network?
  • What is the skill level of these people?
  • What are their attitudes toward computers and computer applications?
  • How developed are the organizational documented policies?
  • Has some data been declared mission critical?
  • Have some operations been declared mission critical?
  • What protocols are allowed on the network?
  • Are only certain desktop hosts supported?
  • Who is responsible for LAN addressing, naming, topology design, and configuration?
  • What are the organizational human, hardware, and software resources?
  • How are these resources currently linked and shared?
  • What financial resources does the organization have available?
    • Documenting the following requirements allows for an informed estimate of costs and timelines for projected LAN design implementation. It is important to understand performance issues of any existing network. Availability measures the usefulness of the network. Many things affect availability, including the following: Every customer has a different definition of availability. For example, there may be a need to transport voice and video over the network. These services may require more bandwidth than is available on the network or backbone. To increase availability, more resources can be added, but adding more resources will increase the cost of the network. Network design tries to provide the greatest availability for the least cost. The next step in designing a network is to analyze the requirements of the network and its users. Network user needs constantly change. As more voice and video-based network applications become available, the necessity to increase network bandwidth grows too. Another component of the analysis phase is assessing the user requirements. A LAN that is incapable of supplying prompt and accurate information to its users is useless. Steps must be taken to ensure that the information requirements of the organization and its workers are met. The next step is to decide on an overall LAN topology that will satisfy the user requirements. In this curriculum, concentration will be on the star topology and extended star topology. The star topology and extended star topology uses Ethernet 802.3 CSMA/CD technology. CSMA/CD star topology is the dominant configuration in the industry. LAN topology design can be broken into the following three unique categories of the OSI reference model: The final step in LAN design methodology is to document the physical and logical topology of the network. The physical topology of the network refers to the way in which various LAN components are connected together. The logical design of the network refers to the flow of data in a network. It also refers to the naming and addressing schemes used in the implementation of the LAN design solution. Important LAN design documentation includes the following:
    Content 5.1 LAN Design 5.1.4 Layer 1 design One of the most important components to consider when designing a network is the physical cabling. Today, most LAN cabling is based on Fast Ethernet technology. Fast Ethernet is Ethernet that has been upgraded from 10 Mbps to 100 Mbps, and has the ability to utilize full-duplex functionality. Fast Ethernet uses the standard Ethernet broadcast-oriented logical bus topology of 10BASE-T, and the CSMA/CD method for MAC addressing. Design issues at Layer 1 include the type of cabling to be used, typically copper or fiber-optic, and the overall structure of the cabling. Layer 1 cabling media includes types such as 10/100BASE-TX Category 5, 5e, or 6 unshielded twisted-pair (UTP), or shielded twisted-pair (STP), 100BaseFX fiber-optic cable, and the TIA/EIA-568-A standard for layout and connection of wiring schemes. Careful evaluation of the strengths and weaknesses of the topologies should be performed. A network is only as effective as its underlying cable. Layer 1 issues cause most network problems. A complete cable audit should be conducted, when planning any significant changes for a network, to identify areas that require upgrades and rewiring. Fiber-optic cable should be used in the backbone and risers in all cable design settings. Category 5e UTP cable should be used in the horizontal runs. The cable upgrade should take priority over any other necessary changes. Enterprises should also make certain that these systems conform to well-defined industry standards, such as the TIA/EIA-568-A specifications. The TIA/EIA-568-A standard specifies that every device connected to the network should be linked to a central location with horizontal cabling. This applies if all the hosts that need to access the network are within the 100-meter distance limitation for Category 5e UTP Ethernet. In a simple star topology with only one wiring closet, the MDF includes one or more horizontal cross-connect (HCC) patch panels. HCC patch cables are used to connect the Layer 1 horizontal cabling with the Layer 2 LAN switch ports. The uplink port of the LAN switch, depending on the model, is connected to the Ethernet port of the Layer 3 router using a patch cable. At this point, the end host has a complete physical connection to the router port. When hosts in larger networks are outside the 100-meter limitation for Category 5e UTP, more than one wiring closet is required. By creating multiple wiring closets, multiple catchment areas are created. The secondary wiring closets are referred to as intermediate distribution facilities (IDFs). TIA/EIA-568-A standards specify that IDFs should be connected to the MDF by using vertical cabling, also called backbone cabling. A vertical cross-connect (VCC) is used to interconnect the various IDFs to the central MDF. Fiber-optic cabling is normally used because the vertical cable lengths are typically longer than the 100-meter limit for Category 5e UTP cable. The logical diagram is the network topology model without all the detail of the exact installation paths of the cabling. The logical diagram is the basic road map of the LAN including the following elements: The logical diagram is essential when troubleshooting network connectivity problems. If Room 203 loses connectivity to the network, by examining the cut sheet it can be seen that this room is running off cable run 203-1, which is terminated on HCC 1 port 13. Using a cable tester it can be determined whether the problem is a Layer 1 failure. If it is, one of the other two runs can be used to reestablish connectivity and provide time to troubleshoot run 203-1.
    Content 5.1 LAN Design 5.1.5 Layer 2 design The purpose of Layer 2 devices in the network is to provide flow control, error detection, error correction, and to reduce congestion in the network. The two most common Layer 2 networking devices are bridges and LAN switches. Devices at Layer 2 determine the size of the collision domains. Collisions and collision domain size are two factors that negatively affect the performance of a network. Microsegmentation of the network reduces the size of collision domains and reduces collisions. Microsegmentation is implemented through the use of