🌐 Multi-AS Content Delivery Network (CDN) with Hierarchical QoS

Simulation Environment: CORE Emulator v9.2.1 UC: Redes de Computadores II
Institution: Universidade do Minho Project Grade: 18 / 20 Values

---

📄 Overview

This repository contains the network architecture and configuration scripts for a distributed Content Delivery Network (CDN) simulated across a multi-domain topology. The infrastructure models a realistic Internet transit system, combining inter-domain routing, traffic engineering, automated content replication, and strict quality of service optimization.

🛠️ Implemented Features & Protocols

• Routing Engine:

  • BGP (eBGP & iBGP): Manages inter-AS policies and internal routing updates over isolated paths.
  • OSPFv2: Deployed within the transit core using multi-area segmentation and Route Reflection.
  • RIPv2: Distance-vector routing applied inside the local access networks.

• Anycast Architecture:

  • HTTP Anycast: Georedundant web content delivery sharing the prefix 172.16.0.10/32.
  • DNS Anycast (BIND9): Distributed domain name resolution (www.cdn.com) running over 172.16.0.53/32.

• Secure Core Isolation:

  • GRE Tunnel: Point-to-point overlay link used exclusively for internal Unicast management traffic (192.168.0.0/30).
  • TCP Tuning: Optimized with a strict 1400 bytes MTU and 1360 bytes MSS Clamping via iptables to prevent overlay fragmentation.

• Content Automation:

  • FTP Sync (vsftpd): Automated file replication pipeline between PoPs.
  • Pipeline: Automated Bash scripts running via cron that force traffic through the GRE interface and handle atomic local transfers using a quarantine directory.

• Quality of Service (DiffServ):

  • Traffic Marking: Packet classification at the source via iptables mangle using DSCP CS4 (HTTP VIP) and AF11 (FTP) classes.
  • Hierarchical Token Bucket (HTB): Bandwidth scheduling over a shared 10 Mbps bottleneck link, securing class guarantees, capacity borrowing, and automatic descarding of unclassified Best Effort traffic during high-congestion tests (netem delay 2ms).

📂 Repository Structure

• multi-as-topology.xml: Core Emulator project file containing all node configurations and topology definitions.
• more about pt-pt/: Project statements (PDFs), visual topology, and the final technical report in Portuguese.
  • For detailed configuration analysis and implementation logic, please refer to the report in this directory.

⚙️ Prerequisites & Dependencies

To ensure all virtual nodes and services start correctly within the CORE Emulator, the host Linux operating system must have the following packages installed:

• Routing Engine:
  • quagga (Required for OSPF, BGP, and RIP routing daemon execution)
• CDN Application Services:
  • bind9 (DNS Server)
  • vsftpd (FTP Server for automated replication)
  • apache2 or lighttpd (HTTP Web Server)
• Traffic Engineering & Testing Tools:
  • iperf (Traffic generation for QoS congestion testing)
  • curl (File transfer and FTP automation scripts)
  • iptables & iproute2 (Required for DiffServ packet marking and HTB Traffic Control)

Quick installation command (Debian/Ubuntu hosts):

sudo apt update
sudo apt install quagga bind9 vsftpd apache2 iperf curl iptables iproute2