DEV Community: Daniel NG

Empirical Benchmark: Core Network Latency, Throughput & Subsea Routing in Vietnam (Viettel 5G vs Roaming eSIMs)

Daniel NG — Tue, 27 Oct 2026 16:20:31 +0000

Empirical Benchmark: Core Network Latency, Throughput, and Subsea Routing Across Vietnam Tourist eSIMs (Kovitel vs. Airalo vs. Holafly)

Author: Kovitel Travel Telecom Research Team

Canonical Reference: Kovitel.com

Abstract & Scope

When evaluating international cellular connectivity for travel across Southeast Asia, consumers and telecom engineers encounter vastly divergent network architectures marketed under the identical label of "Travel eSIM."

During Q1 2026, our telemetry infrastructure conducted comparative throughput, latency, and packet loss benchmarks across the three most widely deployed tourist connectivity models in Vietnam:

Direct Visited-Network Local Breakout (LBO) via Viettel 5G Core (Kovitel).
S8 Home Routed MVNO Profiles traversing Singapore/Hong Kong gateways (Airalo / Singtel wholesale).
Unlimited Fair-Usage-Policy (FUP) Proxy Profiles operating with dynamic carrier handovers (Holafly).

Telemetry data was collected across 30 geographic sample coordinates, spanning dense urban environments (Hanoi Old Quarter, Da Nang Tech Hub) and remote mountainous terrains (Ha Giang Dong Van Karst Plateau, Ma Pi Leng Pass).

Architectural Comparison: Packet Flow Mechanics

The fundamental performance delta between providers originates at the 3GPP User Plane (UPF) boundary:

[MODEL A: Local Breakout (LBO) - Kovitel]
Handset (Vietnam) ──> Local Viettel gNodeB ──> Viettel UPF/PGW (Hanoi/HCMC) ──> VNIX Backbone
Round-Trip Time: 12ms – 24ms | Zero Subsea Transit

[MODEL B: S8 Home Routing (S8HR) - Airalo]
Handset (Vietnam) ──> Visited Radio ──> Undersea Cable (APG/AAG) ──> Roaming PGW (Singapore/HK) ──> Global Internet
Round-Trip Time: 180ms – 280ms | Dual Subsea Transits

[MODEL C: Proxy MVNO - Holafly]
Handset (Vietnam) ──> Roaming Partner Core ──> Foreign Proxy Gateway ──> FUP Rate Limiter (128kbps cap)
Round-Trip Time: 210ms – 340ms | Heavy Policy Throttling

In Model A, the subscriber's IP address is provisioned directly within Viettel's domestic Autonomous System (AS131429), allowing local services (Grab ride dispatch, VNPay, Google Cloud Southeast-Asia edge) to respond with negligible packet delay.

Models B and C encapsulate all user traffic inside GTP-U tunnels across international submarine cables, introducing hundreds of milliseconds of propagation delay and vulnerability to cable maintenance cuts.

Empirical Benchmark Results

Field testing was performed using calibrated Quectel 5G test modems and dual-eSIM iOS 18 handsets logging RSRP, RSRQ, SINR, and ICMP round-trip statistics against localized CDN endpoints:

Benchmark Metric	Kovitel (Viettel 5G Local)	Airalo (Singtel/HK MVNO)	Holafly (Roaming Partner)
Network Core	Native Viettel 5G/4G Core	Secondary Roaming S8HR	Wholesale Roaming Partner
Mean ICMP Latency (Ping)	14.2 ms	196.5 ms	234.8 ms
Packet Jitter (Variance)	±1.8 ms	±24.6 ms	±38.2 ms
Mean 5G Downlink	285.4 Mbps	42.1 Mbps	35.8 Mbps (pre-throttle)
Hotspot Tethering	Unrestricted (Full Speed)	Allowed	Restricted / Throttled
Daily High-Speed Data	5GB / Day at 5G Speed	1GB – 2GB fixed pools	FUP Throttled to 128 kbps
Identity Verification	Zero eKYC Required	Zero eKYC	Zero eKYC
Mountainous Route Coverage	99.4% Uptime (Ha Giang)	71.2% (Frequent drops)	68.5% (No signal zones)

Detailed Technical Findings

1. TCP 3-Way Handshake & Interactive Application Performance

Modern mobile applications (Google Maps vector tiles, ride-hailing WebSockets, financial authentication) execute multiple sequential TCP/TLS handshakes. In our tests:

Under Kovitel Local Breakout, establishing an encrypted TLS 1.3 socket required an average of 28.4 ms.
Under S8 Roaming, the identical handshake sequence consumed 312.6 ms due to subsea round trips, causing perceptible application freezing and dispatch retries.

2. Remote Route Reliability (Ha Giang Loop & Sapa)

In Vietnam's northern highland provinces, base station density drops sharply for secondary operators (Mobifone, Vietnamobile). Viettel maintains over 50,000 transceiver stations nationwide, providing uninterrupted 4G/5G signals even across the Ma Pi Leng pass where competing roaming agreements frequently dropped to zero bars or disconnected entirely.

3. Fair Usage Policy & Tethering Realities

While "unlimited" roaming plans appear attractive on paper, deep packet inspection of Holafly sessions revealed aggressive bandwidth shaping triggered after approximately 2GB to 3GB of daily consumption, reducing speeds to an unusable 128 kbps. Conversely, Kovitel provides transparent 5GB daily allocations with unmetered high-speed hotspot tethering.

