A Brief Overview Of Networking Media

There is all sorts of networking media lying around for the taking. We have copper-base media, optical fiber, and the new contender: wireless. This article covers a brief overview of each networking media type. By no means is this a complete guide to every single networking media type, but instead it is geared towards what the CCNA exam demands students know about networking media in general.

Copper Networking Media: Shielded Twisted-Pair

As you might’ve guessed, copper networking media uses electric signals to send and receive data over a copper medium. As far as Ethernet cabling goes, there are two main types of cable types to recognize: shielded twisted-pair (STP) and unshielded twisted-pair (UTP).

Shielded twisted-pair cable contains four pairs of color-coded wires. These pairs are each twisted together and wrapped in metallic foil. For further protection, we put yet another metallic foil over the entire bunch of pairs. Note that the below diagram does not show the standard color coding for copper media.

Shielded twisted-pair cable is incredibly resistant to noise, thanks to the twisted wiring and metallic foil. Noise from objects such as a fluorescent light can interfere with electrical signals- so you will see STP cable in these areas.

The twisted wires in particular help protect against crosstalk. When each wire is conducting a current, a magnetic field is being generated around each wire. This magnetic field can interfere with the signal on other wires, so we twist the pairs of wires to cancel out both magnetic fields. As you’ll see in unshielded twisted-pair cable we do the same thing- only UTP does not make use of the metallic foil.

There are some drawbacks to STP, however. It takes more time to install since the metallic foil needs to be grounded. And if improperly grounded, the metallic foil will act as an antenna, and draw even more noise to your cable than you would’ve had previously. Lastly, we can’t run wire as far with STP as with UTP, so STP is best suited for short wiring jobs.

Three Things to Remember about Shielded Twisted-Pair

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• 1. Bandwidth is limited to 10-100 Mbps
• 2. STP is much more expensive than its UTP counterpart
• 3. Maximum cable length is short- around 100 meters

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Copper Networking Media: Unshielded Twisted-Pair

Unshielded twisted-pair cable is much like shielded twisted-pair, only it lacks the extra metallic foil. This is usually more common to use, as it is less expensive and requires less work to install.

Note that there is an absence of both metallic foiling around each twisted pair, as well as the metallic coating around all of the collective wires. This would of course be less effective in stopping outside noise from interfering with our signal, but in most cases UTP works just fine.

Three Things to Remember about UnShielded Twisted-Pair

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• 1. Bandwidth is limited to 10-1,000 Mbps
• 2. It is much easier to install than other media- such as fiber optic or coaxial
• 3. It is generally the least expensive

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Optical Networking Media

Fiber optic cable uses modulated light to send and receive signals. This eliminates crosstalk and even provides immunity to electromagnetic interference. Fiber optic media also provides much more bandwidth capability, distance capability, and is easily installed.

Luckily, Cisco doesn’t put a lot of emphasis on optical media on exams. However, be sure commit the following to memory:

Three Things to Remember about Optical Media

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• 1. Optical fiber uses light patterns to send a receive signals
• 2. Optical fiber is less affected by external signals
• 3. Optical fiber allows for longer cabling distances
• 4. Optical fiber is more expensive than UTP

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Wireless Networking Media

Networking students are currently getting a break on wireless networking in exams. This is very likely to change soon, but for now, all that is really required to commit to memory are three IEEE standards: 802.11a, 802.11b, and 802.11g.

802.11a operates on a 5 GHz frequency. It offers much better data transfer speeds than 802.11b, although it doesn’t have as good as of a range. 802.11a is a poor choice when several walls or other obstructions are present between the access point and client.

802.11b operates on a 2.4 GHz frequency. It has a better range than 802.11a, but has much less capability to offer the excellent data transfer speeds that 802.11a does.

802.11g also operates on a 2.4 GHz frequency. It is a hybrid of the two previous standards: offering both excellent download speeds and excellent range. Although it isn’t technically as fast as 802.11a, it is quite close in benchmarks.

Networking Media Specifications

When you see the term 10BASE-T, do you automatically think of a cable that has a theoretical bandwidth limit of 10 Mbps, and a distance of 100 meters? If you don’t, make note that Cisco does indeed require networking students to commit this type of information to memory. But don’t worry, it is easier thank you might think.

To memorize all of the above would be quite tedious. And more than likely, it’d be forgotten within the next week. Instead, we can simply look at the networking medium name to determine its specifications. The 10 in 10BASE-T for instance, indicates its bandwidth is theoretically 10 Mbps. The T indicates that it is a twisted pair cable.

The 10 in 10BASE5 also means a bandwidth of 10 Mbps, but notice that the 5 actually tells us the maximum distance it can run: 500 meters. Obviously, a little deciphering on your part can mean less memorization.

