Computer Networking Media (Cables)

They are TWO Types of Media's Used in Computer Networking Such as
    1. Bounded Media: Bounded media are the physical links through which signals are confined to narrow path. Bounded media are made up of a external conductor(usually copper) bounded by jacket material. These are also called guided media.

    2.Unbounded media:unbounded media does not require cabling and includes satellite, microwave and radio transmission. Wireless connections, including 802.11b and 802.11g, are examples of unbounded media. Today, bounded media continue to be more common than unbounded.

In computer network, media refers to the cables linking workstations together. There are many different types of transmission media, the most popular being twisted pair cable (normal electrical wire), coaxial cable (the type of cable used for cable television), and fiber optical cable cable (cables made out of glass).

Twisted Pair Facts
Twisted pair cables support a wide variety of fast, modern network standards. Twisted pair cabling is composed of the following components:

• Two wires that carry the data signals (one conductor carries a positive signal; one carries a negative signal). They are made of 22 or 24 gauge copper wiring.
• PVC plastic insulation surrounds each wire.
• Two wires are twisted to reduce the effects of electromagnetic interference (EMI) and crosstalk. Because the wires are twisted, EMI should affect both wires equally and can be cancelled out.
• Multiple wire pairs are bundled together in an outer sheath. Twisted pair cable can be classified according to the makeup of the outer sheath:
  • Shielded Twisted Pair (STP) has a grounded outer copper shield around the bundle of twisted pairs or around each pair. This provides added protection against EMI.
  • Unshielded Twisted Pair (UTP) does not have a grounded outer copper shield. UTP cables are easier to work with and are less expensive than shielded cables.

The table below describes the different unshielded twisted pair (UTP) cable types (categories).

Type	Connector	Description
Phone cable	RJ-11	Used to connect a PC to a phone jack in a wall outlet to establish a dial-up Internet connection. Has two pairs of twisted cable (a total of 4 wires).
Cat 3	RJ-45	Designed for use with 10 megabit Ethernet or 16 megabit token ring.
Cat 5	RJ-45	Supports 100 megabit and 1 gigabit Ethernet and ATM networking.
Cat 5e	RJ-45	Similar to Cat 5 but provides better EMI protection. Supports 1 and 10 gigabit Ethernet (gigabit connections require the use of all four twisted pairs).
Cat 6	RJ-45	Supports high-bandwidth, broadband communications.

The table below describes the two types of connectors used with twisted pair cables.

Connector	Description
RJ-11	Has 4 connectors Supports up to 2 pairs of wires Uses a locking tab to keep connector secure in outlet Used primarily for telephone wiring
RJ-45	Has 8 connectors Supports up to 4 pairs of wires Uses a locking tab to keep connector secure in outlet Used for Ethernet and some token ring connections

Each type of UTP cable can be substituted for any category below it, but never for a category above. For example, Cat 6 can be substituted for a task requiring Cat 5e; however, neither Cat 5 nor Cat 3 should be used for this particular task.

Coaxial Cable Facts

Coaxial cable is an older technology that is usually implemented with a bus topology. It is not suitable for ring or star topologies because the ends of the cable must be terminated. It is composed of two conductors, which share a common axis, within a single cable.
Coaxial cable is built with the following components:

• Two concentric metallic conductors:
  • The inner conductor, which carries data signals. It is made of copper or copper coated with tin.
  • The mesh conductor is a second physical channel that also grounds the cable. It is made of aluminum or copper coated tin.
• The insulator, which surrounds the inner conductor. It keeps the signal separated from the mesh conductor. It is made of PVC plastic.
• The mesh conductor, which surrounds the insulator and grounds the cable. It is made of aluminum or copper coated tin.
• The PVC sheath, which is the cable encasement. It surrounds and protects the wire. It is made of PVC plastic.

Coaxial cable has the following advantages and disadvantages:

Advantages	Highly resistant to EMI (electromagnetic interference) Highly resistant to physical damage
Disadvantages	Expensive Inflexible construction (difficult to install) Unsupported by newer networking standards

The table below describes the different coaxial cable grades.

Grade	Uses	Conductor	Resistance Rating
RG-58	Ethernet networking	Tin-coated copper	50 ohms
RG-59	Cable TV and cable networking	Copper-plated steel	75 ohms
RG-6	Satellite TV	Solid copper	75 ohms

The table below describes the two types of connectors used with coaxial cable.

