Architecture

Table of Contents

1. Overview
   1. Design Goals
   2. Technology Stack
   3. How It Works
2. Per-Region Resources
3. Latency Measurement Types
   1. WebSocket (Primary)
   2. HTTP Ping
   3. Blob Storage
4. Network Path
5. Regenerating Diagrams

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Overview

The Azure APAC Latency Test is a distributed measurement platform that deploys lightweight infrastructure across 14 Azure regions in Asia-Pacific. It enables real-time latency measurement from any client browser using three complementary protocols — WebSocket, HTTP, and Blob Storage — to provide a complete picture of network performance across the region.

Design Goals

Goal	Approach
Low cost	Standard_B2s VMs (~$30/mo each), no premium SKUs
Idempotent deployment	Scripts can be re-run safely; create-or-skip logic
Client-side measurement	All latency measured from the browser — no server-to-server
Multi-protocol	WebSocket (persistent), HTTP (request/response), Blob (storage layer)
Minimal dependencies	Azure CLI only, no Terraform/Bicep required
Comprehensive APAC coverage	14 regions including new markets (Indonesia, Malaysia, New Zealand)

Technology Stack

Layer	Technology	Details
Frontend	Angular 17	Real-time dashboard with Chart.js visualizations
WebSocket Server	Node.js + ws	Echo server on port 8080, measures true RTT
HTTP Server	nginx	Lightweight reverse proxy, HEAD request on port 80
Storage	Azure Blob (Static Website)	1KB test payload, measures storage layer latency
Compute	Ubuntu 24.04 LTS on B2s	cloud-init provisioned, systemd-managed services
Networking	NSG + Public IP (Static)	Inbound 80/8080 only, no outbound restrictions
Deployment	Bash + Azure CLI	Idempotent scripts in deploy/ directory

How It Works

1. Deploy — Azure CLI scripts provision 14 VMs + 14 Storage Accounts across APAC
2. Measure — Angular app opens connections from the user’s browser to each region
3. Compare — Dashboard shows latency differences by protocol and region in real-time
4. Analyze — Results reveal physical distance impact, protocol overhead, and regional maturity

Per-Region Resources

Each of the 14 regions contains:

Resource	Name Pattern	Purpose
Resource Group	rg-latency-{region}	Logical container
VM	vm-latency-{region}	WebSocket + HTTP endpoint
NSG	nsg-latency-{region}	Firewall rules (80, 8080)
Public IP	pip-latency-{region}	Static IP for testing
Storage Account	latency{region}	Blob latency endpoint

Latency Measurement Types

WebSocket (Primary)

• Persistent TCP connection on port 8080
• Measures true round-trip time for data echoing
• Most accurate for real-time application latency

HTTP Ping

• HEAD request to nginx on port 80
• Measures HTTP request/response overhead
• Includes TCP + TLS setup on each request

Blob Storage

• HEAD request to Azure Storage static website
• Measures storage infrastructure latency
• Includes DNS + TLS + storage front-end processing

Network Path

Client → ISP → Azure backbone → Region POP → VM NIC → Application

Latency is dominated by:

1. Physical distance (speed of light in fiber)
2. Network hops (routing efficiency)
3. TLS overhead (for HTTPS/WSS)
4. Application processing (negligible for echo)

Regenerating Diagrams

The architecture diagrams are generated using mingrammer/diagrams. To regenerate:

pip install diagrams
cd docs/diagrams
python3 architecture.py

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