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AOIT Computer Networking

Lesson 14Advanced Topics in

Computer NetworkingTeacher Resources

Resource Description

Teacher Resource 14.1 Presentation 1 and Notes: Wi-Fi Technology (includes separate PowerPoint file)

Teacher Resource 14.2 Guide: Configuring a Wireless Router

Teacher Resource 14.3 Gallery Walk: Wireless Security Risks and Solutions (separate PDF file)

Teacher Resource 14.4 Presentation 2 and Notes: Introduction to Voice over Internet Protocol (VoIP) (includes separate PowerPoint file)

Teacher Resource 14.5 Guide: Setting Up a Teleconference Using VoIP

Teacher Resource 14.6 Quiz: Wi-Fi and VoIP

Teacher Resource 14.7 Answer Key: Wi-Fi and VoIP Quiz

Teacher Resource 14.8 Key Vocabulary: Advanced Topics in Computer Networking

Teacher Resource 14.9 Bibliography: Advanced Topics in Computer Networking

Copyright © 2008–2016 NAF. All rights reserved.

AOIT Computer NetworkingLesson 14 Advanced Topics in Computer Networking

Teacher Resource 14.1

Presentation 1 Notes: Wi-Fi TechnologyBefore you show this presentation, use the text accompanying each slide to develop presentation notes. Writing the notes yourself enables you to approach the subject matter in a way that is comfortable to you and engaging for your students. Make this presentation as interactive as possible by stopping frequently to ask questions and encourage class discussion.

This presentation describes the standards for Wi-Fi technology and explains how Wi-Fi technology has evolved in recent years.

Presentation Notes



Earlier in this course, you learned that computers use electric signals to communicate. These electric signals are depicted as a square wave because they have two states: on and off. In contrast, radios use analog signals with a continuous wave.

On the physical layer, wireless networks also use modulated radio signals, but they are transmitted through the air instead of via wires and cabling. Wi-Fi is simply a radio used in computer devices.

Presentation Notes



Wi-Fi devices use one of two unlicensed radio frequencies, 5 GHz or 2.4 GHz, to communicate. Using 2.4 GHz can cause interference from appliances like microwave ovens and cordless telephones that use the same frequency. Wi-Fi devices must be on the same frequency to communicate with each other.

The signal bandwidth is measured in megahertz. Over the past two decades, the signal bandwidth for Wi-Fi has increased from 20 MHz to 80 MHz. Increasing the bandwidth increases the amount of data that can be transferred, thus increasing the speed (or megabits per second) of the router.

Effective Wi-Fi communication requires a fast, stable connection. The criteria listed on this slide are defined in the IEEE 802.11 standard for Wi-Fi communication.

Presentation Notes



In 1999, the first standard for Wi-Fi devices was released. Although the data transfer speed for the 1999 standard seems very slow to us today, in 1999 it was quite exciting to have Wi-Fi at all.

Other noteworthy standards have followed:

802.11b (1999) offered a range of 300 feet, but a data transfer rate of only 11 megabits per second.

802.11g (2003) offered a range of 300 feet and a data transfer rate of 54 megabits per second.

802.11n (2009) was an important step forward because there was potential to be faster than a wired network, with 430 megabits per second and a range of over 300 feet.

The network doesn’t always perform at the speed and range advertised. This is because walls, trees, and appliances can cause interference with the signal; this slows the network and prevents the signal from traveling as far. Other wireless devices broadcasting in the same area can cause interference, too. And when the computer is farther from the wireless router, the network speed slows considerably.

Presentation Notes



The emergence of the 802.11n standard in 2009 increased the maximum data rate from 54 Mbit/s to 430 Mbit/s by using multiple antennas at both the transmitter and receiver so that there were four streams of data instead of one. This is called MIMO (multiple input, multiple output). The antennas at each end of the communications circuit are combined to minimize errors and optimize data speed. This helps eliminate shadow signals from buildings and bad reception. 802.11n devices were much faster and more reliable and worked across greater distances than devices using earlier standards.

