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Factors affecting VoIP quality
There are several factors that profoundly impact the quality of voice over the Internet. These factors can be described in terms of their general affect on VoIP quality: Negative or Positive.
Negative Factors
Of the three negative factors for VoIP performance, the first one is delay, which results in echo and talker overlap. The second one is jitter, which is essentially the variation in delay. The third problem is packet loss. These factors are explained in much more detail below.
DelayDelay results in echo and talker overlap. Echo becomes a problem when the round-trip delay becomes high. Talker overlap (the problem of one caller stepping over the other talker’s speech) becomes significant if the one-way delay becomes greater than 250 milliseconds.
JitterJitter is essentially the variation in delay. This is primarily introduced because of the variation in inter-packet arrival time.
Packet Loss
Packet loss is a constant problem in packet-based networks. In a circuit-switched network, all speech in a given conversation follows the same path and is received in the order in which it is transmitted. If something is lost, the cause is a fault rather than an inherent characteristic of the system.
Apart from these factors there could be impairments caused by codecs. These impairments are due to the distortion introduced by the codec and due to the interaction of network effects with codec operation. Speech coding and compression Both speech coding and compression have been used in the traditional telephony for over two decades. With the exception of the local loop, almost all voice is carried over the PSTN in digital format. The received analog voice undergoes an analog-digital conversion at 8000 samples per second with 8 bits per sample, producing a 64 kbps digital data stream. A codec is the device that performs the conversion from analog voice into a digital format and vice-versa. The standard method used in traditional telephony is PCM (pulse code modulation) implemented by using a codec that conforms to ITU-T standard G.711. Most humans can hear sound up to about 20 KHz, but the traditional telephony uses low-pass filtering to remove everything but approximately the lower 4 KHz of the speech signal. In addition to this, voice over packet networks commonly use low bit rate codecs for compressing the received noise. These low bit rate codecs preserve the parts of the speech that are of important to the human listener taking out those parts that are not of any importance such as silence, redundantly long words. This is generally known as perceptual coding and is used in a number of other areas too, such as MPEG-2 video compression, JPEG image compression and MP3 audio. Standardized codecs have been tested with multiple speakers and multiple languages. The results can be tabulated as below.
Here MOS is the measurement for voice clarity. This is explained in detail later in this chapter.Positive Factors
Of the two positive factors for VoIP performance, the first one is bandwidth, which is absolutely necessary for adequate performance. The second factor is prioritization. Prioritization becomes increasingly important as the network gets congested.
Bandwidth
One of the greatest challenges of VoIP is voice quality, and one of the keys to improving voice quality to an acceptable level is bandwidth. Therefore, additional bandwidth is certainly needed, if only to support additional traffic as demand for VoIP continues to grow. While additional bandwidth is a necessity for a network that is required to support voice in addition to the data traffic that is might have carried all along, additional bandwidth is not, by itself, a complete solution for the QoS issue.
PrioritizationOnce sufficient bandwidth is available to enable high-quality voice transfer, we need to control and prioritize access to the available bandwidth. As this regulation is not exerted over the Internet presently and because the IP is designed completely for the transfer of the data from its outset, depending upon the usage of the bandwidth, voice quality over the Internet might vary from acceptable to atrocious.

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Bluetooth Technology

Bluetooth Introduction
Well it isn't some strange form of tooth decay as you might initially imagine. Bluetooth is the name of a new and fifth generation technology that is now becoming commercially available. It promises to change significantly the way we use machines. By the way if, you are wondering where the Bluetooth name originally came from, it named after a Danish Viking and King, Harald Blåtand (translated as Bluetooth in English), who lived in the latter part of the 10th century. Harald Blåtand united and controlled Denmark and Norway (hence the inspiration on the name: uniting devices through Bluetooth). He got his name from his very dark hair which was unusual for Vikings, Blåtand means dark complexion. However a more popular, (but less likely reason), was that Old Harald had a inclination towards eating Blueberries , so much so his teeth became stained with the colour, leaving Harald with a rather unique set of molars. And you thought your teeth were bad hahaha.....
Take a look around
Look around you at the moment, you have your keyboard connected to the computer, as well as a printer, mouse, monitor and so on. What (literally) joins all of these together?, they are connected by cables. Cables have become the bane of many offices, homes etc. Most of us have experienced the 'joys' of trying to figure out what cable goes where, and getting tangled up in the details. Bluetooth essentially aims to fix this, it is a cable-replacement technology.

