Campus Network Architecture

Campus network architecture has evolved rapidly over the last decade or more. The number of services supported in a campus environment has evolved just as quickly, if not more so. The basic infrastructure has traditionally been summed up under the Cisco Hierarchical Network Model mentioned in the previous section.

This remains the case because that model scales very well. The role has expanded somewhat on its own to include technologies such as quality of service (QoS), Multiprotocol Label Switching Virtual Private Networks (MPLS VPN), IPsec VPN, Hot Standby Router Protocol (HSRP), and more. Shifting topological ideology has seen a dramatic increase in the number of enterprise networks shifting from traditional Layer 2 switching to Layer 3 switching at the Access and Distribution layers. The campus network architecture is meant to provide enterprise corporate headquarters sites (which might mean a single building or multiple buildings in a common geography) with a means of consolidating and simplifying network support and administration while increasing service and application offerings to the user community. Figure 1-3 illustrates the campus network architecture.

Figure 1-3 Campus Network Architecture

Access

Distribution

Data Wireless Voice

VLAN VLANs VLAN

Data Wireless Voice

VLAN VLANs VLAN

Distribution

Campus services are changing in nature from traditional stateless (connection and/or session unaware and packet switching) to stateful services requiring highly available, redundant devices to track sessions and connections at all times. Meeting this need requires changes in the basic networking paradigm.

For example, a wireless client roaming throughout a wireless-enabled campus using both a laptop and a Cisco 7920 802.11b IP Phone would need to have the ability to seamlessly home from access point to access point with no interruption in service. This is especially true of voice calls in progress. The presence of voice and data together would necessitate a fully QoS-enabled network for both wired and wireless connected devices. An access point would be required to be able to exchange session state information and user/device credentials with no user interaction.

This poses only a single example of the need for campus evolution to accommodate dynamic needs of users and devices. Also, as the evolution progresses and more devices become network-dependent, the need to eliminate any/all single points of failure becomes more and more critical as a factor to success.

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