With the 802.11n standard, residences and businesses began relying more and more on wireless networks. Many vendors developed consumer-grade products like wireless routers and networking cards based on the 802.11n standard even before the rules for it were finalized, hoping they would be able to upgrade the early products to the final standard.

When wireless-n (based on the 802.11n standard) came out it doubled bandwidth from 20 MHz to 40 MHz; wireless-ac (based on the 802.11ac standard) has doubled it again to 80 MHz. Doubling the bandwidth increases the amount of data that can be transferred, thus increasing the speed (or megabits per second) of the router.

The 802.11ac standard also uses MIMO technology with multiple antennas. It is capable of using up to eight antennas, surpassing the 802.11n limit of three. However, first-generation wireless-ac models are only being made with up to three antennas.

Image retrieved from http://commons.wikimedia.org/wiki/File:Wireless_tower.svg and reproduced here under the terms of the GNU Free Documentation License (http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License).

Presentation Notes



Because 802.11ac is fairly new, many computers and devices in use today will need a USB adapter or a new wireless card to take advantage of the technology’s capabilities. That means your computer or device will work, but it will most likely need an upgrade or an adapter before you will see improved performance.

In the foreseeable future, all computers and devices will be 802.11ac-capable and your Internet access will be as fast as your provider permits, not as fast as your router’s speed.

Presentation Notes



In the future, 802.11ac routers will deliver even higher throughput and better range. One of the most interesting new developments is beamforming, which is an optional feature of the 802.11ac standard. On today’s wireless routers and clients, signals go out from devices in concentric rings, like the ripples that develop when you throw a stone into a pond. Beamforming is a new process by which the router and the client exchange information to determine the optimal path their signals should travel. Instead of broadcasting everywhere, the router and client focus and concentrate their signals. This makes the signals stronger.

Image retrieved from http://www.techhive.com/article/2000190/three-minute-tech-ieee-802-11ac.html and included here under fair-use guidelines of Title 17, US Code. Copyrights belong to respective owners. Image courtesy of Netgear.

Presentation Notes



When you are looking for any product for wireless networking—whether it’s a wireless router for your home or a computer with a wireless networking card, you will want to find out which wireless standard is offered and whether all of the pieces are compatible. For example, if you have a computer with an old wireless adapter using 802.11a, it won’t be compatible with a router that offers 802.11ac. If you are getting a new wireless router for your home, you will need to consider whether to get 802.11n, which is likely to be compatible with your other equipment, or whether to get the newest standard, 802.11ac, and update your other equipment as necessary.

Presentation Notes



Wi-Fi is an extremely important technology in today’s world of networking. Understanding how the technology has evolved over the past two decades will help you to appreciate the advances we are seeing today.

Presentation Notes



Wi-Fi for computer networking uses modulated radio signals to transmit data across distances.

Different wireless standards—802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac—use different modulation technologies and frequencies and provide different levels of service.

To use wireless technology, your network adapter must be compatible with the router.

The latest standard is 802.11ac. It makes your Internet as fast as your provider, not your router.

Presentation Notes




Guide: Configuring a Wireless RouterEvery router will have a slightly different navigation structure for changing its configuration settings. Below are the major settings to configure on any router.

Network Name (SSID or Service Set Identifier)This is the name that gets broadcast to computers that are listening for wireless signals. A client computer looking for a wireless network to join will show lists of the networks available. This is the name that will appear. Routers usually default to their make or model number; for example, 2Wire201, Netgear. You should change the name so that you can identify the network, and also for security reasons, so that people are less likely to jump on your network and hog your bandwidth or try to hack your computers.

Encryption/Logon PasswordThis is the password you’ll use to connect with the wireless network from your computer. Again, many routers have a default password. Some default to common passwords like “admin” or “password”; these are insecure because they are easy to guess. Others use a serial number or another number written on the router box. For security reasons, you’ll also want to set a unique alphanumeric password for logging on to your network.