How Does Bluetooth Work?
The answers to all your questions are here in varying levels of detail to meet everyone’s needs. The information ranges from high-level overviews of the short-range wireless technology to detailed specification documents. Read about Bluetooth technology benefits to the consumer as well as the enterprise. Better understand how Bluetooth technology works. Compare Bluetooth wireless technology to other similar short-range wireless technologies. Dig deeper into the specifications to fully comprehend the various levels of Bluetooth technology from the baseband to profile and application levels. Educate yourself on how to keep your Bluetooth devices secure. Use the glossary as a reference as you run across new Bluetooth terminology. Consider this your Bluetooth classroom and explore.Conceived initially by Ericsson, before being adopted by a myriad of other companies, Bluetooth is a standard for a small , cheap radio chip to be plugged into computers, printers, mobile phones, etc.A Bluetooth chip is designed to replace cables by taking the information normally carried by the cable, and transmitting it at a special frequency to a receiver Bluetooth chip, which will then give the information received to the computer, phone whatever.
How about the Bluetooth ?
That was the original idea, but the originators of the original idea soon realised that a lot more was possible. If you can transmit information between a computer and a printer, why not transmit data from a mobile phone to a printer, or even a printer to a printer?. The projected low cost of a Bluetooth chip ($5), and its low power consumption, means you could literally place one anywhere.

Ideas
With this viewpoint interest in Bluetooth is soaring, lots of ideas are constantly emerging, some practical and feasible e.g.: Bluetooth chips in freight containers to identify cargo when a lorry drives into a storage depot, or a headset that communicates with a mobile phone in your pocket, or even in the other room, other ideas not so feasible: Refrigerator communicating with your Bluetooth-enabled computer, informing it that food supply is low, and to inform the retailer over the internet.

The future of Bluetooth
Whatever the ideas, Bluetooth is set to take off. To be honest it's going to be forced down the consumers necks, whether they want it or not, as too many companies have invested in it. This website is generally geared towards the technical issues surrounding Bluetooth, and its implementation in real life. But free feel to have a look around anyway, and see why this technology will have such a big impact on our lives. If you're a complete beginner & you want to know more go to the other pages on the website: the tutorials has a reasonably in-depth guide to Bluetooth (can be quite technical in parts though), our members-only download page has some more general introductions to Bluetooth to download. Also check out the resource center, articles, glossary & knowledge base to further enhance your Bluetooth education. There are also related Resource Centers on IEEE 802.11 WiFi Wireless LANs, HomeRf, GPS SyncMl, ZigBee and other mobile and wireless technologies

