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CompTIA A+ Study Guide (220-601 and 220-602)
Networks - Network Types
Introduction:
In this section, we will take a look at the various networking
technologies that an A+ technician will likely run across and will be
tested on the exam.
Network Models:
There are 2 basic network models as follows:
- Peer-to-Peer - A peer to peer network is one in which lacks a dedicated server and every computer acts as both a client and a server. This is a good networking solution when there are 10 or less users that are in close proximity to each other. A peer to peer network can be a security nightmare, because the people setting permissions for shared resources will typically not be overly savvy. Thus is only recommended in situations where security is not an issue. In recent years, a couple of new peer-to-peer network types have evolved including USB and firewire network connections, infrared via PDAs and cell phones, and Ad Hoc wireless connections.
- Client/Server - This type of network is designed to support a large Number of users and uses dedicated server(s) to accomplish this. Clients log on to the server(s) in order to run applications or obtain files. Security and permissions can be managed by 1 or more administrators which cuts down on the aforementioned less savvy users from medling with things that they shouldn't be. This type of network also allows for convenient backup services, reduces network traffic and provides a host of other services that come with the network operating system (NOS).
LANs
and WANs:
A local area network (LAN) is a computer network that spans a relatively
small area, such as a single office or office building, and typically
offers high-speed communications. Most LANs are confined to a single
building or group of closely located buildings. However, one LAN can be
connected to other LANs over any distance via telephone lines, coaxial
cable, satellite, etc. creating a WAN (discussed below). Most LANS of
today utilize Ethernet and/or Wi-Fi connections. More about LAN and
Ethernet technologies will be discussed in the next section titled,
"Network Connections and Cabling".
A
wide area network (WAN) computer network that spans a relatively large
geographical area. Typically, a WAN consists of two or more local-area
networks (LANs). Computers connected to a wide-area network are often
connected through public networks, such as the telephone system, leased
lines (ISDN), satellite, microwave, or other connection method. The
connected LANS can be on another in a building, or as far away as in
another country. The largest WAN in existence is the Internet.
Wireless
Networking:
As the name implies, wireless networks allow computers to comunicate
without the use of cables. There are 2 main wi-fi standards - IEEE
802.11b and IEEE 802.11g. The main difference between the 2 standards is
speed; 802.11b operates at 11mbps and 802.11g works at a speed of
54mbps. 802.11 defines two pieces of equipment, a wireless station,
which is usually a PC or a Laptop with a wireless network interface card
(NIC), and a Wireless Access Point (WAP), which acts as a bridge between
the wireless stations and Distribution System (DS) or wired networks. A
wireless access point will support up to 32 wireless devices. An 802.11
wireless network adapter can operate in two modes, Ad-Hoc and
Infrastructure. In infrastructure mode, all your traffic passes through
a wireless ‘access point’. In Ad-hoc mode your computers talk directly
to each other in a peer-to-peer mode and do not need an access point at
all.
Bluetooth (IEEE 802.15.1), originally developed by Ericsson and later
formalized by the Bluetooth Special Interest Group (SIG), is a
specification for wireless personal area networks that facilitates the
exchange of data between electronic devices, such as mobile phones, PDAs,
laptops, personal computers, printers and digital cameras. The devices,
containing a low-cost transceiver, connect to each other using a short
range radio frequency (2.45 gHz) of up to 328 feet. Each Bluetooth
enabled device is assigned a unique 48-bit address and a 24-bit class
identifier. The class identifier provides information as to the nature
of the device (phone, PC, etc.) and is transmitted to other devices
performing an inquiry.
Infrared technology uses light beams to transmit data and uses a
line-of-sight connection. Line-of-sight means that the devices
communicating with each other must have an unobstructed "view" of each
other. They can be used for transmitting data between PDAs or cell
phones. This technology previously connected at a speed of about 115
kbps while advanced technologies for connecting 2 networks together
between buildings can run as high as 10 gbps and extend several miles.
Windows XP supports VFIR (Very Fast Infrared) which can transmit at up
to 16Mbps and has become common.
| Standard | Frequency | Description | Maximum Length | Speed |
| 802.11b - WiFi | 2.4 Ghz | Wireless networking commonly used in homes and SOHO environments. Being replaced by the faster 802.11g standard. Uses a wireless access point (WAP) to connect to other wireless computers. | 150+ feet | 11 mbps |
| 802.11g - WiFi | 2.4 Ghz | Wireless networking commonly used in homes and SOHO environments. Uses a wireless access point (WAP) to connect to other wireless computers. Backward compatible with 802.11b | 150+ feet | 54 mbps |
| Infrared - IrDA | Uses light, not radio frequencies | Uses line of sight connections making it useful for sharing data between personal devices. | 150+ feet | Usually 16mbps - high powered beams can reach 10Gbps |
| Bluetooth | 2.4 Ghz | See above | Up to 30 feet | 721 kbps |