What shared international bandwidth means for VPN quality out of Vietnam

If you have ever run a VPN on a VPS in Hanoi or Ho Chi Minh City and wondered why throughput to your office in Shenzhen, Singapore, or the US West Coast fluctuates wildly between Monday morning and Friday evening, you are not imagining it. The root cause is almost never the CPU or the disk. It is the difference between domestic and international bandwidth, a distinction most Vietnam VPS providers state in their plan specs but rarely explain. This article walks through exactly what "shared international bandwidth" means, why your 2 GB RAM Vietnam VPS can saturate its domestic 100 Mbps link without breaking a sweat yet struggle to maintain 5 Mbps to a server in Guangdong, and how to test rather than guess.

Why the numbers look different

A typical Vietnam VPS with dedicated IPv4 comes with two distinct bandwidth allocations: domestic and international. Domestic bandwidth refers to traffic that stays inside Vietnam, routed through Viettel, VNPT, FPT Telecom, or CMC Telecom (the four major Vietnamese carriers). This traffic is unlimited with no data cap and runs at 100 Mbps by default on a 1 Gbps port. That 100 Mbps is the speed limit imposed at the account level, not the port speed, a critical detail many posts get wrong. The port itself is 1 Gbps, meaning the underlying infrastructure can handle bursts; you are simply rate-limited to 100 Mbps for domestic flows.

International bandwidth, by contrast, is a shared pool. The provider buys capacity on submarine cables, primarily the Asia-America Gateway (AAG), the Asia Submarine-cable Express (ASE), and the Southeast Asia-Middle East-Western Europe 5 (SEA-ME-WE 5), and divides that capacity among all tenants. Because the cost of international transit is multiple times higher than domestic peering, providers deliberately oversubscribe it. The result: your VPN traffic to a server outside Vietnam shares a pool of roughly 4 to 10 Mbps with every other customer on the same node.

越南 VPS 的国内带宽为 100 Mbps，国际带宽为共享的 4 to 10 Mbps。

A Vietnam VPS typically gives you 100 Mbps domestically and a shared 4 to 10 Mbps pool for international traffic.

This is not unique to Vietnam, every provider in Southeast Asia applies the same model. The difference is the size of the pool and the number of tenants drawing from it. A well-provisioned node in a Tier 3 datacenter such as Viettel IDC or VNPT IDC might give you closer to 10 Mbps to Singapore during off-peak hours. The same node may drop to 2 Mbps on a Tuesday evening during a cable repair event.

What happens during peak hours and cable faults

The shared pool is not static. Its effective capacity depends on three factors:

• Local evening hours (19:00 to 23:00 ICT): Vietnamese residential users come online, streaming, gaming, video calls. Their traffic saturates the international uplink. Your VPN throughput to a server in Kunming or Hong Kong can fall by 40 to 60 % without any change on your VPS.
• Submarine cable repairs: The AAG alone has suffered more than a dozen major disruptions since 2017. When a cable segment between Vietnam and Singapore goes down, the remaining cables take the load. Providers re-route traffic, latency spikes, and the shared pool shrinks further. A repair that takes three weeks is not unusual.
• Cross-border traffic to China: Traffic from Vietnam to mainland China crosses terrestrial fibre via Guangxi or Yunnan border gateways, plus submarine segments near Hong Kong. This route is also shared and subject to congestion at the China-ASEAN exchange points. A cross-border China Vietnam workflow, e.g. a team in Nanning connecting to a database in Ho Chi Minh City, perceives this congestion as intermittent packet loss and jitter.

The key takeaway: you can run a 10 GB file transfer between two servers inside Vietnam and saturate the domestic 100 Mbps link consistently. The same transfer to a server in Shenzhen will top out at whatever the international pool allows at that moment, and that number changes hour by hour.

How to test your actual international throughput

Do not trust the provider's advertised number for international bandwidth. Test it yourself, and test it at multiple times of day. Here is a three-step method that works from any Linux VPS or Windows VPS:

1. Measure latency and loss with MTR

MTR (My Traceroute) combines ping and traceroute into a single output. It shows every hop between your VPS and a target, plus the packet loss at each hop. Run it to a server in your target region:

mtr --report --report-cycles 10 8.8.8.8
mtr --report --report-cycles 10 203.0.113.1   # a real IP in your target region

Look for loss at the third or fourth hop, that is often where your traffic leaves the domestic network of Viettel or VNPT and enters the international transit layer. Loss above 5 % at that hop means the international pool is congested.