Most alphanumeric passwords are a type of Wired Equivalent Privacy, or WEP, password. These are relatively insecure in general, even if you have chosen a strong one, because bots and machines can keep pestering the router with automatically generated passwords until they find the right one to get in.

A better encryption method is to use a Wi-Fi Protected Access (WPA or WPA2) key, which creates a stronger 128-bit encryption key. This is a long string of numbers and letters in hexadecimal that is much harder for a bot to decrypt and hack.

Router PasswordHere is another important password to choose carefully: the one needed to log in to the router from your computer and change its settings. If someone can get into your router, they can perform all sorts of dirty tricks, like configuring it to send you to the wrong websites when you try to go online, collecting your personal data to sell to ID thieves, or even locking you out of your own system. Choose a good password so that you’re the only one who has control over your settings.

Changing ChannelsSince wireless networks broadcast via radio waves, they can use different frequencies to communicate. There are 11 channels used for wireless networking. Most routers by default are set to channel 6. This means that if too many others are broadcasting nearby, channel 6 will be full of traffic and might start to run slow. It’s a good idea to change the channel on your router to something low, 1–3, or high, 9–11, so that other networks don’t interfere with your wireless signal. This way you’ll get the best performance out of your router. However, other routers can change their channels too, so if your signal is still low after changing this setting, try changing it again to something else and experiment to find the optimal setting. A software application called a Wi-Fi sniffer can be used to identify nearby Wi-Fi networks and which channel they are broadcasting on.



Disable Broadcasting (“Going Invisible”) For ultimate security, configure your router so that it doesn’t broadcast its name to all computers that are listening nearby. Most routers allow you to make your network private. This is especially useful in home networks when you have only a few computers on the network and rarely add new ones. If you disable broadcasting, then you will have to know the network’s SSID name and password to connect.

In some situations, going invisible isn’t a good setting to use. If you want a lot of people to be able to easily find and log in to and out of your network—for example, if you’re setting up a hotspot for coffee shop customers—you’ll want them to find the router’s name automatically and log in easily. But for private networks where only your employees are meant to log on, it might be a good option.

ScreenshotThe following is a screenshot of the wireless settings configuration panel in a common 2Wire-brand wireless DSL modem.




Presentation 2 Notes: Introduction to Voice over Internet Protocol (VoIP)

Before you show this presentation, use the text accompanying each slide to develop presentation notes. Writing the notes yourself enables you to approach the subject matter in a way that is comfortable to you and engaging for your students. Make this presentation as interactive as possible by stopping frequently to ask questions and encourage class discussion.

This presentation introduces students to voice over Internet Protocol: how it works and its benefits and drawbacks.

Presentation Notes



VoIP uses your Internet connection to send live voice information such as a telephone call. You need special hardware and software that can capture your voice as you speak, translate it into digital data, and send it across the network/Internet.

If you are calling a regular phone number, the signal is converted to a regular telephone signal before it reaches the destination. VoIP can allow you to make a call directly from a computer, a special VoIP phone, a traditional phone connected to a special adapter, or a cell phone. In addition, wireless hotspots in locations such as airports, parks, and cafés allow you to connect to the Internet and may enable you to use VoIP service wirelessly.

VoIP is available for individuals from a variety of vendors such as Skype, AOL Instant Messenger, and Google. However, implementing VoIP service for a large business is quite different from using VoIP on a home computer.

Image retrieved from http://commons.wikimedia.org/wiki/File:Voip-typical.gif on April 17, 2013, and reproduced here under the terms of the Creative Commons Attribution 1.0 Generic license (http://creativecommons.org/licenses/by/1.0/deed.en). Image courtesy of BroadVoice.

Presentation Notes



Different types of protocols for networking have different ways of sending data across the cables. Let’s review a couple of important ones:

In Asynchronous Transfer Mode, or ATM, a direct connection is established in order to make sure data is routed swiftly and is received in sequential order. The data cells are a certain length. (ATM uses cells rather than packets.) Historically, this meant ATM was more reliable for Internet telephone calls.

