Wiring Closets
In Semester 1 chapter 8 we learned that in a star topology, horizontal runs must be attached to a central point. "TIA/EIA-569 specifies each floor must have a minimum of one wiring closet. Additional wiring closets should be provided for each 1,000m2, when the area of the floor that is served exceeds 1,000m2, or the horizontal cabling distance exceeds 90m." In the Desert View LAN, each building has a wiring closet where all horizontal runs terminate. No building exceeds 1,000m2, so additional wiring closets are not required in any building. Guidelines for recommended wiring closet sizes were followed when possible, although in some buildings I had to choose between putting the closet in a secure area which was smaller than recommended, and a larger area which was less secure. In Wing 1, the wiring closet is 9ft x 5ft, which is smaller than is desirable, while in Wing 2 the closet had to be placed in a classroom because no secure closet of suitable size exists.
In both chapters 8 and 9, We also learned that certain environmental conditions must be satisfied, including HVAC issues, locations and types of lighting, room access, and cabling support. In the Desert View LAN, each wiring closet has horizontal cabling protected by conduit as it enters the room. The conduit is sealed with fire retardant to prevent fire damage. Each closet with a distribution rack provides at least 30.5cm of clearance space around the rack for physical access by workers and repairmen. In secure closets not located in classrooms, the cabling is supported by ladder rack between the wall and the distribution rack. Each secure closet also specifies incandescent lights rather than fluorescent to reduce electromagnetic interference. Closets also specify no drop ceilings, and a secure door which opens outward. Humidity is not expected to be a problem, although excessive heat is a concern. An air conditioning unit will be placed in the main distribution facility, where five of the six network servers, the LAN switch, and the router are located. In classroms with wiring cabinets, each cabinet has ventilation and fans to keep network equipment at a suitable temperature.
In selecting a location for a wiring closet, we learned that the wiring closet should be in a central location, and workstations should fall within a 50m catchment area of the closet. In the Desert View LAN, all wiring closets are located such that all classrooms fall within that 50m catchment.
In semester 1 chapter 9, we learned about the importance of patch panels as an interconnecting device for connecting horizontal runs to networking devices. In the Desert View LAN, all horizontal cabling terminates at a patch panel, and no device directly connects to any other device without going first through a patch panel. This necessitated the use of jumpers in many cases. The equipment list also provides for punch tools for terminating Cat 6 horizontal cabling.
Cabling
Also in semester 1 chapter 8 we learned about cabling standards. TIA/EIA-568-A specifies four types of backbone cabling, of which 62.5/125mm multimode optical fiber is the most common. Fiber optic cabling is specified for use between buildings because it does not conduct electricity, and therefore eliminates problems caused by different earth grounds. The Desert View LAN conforms to these standards, using 62.5/125mm multimode fiber between each building. TIA/EIA-568-A also specifies that the maximum distance from the HCC to the MCC is 6560ft. All vertical cabling in the Desert View LAN falls well within this maximum distance.
In semester 1 chapter 9, we also learned about the importance of documenting cable runs with a rough diagram of cabling runs, and a naming scheme for each cable. In the Desert View LAN, a cutsheet was created, as well as a sheet decribing the naming scheme for cabling. The equipment list also includes a handheld printer for making labels for cables, patch panel outlets, and wall outlets.
In chapter 9 we also learned about using raceway to enclose cable within a classroom. In the Desert View LAN, all cabling within each classroom is run through raceway. Chapter 9 also taught us about running cable through attics and drop spaces. The equipment list includes fish tape and a dart gun for stringing cable.
Chapter 9 also taught us the importance of testing the network after installation to find split pairs, signal attenuation, near-end crosstalk, noise, and interference, as well as establish a baseline for network operations. The equipment list therefore also includes a multimeter, a cable meter, and a cable tester.
LAN Switching
In Semester 3 chapter2 we learned about the problems of network congestion and ways to use switching to alleviate these problems. Ethernet operates through broadcasts across the physical medium, and becomes burdened when there are too many users attempting to access the same bandwidth simultaneously. Switches create a virtual circuit between communicating nodes, creating a network that acts like it only has two nodes which share the available bandwidth between them. Since switches are more expensive than hubs, however, many businesses migrate slowly by connecting hubs to switches until the hubs can be replaced. In the Desert View LAN, this is how the network has been implemented. The nodes in each classroom are connected to hubs, so they share a single bandwidth domain. However, each hub is connected to a switch port in the IDF, and each IDF switch is connected to a switch port on the LAN switch in the MDF. By using switches to segment the LAN, multiple bandwidth domains can be created within the broadcast domain, allowing the available bandwidth to be used more efficiently.
Chapter 2 also introduced the concept of VLANs, which was expanded in chapter 3. A VLAN allows the broadcast domain to be segmented, so that the nodes attached to each port on the switch act like they are on physically separate switches. This allows users located across large areas to share a single broadcast domain, and provides some security from intrusion by unauthorized users. In the Desert View LAN, students and administrators are on separate VLAN networks, even though they are located within the same physical buildings. Nearly every IDF has separate switches for curriculum and administration users (two IDFs, the P.E. building and the Maintenance building, have a VLAN switch rather than separate switches), but each switch connects to a different port on the LAN switch, which is divided into separate port-centric VLANs for each network. The drawback is that a router is required to allow communication between the VLANs. The router used in the Desert View LAN has two Ethernet ports to connect the separate VLANs together.
Network Security and Data Recovery
In Semester 1 chapters 8 and 9, and semester 3 chapter 8, we learned about the use of surge suppressors and UPS to prevent power problems, including spikes, surges, sags, brownouts, and blackouts. In the Desert View LAN, a UPS is located in the MDF and in IDFs located in secured rooms. Commercial-grade surge suppressors which substantially exceed UL standards are located in classroom wiring cabinets, and for workstations. We learned that MOV-based surge suppressors are not the best choice, and should be located away from network devices; however, in the Desert View LAN it was not always possible to locate surge suppressors away from network devices, and the protection of an MOV-based suppressor was considered to be better than none.
In Semester 3, chapter 8 we learned about fault tolerant storage devices through the use of RAID. One of the most common forms is RAID 5, which stripes data and parity across multiple disks. This allows data to be reconstructed if a drive fails. In RAID 5, the drives are also "hot swappable," meaning that a drive can be removed and replaced without shutting down the server. In the Desert View LAN, all servers have 5 drives and an operating system capable of supporting RAID 5.
In Semester 3 chapter 8, we also learned about using tape backup units to recover data in case of catastrophe that causes both the UPS and surge suppressors to fail and the RAID 5-enabled drives to fail. On the Desert View LAN, a tape backup system is provided to back up both the administrative and curriculum file servers.
As we learned in chapter 8, viruses also pose a danger to networks. A virus is a piece of malicious software that can infect and spread throughout a network. The Desert View LAN will use an antivirus suite, with licenses for each workstation and each server.
Documentation
In semester 1 chapter 9 and in semester 3 chapter 8, we learned that network documentation is the most important (and least performed) task in the network. Documentation includes cutsheet diagrams, MDF and IDF layouts, server and workstation configuration details, software listings, maintenance records, security measures, and user policies. On the home page, links to items covering all of these documents can be found, aside from maintenance records which will be created after the network is put into place and baselines established.