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Selecting Network Hardware
- Cost
- Scalability
- Reliability
- Management
- New network: Topology drives the hardware choice
- Existing network: Existing hardware affects the topology choice and hardware choices
- A network’s transmission media is a long-term investment.
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Four types of wired media:
- Coaxial cable (using copper wire)
- Shielded twisted-pair (using copper wire)
- Unshielded twisted-pair (using copper wire)
- Fiber optic (using glass or plastic)
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Building codes designate:
- how or where cable can be routed
- the use of conduits
- the type of cable insulation (plenum insulation)
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Installation concerns:
- Avoiding high-traffic areas
- Conduits should not contain electrical lines
- Copper wires can pick up voltages through induction
- Avoid sources of electromagnetic interference (EMI) and RFI (radio-frequency interference)
- Physical damage of fiber optic cable or copper wire
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Coaxial Cable
- Consists of a central copper wire covered with dielectric (plastic insulator) shielded by foil wrapping or braid with a plenum or PVC outer jacket
- Types of coax vary by:
- -Size of central copper core
- -Cable impedance (measured in ohms)
- Various coax for different transmission types (Cable TV, Thicknet, Thinnet, etc.)
- Radio grade (RG) classification
- -Defines size of copper center and diameter of outer jacket
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Thicknet
- (10Base5)
- Original cabling used in Ethernet networks.
- Typically used vampire and drop (DIX) cables.
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Thinnet
- 10Base2
- Smaller in diameter than Thicknet and is easier to work with.
- Uses BNC connectors (barrel connectors or T connectors)
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Base in 10Base5 means
- Baseband carries 1 signal on 1 wire.
- Broadband carries multiple signals an the same wire.
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Thinnet Coaxial Cable Advantages:
- Easier to install (than Thicknet).
- Small in diameter.
- Shielding can reduce EMI and RFI.
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Thinnet Coaxial Cable Disadvantages:
- When cable breaks, the network goes down.
- Cable must be grounded to prevent interferences.
- More expensive than twisted pair cable.
- Connectors and compatible NICs can be expensive.
- Does not support high-speed transmissions.
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STP
- Shielded twisted-pair (STP) is made up of pairs of copper wires that are twisted together
- STP is subject to near-end crosstalk and EMI
- not asked
- Five STP types used for different implementations:
- Type 1 (IBM Token Ring)
- IBM data connectors developed for use with IBM cabling
- Type 2
- Type 6
- Type 8
- Type 9
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STP Cable structure
- from inside out:
- Coductor wire covered with Dielectric twisted in pairs.
- Foil shield
- braid shield
- Jacket
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Shielded Twisted Pair Advantages:
- Shielding reduces EMI and RFI
- STP can be used with RJ connectors, which are common and inexpensive, instead of the IBM hermaphroditic connectors
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Shielded Twisted Pair Disadvantages:
- Must be properly grounded
- More expensive than UTP
- Difficult to terminate
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UTP
- Unshielded twisted pair is color-coded copper wires without insulation
- Most common implementation of copper media
- Different categories determined by:
- -numbers of twisted pairs
- -transmission rates
- -implementations
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Common UTP Categories
- Category 5: Ethernet, 100BaseX networks
- Category 5e: Ethernet, 100BaseX – 1000BaseX networks
- Category 6e: 10Gigabit Ethernet (10GBaseT)
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Unshielded Twisted Pair Advantages:
- It’s inexpensive and easy to install.
- It’s easy to terminate.
- It’s widely used and tested.
- It’s easy to maintain and troubleshoot.
- Patch cables come precut in most popular lengths.
- It supports many network types.
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Unshielded Twisted Pair Disadvantages:
- It’s susceptible to interference.
- It’s prone to damage during installation if mishandled.
- It’s prone to physical damage if routed through traffic areas and not protected.
- Distance limits are often misunderstood or not followed.
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