Campus Network Herarchical Design

Over time, the hierarchical approach in designing a network has proven as the most effective. The goal in designing a Campus network is to divide buildings, floors, workgroups, and server farms into different layer 3 groups to prevent network faults from effecting a large scale of the network. The layers in a hierarchical design are:

  • Core: The core is the central thoroughfare for corporate traffic. All other parts of the network eventually feed into the core. You should design the core to switch packets as quickly as possible. This level should not include operations that might slow the switching of the packet: The distribution layer should handle any packet manipulation or filtering that needs to occur.

  • Distribution: The distribution layer should provide policy-based connectivity between the access layers and the core layer. It is at this layer that packets should be filtered or manipulated. Therefore as the packets are routed to the core, the core just simply needs to switch them quickly to the destination distribution location.

  • Access: The access layer provides user access to the network. It is at this point that users are permitted (or denied) access into the corporate network. Typically, each person sitting at a desk has a cable that runs to a wiring closet and connects to a switch; hence, this level is where the user accesses the network.

When correctly designed, a campus network can enhance business efficiency and lower operational cost. Additionally, a properly designed network can position a business for future growth. A modular or hierarchal network is made from building blocks that are easier to replicate, redesign, and grow. Each time a module is added or removed, there shouldn’t be a need to redesign the whole network. Distinct blocks can be put into and out of service without impacting other blocks

or the network core. This greatly enhances troubleshooting, isolating problems, and network management.

Campus Design Best Practices

  • Redundancy, redundancy is a key of a highly available network. However, too much redundancy can actually be a bad network. It causes the network to hard to reach convergence, and also it is hard to troubleshoot and manage the network.

  • High availability, this refer to the ability of the network to recover from failures. High availibility should be design at many layers.

    • Layer 1: Redundant links and hardware providealternative physical paths through the network.

    • Layers 2 and 3: Protocols such as spanning tree,HSRP, and others provide alternative path awareness and fast convergence.

    • Application availability: The application server and client processes must support failover for maximum availability.

  • Oversubscription, Oversubscription occurs when there are more trafficgenerating endpoints than the network can accommodate at a single time. QoS

    should be used to ensure that real-time traffic such as voice and video, or critical data such as SAP traffic, is not dropped or delayed.