Intrusion-detection tools to stop hackers cold
Any IS professional worth his salt wants to protect his network, and finding early signs of hacking is a good start. Three years ago, there was only a handful of commercial products to do this, but the market for intrusion-detection tools has now become an embarrassment of riches.
There is host-based monitoring software from Centrax, WebTrends, Axent Technologies, Tripwire Security Systems and Internet Security Systems. These packages will send a warning if they detect misuse of protected files, the operating system or a Web server.
There are network-based scanners sold by Netect, Network Associates, Internet Security Systems and Security Dynamics Technologies. These tools check for holes in firewalls or servers so IS can close them. Or you can download shareware, such as the Satan scanning tool created by Dan Farmer, for free off the 'Net.
Another type of intrusion-detection product guards LANs by inspecting and analyzing packet flows across the network, detecting patterns of connection that indicate an attack. In the packet-peeking crowd are Woodbine, Md., company Network Flight Recorder (NFR) with its product of the same name, Cisco with NetRanger and Network Associates with CyberCop.
Marcus Ranum, NFR president and founder, says the Unix-based NFR product watches up to 18,000 packets per second, analyzing patterns that indicate an attack.
Some packages are going a step beyond detecting intruders by relaying shut-off commands directly to devices such as firewalls without intervention by the network administrator. CyberCop takes this approach by communicating with Network Associates' Gauntlet firewall when it spots hacker activity.
It's getting hard to avoid intrusion-detection tools because these capabilities are being built directly into more and more network gear.
Network-1 Security Solutions' CyberWall distributed firewall, for example, can now look at traffic patterns and report back on problems.
ODS Networks added intrusion-detection capability to its line of high-speed switches. "My idea was, the computers all create audit logs, so let's put that data to work for analysis," says Steve Schall, security product manager at ODS.
Most security experts say we can thank the U.S. Department of Defense and its intelligence agencies for spending huge sums for research that led to this first generation of products.
"Intrusion detection, until two years ago, was toys for geeks," says Bill Hancock, Network-I's chief technology officer.
Catching hackers is tough and at this point, most products work mechanically by matching known patterns of attack against monitored activity. But this is an inflexible approach, Hancock says.
Industry research is now focused on detecting the "statistical anomaly," the unusual traffic pattern that might reveal new, unknown types of attacks. Alternatively, the heuristic adaptive approach relies on expert systems to come up with new monitoring rules based on network statistics. "This is still all hairy-chested macho stuff," Hancock says. "It's rare and difficult to do."
While three years ago there was virtually no commercial intrusion-detection market, sales last year hit $100 million and are expected to double again this year, according to analysts at Aberdeen Group, a consultancy in Boston (see graphic).
Axent Technologies and Internet Security Systems are the market-share leaders at this point, but Aberdeen analyst Jim Hurley emphasizes that intrusion detection is still a fragmented and immature industry. "There's no gorilla established for it yet," he says.
Internet Security Systems has tried to take advantage of its head start by organizing the Adaptive Network Security Alliance. This group aims to define a common technical framework for active response and shutdown against hackers. The framework would let network devices share intrusion information.
About 50 vendors are members of the alliance, but some industry heavyweights, such as Microsoft, IBM and Cisco, are not. So far, the alliance has defined a network management API for intrusion detection, which is supported by Hewlett-Packard's Open View.
Users buying intrusion-detection products naturally want to know: Do they really work?
The International Computer Security Association wants to tackle that question by providing independent testing. It recently organized an intrusion-detection consortium with 10 founding members.
The association plans to clearly define product capabilities in the short term and also hopes to have a buyer's guide out by fall. But the organization doesn't expect to start testing or certifying intrusion-detection products any time soon because association members "are in agreement that, at this point, the industry is too immature for product certification," a spokesman says.
Network professionals believe that intrusion-detection software helps, but in more ways than just spotting hackers.
Ernst & Young deploys the Tripwire file-monitoring software on Unix servers in its intranets to prove that risk-management data wasn't altered. "The regulatory agencies require you have certain capital requirements," Ernst & Young principal Allen Lum says. "We use Tripwire against the risk capital-model programs to make sure the data didn't change."
Intrusion detection is taken very seriously within military networks. And at Naval Sea Systems Command in Dahlgren, Va., the Naval Surface Warfare Center runs several host-based and network-monitoring intrusion-detection products to keep hackers at bay.
The Navy's detection efforts are lead by the "shadow team," which analyzes daily hacker attempts through log reviews. Team leader Stephen Northcutt says his group has deployed the ISS commercial product RealSecure as well as two home-grown systems, the Network Intrusion Detector, made by the Department of Energy, and Shadow, designed by the Navy.

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Nokia Codes Tips and Tricks

To check the IMEI (International Mobile Equipment Identity) Type-
*#06#
Information you get from the IMEI-
XXXXXX XX XXXXXX X
TAC FAC SNR SP

· TAC = Type approval code
· FAC = Final assembly code
· SNR = Serial number
· SP = Spare
To check the phones Software revision type-
*#0000#
Information you get from the Software revision-
V 05.31
18-02-99
NSE-3
· 1ST Line = Software revision
· 2ND Line = The date of the software release
· 3RD Line = Phone type
To enter the service menu type-
*#92702689# (*#WAR0ANTY#)
· Serial number (IMEI)
· Production date (MM/YY)
· Purchase date (MM/YY) You can only enter the date once.
· Date of last repair (0000=No repair)
· Transfer user data to another Nokia phone via Infra-Red
Clock Stopping
To check weather your SIM Card supports clock stopping type-
*#746025625# (*#SIM0CLOCK#)

Revealing the Headphone and Car-Kit menus
Please note that if you do these next tricks, the new menus can't be erased without retoring the factory default settings. To do these tricks you need to short-circuit the pins on the bottom of the phone next to where you plug in you charger.