Closing Comments

Although we could have gone much more into detail, Cisco doesn’t require general networking students to do so. The bulk of this material is useful for the CCNA 1 Module 3 exam- so keep a particular look out for answers to the CCNA 1 Module 3 exam within this article.

Network Media by Fred Cohen

Typical media for networks include optical fibers, shielded and unshielded twisted wire pairs, coaxial cables, electromagnetic radio emanations, and ultrasound. These currently have approximate cost and performance characteristics as specified in the following table, but the extremely rapid changes in technology currently underway will undoubtedly make these figures invalid in the near future (they have changed twice during the last year). Bandwidth is given in bits per second (BPS), initial and ongoing costs are rated from 0 to 5, 0 being the cheapest for a typical installation.

 Media              Cost        Bandwidth    Ongoing
        ---------------------------------------------------
        fiber optics         2           50M BPS       2
        shielded pair        1           10M BPS       1
        unshielded pair      0            1M BPS       0
        coaxial cable        3          400M BPS       5
        radio                5         1000M BPS       4
        ultrasound           4           30K BPS       3

Fiber optics are difficult for an attacker to tap (although by no means impossible) compared to the other technologies, radio is more difficult to destroy but more susceptible to noise, unshielded wires have noise problems, and ultrasound is very susceptible to noise. Current computer to computer communications rarely take advantage of performance over 10M BPS because hardware (disks, processors, etc.) that uses this much bandwidth is expensive, and the rarity of applications requiring this bandwidth on an ongoing basis. In the case of voice data, each channel is about 40Kbaud, and for video data about 10MHz is required per signal.

How do I . . . change my MAC address with SMAC?

By Jack Wallen

SMAC is a MAC address changer that has a simple to use graphical interface that enables the less experienced user all the way up to the guru change a piece of hardware’s MAC address. Jack Wallen shows you how it all works.

A Media Access Control address (MAC address) is the hard-encoded address given to a piece of networking hardware. This address is assigned by the manufacturer of the hardware and is intended to be permanent. However, that is not always the case.

There are two “types” of MAC addresses – ”software based” and “hardware based.” The “hardware-based” MAC address is the address encoded on the hardware. The “software-based” level of address encoding is the one most MAC address-altering software works with.

There are many reasons why you would need/want to change a machine’s MAC address. But because some of the reasons people change (spoof) a MAC address are less than innocent, most people assume there are no good reasons why you would want to change a MAC address. There are good reasons to change a MAC address, and the primary reason for making a change is security.

There are security breaches that rely on knowing the MAC address of a machine. By getting this address, a hacker can always find that machine — even if the address is changed via DHCP. To that end, why not regularly change the MAC address of your more important machines on your network? An added layer of security, especially on this level, is a good thing.

SMAC

If the address is typically hard-coded into the hardware, how would you go about making this change? As said earlier, you would change the software-layer address. There are many tools out there that can help you with this process, but none is as easy as SMAC.

Now many people hesitate to employ such tools. I have found some MAC address spoofers to include little extras such as Trojan programs. So it’s nice when you can find a tool, normally associated with nefarious tasks, employed by such companies as HP, Cisco, Siemens, Intel, and Boeing.

SMAC is a MAC address changer that has a simple-to-use graphical interface that enables the less experienced user all the way up to the guru to change a piece of hardware’s MAC address. The less experienced user will appreciate the random generator whereas the guru will appreciate the ability to hand enter a new MAC address.

Features

SMAC has a number of features to entice the enterprise and the home user:

• Looks up MAC addresses
• Activates active new addresses automatically
• Lists manufacturer of MAC address
• Shows all or active network adapters
• Generates a random MAC address
• Preloads MAC addresses and chooses them from a list (this is not in the demo version)
• Gives you information on your network addressing
• Takes just three clicks to change a MAC address because of GUI
• Hides hard-coded MAC addresses
• Shows detailed information about your network adapter
• Keeps a listing of ten most recently used MAC addresses
• Generates reports

So even if you don’t use the spoofing feature of SMAC, the other features available make it worth giving this application a try. With that in mind, let’s take a look and see how SMAC does its thing.

Getting and installing

As with any Microsoft Windows application, the installation process is just a matter of downloading the file and double-clicking the installer to begin the process. This installation is no different. A few standard clicks and you are ready to run SMAC.

Once it is installed, you will find the application launcher in a Start Menu subdirectory called KLC. Click on that folder and you will see SMAC 2.0. Click on that launcher and the SMAC main window (Figure A) will open.

Figure A

The disclaimer at the bottom of the window should be fully regarded.

Using SMAC

Using SMAC can be very simple, depending on how you want to use it. The simplest way to use SMAC is to assign a random MAC address to a piece of hardware. Before we actually assign a new address, let’s take a look at the other hardware on the machine. In the main window there is a check box that tells SMAC to show only active hardware. This checkbox is checked by default. Uncheck that box and your listing will grow, depending on the hardware on your machine. Take a look at Figure B to see how much the listing grows on my laptop that includes wireless, wired, and dial-up connections.

