NETWORKING COMPONENTS By Cleve Rosser

Hubs allow large numbers of computers to be connected on a single or multiple LAN. Each computer plugs into the hub with an Ethernet cable, and information sent from one computer to another passes through the hub. A hub can’t identify the source or the intended destination of the information it receives, so it sends the information to all of the computers connected to it, including the one that sent it. A hub can send or receive information, but it can’t do both at the same time. This makes hubs slower than switches. There are two types of hubs:

1. Passive: The signal is forwarded as it is. 2. Active: The signal is amplified.

They act like a repeater. Hubs operate at the Physical Layer of the OSI Model. Hubs are the least complex and the least expensive of these devices.

HUB $26.99 TO $249

HUB

Switches work the same way as hubs, but they can identify the intended destination of the information that they receive, so they send that information to only the computers that are supposed to receive it. Switches can send and receive information at the same time, so they can send information faster than hubs can. If your home network has four or more computers, or you want to use your network for activities that require passing a lot of information between computers (such as playing network games or sharing music), you should probably use a switch instead of a hub. The most common switching methods are:1. Cut-through: Directly forward what the switch gets.2. Store and forward: Receive the full frame before retransmitting it.Switches operate in the data link layer of the OSI model. Switches cost a little more than hubs.

SWITCH $89.99 TO $425

SWITCH

Routers enable computers to communicate and they can pass information between two networks, such as between your home network and the internet. This capability to direct network traffic is what gives the router its name. Routers can be wired (using Ethernet cables) or wireless. If you just want to connect your computers, hubs and switches work well, however if you want to give all of your computers access to the internet using one modem, use a router. Router works on the 3rd layer of the OSI model. Routers are more expensive than hubs and switches.

Router $153 to $945

ROUTER

A bridge is software or hardware that connects two or more networks so that they can communicate. When two or more networks have different types of networks a bridge allows them to exchange information and share files with all of the computers on the network. An example would be two networks one connected with cat5 cable and the other connected wirelessly. The wired computers can only communicate with wired computers, and the wireless computers can only communicate with wireless computers. Connecting both networks to a bridge will allow them to communicate with each other. Bridges operate on the data link layer but they are less advanced than switches, they are slower because they use software to perform switching.

BRIDGE $65 to $398

BRIDGE

A gateway is connected to two networks that use different network protocols. A gateway is required to convert data packets from one protocol format to another protocol. For instance, it allows communication between TCP/IP clients and IPX/SPX or Apple Talk. A router and gate way both are sometimes used interchangeably but the difference is that a Router works exclusively on the network layer of the OSI model, and the gateway operates at the network layer and above, but most of them at the application layer of the OSI model.

Gateway $169 to $2285

GATEWAY

A firewall is software or hardware that checks information coming from the internet or a network, and then either blocks it or allows it to pass through to your computer. A firewall can help prevent hackers or malicious software from gaining access to your computer through a network or the internet. A firewall can also help stop your computer from sending malicious software to other computers.

FIREWALL $189 to $3500

FIREWALL

Wireless Access points (Aps or WAPs) are specially configured nodes on wireless local area networks. Access points act as a central transmitter and receiver of WLAN signals. Access points are generally small, dedicated hardware devices featuring a built in network adapter, antenna, and radio transmitter. Access points support WI-FI wireless communications Standards. Wireless access points bridge WLANs with a wired Ethernet LAN and also scales the network to support more clients. The wireless access point operates in The physical layer and the data link layer of the OSI model.

Wireless Access Point $54.49 to $695.95

WIRELESS AP

FIREWALLGATEWAY

INTERNET

BRIDGESWITCH

PC

HUB

PC

WAP

ROUTER

LAPTOP

• References:• http://www.vicomsoft.com/learning-center/firewalls/#6• copyright 2009by Pearson Education INC. Sams Teach

Yourself Networking In 24 Hours, Author Uyless D Black• http://www.perle.com/images/Modbus_Gateway_Techni

cal_Note.gif• http://www.vicomsoft.com/images/learning-center/firew

alls/firewalldiagram1.gif• http://t0.gstatic.com/images?q=tbn:ANd9GcRKB844NAO

3dGviHOHa80P2iJj_v4xbaT-YC7Ap4kagsJUcDYvlcw• http://www.hallmarc.net/Networking_Project/hub.gif• http://www.ciscopracticelab.net/wp-content/uploads/20

11/07/01-02-osi-model_1.gif• http://www.eusso.com/models/wireless/GL2454-AP-QA/

GL2454-AP.htm