WAN & Cloud Networking
Understand Wide Area Network (WAN) technologies, SD-WAN, and modern cloud networking concepts like VPCs, Load Balancers, and CDNs.
What is a WAN?
A Wide Area Network (WAN) is a telecommunications network that extends over a large geographical area (cities, states, or countries). Unlike a LAN, which connects local computers, a WAN connects multiple LANs together. The internet is the largest public WAN in the world.
Traditional WAN Technologies
- Leased Lines (T1/E1, T3) — Direct, dedicated physical fiber/copper connections rented from telcos. Extremely secure and reliable with guaranteed bandwidth, but very expensive.
- MPLS (Multiprotocol Label Switching) — A high-performance telecom network routing technique. It directs data from one node to the next using short path labels rather than long network addresses, bypassing complex routing tables.
- Broadband VPN — Using public internet connections secured by an encrypted VPN tunnel. Much cheaper than leased lines but offers no bandwidth or latency guarantees.
Modern Evolution: SD-WAN
SD-WAN (Software-Defined WAN) is a virtual WAN architecture that allows enterprises to leverage any combination of transport services — including MPLS, LTE, and broadband internet — to securely connect users to applications.
An SD-WAN controller centrally manages traffic routing, automatically sending high-priority voice/video traffic over reliable MPLS lines while routing backup traffic or web browsing over cheap public internet connections.
Cloud Networking Fundamentals
As organizations move applications to cloud providers (AWS, Azure, Google Cloud), networking has transitioned from physical cables and racks to virtual interfaces and APIs:
Virtual Private Cloud (VPC)
A private, isolated network space inside a public cloud. You can define your own IP ranges, subnets, route tables, and gateways, giving you complete control over your cloud resources' networking.
Load Balancers
A device or software service that distributes incoming network traffic across multiple backend servers. This prevents any single server from becoming overloaded, improves application performance, and ensures high availability (if one server crashes, traffic is rerouted to others).
- Layer 4 Load Balancer — Routes traffic based on IP address and TCP/UDP ports.
- Layer 7 Load Balancer (Application) — Routes traffic based on application data (e.g., HTTP headers, URLs, cookies).
Content Delivery Networks (CDNs)
A globally distributed network of proxy servers and data centers. CDNs cache website files (images, videos, HTML) at edge servers closer to the user's physical location. This reduces page load latency and saves origin server bandwidth.
When you watch a video on Netflix, the video is likely streamed from a CDN server in your city rather than Netflix's primary servers thousands of miles away.
What's Next?
Learn how to troubleshoot WAN and internet connectivity in Network Troubleshooting & Tools, or explore virtualization concepts in SDN & Virtualization.