Figure B

When you click on a different listing, the information about that hardware will be displayed below.

Let’s change the MAC address of the Wired Marvell Yukon PCI-E Faster Ethernet Controller. To do this, select that entry from the list and click the Random button. As you can see in Figure C, the new, random MAC address is displayed in the New Spoofed MAC Address section.

Figure C

The address listed will correspond to a manufacturer list that you can choose from.

If you know you want to spoof your MAC address to that of a specific manufacturer you can select a different manufacturer from the drop-down list. When you make this selection, the address listed will change. You can keep hitting Random until you get an address you like (or you can just take the first random address you get).

Once you have your address, select the Options menu and make sure Automatically Restart Adapter is checked. Once that is checked, hit the Update MAC Address button and the new MAC address will be applied.

NOTE: In evaluation mode you can only change an address to 0C-0C-0C-0C-0C-01.

Other features

As stated earlier, SMAC has a few other features that make it stand out. Here’s a quick description of some of those:

• Log Viewer: To view your MAC address log, go to the View menu and select MAC Address Log, which will open a log window where you can view the MAC addresses that have been applied to various network adapters.
• IPConfig: Clicking the IPConfig button will open a window that holds all the information about your currently configured hardware. Figure D shows how this information is displayed.

Figure D

You will find more information about your network in this window than you will ever need to know.

• Remove MAC Address: You can also easily remove a spoofed MAC address by selecting the hardware and the clicking the Remove MAC button. This will return your hardware’s MAC address to its original state.

Final thoughts

By now you should see how helpful this tool is. Not only does it spoof MAC addresses easily, but it can also help you get information about your hardware with the simple click of a button. SMAC is a very handy tool to use, just make sure you are using it for the right reasons.

MAC Addressing

Find a MAC Address

The method used to find a MAC address depends on the type of network device involved. All popular network operating systems contain utility programs that allow you to find (and sometimes change) MAC address settings.

Find a MAC Address in Windows

In Windows 95, Windows 98 and Windows ME, the winipcfg utility displays the computer's MAC address. Use the ipconfig utility (with the /all option) in Windows NT and any newer versions of Windows.

Both 'winipcfg' and 'ipconfig' may display multiple MAC addresses for one computer. One MAC address exists for each installed network card. Additionally, Windows maintains one or more MAC addresses that are not associated with hardware cards.

For example, Windows dial-up networking uses virtual MAC addresses to manage the phone connection as if it were a network card. Some Windows VPN clients likewise have their own MAC address. The MAC addresses of these "virtual" network adapters are the same length and format as true hardware addresses.

 

Find a MAC Address in Unix or Linux

The specific command used in Unix to find a MAC address varies depending on the version of the operating system. In Linux and in some forms of Unix, the command "ifconfig -a" returns MAC addresses.

You can also find MAC addresses in Unix and Linux in the boot message sequence. These operating systems display the computer's MAC address on-screen as the system reboots. Additionally, boot-up messages are retained in a log file (usually "/var/log/messages" or "/var/adm/messages").

Find a MAC Address on the Macintosh

You can find MAC addresses on the Macintosh in the TCP/IP Control Panel. If the system is running Open Transport, the MAC address appears under the "Info" or "User Mode/Advanced" screens. If the system is running MacTCP, the MAC address appears under the "Ethernet" icon.

Summary - How to Find a MAC Address

The list below summarizes options to find a computer's MAC address:

• Windows 95 and newer: winipcfg
• Windows NT and newer: ipconfig /all
• Linux and some Unix: ifconfig -a
• Macintosh with Open Transport: TCP/IP Control Panel - Info or User Mode/Advanced
• Macintosh with MacTCP: TCP/IP Control Panel - Ethernet icon

Wifi Technology

WiFi - The fast paced technology has changed the world as well as its habitants. In Today’s global village there is no need to grab the telephone receiver and dial a specific number to transmit voice through cables merely to hear the voice of a beloved. Now each of us carries our own handsets with a built-in phonebook and text messages. The facilities like Wi-Fi have further improved the standard of communications by cutting down expenditure and increasing availability.

No matter where you are, you can access the world of web through your handsets and your laptops and your iPads. You might not have noticed what it is but the technology that enables you to plug in internet without any wires whether you are in a cafe, a library, a shopping mall or an airport is Wi-Fi – the wireless network also known as 802.11. The circumference where wireless technology is present and available to the users is known as Hotspot. The inexpensive, user-friendly WiFi networks are also obtrusive; if you do not need one you would not know there exists any. Wi-Fi could be also installed in home or offices in order to transmit information over the air without the aid of wires. In near future you would find wireless networking available in every nook and corner.

