet Data Center) Links: P50 latency: 10.64% increase / P95 latency: 103.41% increase

CDN (Content Delivery Network) Links: P50 latency: 12.66% increase / P95 latency: 81.08% increase

4. Device-Model Analysis: iOS 26.x SRTT Degradation Scope

Granular analysis of iOS 26.x samples across different device models reveals that network SRTT degradation is not universal but rather specific to certain iPhone models.

These measurements indicate a substantial regression in network performance across both data center and content delivery pathways.