Functionality
To ensure fast response time on the Desert View LAN, each server is connected to the backbone via 100 Mbps connections, ensuring rapid response from the server to any request. High throughput is assured with the campus backbone running between the main LAN switch in Wing 3 West and the switches in each individual building's IDF running at 1 Gbps. From the building IDF to each classroom, the horizontal cabling is running at 100 Mbps. The classroom hubs represent a bottleneck, with bandwidth is reduced to 1 Mbps per workstation. This meets the demand outlined for the initial implementation, and allows for the hubs to be replaced gradually with switches to microsegment the network and deliver much higher bandwidth to the workstation without requiring re-cabling. This fulfills the second element of functionality, which is high throughput.

Reliability has been ensured via redundant backbone runs, and redundant runs from the hub to the workstation outlet. Two fiber pairs run from the MDF to the IDF, one in use and the other a backup. In case the active run fails, the redundant run can be activated by simply moving a patch cable to the other jack on the patch panel in the MDF and the IDF. In each classroom, each curriculum wall outlet contains four active outlets and one inactive backup, and the administrative wall outlet contains one active jack and one inactive backup. If a jack fails, the backup can be activated by moving a patch cable on the patch panel in the classroom wiring cabinet.

In addition, management stations using SNMP will be used to track network traffic patterns and help identify potential problems before they erupt.

At the WAN level, fast response time, high throughput, and reliability have also been considered. Each WAN core router is connected to each other router by four T1 links, to provide load-balancing and redundancy. In the future, as WAN bandwidth demands increase, the T1 links will be replaced by two redundant fractional T3 links. The bottleneck at this level is the T1 link to the school.

For Internet access, the connection from the WAN core router to the Firewall/NAT router is running at 1 Gbps, the connection from the Firewall router to the Public Access router is running at 100 Mbps, and the connection from the Public Access router to the Internet is running over a Frame Relay link with a CIR of 1.544 Mbps, equivalent to a T1. We also plan to upgrade this link to fractional T3 speed in the future. Traffic will be slowed by the Firewall router, as it will have to test traffic against its ACLs, and again at the T1 link to the school.

Scalability
On the Desert View LAN, each workstation will be operating at 1 Mbps. Projected growth over the next seven to ten years includes a 100-fold increase in LAN throughput. As mentioned above, the horizontal and vertical cabling can already support 100 Mbps throughput, with the bottleneck being the hubs in each classroom. By replacing the hubs over time with switches and microsegmenting, usable bandwidth can be increased to 100 Mbps, without any of the existing cabling or other equipment needing to be replaced.

WAN core throughput is expected to double in the same time period. Currently, each WAN core router is connected by four T1 links. With each link running at 1.544 Mbps, the bandwidth between each router is 6.176 Mbps. In order to deliver double the bandwidth, or 12.352 Mbps, we plan to replace the four T1s with two redundant fractional T3s. The Cisco 7206VXR routers that we have chosen will accomodate T3s by replacing the network modules.

District Internet connection throughput is expected to increase 10-fold in the next seven to ten years, which means that the current CIR of 1.544 Mbps must increase to 15.44 Mbps. We also plan to update this link to fractional T3 speed to realize this increase in throughput, which will again involve replacing the network module on the router.

Adaptability
The Washington Elementary School District network was designed to be "modular," so that upgrades could be easily accomplished. All devices are connected through labeled patch panels, so that a device can be disconnected and a new device inserted into the panel and connected into the network with minimal disruption. This helps us to plan for the classroom hubs to be replaced with switches, for example, to accomodate the increase in throughput, or for a WAN core router to be disconnected long enough to replace a network module, and then be reinserted into the network. This gives us flexibility to upgrade to newer technologies as they become available, without requiring rewiring or long periods of network downtime.

Manageability
SNMP will be used across the network to facilitate network management. On the Desert View LAN, both the curriculum and the administrative networks have a management server that will collect statistical data about traffic flow and protocols on the network, and allow management of all hubs and switches on the network, with the exception of the Black Box hubs located in the double portable classrooms. The management server on the administrative network will consolidate information in one place, so that the District administration will be able to access the collected SNMP data from the school network. The administration will also be able to access either management server to directly manage the devices on their respective networks. Each school will also have a modem connection to the site router, allowing the district administrator to dial in and remotely maintain and administer the router.