Network Cable Standards and Topologies

Coaxial Cable Standards

10Base5 (Thicknet)

Standard for using thick, RG-8-type coaxial cable.
Implements 10 Mbps baseband Ethernet networks using a bus topology.
'5' represents 500 meters (m), the maximum length of a network bus.
10Base5 means 10 Mbps, using baseband signaling, with a segment no longer than 500 meters.
Also called 'Thicknet' or 'Yellow Wire'.
Includes two layers of foil shielding and a copper mesh shield.
A separate transceiver connects a computer to the main bus cable.
Transceiver connects to the NIC (Network Interface Card) using an Attachment Unit Interface (AUI) cable.
Today’s NICs include the transceiver.

10Base2 (Thinnet)

Standard for using thin, RG-58-type coaxial cable.
Implements 10-Mbps baseband Ethernet using a bus topology.
'2' stands for approximately 200 m (185 m to be precise), the maximum operational length.
Also called 'Thinnet,' 'ThinLAN,' and 'Cheapernet'.
Uses bayonet mount T-connectors, called BNC connectors.
BNC connectors are used to connect computers to a thin coaxial cable bus (10Base2) or terminate the ends of a bus.
BNC barrel connector joins two Thinnet cables.
BNC terminator terminates the end of a cable, acting as a resistive load (two are needed per bus).
BNC adapters connect different cable types, such as Thinnet to Thicknet.
In most 10Base2 implementations, the network adapter performs the transceiver functions.
The first and final connectors include a 50-ohm terminating resistor to eliminate reflected signals.

Limitations of Coaxial Cable

Good EMI/RFI resistance due to shielding.
Bulky and difficult to install.
A cable break can disable the entire network segment.
Limited to 10 Mbps.
Largely overtaken by twisted pair and fiber-optic cable in modern networks.

Network Interface Card (NIC)

A computer expansion card that permits connecting a network cable to a personal computer.
Connects a node to a network using copper, fiber, or wireless media.

Bus Topology

A network topology where all devices are connected to a single cable, called the 'bus.'
The bus cable allows all devices to receive the same signal simultaneously.

Attachment Unit Interface (AUI)

AUI stands for Attachment Unit Interface.
Specifies how a cable connects to an Ethernet card.
A physical and logical interface.
Defined in IEEE 802.3 standard for 10BASE5 Ethernet.

Twisted Pair Cable

Overview

Consists of two or more pairs of thin, stranded, insulated copper wires twisted to cancel EMI/RFI.
Two standard varieties: unshielded twisted pair (UTP) and shielded twisted pair (STP).
Screened twisted pair (ScTP), also known as foil twisted pair (FTP), is another name for shielded twisted pair cable.

Unshielded Twisted Pair (UTP)

Most popular LAN cabling due to being inexpensive, light, flexible, and easy to install.
Relies on twisted pairs to minimize EMI/RFI; it is not shielded.
The number of twists ranges from 2 to 12 per foot, depending on the cable type.
Must meet higher criteria than standard telephone cable.

UTP Standards

EIA/TIA and UL have established compatible standards for rating UTP cable.
UL uses the term 'levels,' and EIA/TIA uses the term 'categories.'
The UL standard includes fire safety performance criteria similar to the NEC.

Categories of UTP

Category 1 (CAT-1): Cables such as POTS and ISDN.
Category 2 (CAT-2): Cables were used on 4-Mbps Token Ring networks and LANs operating at 1 Mbps or less.
Category 3 (CAT-3): Defined by EIA/TIA 568-B for data networks using transmission frequencies up to 16 MHz.
Category 4 (CAT-4): Cables were used on 16-Mbps Token Ring networks and data networks using transmission frequencies up to 20 MHz.
Category 5 (CAT-5): Frequently used for 10/100-Mbps Ethernet LANs and data networks using transmission frequencies of up to 100 MHz.
Category 5E (enhanced) (CAT-5e): Defined by EIA/TIA 568-B for data networks using transmission frequencies of up to 100 MHz and 100-Mbps Ethernet or 1000BASE-T Gigabit Ethernet over twisted pair.
Category 6 (CAT-6): Defined by EIA/TIA 568-B for data networks using transmission frequencies up to 250 MHz.
Category 6A (augmented) (CAT-6a): Defined by EIA/TIA 568-B for data networks using transmission frequencies up to 500 MHz and 10GBase-T 10 Gigabit Ethernet (10 GigE) over twisted pair.
Category 7 (CAT-7): Defined by ISO/IEC 11801 for data networks using transmission frequencies up to 600 MHz. Shielded Foil Twisted Pair (S/FTP) with individually shielded pairs, designed for 40 Gigabit and 100 Gigabit Ethernet.
Category 7A (CAT-7a): Defined by ISO/IEC 11801 for data networks using transmission frequencies up to 1,000 MHz and constructed like CAT-7 with S/FTP.
Higher-category UTP cables are made from higher-quality materials and tighter cable twists.
Currently, only Category 5 or higher standard cable is recommended for data network installations.

Installation Considerations

Combining network sections with different cable categories is possible but not optimal.
Should try to use the same category throughout a network.
Special care must be taken when installing CAT-5 or CAT-6 cabling systems.
Cable must meet specifications, and high-quality connectors must be used.
When connecting CAT-5 cable, no more than 0.5 inch (1.3 cm) of the twist should be unraveled.
Care must be taken not to exceed the cable's bend radius or crimp it.
Exceeding bend radius or crimping can cause misalignment of the twisted pair and transmission errors.
Twisted pair cables must be terminated on connectors of the same cable category or higher.
For example, CAT-5 cable terminated on CAT-3 connectors will perform at CAT-3 data rates.

10BaseT Networking

10BaseT Adapters

Typically include the transceiver circuitry and do not require an external transceiver.
Uses a star topology.

Star Topology

Each station is connected to a port on a multiport hub, providing a central wiring point.
The hub functions as a repeater, broadcasting incoming signals to every station attached to the hub.

RJ-45 Connectors

Each end of the twisted pair cable is equipped with an RJ-45 connector.
An eight-position eight-pin modular connector used to connect Ethernet cables to compatible equipment.

Advantages of 10BaseT

Lower cost and relative ease of installation.
Star topology allows for efficient management, maintenance, fault isolation, and reconfiguration of a LAN.

Star Network Design

Overview of Star Topology

All devices are connected to a central hub or switch.
Also known as a hub-and-spoke topology.

How it Works

The central hub acts as a server, and the connected devices are clients.
Devices pass messages to the central hub, which then forwards the message to the intended recipient.

Advantages of Star Topology

Reliable connections between multiple devices.
Easy troubleshooting due to the central hub.
Centralized management.

Disadvantages of Star Topology

The entire network fails if the switch fails.
A wired star topology requires a lot of cable and in a large network can be expensive.

Cable Types and Specifications

Shielded Twisted Pair (STP) Cable

Cable consists of two or more twisted pairs of copper wire surrounded by flexible insulation, a foil shield, a drain wire, and an outer plastic sheath.
Provides considerably more resistance to EMI/RFI than UTP.
Bulkier, less flexible, and more expensive to install.

Screened Twisted Pair (ScTP) Cable

According to TIA, screened twisted pair (ScTP) cable consists of four copper pairs of unshielded twisted wires of a single overall aluminum foil mesh shield with a polyvinyl chloride (PVC) jacket.
ScTP cabling performance characteristics (bandwidth, frequency range) place it in the EIA/TIA cable CAT-5.

Token Ring Networks

Overview of Token Ring

A ring type of local area network (LAN) in which a supervisory frame, or token, must be received by an attached terminal before transmitting.