Free Certification Practice Tests and Study Guides
Join Us! | Login | Help




A+ Study Guide: Domain 5.0: Networks - Network Connections and Cabling


:: Return to the Index ::

Contents:
Introduction
Cabling
Connectors
Ethernet LAN Types
Remote Access

Introduction:
In this section, we will take a look at the various LAN and WAN network types as well as the cables and connectors used in modern networks.

Cabling:
The most common form of LAN uses Ethernet which is a collection of standards and specifications that define wiring and signaling for the network. There are a wide variety of standards and cable types. The most common cable types are discussed below:

Coaxial - Older ethernet technologies such as 10Base5 and 10Base2 used coaxial cable (RG-58). These network types are no longer in use. This type of network connection has made a recent comeback and is being used for broadband cable internet connections (RG-59).

Unshielded Twisted Pair (UTP) - UTP is a cable type that consists of two or more insulated copper conductors in which each pair of conductors are twisted around each other. Category 1 UTP cables are used for telephony connections. Category 3 and higher are used for Ethernet LAN connections. UTP is inexpensive and easy to work with.

Shielded twisted pair (STP) - This type of cable is the same as unshielded twisted pair (UTP), except that it has shielding around it to provide more protection against electromagnetic interference (EMI). Because of its higher cost, it is typically only used in environments where it is necessary.


Fiber Optic - Previously only used for WAN connections, fiber optic cabling is now increasingly being used on LANs as well for its capacity for longer distance and higher speeds. A fiber-optic system is similar to the copper wire system (UTP/STP), however, fiber-optics use light pulses to transmit information down fiber lines instead of using electronic pulses to transmit information down copper lines. Fiber cables are made of transparent glass or plastic fibers which allow light to be guided from one end to the other. There are 2 types of fiber cabling - Single-mode fiber (SMF) and multi-mode fiber (MMF). MMF is the most common type used, however, SMF can support longer distances and higher speeds. Fiber internet is one of the most popular choices today.

A plenum area is the air return for an air conditioning system. In most buildings, the plenum area above a drop ceiling is used as the source of air for the air conditioning systems. Wire and cable are usually installed in this area, and if that wire burns during a fire, it will emit toxic fumes. The fumes could carry to the rest of the building through the air conditioner, and, as a result, the fumes could harm others. Plenum grade cabling is required in these types of installations because it is resistant to fire and does not emit poisonous gasses when burned. PVC cable (the standard variety), while cheaper, will emit poisonous gases in extreme heat or fire. Plenum grade cabling is quite a bit more expensive.

The various cable types vary in their capacity to transmit data. The definition of the word "bandwidth" can get complicated, but for the purposes of the A+ exam, this term will mean the transmission speed on a network. This next table lists the transmission speeds/bandwidth of the various cable types.

Transmission Medium Transmission Speed
cat 3 twisted pair 10 mbps
cat 5 twisted pair 100 mbps
cat 5e twisted pair 1 gbps
cat 6 twisted pair 10 gbps
Fiber Optic 100 mbps - 1 gbps

Connectors:
Just like their are a variety of cable types, there are a variety of connectors used with these cables. Let's take a look at the most common ones - please note that the images are not to scale.

BNC - This connector has found uses with both broadcast television equipment and computer networks. With regards to networking, this connector was used on early 10Base-2 (Thinnet) Ethernet networks. It has a center pin connected to the center coaxial cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to the female connector.

F Connector - This connector is the one used for home broadband cable connections with coaxial cable. This male connector screws onto the female counterpart. The connection typically runs coax from the wall outlet to the cable modem. The cable modem will have a RJ-45 jack for connection a computer or wireless access point.


RJ-11 - Short for Registered Jack-11, a four or six-wire connector used primarily to connect telephone equipment in the United States (POTS). The cable itself is called category 1 (Cat 1) and is used for dial-up connections. Modems have rj-11 jacks that connect them to the wall outlet.



RJ-45 - Short for Registered Jack-45, it is an eight-wire connector used commonly to connect devices on Ethernet LANs. RJ-45 connectors look similar to RJ-11 connectors used for connecting telephone equipment, but they are larger.



ST Connector - The ST connector is a fiber optic connector which uses a plug and socket which is locked in place with a half-twist bayonet lock. The ST connector was the first standard for fiber optic cabling. ST Connectors are half-duplex.


SC Connector - The SC connector is a fiber optic connector with a push-pull latching mechanism which provides quick insertion and removal while also ensuring a positive connection. SC Connectors are half-duplex.



LC - The LC connector is just like a SC connector only it is half the size. Like SC connectors, LC connectors are half-duplex.



MT-RJ - Stands for Mechanical Transfer Registered Jack. It is a newer fiber optic connector that somewhat resembles a RJ-45 connector. It has a small size, low cost, easy installation, and supports full-duplex.

Ethernet LAN Types:
Now that we have gone through the various cables and connectors, let's put it all together and look at the most common ethernet types in use today.

Name Cable Type Connector Maximum Length Speed
10Base-T Category 3 or better UTP cable RJ-45 100 meters(328 ft) 10 mbps
10Base-FL Fiber optic cable ST, SC, LC, MT-RJ 2000 meters 10 mbps
100Base-TX Cat 5 twisted pair RJ-45 100 meters(328 ft) 100 mbps
100Base-FX Fiber Optic ST, SC, LC, MT-RJ 2000 meters 100 mbps
1000Base-T CAT5e or higher RJ-45 100 meters(328 ft) 1 gbps

Note that there are emerging fiber optic technologies such as laser over fiber that have faster speeds and longer distances, but are probably outside the scope of the A+ exam. Also note that wireless networking types are covered in a different section of this guide.

Remote Access:
For the purposes of the A+ exam, you will need to be familiar with the following methods of connecting to the internet:

Network Type Speed Connection Description
Dial-up connection (POTS) Up to 56 Kbps Twisted pair with RJ-11 connector. Rapidly being replaced by broadband technologies such as DSL and cable.
Integrated Services Digital Network (ISDN) 128 kbps Twister pair with RJ-11 connector. Business access
Digital Subscriber Line (DSL) 256 Kbps to 8 Mbps Twisted-pair with RJ-45 connector. Home, small business, and enterprise access using existing phone lines.
Cable modem 512 Kbps to 52 Mbps Coaxial cable with F connector. Home, business, school access
Satellite 400 kbps Satellite Dish Rural and remote areas
Cellular Broadband Up to 2.4 mbps Cell phone Access on the go.

Additional Notes:
  • Dial-up networking is fading away with the adoption of faster technologies.
  • ISDN service is an older, but still viable technology offered by phone companies in some parts of the U.S.. ISDN requires an ISDN adapter instead of a modem, and a phone line with a special connection that allows it to send and receive digital signals.
  • ADSL allows you to connect to the internet via your phone line, but allows you to use your phone while connected to the internet. Unlike a cable modem, the speed is stable.
  • Cable modems are much faster generally than ADSL, however, your mileage will vary depending on how many other people are using the bandwidth on your segment.
  • Satellite connections come in two types - 1-way and 2-way. 1-way satellites only accept signals and 2-way connections send and receive. Satellite connections can be affected by weather.
Further Reference: Networking Tutorials







IT Showcase