1. To activate the "Headset" menu, you need to short-circuit pins "3" and "4". After a short time the word "Headset" will be shown in the display. Menu 3-6 is now enabled.
2. To activate the "Car" menu, you need to short-circuit pins "4" and "5". After a short time the word "Car" will be shown in the display. Menu 3-7 is now enabled.

THE REBOOT TRICK
This should work on all software versions of the 6110.
1. Go to the Calendar (Menu-8)
2. Make a note or reminder.
3. Enter some text into the edit box.
4. Hold "Clear" until the whole text is cleared, then press "Back".
5. Press "0". The main screen will now be showing but a space appears on the screen. (you can't see it)
6. Enter 4 digits (e.g. 1234).
7. Use the down arrow to move the cursor to the left side of the numbers and the space (Down arrow twice).
8. Now enter 6 digits and press the call button.

Wait for a few seconds, the screen should start to flash and reboots. It should alsowork on other menus like the "Profiles" menu.

EFR CALL QUALITY
To activate EFR (Enhanced Full Rate) Enter the code-
*3370#
This improves call quality but decreases batterylife by about 5%
To deactivate it, Enter the code-
#3370#

THE JAMES BOND TRICK
If you short-circuit theleft middle and right pins on the bottom of the phone with all connections touching each other, the Nokia software hangs! The profile "Headset" will be activated. Before you do this just activate the "Automatic Answer" in the headset profile and set the ringing volume to "Mute". Now you can use your phone for checking out what people are talking about in a room. Just place it under a table in a room and call it. The phone receives the call without ringing and you can listen to what people are saying.

NETWORK MONITOR
There is a hidden menu inside your Nokia phone. If you want to activate it, you'll have to re-program some chips inside of your phone.
1. Check your software version. You can only continue if you have v4.33, v4.73 or v5.24.
2. Take apart the phone.
3. De-solder the EEPROM (ATMEL AT 24C64).
4. Read out the data with an EEPROM programmer and save it to a file (Backup).
5. If you have v.33 or v4.73, change the address "03B8" from "00" to "FF".
6. If you have v5.24 then change the address "0378" from "00" to "FF".
7. Write the new data to the EEPROM and solder it back to the phone,
8. Power on your phone and you should have "Netmonitor" enabled.
The Network Monitor gives you the following information.

· Carrier number
· MS RX Level in DBM
· Received signal quality
· MS TX power level
· C1 (Path loss criterion, used for cell selection and reselection). The range is -99 to 99.
· RTL (Radio link timeout).
· Timeslot
· Indication of the transmitter status
· Information on the Network parameters.
· TMSI (Temporary Mobile Subscriber Identity).
· Cell identification (Cell ID, Number of cells being used).
· MCC (Mobile country code)
· MCN (Mobile network code)
· LAC (Location area code)
· Ciphering (On/Off)
· Hopping (On/Off)
· DTX (On/Off)
· Discard cell barred information

CHECK SIM-LOCK
Note - If you bought your Nokia on UK Vodafone or UK Cellnet you do not need to check this because they both transmit on GSM900, and they don't lock the phones. However if you bought your phone on UK Orange or UK One2one your phone may be blocked. The reason is that they both transmitt on GSM1800. To make a call on GSM1800 you need what is known as a "Dual band" phone. A dual band phone is able to transmit on both GSM900 and GSM1800, so they lock the phones so you can't use it with any other network simcard. If you find that your phone is locked you can try different software to unlock it. (we havn't found one that works yet), or you can ask your service provider who will gladly exchange the 10 digit code for about £35.
This is how to check the status of the 4 different locks. Aslo don't try entering the wrong number, because after 3 times it will block the phone for good.

There are 4 different locks on your Nokia phone.
· COUNTRY-LOCK
· NETWORK-LOCK
· PROVIDER-LOCK
· SIMCARD-LOCK
The code to read out the sim-lock status of your phone is

#PW+(MASTERCODE)+(Y)#
· # = DOUBLE-CROSS
· W = PRESS "*" THREE TIMES
· P = PRESS "*" FOUR TIMES
· + = PRESS "*" TWO TIMES
· MASTERCODE = 1234567890
· Y = NUMBER 1 TO 4
The master code is a secret code. The code has 10 digits, To read out the sim-lock status you can enter every combination you want!
"Y" Shows the status of the network-lock. Here you can enter a number from "1" to "4". The "4" is for the sim-card lock.

