Radio Wave Networks

The true home wireless LAN (WLAN) uses low frequency radio waves to transmit data between computers. Each computer has an adapter that sends and receives radio signals. Since radio frequencies can penetrate most indoor walls and obstacles, a line-of-sight between computers isn't required.


Just as radio reception degrades the farther you are from the transmitter so network speeds slow the farther you are from the other networked computers. Network performance can also be affected by the type of construction in your home. For example, it's harder for radio waves to penetrate concrete than drywall and the more walls separating your computers, the slower the network.

Wireless Protocols
At the moment there are two wireless protocols vying for prominence. HomeRF is the less expensive of the two and can transfer data at 1.6 Mbps, allowing computers to be up to 50 m (150 ft) apart. HomeRF provides adequate performance for most networking tasks but is under-powered when it comes to playing raw CD audio across a network or streaming any video content. Fortunately a 10 Mbps version of HomeRF is now available and worth considering.

The 802.11b protocol (Wi-Fi) is gaining in popularity and support as prices come down though it is still an expensive option for the home. Wi-Fi requires more equipment than HomeRF which contributes to the cost. However, at 11 Mbps with up to 500m (1600 feet) between devices it's powerful enough for full-motion digital video. It also supports other computing devices such as PDA's.

For households with Macs, Wi-Fi is a good choice because recent Apple models can be fitted with an Airport card, an inexpensive option that uses the 802.11b standard. Wi-Fi is also being adopted for wireless connectivity in public places, college campuses and the workplace, using the same network adapter one would use in the home. Microwave ovens and 2.4GHz portable phones are a potential source of interference with 802.11b networks though often problems can be fixed by moving devices.

Interface
Wireless adapters come in several forms including USB, parallel port, ISA, PCI and PC Card. External parallel port and USB adapters have built in radio antennae and plug into your computer. Internal network cards either have antennae attached to them directly or by a cord that plugs into the card. PC Card adapters with attached antennae are available for laptops.

Access Points
An Access Point is a transmitter/receiver that can connect an 802.11b network to a wired LAN. Access points can also be used to increase range by acting as a relay point, retransmitting a signal from one wireless network to the next. The average home should be small enough to do without access points which are geared more to campus or corporate settings with a price tag between $300-1000.

Performance
Since numerous factors influence wireless transmission you'll rarely approach the maximum networking speeds set out by the various wireless protocols. Data transfer can vary between 30-60% of the stated maximum depending on adapter interface, distance between computers and obstacles in the way. HomeRF is slower than Ethernet, usually under 1 Mbps. Wi-Fi wireless LANs transmit in the 3.5 to 4.5 Mbps range.

Price
Wireless networking offers the greatest flexibility and mobility, but at a price. Kits vary in cost depending on the interface and protocol you choose. The least expensive kits (2 adapters) are based on HomeRF with prices in the range of $150-300. Wi-Fi kits are $300 plus.

Interoperability
The proliferation of wireless standards means that interoperability is a big issue. In theory, products from different manufacturers that adhere to the same protocol and display the logo of one the organizations (like HomeRF or WiFi) should work together, but there's a potential for headaches. Although various organizations are trying to make the different wireless standards compatible, you should avoid mixing products that use different protocols.

Hybrid Networks
If you have both Macs and PCs, choosing a wireless network can be a little more challenging. Intelogis' power line kits do not support Macs, but some HomePNA products do. Depending on the type of Mac you have you can use PCI, USB or Ethernet-to-phone-line adapters to create a phone line network with your Mac.

True wireless networks will also support cross-platform networks, but most products are for one platform only. For example, Apple's AirPort products are Mac only, and the majority of wireless home network kits are PC only. There are a few kits that will work with PC and Linux. At the moment no manufacturer makes a PCI or USB product that will support both Mac and PC, but 3Com has stated it plans to add Mac support to its wireless products in the future.

If you're really determined and have deep pockets, you can buy an Apple AirPort base station or an Orinoco (formerly WaveLan) access point; both follow the IEEE 802.11b protocol. Both types of access points can connect to Macs and PC's with any 802.11 b compliant wireless adapter. You can even use the AirPort base station in an all PC network. If you have a laptop, Farallon makes a PC Card adapter that will connect a Mac or PC laptop to an 802.11b compliant access point. Two laptops with this PC Card can network to each other without an access point.








186 Router and Routing

row´ter) (n.) A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect. Routing is a process preformed by a router which moves packets of data around the Internet. A router makes sure that a message is sent and received and is part of what makes TCP/IP such a useful protocol suite.