However, most of the Internet now uses Internet Protocol, or IP, to transmit information; this breaks data into packets and routes them across the Net from node to node. Packets might take different routes even if they’re headed for the same destination. Upon arrival, they are reassembled in sequential order.

Voice over IP, or VoIP, makes it possible to send voice information like data packets in IP. VoIP compresses voice or sound waves into UDP (User Datagram Protocol) data packets and then sends them from node to node on the Internet. The packets are labeled with headers that explain the destination of the packet and the packet sequence, and then each packet is sent separately depending on the route that’s quickest at the moment.

VoIP presents some challenges, because on a telephone call, everything needs to happen swiftly and in the right order. So, if Packet A is late but Packets B, C, and D arrive on time, Packet A is dropped. The others are uncompressed and translated to sound waves so that the receiver can hear what’s being said. If lots of packets are lost, the voice quality you hear is bad.

Presentation Notes



Home users and small-business consumers can easily use free VoIP services to make calls over the Internet. Instant-messaging software like AIM and Google’s Gmail offer an audio capability so that users can speak with each other, and Skype allows free outgoing calls.

For regular telephone service, consumers can also subscribe to a home VoIP service that assigns them a personal telephone number and allows them to both make and receive calls.

Presentation Notes



VoIP is more than just a different way to make phone calls. Since it uses data packets, it also integrates well with computer networks and computer systems. Some of the most useful features involve accessing information off a shared server, such as a company phone directory. Employees in a company that uses VoIP can click a box on their computer screen, type the name of another employee they want to call, and press Enter, and their phone will ring the other employee. This makes it simpler to make calls, especially in large organizations.

Some systems are more capable than others. Most will let you set different answering machine messages for different situations, and will send you email when you have new voicemail messages. Some also save a history of your calls, record phone calls for you, and do other things, too.

Many companies that have a telemarketing department or that provide a customer service hotline can benefit in other ways from the way VoIP integrates telephones and computers. For example, when you call a technical support line, an automated machine might ask for your name, the serial number of the product, and what problem you’re having, and then access your account information automatically. The system that does this is called an integrated voice response system. When the system connects you with a customer service representative, the representative’s computer might pop up a screen that tells about your product and any previous calls you’ve made.

Presentation Notes



Although VoIP is pretty easy to use and quality is usually good for home use, installing a VoIP system in a large business requires a lot of time, money, and skill. VoIP users need phones and other network equipment, which gets expensive. The biggest concern for a large business is having enough bandwidth, but upgrades to routers and switches are also required. For large business implementations, staff need to set up the system and help users get used to the new system. If your Internet service doesn’t provide the bandwidth and speed needed, then call quality might not be good enough. To improve the call quality, companies often implement QoS (quality of service) to give voice packets a higher priority than web traffic, but this is another big upgrade.

The VoIP industry is still very young. Many vendors that offer software and services to home users or small businesses are small and may be unreliable, and have been struggling to stay in business. Companies like Cisco offer solutions for large businesses. Some businesses use open-source software to set up their own system, instead of buying software and service from a vendor. However, this can be very time-consuming to set up and requires the staff to understand very well what they are doing, so it’s not an option that all businesses can pursue. For these reasons, many companies are not switching over to VoIP services yet. But it is coming in the future. As Internet speeds get faster and as more bandwidth becomes available for less money, and as more companies grow and mature in the VoIP space, it will become easier for businesses to switch to VoIP telephone systems.

Presentation Notes



VoIP has lots of advantages over regular phone service, even though there are still a few kinks in the system. Most of these disadvantages are being overcome as technology changes and innovations continue. It is possible that VoIP will eventually replace traditional phone service. VoIP has started to receive widespread consumer acceptance, and there is a tremendous amount of work being done to increase the reliability and usefulness of VoIP.

Presentation Notes




Guide: Setting Up a Teleconference Using VoIPPreparationBefore class, contact a NAF academy advisory board member or another local professional who can spend 10 or 15 minutes talking to the class about VoIP and demonstrating what it can do for businesses.

