Table  2-3.—Types  of  backbone  cable. Connection  to  the  backbone  network  may  require  a bridge,  router,  gateway,  concentrator  or  hub,  depending on the architectures of the various LANs and the backbone itself. The connectors used will also depend on the type of cable used for the backbone. If the backbone is coaxial cable, you would use a T-connector and barrel connectors to make the connection to another cable or a hardware device. The backbone manages the bulk of the traffic, and it may connect several different locations, buildings, and even smaller networks. The backbone often uses a higher-speed  protocol  than  the  individual  local  area network (LAN) segments. One obstacle to a successful backbone network is the high bandwidth that may be required to handle potentially  heavy  traffic.  Because  of  this  consideration, fiber-optic  cable  is  the  most  sensible  cabling  for backbone networks. NODES The computers, or nodes, in a network may be used for workstations, servers, or both. PCs need a network interface   card   (NIC)   installed   for   networking capabilities. The NICs mediate between the computer and the network  by  doing  the  necessary  processing  and translation to enable users to send or receive commands and data over the network. NICs are designed to support a particular network architecture, such as Ethernet® or ARCnet®. To connect a node directly to a backbone, you would use a drop cable for the connection. Nodes are normally connected to the backbone indirectly through a concentrator or a hub rather than with a drop cable. The elements needed to connect a node to a network include  the  following: e l l l Cable: twisted-pair, coaxial, or fiber-optic Wiring centers: hubs or concentrators Intranetwork  links:  connectors,  repeaters,  and  so on Internetwork  links:  bridges,  routers,  gateways, and so on The  cable  provides  a  transmission  medium,  as  well as the physical link between the nodes on the network. Connectors and repeaters attach cable sections to each other;  connectors  and  transceivers  attach  NICs  to  a cable  and,  thereby,  to  the  network.  Transceivers  enable different types of cable to be attached to each other. Terminators absorb a transmission at the end of a network, preventing the signal from traveling back in the  other  direction  on  the  network.  The  types  of intranetwork  links  allowed  in  the  network  depend  on the type of cable used and on the network topology used. Wiring centers serve as a focal point for network elements,  and  may  influence  the  logical  arrangement  of nodes  on  the  network. Internetwork   links   may   be   bridges,   routers, gateways,  and  soon.  Such  components  serve  to  connect networks to each other. The type of internetwork link depends on whether the two networks are the same or not, and the amount of translation that is needed. NETWORK  SERVER A server is the central computer in a network, and is responsible for managing the network. The server provides some type of network service. It may be hardware, such as a file server, or software, such as network level protocol for a transport level client. The   server   provides   its   service   to   other workstations on the network or to other processes. In a server-based  network,  the  most  important  hardware server is the fileserver, which controls access to the files and data stored on one or more hard disks. 2-9