To be able to successfully start routing a router uses headers and a forwarding table to find the destinations for packets. A router uses the ICMP protocol section of the TCP/IP protocol suite. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

Very little filtering of data is done through routers

Definition: A network gateway is an internetworking system, a system that joins two networks together. A network gateway can be implemented completely in software, completely in hardware, or as a combination of the two. Depending on their implementation, network gateways can operate at any level of the OSI model from application protocols to low-level signaling.

A Cisco router is a computer device that receives or forwards data packets to and from the Internet towards a destination in the process called routing. A router is the essential component of the computer networking that enables any sent data to arrive at the right destination.

As an illustration, imagine that the Internet is the world and one computer is one household. Other computers connected through the Internet are households around the world. Say one household will send a letter to another household in any part of the world. The letter has an address right? And that address would determine the destination of the letter. But without one reading the address, the letter would not arrive to the right receiver. The letter also would not be able to reach the intended receiver if there is not medium. This medium would be the courier. And the courier of the computer data is the router.

A router (broadband router) is also a device that enables two or more computer to receive data packets from the Internet under one IP address at the same time.

Remember that to be able to connect to the Internet, a computer must have an IP address unique from the rest of the computers. Therefore, every computer connected to the Internet has it own IP address. It is like having a fingerprint or ID as an access pass to be able to enter the web. With the presence of the router, this “fingerprint” or “ID” could be shared by two or more computer at the same time.

In simplest form, a router makes two or more computer use the Internet at the same with one access pass.

One more thing: a computer with cable modem could also be considered as a router. In this, the computer would do the process of routing like normal routers do. Other computers are then connected to the computer with Internet connection that would give it with the Internet connection. The computer with cable modem has the direct contact with the Internet and the ones connected to it are sharing the connection.

Why would anyone need a router?

For households with two or more computers who would want to have Internet connection to every computers they have, taking subscription for each would be too much. The solution is to buy a router that would enable every computer in the house to have an Internet connection. In the definition above, the broadband router would act as a hub to the existing Internet connection.

If the router is comparable to a hub, would it affect the Internet speed?

It should be taken into consideration that once a single Internet connection is divided, the connection speed is affected. But there are some broadband routers that would bring minimal slowdown to the Internet speed and the effect might not even be big.

Internet speed would also depend on the type of application used in a router. While some would inflict little effect on the speed like online games, others would terribly slowdown your connection and even hinder you to use the Internet at all.

Usually, offices use a more sophisticated router to redirect Internet connections to the large number of computers. These routers would give better data packeting compared to a typical router used at home that results to faster Internet speed.

When it comes to deciding to undergo computer training, you may be interested in getting the basics before applying for the right certifications, if you already have heard about CCNE, CCIE, CCNP and CCNA certification.

The first thing you need to know before deciding is that Cisco actually offers 3 different levels of general certification, which represents in each case increasing levels of expertise.

The first step in Cisco networking and computer training always begins at the Associate level, which is the foundation or apprentice level of Cisco certification.

After the Associate Level, comes the Professional, which is the journeyman or advanced level of networking certification, and finally the Expert level, standing for the CCIE, the highest level of achievement for network professionals, certifying an individual as master or expert of the IT industry.

Cisco certifications, Associate, Professional, or Expert (CCIE) are the tools anyone may need developing a professional career, with different tracks across these levels according to your career needs.

There are also a variety of Specialist certifications such as including CCNP, CCNE and CCNA certification, available to certify knowledge in specific solutions, technologies or job roles, with new certifications added to Cisco's list regularly.

Computer training and general certifications are divided in six paths:

- Routing and Switching, certification aimed at professionals who install and support any Cisco technology-based networks in which LAN and WAN routers and switches reside.

-Design certification, is the path for those professionals who design Cisco technology-based networks in which LAN and WAN routers and switches reside.

-Network Security, certification directed to network professionals who are in charge of design and implement Cisco Secure networks.

- Service Provider, certification aimed at professionals who work on infrastructure or access solutions in a Cisco end-to-end environment within the telecommunications arena.

- Storage Networking certification, intended for professionals implementing storage solutions over extended network infrastructure, but using multiple transport options.

- Voice certification, for those professionals who install and maintain Voice solutions over IP networks.

Cisco’s most popular computer training certifications are:

CCNP certification (Cisco Certified Network Professional), indicates a network professional who can install, configure, and troubleshoot local and wide area networks for enterprise organizations with networks from 100 to more than 500 nodes.

CCNE certification (Cisco Certified Network Engineer) and CCNA certification (Cisco Certified Networking Associate) develops the respective computer training and skills required to individually pursue the Cisco Certified Professional (CCNP) certification noted above, part of the 3 basic CISCO levels.

Cisco Router or Computer training for these certifications give the knowledge to design, install, configure, maintain, and troubleshoot networks, ensuring that students emerge with the skills necessary for the Internet marketplace.