2. Run iperf3 to a test server outside Vietnam

Iperf3 is the standard tool for bandwidth measurement. Set up a receiver on a server in, say, Singapore or Hong Kong, then measure from your Vietnam VPS:

# On the remote server (receiver)
iperf3 -s -p 5201

# On your Vietnam VPS (sender)
iperf3 -c <remote-ip> -p 5201 -t 30 -P 4

Run this at 09:00, 14:00, and 21:00 local time. A consistent result above 8 Mbps at all three times suggests the node is well-provisioned. A result that drops below 2 Mbps in the evening is the shared pool showing its limits. If you rent a Windows VPS with RDP, you can install iperf3 from a binary or use a PowerShell wrapper, the same logic applies.

3. Test a real application transfer

Use scp or rsync (Linux) or robocopy (Windows) to move a 100 MB test file between your VPS and a server in your target country. Time the transfer and calculate the effective throughput. This number will always be lower than iperf3 because of protocol overhead and disk I/O, but it is the number that matters for your actual work.

Why shared international bandwidth is not a flaw

It is easy to read the previous sections and conclude that a VPS with full root access in Vietnam is only useful for domestic workloads. That conclusion is wrong. The shared international pool is a deliberate trade-off that keeps the monthly billing VPS affordable for the vast majority of use cases that touch Vietnam:

• A WordPress VPS with LiteSpeed hosting a Vietnamese audience: the 100 Mbps domestic link handles all local visitors. The international pool only serves the occasional overseas admin login.
• A self-hosted GitLab VPS for a Vietnamese development team: push/pull operations stay domestic. CI/CD pipelines that fetch dependencies from npm or Docker Hub use the international pool, but those are short bursts.
• A Windows Server VPS RDP used by a remote team in Guangzhou connecting to a Vietnam-based application: the RDP session itself is low-bandwidth (200 to 500 Kbps). The bottleneck is the latency, not the pool size. Latency from Vietnam to Guangzhou is typically 30 to 60 ms, perfectly usable.
• A VPS for automation workflows running n8n or custom scripts that poll APIs: most API calls are under 10 KB. Even a 2 Mbps international link handles hundreds of requests per second.

The problem only appears when you treat a Vietnam VPS as a general-purpose international VPN server, for example, routing all your team's web traffic through it to access Facebook from a Chinese location, as some VPS for Chinese users guides suggest. A single 1080p YouTube stream needs 5 Mbps. A team of five people sharing one VPN into Vietnam would saturate the pool during every video call. For that use case, the provider's colocation offer, 100 Mbps commit on a 1 Gbps port, is the realistic path.

This is also why a China to Vietnam VPS setup works well for chat, database queries, and RDP but poorly for bulk streaming. Know your traffic profile before you buy.

The dedicated countermeasure: colocation or a dedicated server

If your workload genuinely requires sustained international throughput, a VPN for a remote team that transfers large files daily, a real-time video processing pipeline, or synchronising a multi-terabyte database, the shared pool is not enough. The provider's dedicated server and colocation options solve this differently:

• Dedicated server Vietnam: You get a dedicated IPv4 with free rDNS and an IPKVM. The international bandwidth is still on a shared uplink, but you are the only tenant on that machine, so no neighbour contention at the host level.
• 1U rack colocation Vietnam in a Tier 3 datacenter with a 100 Mbps commit on a 1 Gbps port: you buy guaranteed international capacity. This is the only way to get a predictable 100 Mbps to Singapore or Hong Kong.

Most teams do not need that. The 4 to 10 Mbps shared pool handles email, SSH, RDP, API calls, database queries, and web browsing for small teams without issue. The trick is knowing when you have outgrown it, and having a clear upgrade path.

How to choose a VPS plan based on bandwidth

Avoid comparing VPS pricing solely by RAM and CPU. The bandwidth profile matters more than the core count for any externally-facing workload. Here is a quick rubric for deciding between the VNLite and VNx tiers at standard Vietnamese VPS pricing:

Notice that the 2 GB RAM VPS (VNLite) is perfectly adequate for a small team's RDP or a low-traffic website. The bottleneck is bandwidth, not memory. Conversely, a 4 GB RAM VPS or 8 GB RAM VPS is wasted on a VPN that never sees more than 3 Mbps because the international pool is the constraint.

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