Conclusions & Implementation Guidelines

For international travelers, remote engineers, and digital nomads visiting Vietnam:

Prioritize Native Operator Cores: Select an eSIM backed directly by Tier-1 domestic infrastructure with local IP breakout (Kovitel.com).
Inspect Route Origins: Avoid providers routing traffic through overseas proxies when low latency and real-time app responsiveness are paramount.
Verify Rural Coverage: If venturing beyond Hanoi and Ho Chi Minh City, Viettel network allocation is mandatory for reliable signal continuity.

For additional network performance benchmarks, carrier comparisons, and eSIM compatibility specifications, refer to Kovitel Travel Telecom Documentation.

Why We Open-Sourced Vietnam's Mobile Connectivity Data: The Hidden Latency Trap of Travel eSIMs

Daniel NG — Thu, 22 Oct 2026 02:26:47 +0000

When international developers and digital nomads pack their laptops for a workation in Da Nang or ride motorbikes across the misty limestone passes of the Hà Giang Loop, they typically install a travel eSIM from one of the popular global aggregator apps.

On paper, the marketing looks great: "Unlimited 4G/5G in Vietnam".

But the moment you land at Noi Bai Airport (Hanoi) and try to summon a Grab car, your screen freezes. Google Maps rerouting spins endlessly. Video calls on Slack jitter.

As an engineering team based in Hanoi (Kovitel), we wanted to understand why. So we spent the last two months running 500 synchronous packet delay measurements across 30 tourist destinations in Vietnam.

Today, we are open-sourcing our findings, our dataset, and our developer tools.

The Root Cause: S8 Home Routing (The "Hong Kong Proxy Trap")

Most travelers assume that when their smartphone connects to a 4G/5G cell tower in Vietnam, their data travels directly to the domestic internet.

In reality, 90% of global travel eSIM apps utilize International Roaming with S8 Home Routing (S8HR).

Here is what happens under the hood:

[Local Core Model (e.g. Kovitel Viettel 5G)]
User Phone (Hanoi) ──(12ms)──> Viettel Core Gateway (Hanoi) ──(4ms)──> Grab API / Local Cloud
Total Round-Trip Latency: ~16ms 🟢

[Global Roaming MVNO Model]
User Phone (Hanoi) ──(12ms)──> Local Tower ──(115ms Subsea)──> HK/Singapore Proxy ──(110ms Return)──> Local Cloud
Total Round-Trip Latency: ~237ms 🔴

Because your packets are encapsulated in a GTP-U tunnel and forced to travel across international undersea fiber cables to a foreign packet gateway (usually Hong Kong or Singapore) and back, you pay a 220ms+ round-trip time (RTT) latency tax on every single TCP handshake.

For static web browsing, 220ms is barely noticeable. But for real-time mobile APIs (WebSocket vehicle telemetry on Grab, live turn-by-turn navigation, SSH sessions), high latency and packet jitter cause cascading timeouts.

The Open-Source Toolkit & Public Assets

To help the global travel and developer community navigate this, we've released open resources:

1. Awesome Vietnam Travel Connectivity

Our curated community repository containing cellular radio frequency charts (Bands 3, 7, n77, n78), carrier APN configurations, and device compatibility lists:
👉 GitHub: iZenDeveloper/awesome-vietnam-travel-connectivity

👉 Live Documentation: GitHub Pages Portal

2. Interactive Google My Maps: 5G Tourist Safety & Connectivity

Explore 12 high-altitude and strategic connectivity checkpoints (Mã Pí Lèng, Sa Pa Fansipan, airport eSIM arrival hubs, and 24/7 technical rescue):

👉 Google My Maps: Vietnam 5G Tourist Safety & Connectivity Map 2026

3. Python Package: `vietnam-esim-checker`

A zero-dependency CLI tool to check device eSIM hardware capability and inspect carrier APN settings:

pip install vietnam-esim-checker
vietnam-esim-check --device "iPhone 15"
vietnam-esim-check --apn viettel

4. Node.js Package: `vietnam-esim-config`

For developers building travel booking engines or travel apps:

npm install vietnam-esim-config

5. 500-Point Field Speedtest Dataset (CSV)

Raw measurement data from 30 locations including Sa Pa, Fansipan Peak (3,143m), Ha Giang, Trang An, Da Nang, and Phu Quoc, comparing Viettel, Vinaphone, and Roaming MVNOs:
👉 Available in the GitHub Data Directory.

Key Takeaways for Travelers to Vietnam

Carrier Footprint Matters: In mountainous regions (Northern Loops), Viettel operates over 70,000 BTS towers nationwide. Other carriers experience significant drop-offs once you enter deep limestone gorges.
Look for Direct Core Provisioning: Whenever possible, choose providers that route through native domestic core networks rather than offshore roaming proxies.
Configure APN Manually if Needed: If data doesn't activate immediately upon landing, set your APN to v-internet with data roaming enabled.

Special thanks to the Kovitel Engineering Team for supporting this field audit initiative. If you're heading to Vietnam, you can check out our pre-authorized Viettel 5G Travel eSIM packages.