Campus Network Architecture

Why do we use Hierarchical LAN Design Models ? 

We divide the network architecture into modular layers so that we can achieve the following,
  1. Each Layer implements and performs a specific function
  2. Helps the network to scale easily 
  3. Provides Fault isolation and facilitates easier troubleshooting
Modular Building Blocks:
Hierarchical LAN Design breaks the network into 3 building blocks:
  1. Access Layer 
  2. Distribution Layer 
  3. Core Layer

Campus Network Architecture:

The Access Layer
  • Access Layer AKA the “Network Edge” it’s the block where the end user devices are attached. 
    • End User Devices – PC’s, IP Phones, Wireless Access Points, Printers, IP Cameras .. etc.
  • Provides high bandwidth access to both wired and wireless users, Since it’s the First hop for Quality of Service (QOS) trust points.
  • Access Layer can be logically segment using VLANs, where we can have different logical networks for performance, management and security
  • Communication between the Access Blocks occurs through distribution blocks,
    • The Access switches connect North/South to distribution switches
    • Access switches are not connected East/West to each other

The Distribution Layer
  • Aggregates access layer switches in the building or campus, thereby reducing the number of cable runs and avoids daisy chaining of access switches
  • Normally Layer 2 Spanning-Tree Protocol (STP) is configured southbound to the access layer and Layer 3 Routing is configured northbound to the Core Layer. Hence it provides a boundary between layer 2 and layer 3
  • Distribution Layer is the logical place for summarising IP address space northbound (or) upstream to the core
  • Distribution switches should be deployed in pairs for redundancy(Node redundancy) if an individual switch is lost, Traffic flow stills happens around the failed node.
  • Distribution switches interconnect with each other using Layer 2 or Layer 3 links depending on the design.

The Core Layer
  • Core Layer is the backbone and aggregation point for multiple networks
  • Provides high speed Layer 3 connectivity between distribution blocks and the following,
    • The WAN – Private access to multiple remote sites or to cloud providers (aws, azure .. etc.) 
    • The Internet – Regular Internet connectivity and or to connect remote VPN users.
    • The Data Center – ecommerce or big data transactions 
  • The Network Services Layer – Authentication, Load Balancing .. etc.
  • Reduces the cabling needs from N x (N-1)/2 to N links for distribution switches. 

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