NETWORKING
OVERVIEW
A structured cabling system is a complete system of cabling and associated hardware, which provides a comprehensive telecommunications infrastructure. This infrastructure serves a wide range of uses, such as to provide telephone service or transmit data through a computer network. It should not be device dependent.
We further define a structured cabling system in terms of ownership. The structured cabling system begins at the point where the service provider (SP) terminates. This point is the point of demarcation (demarc) or Network Interface Device (NID).
Every structured cabling system is unique. This is due to variations in:
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The architectural structure of the building, which houses the cabling installation;
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The cable and connection products;
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The function of the cabling installation;
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The types of equipment the cabling installation will support -- present and future;
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The configuration of an already installed system (upgrades and retrofits);
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Customer requirements; and
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Manufacturer warranties.
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The methods we use to complete and maintain cabling installations are relatively standard. The standardization of these installations is necessary because of the need to ensure acceptable system performance from increasingly complex arrangements.
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The benefit of standards include:
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Consistency of design and installation;
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Conformance to physical and transmission line requirements;
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A basis for examining a proposed system expansion and other changes; and
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Uniform documentation.
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BACKBONE OF CABLING
From the entrance facility, the structured cabling network branches out to other buildings, as well as from floor to floor within a building on the backbone cabling system. We use the term backbone to describe the cables handling the major network traffic.
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The ANSI/TIA/EIA-568-A standard defines backbone cabling as follows: "The function of the backbone cabling is to provide interconnections between telecommunications closets, equipment rooms, and entrance facilities in the telecommunications cabling system structure. Backbone cabling consists of the backbone cables, intermediate and main cross-connects, mechanical terminations, and patch cords or jumpers used for backbone-to-backbone cross-connection. Backbone cabling also includes cabling between buildings."
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Interbuilding and intrabuilding are two types of backbone cables. Interbuilding backbone cable handles traffic between buildings. Intrabuilding backbone cable handles traffic between closets in a single building.
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This standard identifies two levels of backbone cabling. First-level backbone is a cable between a main cross-connect (MC) and intermediate cross-connect (IC) or horizontal cross-connect (HC). Second-level backbone exists between an IC and HC.
MAIN PART OF CABLING
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Cable pathways: shafts, conduits, raceways, and floor penetrations (such as sleeves or slots) that provide routing space for the cables.
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The actual cables: optical fiber, twisted-pair copper, coaxial copper, or some combination of these. (Note: You should avoid areas where potential sources of EMI or electromagnetic interference may exist when planning the routing and support structure for copper cabling.)
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Connecting hardware: connecting blocks, patch panels, interconnections, cross-connections, or some combination of these components.
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Miscellaneous support facilities: cable support hardware, firestopping and grounding hardware. Note: The terms horizontal and backbone (previously called riser) evolved from the orientations typical for functional cables of these types. However, the physical orientation of the cabling has no bearing on classifying the cable as horizontal or backbone.