Connector	Description
F-Type	Twisted onto the cable Used to create cable and satellite TV connections Used to hook a cable modem to a broadband cable connection
BNC	Molded onto the cable Used to create Ethernet network connections

Fiber Optic Facts

To connect computers using fiber optic cables, you need two fiber strands. One strand transmits signals, and the other strand receives signals. Fiber optic cabling is composed of the following components:

• The core carries the signal. It is made of plastic or glass.
• The cladding maintains the signal in the center of the core as the cable bends.
• The sheathing protects the cladding and the core.

Fiber optic cabling offers the following advantages and disadvantages:

Advantages	Totally immune to EMI (electromagnetic interference) Highly resistant to eavesdropping Supports extremely high data transmission rates Allows greater cable distances without a repeater
Disadvantages	Very expensive Difficult to work with Special training required to attach connectors to cables

Multi-mode and single mode fiber cables are distinct from each other and not interchangeable. The table below describes multi-mode and single mode fiber cables.

Type	Description
Single Mode	Transfers data through the core using a single light ray (the ray is also called a mode) The core diameter is around 10 microns Supports a large amount of data Cable lengths can extend a great distance
Multi-mode	Transfers data through the core using multiple light rays The core diameter is around 50 to 100 microns Cable lengths are limited in distance

Fiber optic cabling uses the following connector types:

Type	Description
ST Connector	Used with single and multi-mode cabling Keyed, bayonet-type connector Also called a push in and twist connector Each wire has a separate connector Nickel plated with a ceramic ferrule to insure proper core alignment and prevent light ray deflection As part of the assembly process, it is necessary to polish the exposed fiber tip to ensure that light is passed on from one cable to the next with no dispersion
SC Connector	Used with single- and multi-mode cabling Push on, pull off connector type that uses a locking tab to maintain connection Each wire has a separate connector Uses a ceramic ferrule to insure proper core alignment and prevent light ray deflection As part of the assembly process, it is necessary to polish the exposed fiber tip
LC Connector	Used with single- and multi-mode cabling Composed of a plastic connector with a locking tab, similar to a RJ-45 connector A single connector with two ends keeps the two cables in place Uses a ceramic ferrule to insure proper core alignment and prevent light ray deflection Half the size of other fiber-optic connectors
MT-RJ Connector	Used with single and multi-mode cabling Composed of a plastic connector with a locking tab Uses metal guide pins to ensure it is properly aligned A single connector with one end holds both cables Uses a ceramic ferrule to insure proper core alignment and prevent light ray deflection

Ethernet Specifications

Ethernet standards are defined by the work of the IEEE 802.3 committee. The following table compares the characteristics of various Ethernet implementations.

Category	Standard	Bandwidth		Cable Type	Maximum Segment Length
Ethernet	10BaseT	10 Mbps (half duplex) 20 Mbps (full duplex)		Twisted pair (Cat3, 4, or 5)	100 meters
	10BaseFL	10 Mbps (multimode cable)		Fiber optic	1,000 to 2,000 meters
Fast Ethernet	100BaseT4	100 Mbps (half duplex) 200 Mbps (full duplex)		Twisted pair (Cat5 or higher) Uses 4 pairs of wires	100 meters
	100BaseFX	100 Mbps (multimode cable)		Fiber optic	412 meters
Gigabit Ethernet	1000BaseT	1,000 Mbps (half duplex) 2,000 Mbps (full duplex)		Twisted pair (Cat5e)	100 meters
	1000BaseCX (short copper)			Special copper (150 ohm)	25 meters, used within wiring closets
	1000BaseSX (short)			Fiber optic	220 to 550 meters depending on cable quality
	1000BaseLX (long)				550 (multimode) 10 Km (single-mode)
10 G Ethernet	10 GBaseSR	10 Gbps (full duplex only)		Fiber optic	2 to 300 meters
	10 GBaseLR				2 to 10 kilometers
	10 GBaseER				2 to 40 kilometers

You should also know the following facts about Ethernet:

• The maximum cable length for UTP Ethernet "T" implementations is 100 meters for all standards.
• You may also see 10Base2 and 10Base5 Ethernet implementations, both of which are older implementations using coaxial cable. You will not be required to know these for the Network+ exam.
• Ethernet standards support a maximum of 1024 hosts.