If an advisory board member isn’t available, see if the school principal, someone from the school’s technical service department, a parent, or a local businessperson can give a live talk over instant-messaging video.

Setting Up the EquipmentHave students help set up the equipment for the videoconference. Use a computer that has Internet access and that’s hooked up with a microphone and a webcam. Then hook up the computer to an LCD projector so that the class can see the video feed displayed on a screen.

Many common chat programs, such as Google Chat (http://www.google.com/chat/video), support video chat, which works on VoIP technology. Skype also offers free video calls (http://www.skype.com/en/features/video-chat/).

Another possibility is to use a web conferencing solution like Adobe Connect, to use screen sharing, chat, notes, audio, and video to conduct a meeting: http://www.adobe.com/products/adobeconnect.html.

Speaking TopicsPrep the speaker ahead of time on what the class is discussing. If possible, have the speaker describe features of a VoIP phone system and cool ways it can integrate with the computer to do fancy things like record people’s phone conversations, display a log of calls on the computer screen, or email users their voicemail messages. The speaker might also describe any challenges or special experience he or she has had using or deploying a VoIP infrastructure.

Anyone who uses VoIP in his or her organization might be able to describe some of the basic features. A sales-focused organization might also be able to talk about how VoIP can integrate with other software and provide other benefits. For example, many sales-focused organizations will integrate their VoIP phone system with a customer relationship management software platform that uses integrated voice recognition in the automated phone system. This integrated system can do many things, such as authenticate callers, automatically pull their records, and then display a screen for the call representative that indicates who is calling in. The system can then log all the calls a certain customer makes into the system, and the call agents can type in information about the reason for the call and whether it was resolved. The VoIP system can also ask a customer the reason for a call, connect the caller with a representative who has enough background to help, and record conversations for a supervisor to review.

If finding a business speaker is not feasible, the videoconference could be held with a principal or teacher who discusses how technology in general is changing the ability of people in distant locations to do business with each other. Or, find a short online video or demonstration of some of the features of VoIP.




Quiz: Wi-Fi and VoIPStudent Name:_______________________________________________ Date:___________

1. Describe the capabilities of a Wi-Fi device that conforms to the 802.11ac standard.

2. Describe how a wireless computer keyboard using Bluetooth technology works.

3. Explain three important changes to make when configuring a wireless router so that it is secure for home networking.

4. Briefly describe two security threats on a Wi-Fi network and how to prevent them.

5. Briefly explain how VoIP works.




Answer Key: Wi-Fi and VoIP Quiz

1. Describe the capabilities of a Wi-Fi device that conforms to the 802.11ac standard.

The 802.11ac standard for Wi-Fi improves both connectivity and speed:

o Uses 5 GHz radio frequency to reduce signal interference

o Up to 8 antennas creates 80 MHz of signal bandwidth, which increases the amount of data that can be transferred

o Up to 1.3 gigabits of data per second

o Signal can travel at least 300 feet

2. Describe how a wireless computer keyboard using Bluetooth technology works.

Bluetooth devices such as keyboards, mice, and phone headsets use the same frequency as some 802.11 Wi-Fi networks; however, they pull much less energy and transmit at a more limited range. Bluetooth technology is good for low-power devices that are close to the device they are communicating with, such as computer peripherals.

3. Explain three important changes to make when configuring a wireless router so that it is secure for home networking.

Users should always change the default user names and passwords on the router, including the SSID (router name), the router’s login password, and the encryption key or password used to log on. WPA keys are more secure than WEP keys, but either is better than no password at all. Users can add security by disabling the router from broadcasting its name to listening devices in range.

4. Briefly describe two security threats on a Wi-Fi network and how to prevent them.

Security threats include those described in Student Resource 14.3, Reading: Wireless Security Risks and Solutions, and Teacher Resource 14.3, Gallery Walk: Wireless Security Risks and Solutions. Threats described include keyloggers, Bluetooth snarfing, and pharming, and some of the prevention methods include using firewalls, changing the wireless security passwords and configurations, turning off Bluetooth devices when they’re not in use, and not visiting insecure sites while at a hotspot.

