Overview
This lecture explains the three-tiered network architecture commonly used in enterprise networks, its components, alternatives, and the concepts of east-west and north-south traffic flows.
Three-Tiered Network Architecture
- Three-tiered architecture consists of core, distribution, and access layers.
- The core layer houses critical resources like servers, applications, and databases.
- The distribution layer serves as the midpoint, connecting users to core resources, typically via redundant switches.
- The access layer is where users connect, often through switches located near them, such as on the same floor.
- Multiple links between layers provide redundancy in case of device failures.
- This architecture can span multiple buildings with each building's access switches connected to distribution switches, which then connect to the core.
Collapsed Core Architecture
- Smaller organizations may use a two-tier collapsed core architecture, combining core and distribution layers.
- Collapsed core reduces equipment cost and simplifies troubleshooting.
- This design has less redundancy, making it less resilient to device failures.
Traffic Flow in Data Centers
- East-west traffic refers to data moving within the same data center (fast response, internal security).
- North-south traffic is data entering or leaving the data center (from/to external sources like the Internet).
- North-south traffic often requires stronger security controls due to external risks.
Key Terms & Definitions
- Core Layer — Central network tier hosting main resources and data.
- Distribution Layer — Middle layer connecting access switches to the core, often providing redundancy.
- Access Layer — Network edge where user devices connect.
- Collapsed Core — Two-tier network design merging core and distribution layers.
- East-West Traffic — Data flow within a data center.
- North-South Traffic — Data flow entering or leaving a data center.
Action Items / Next Steps
- Review diagrams of three-tiered and collapsed core architectures.
- Understand the differences between east-west and north-south traffic for network security planning.