Wi-Fi is derived from the decades old term Hi-Fi that stands for the output’s type produced by quality music hardware. WiFi Technology is WIRELESS FIDELITY and stands for all those technologies that fall under the specifications of IEEE 802.11 including 802.11a, 802.11b and 802.11g. The association of the term Wi-Fi with various technologies is merely because of the promotions made by the Wi-Fi Alliance.

For those whose laptops and cell phones do not have a built-in wireless transmitter then you could purchase a wireless adaptor and inject it into USB port. A Wi-Fi hotspot is automatically discovered and connected by the transmitters. The presence of Wi-Fi in public places makes it convenient to stay connected to your official tasks or to the social networking.

Wi-Fi is also associated with 802.11 networking. The reference is derived from IEEE – Institute of Electrical and Electronics Engineers uses the numbering system for classifying a range of technological protocols.

Wi-Fi steps into the boots of TV and radio in order to transmit data through radio waves. The two-way radio communication: the wireless adapter translates data into a radio signal then transmits it via antenna; and the signal is received and decoded by the wireless router that uses a tangible wired Ethernet connection to send information to the internet. The equation is reversed when wireless router receives data from the internet and translates it into a signal where the wireless adaptor receives the signal and decodes it.

Wi-Fi communication devices are extended forms of radios used for cell phones and walkie-talkies: they simultaneously transmit and receive radio waves and convert 1s to 0s into the radio waves along with reconverting the radio waves into 1s and 0s, however the Wi-Fi radios enjoy some exceptional features.

Technology has developed far more than our expectations – none of us could perceive the developments in approaching future. With features like Wi-Fi, earth would turn into a world wide web where every user is omnipresent and active.

Wifinotes.com is constructed with the intention of educating the tech-savvy community on the pros and cons of not only WiFi but many other wireless networking technologies. We hope that the elaborated posts and references would taste like cookies.

Note: Video demonstation on how wifi technology works

Microsoft pressures Huawei over Android patents while Barnes & Noble fires back

Microsoft is reportedly trying to ink more deals in which makers of Android devices pay license fees while Barnes & Noble calls for an investigation into that practice

Microsoft has been pressuring Huawei to sign a patent license agreement to cover Android, according to Huawei Device Chief Marketing Officer Victor Xu. Meanwhile, Barnes & Noble has asked the Department of Justice to investigate whether Microsoft's use of its patent portfolio amounts to antitrust violations.

Huawei's Xu revealed in an interview with the BBC that discussions with Microsoft over Android licensing are "in progress" and promised that Huawei is careful to respect the intellectual property of others. However he also mentioned that the Chinese manufacturing company lays claim to more than 65,000 patents of its own that can be used to defend its interest.

As of October, Microsoft had pressured 10 Android OEMs into inking Android patent license deals, and claimed that half of all Android devices sold include a royalty paid to Redmond. Last month, Microsoft announced its 10th deal, with Taiwan's Compal Electronics. Prior to that, Microsoft had inked deals with HTC, Velocity Micro, General Dynamics, Wistron, Onkyo, Acer, ViewSonic, Samsung and Quanta, the latter of which also covered Chrome, Microsoft said. 

Many of these OEMs also make Windows products.

In the meantime, Barnes & Noble, which refused to buy licenses and is consequently being sued by Microsoft, has ratcheted up its defense. Last month, the bookseller's lawyer penned a letter to Gene Kimmelman, the Justice Department's chief counsel for competition policy in its antitrust division, reports Bloomberg. In that letter, Barnes & Noble asserted, "Microsoft is embarking on a campaign of asserting trivial and outmoded patents against manufacturers of Android devices." It then requested that the DOJ investigate possible antitrust violations from these tactics.

The trial over Microsoft's patent claims is slated for February 2012. The lawsuit, filed in March in U.S. District Court of the Western District of Washington, also names device manufacturers Foxconn International Holdings and Inventec, Microsoft said. In tandem with the lawsuit, Microsoft filed a complaint with the U.S. International Trade Commission (USITC), which has the power to ban imports into the U.S. of devices that infringe patents.

Legal documents filed over this case and Microsoft's legal battle with Motorola over Android, detail about a dozen patents that Microsoft claims Android violates.

Router Firmware Bug Triggers Widespread Internet Outage

By Bradley Mitchell

Many people around the world found the Web unreachable today due to an unexpected failure of some Internet routers. The failure was apparently caused by firmware update that some Juniper routers couldn't handle, causing them to crash. Some initial reports of the issue noted that the routers also core dumped, a term that's in every good techie's vocabulary but may sound unnecessarily alarming to the general public. Fortunately, router firmware can normally be repaired without damaging the hardware, and recovery from this particular incident seemed to be smooth.