SIM-LOCK CHECKS
· #PW+1234567890+1# = GIVES PROVIDER-LOCK STATUS
· #PW+1234567890+2# = GIVES NETWORK-LOCK STATUS
· #PW+1234567890+3# = GIVES COUNTRY-LOCK STATUS
· #PW+1234567890+4# = GIVES SIM-CARD-LOCK STATUS.

Cell Phone Viruses

For malicious computer hackers and virus writers, the next frontier in mischief is the mobile phone. A phone virus or a "Trojan Horse" program might instruct your phone to do "extraordinary things". It might call the White House or the police with a bizarre hoax. It might forward your personal address book to a sleazy telemarketing firm. Or it could simply eat into the phone's operating software, shutting it down and erasing your personal information. Similar nasty hijinks have already dogged cell phone owners in Japan and Europe. If a malicious piece of code gets control of your phone, it can do everything you can do. It can call toll numbers. It can get your messages and send them elsewhere. It can record your passwords. As cellular phones morph into computer-like "smartphones" able to surf the Web, send e-mail and download software, they're prone to the same tribulations that have waylaid computers over the past decade. Think of cell phones as just another set of computers on the Internet. If they're connected to the Internet they can be used to transmit threats and attack targets, just as any computer can. And yes, it's technically possible now ! In Japan, deviant e-mail messages sent to cell phones contained an Internet link that, when clicked, caused phones to repeatedly dial the national emergency number. The wireless carrier halted all emergency calls until the bug was removed.
In Europe, handsets short message service, or SMS, has been used to randomly send pieces of binary code that crashes phones, forcing the user to detach the battery and reboot. A new, more sinister version keeps crashing the phone until the SMS message is deleted from the carrier's server. In the United States, relatively primitive cell phone technology keeps users immune from such tricks, for now. Phone hacking is nothing new. In the 1970s, so-called "phone phreakers" made free phone calls -- and even gained control of major phone trunk lines -- by whistling certain tones into the receiver.
It is indeed possible to control the entire network, and do anything an cellphone operator can do. Now, at least three software companies have released personal security software for emerging smartphones, girding for a new wave of phone viruses and Captain Crunch-style tricks. F-Secure is one such firm, selling antivirus and encryption software for smartphone operating systems made by Palm, Microsoft and the Symbian platform common in Europe. Thus far, there have been no publicized reports of phone hacking or viruses, although viruses have attacked handhelds running the Palm operating system. Microsoft predicts deviant code will soon emerge for handhelds running its Pocket PC software. Both operating systems are expected to be used increasingly in smartphones. A virus is a piece of malevolent code that self-replicates, while a Trojan horse does not but can be just as destructive. The pranks in Europe and Japan created virus-like havoc, but did not propagate like a full-fledged virus. For virus writers who crave notoriety by wreaking maximum havoc, there are still too few smartphones, and no widespread software platform to attack. That is starting to change. Until recently, cell phone operating systems were "closed," unable to download software. But new smartphones -- like the Nokia Communicator, Handspring's Treo, Motorola's Java Phone and Mitsubishi's Trium-Mondo -- are open to such third-party downloads. At the same time, software developers' tools available for designers of such programs as games and currency converters can also be used to create malicious applications. It's possible for anyone to make custom software for this platform. Teens can download development tools and write their own software. It's these third-party programs that worry experts. If one is disguised as a Trojan horse, an infected phone could make some calls on its own. The website "virus.cyberspace.sk" posted a bulletin exhorting readers to create phone viruses. It stated, "We are starting Cell Phone Virus Challenge. Any contribution welcomed.". The page has since been taken down.
Soon, mobile phone owners will be obliged to install security software like "personal firewalls" that used to be reserved for Internet servers. That's where things are going. It's the same threat as the wired world: people posing as you, stealing your identity or your personal information, and using your information for malicious purposes. Cell phone users can avoid this, of course, by sticking with their old "dumb" phones. There are trade-offs. Do you want a phone with a tiny monochrome screen where you can only make phone calls? That's much more secure.