Overview
This lecture explains the three-tiered network architecture commonly used in enterprise networks, discusses alternative designs, and describes network traffic flow types.
Three-Tiered Network Architecture
- A three-tiered architecture includes the core, distribution, and access layers.
- The core layer is the central point for critical resources like servers, applications, and databases.
- The distribution layer connects users to core resources and provides redundancy with multiple switches.
- The access layer consists of switches close to end-users, usually on the same building floor.
- Users connect to the access layer, which connects to the distribution layer, and then to the core.
- Multiple links between layers ensure redundancy for communication paths.
Network Structure Example
- In multi-building campuses, each floor's users connect to an access switch.
- Access switches link to distribution switches, which connect to the central core (often in a data center).
- This design allows for resilient communication between buildings and floors.
Collapsed Core (Two-Tier) Architecture
- Smaller organizations may use a two-tier (collapsed core) architecture that combines the core and distribution layers.
- The access layer remains unchanged in collapsed core designs.
- This approach simplifies network design and is less expensive but offers less redundancy.
East-West and North-South Traffic Flows
- East-west traffic occurs within the same data center, moving between internal devices.
- East-west traffic usually has fast response times due to local network proximity.
- North-south traffic moves into or out of the data center, such as data from or to the Internet.
- North-south traffic requires different security measures since sources or destinations may be external.
Key Terms & Definitions
- Core Layer — The central tier in network architecture hosting critical resources.
- Distribution Layer — The midpoint tier, connecting users to core resources and providing redundancy.
- Access Layer — The tier where end-users connect to the network, typically via local switches.
- Collapsed Core — A two-tier design combining core and distribution layers for simplicity.
- East-West Traffic — Data flow within the same data center or local network.
- North-South Traffic — Data flow entering or leaving the data center or network perimeter.
Action Items / Next Steps
- Review diagrams of three-tiered and collapsed core network architectures.
- Understand scenarios where each architecture is appropriate.
- Be able to distinguish between east-west and north-south traffic in network diagrams.