5. Briefly explain how VoIP works.

VoIP compresses voice information into data packets and routes them on the fastest path across the Internet from node to node. It is a connectionless protocol like the way data packets are transmitted using IP. But since voice has to be on time in order to be fast, sequential, and make sense, any dropped or corrupted packets can ruin the call quality. So it can be used only on networks geared toward speed and quality, with good-quality routers and wiring and high bandwidth.




Key Vocabulary: Advanced Topics in Computer Networking

Term Definition

802.11 The articles defining wireless computer networking standards for the industry, including 802.11a, b, g, and n. The standards vary in terms of modulation techniques, power, radio frequency, and range.

Bluetooth A wireless standard for low-power and close-range devices such as cell phone headsets or wireless computer devices like keyboards or mice.

channel In a wireless network, users can choose what channel to have their network broadcast from; this helps reduce interference from other wireless networks in the area.

hotspot The area in which a wireless network is broadcasting, where users can log on with compatible computers or other wireless devices.

keylogger A piece of software that can log each keystroke and record information about what a user is typing, and then relay it back to an administrator or hacker.

pharming The practice of redirecting traffic from a website or a router to the hacker’s website, usually for the purpose of stealing information.

radio frequency ID (RFID) Radio frequency ID tags are used to inventory packages, clothing, or other information. They store information about objects and allow the information to be retrieved wirelessly with a separate radio device.

service set identifier (SSID) The name of the wireless network that gets broadcast to wireless computers and devices that are listening in.

snarfing The word snarf originally comes from a cartoon invented in the 1980s. In networking, it means to hack a Bluetooth signal and intercept and steal private data; for example, stealing the address book information from a local cell phone broadcasting via Bluetooth.

teleconference A meeting with three or more individuals over the phone; can be held over a VoIP connection.

virtual private network (VPN)

A secure connection a company can set up so that its remote workers can log in to the company network securely, even from an unsecured connection. This is accomplished by “tunneling,” or adding a second packet header to the data, which gets decrypted at the destination.

voice over Internet Protocol (VoIP)

The protocol for compressing and routing voice packets over the Internet using typical Internet infrastructure.

WEP A type of encryption for wireless networks that is better than having no



encryption but not as secure as WPA keys.

Wi-Fi Wireless standards for computer networks.

WiMax A wireless technology developed for large-scale wireless implementations such as citywide wireless networks.

WPA A type of encryption recommended for wireless networks because it is more secure than WEP. WPA-2 is the more recent standard used for Wi-Fi encryption.




Bibliography: Advanced Topics in Computer Networking

The following sources were used in the preparation of this lesson and may be useful for your reference or as classroom resources. We check and update the URLs annually to ensure that they continue to be useful.

PrintLowe, Doug. Networking All-In-One Desk Reference for Dummies, 2nd ed. Indianapolis, IN: Wiley, 2005.

OnlineAmah113. “Protocols of VoIP.” Wikimedia Commons, http://commons.wikimedia.org/wiki/Image:Pvoip.gif (accessed November 6, 2015).

“Bluetooth.” Wikipedia, http://en.wikipedia.org/wiki/Bluetooth (accessed November 6, 2015).

Bluetooth.com, http://www.bluetooth.com (accessed November 6, 2015).

“Garage Door Opener.” Wikipedia, http://en.wikipedia.org/wiki/Garage_door_opener (accessed November 6, 2015).

“How VoIP Works.” Wikimedia Commons, http://commons.wikimedia.org/wiki/Image:Voip_HowItWorks_0203v2.jpg (accessed November 6, 2015).

“Infrared.” Wikipedia, http://en.wikipedia.org/wiki/Infrared (accessed November 6, 2015).

Shootthedevgru. “VoIP Phone Aastra 53i.” Wikimedia Commons, http://commons.wikimedia.org/wiki/Image:Aastra_53i.JPG (accessed November 6, 2015).


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