ROUTERS AND SWITCHES
Routers and Switches are very important components of netwotl hardware.When it comes to computer networking, particularly when it comes to understanding the terminology used to describe network hardware diferent technologies involved in these components have to be understood.
Most of the technicians have a tendency to use these names interchangeably. It has to be noted that a hub, switch and a router are not all the same. It is better to understand what is the difference between an Ethernet hub and/or switch and a broadband router.
The functions of a router, hub and a switch are quite different from one another, even if at times they are all integrated into a single device. Let's start with the hub and the switch since these two devices have similar roles on the network. Each serves as a central connection for all of your network equipment and handles a data type known as frames. Frames carry your data. When a frame is received, it is amplified and then transmitted on to the port of the destination PC. The big difference between these two devices is in the method in which frames are being delivered.
In a hub, a frame is passed along or "broadcast" to every one of its ports. It doesn't matter that the frame is only destined for one port. The hub has no way of distinguishing which port a frame should be sent to. Passing it along to every port ensures that it will reach its intended destination. This places a lot of traffic on the network and can lead to poor network response times.
Additionally, a 10/100Mbps hub must share its bandwidth with each and every one of its ports. So when only one PC is broadcasting, it will have access to the maximum available bandwidth. If, however, multiple PCs are broadcasting, then that bandwidth will need to be divided between all of those systems, which will degrade performance.
A switch, on the other hand, keeps a record of the MAC addresses of all the devices connected to it. With this information, a switch can identify which system is sitting on which port. So when a frame is received, it knows exactly which port to send it to, which significantly increases network response times. And, unlike a Hub, a 10/100Mbps switch will allocate a full 10/100Mbps to each of its ports. So regardless of the number of PCs transmitting, users will always have access to the maximum amount of bandwidth. It's for these reasons why a switch is considered to be a much better choice then a hub.
Routers are completely different creatures. Where a hub or switch is concerned with transmitting frames, a router's job, as its name implies, is to route packets to other networks until that packet ultimately reaches its destination. One of the key features of a packet is that it not only contains data, but the destination address of where it's going.
A router is typically connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network (ex. your pc or workgroup and EarthLink). Routers are located at gateways, the places where two or more networks connect. Using headers and forwarding tables, routers determine the best path for forwarding the packets. Routers use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.
Today, a wide variety of services are integrated into most broadband routers. A router will typically include a 4-to-8 port Ethernet switch (or hub) and a Network Address Translator (NAT). In addition, they usually include a Dynamic Host Configuration Protocol (DHCP) server, Domain Name Service (DNS) proxy server and a hardware firewall to protect the Local Area Network (LAN) from malicious intrusion from the Internet.
All routers have a Wide Area Network (WAN) Port that connects to a DSL or cable modem for broadband Internet service and the integrated switch allows users to easily create a LAN. This allows all the PCs on the LAN to have access to the Internet and Windows file and printer sharing services.
Some routers have a single WAN port and a single LAN port and are designed to connect an existing LAN hub or switch to a WAN. Ethernet switches and hubs can be connected to a router with multiple PC ports to expand a LAN. Depending on the capabilities (kinds of available ports) of the router and the switches or hubs, the connection between the router and switches/hubs may require either straight-through or crossover (null-modem) cables. Some routers even have USB ports, and more commonly, wireless access points built into them.
Some of the more high-end or business class routers will also incorporate a serial port that can be connected to an external dial-up modem (useful as a backup in the event that the primary broadband connection goes down) and a built in LAN printer server and printer port.
Besides the inherent protection features provided by the NAT, many routers will also have a built-in, configurable, hardware-based firewall. Firewall capabilities can range from the very basic to quite sophisticated. Among the capabilities found on leading routers are those that permit configuring TCP/UDPports for games, chat services and the like, on the LAN behind the firewall.
So, in short, a hub glues together an Ethernet network segment, a switch can connect multiple Ethernet segments more efficiently and a router can do those functions plus route TCP/IP packets between multiple LANs and/or WANs; and much more.
CISCO ROUTER 2811
The Cisco 2811 Integrated Services Router is part of the Cisco 2800 Integrated Services Router Series which complements the Integrated Services Router Portfolio.
The Cisco 2811 Integrated Services Router provides the following support:
Wire-speed performance for concurrent services such as security and voice , and advanced services to multiple T1/E1/xDSL WAN rates
Enhanced investment protection through increased performance and modularity
Enhanced investment protection through increased modularity
Increased density through High-Speed WAN Interface Card Slots (four)
Enhanced Network Module Slot
Support for over 90 existing and new modules
Support for majority of existing AIMs, NMs, WICs, VWICs, and VICs
Two Integrated 10/100 Fast Ethernet ports
Optional Layer 2 switching support with Power over Ethernet (PoE) (as an option)
Security
On-board encryption
Support of up to 1500 VPN tunnels with the AIM-EPII-PLUS Module
Antivirus defense support through Network Admission Control (NAC)
Intrusion Prevention as well as stateful Cisco IOS Firewall support and many more essential security features
Voice
Analog and digital voice call support
Optional voice mail support
Optional support for Cisco CallManager Express (Cisco CME) for local call processing in stand alone business for up to36 IP Phones
Optional support for Survivable Remote Site Telephony support for local call processing in small enterprise branch offices for up to 36 IP phones
HOW TO BUILD YOUR COMPUTER
In addition to financial gain you can obtain valuable experience by building your own computer by your self. Although pre-built computers are available in the market for immediate purchase who can guarantee that they have used the best componenst in building the computer. In order to build the computer at lesser cost they may use components of cheaper varities. When you buy a pre-built computer from teh market you are risk to maintain the computer because you have to depend on others for warrenty. When you have built it you may buy necessary components and update it. In order to build your computer by tour own you have to know teh parts and their functions. In additions you have to buy the components at reasonable prices.
The components required to build a computer are as follows:
1. Case with Power supply
2. Motherboard
3. Processor
4 Graphic card
5 CPU
6 Hard Disk
7 Mouse and Key board
8 Monitor
9 Monitoring system
The procedure for building your computer is as follows: Open the case and ensure that the power supply is properly installed. Install the Processor in side the motherboard. Install the cooler in the processor. Carefully install the mother board in the case. Install the graphic card in to the AGP Port. Install the Hard disk Ensure that all cabling work is done satisfactorily. Fix the key board and mouse and provide power supply to start the computer.
SPECIFICATION FOR A DESKTOP COMPUTER
CPU : Desktop – Core 2 Duo 2.66 GHz or faster
System RAM : 2GB
Removable Storage : DVD Drive (DVD+/-RW)
Monitor: CRT or Flat Panel with a minimum resolution of 1024x768 at a screen refresh rate of 75 Hz
Video Card 128 MB Dedicated Memory Card
Operating System : Windows XP Professional with SP2
Ethernet Card: 10/100 Base-T
Wireless Network Card: 802.11 a/b/g
Antivirus: kasperskey Antivirus software with online automatic updates
