|  | 8.10 | Implementing Installation of the Network
| 8.10.3 | Common peripheral ports, external SCSI connections (esp. DB-25), print servers, hubs, routers, brouters, bridges, patch panels, UPSs, NICs, and token ring media filters
Common Peripheral Ports Common peripheral ports include the serial and parallel ports. Serial ports are often used for a workstation's mouse or keyboard, and referred to as a slow port because data can flow only in one direction. Parallel ports are used for devices which are quicker and connect outside of the workstation. Data can be transmitted in both directions, making the connection faster. A printer for example connects to a parallel cable and port to speed up printing processes. Data Bus connectors (DB Connectors) are a "D" shaped connector used to connect serial and parallel cables to the computer. DB connectors are usually referred to with as DB-x, x representing the number of wires, DB-9, DB-15, and DB-25 are most commonly used. External SCSI Connections Small Computer Standard Interface (SCSI) enables workstations to be able to connect to and communicate with peripheral hardware, such as CD-ROMs, disk drives, or scanners. SCSI provides faster data transmission than the parallel port, is used for high-performance systems, and has the capability to chain together up to 7 or 15 devices. Print Server There are two types of print servers, dedicated and non-dedicated. Both types receive requests from end-users and direct the requests to a printer pool. A print server is secure because it has no client access into the network. The difference between dedicated and non-dedicated print servers is dedicated is only used as a print server, while non-dedicated will also have some other network server functions. Hubs Using either twisted-pair or coaxial cabling, hubs connect a number of computers and devices together. Depending on the cabling, hubs can be used to strengthen signals if cables are not long enough and signals begin to fade. Hubs are normally used for star topologies, where each cable segment is connected to the hub. Routers Routers, which operate on the third layer of the OSI Model, route data packets to a destination based on the routing address provided by the data packets. Routers are responsible for addressing and translating logical addresses into the physical address of a packet. Routers are either static or dynamic devices and are normally connected in a mesh topology with other routers. Statically configured routers can not communicate with other routers, they have a determined fixed route, which is manually entered by the administrator. Dynamically configured routers have the ability to communicate with other routers to determine the best path to route a packet by a variety of protocols, including RIP, IGRP, EIGRP, and OSPF. Brouters A brouter is a device, which functions as a bridge and a router. If a brouter receives a packet, it must determine the IP address. If the IP address is not connected to any of its ports, it must route the packet to another location. However, if it receives a packet with an IP address connected to one of its ports, the brouter acts as a bridge and delivers the packet to its destination. Bridges Bridges are devices, which connect two different networks, or network segments, together and filter traffic from each network. The bridge builds a table of physical (hardware) addresses, learning the hosts, which exists on each of its ports. The bridge examines the destination MAC address of each frame; if the destination address is local (on the same bridge port, based on the bridging table), the frame is not sent. However, if the destination MAC address is of a different bridge port from the source address, the frame is forwarded to the non-local destinations. Bridges provide connectivity with Layer 2 filtering. Some bridges will connect networks of differing LAN technologies (like Ethernet to Token Ring). Since the bridge operates at layer 2, it forwards all upper level protocols. - Patch Panels Patch panels, which are an integral part of structured cabling installations, consist of a row of female connectors (or ports) where every cable from different work areas connects directly to the back of the patch panel. They provide support for a UTP, STP, fiber ports, and various CAT ratings of UTP cabling. UPS Uninterruptible Power Supply (UPS) provides protection from spikes and sags that may come over the electrical wires. While the server is plugged in, the battery charger constantly charges the battery. In case of a power outage, the fully charged battery will provide operations to continue or provide enough time for the server to shut down properly. NIC Network Interface Cards (NICs) allow the communication between a computer and the network, providing a physical connection. In order for the computer to interact with the NIC, the computer must have the proper drivers installed. Each NIC is assigned a unique address called the MAC address. This address is also the physical address and is burned onto the NIC by its manufacturer. No two MAC addresses are or can be alike. Token Ring Media Filters A token ring media filter is a passive device, which is used to convert output signals from a token ring NIC, so that it may be compatible with different media types, such as STP cable or different terminations, such as a DB-9 connector. Media filters are also designed to eliminate unwanted high frequency emissions and adjust inputs when using UTP cable.