l  a  crimping  tool,  for  pressing  the  cable  and connector together, and l a die for the specified cable/connection pair, to make sure cable and connector fit properly. Installation  tool  kits  that  include  the  crimping  tool, die, cable, connectors, and cable ties can be purchased from manufacturers. These kits range in price from one or two hundred to several thousand dollars. TOOLS  FOR  TESTING  CABLES.—  Voltmeters and ammeters provide readings of voltage and current, or amperage by tapping into the circuit and recording the electrical activity as it occurs. These recorded values may or may not provide the details about what is happening along the lines of the network. Scanners are much more sophisticated testing tools. Some  of  the  capabilities  of  scanners  include  the following: l l l l l Check for faults in a cable. Test   a   cable’s   compliance   with   network architectures. Monitor performance and electrical activity, given   the   type   of   cable   and   architecture involved. Test  the  cable’s  wiring  sequence. Generate and print a summary of the information obtained from the tests. A powerful scanner can test for cable quality, for the quality of the connections between cable segments, or between cable and device. A less poweful scanner will be able to test for noise, crosstalk, signal attenuation, resistance, cable length, and so on. Software  Testing Diagnostic software can be used to help anticipate or catch problems early and to help deal with the problems  once  they  have  arisen.  Network  versions  of diagnostic  software  may  be  expensive,  but  they  can save  the  system  under  some  circumstances.  For example, virus detection software can save hours of reconstruction   and   reloading   the   system.   Using software to test the hard disk can identify bad disk sectors before data can be written to them and move any data from bad sectors to a safe location. Another use of diagnostic software is performance monitoring  and  analysis,  which  involves  tracking  the networks   behavior.   This   will   help   to   identify 2-8 inefficiencies   and   bottlenecks,   so   they   can   be elimated.   While   monitoring   the   system’s performance, keep careful track of the following: l l l l Operating costs Threats to security User satisfaction User productivity Track these areas especially during the first few weeks after the network is installed. Do not be surprised if  some  of  these  measured  indicators  change  drastically during  this  period.  For  example,  costs  may  drop drastically   after   the   startup   period,   while   user satisfaction and productivity may rise after the initial problems are resolved. NETWORK PHYSICAL CONNECTIONS A network connection is a linkage between network elements. Physical connections concern the cables and connectors  used  to  create  the  physical  layout  of  the network. When building a network, you must first establish the physical connections. NETWORK  BACKBONES Backbone cable refers to the cable that forms the main trunk, or backbone, of a network. Individual nodes and other devices may be connected to this cable using special adapters and a separate stretch of cable. Backbone cable is defined by the Electronics Industries   Association/Telecommunications   Industry Association-568 (EIA/TIA-568) committee as any “behind the scenes” cable; that is, cable running behind walls, in shafts, or under the ground. The   EIA/TIA-568   recognizes   four   types   of backbone cable; they are listed in table 2-3. The use of a backbone network to tie together a number  of  small  access  networks  offers  several advantages over the construction of a single large LAN. The various LANs connected to the backbone are able to operate in parallel, providing greater processing efficiency.  The  multiple-network  approach  is  also  more reliable, since each individual LAN can continue operating if one of the access networks, or even the backbone, fails. The backbone network must also be highly  reliable,  since  the  greater  distances  covered  may make it difficult to locate and repair faults. The LANs that connect to the backbone must be flexible and low- cost in terms of installation and user connection.