Fundamental of VoIP and Security

    CHAPTER NO.3

III. FUNDAMENTAL OF VOIP: This chapter presents the fundamental Issues of VoiP Technology that are: what is the Basic of VoiP security, what is the working procedure of VoiP, and one of the most important issue is, what hardware are necessary for it. These are discussed below one by one.

 A. BASIC OF VOIP : As Traditional telephone system works on circuit switching which means when a call is made a connection is set up between Destination and source in both directions and it is maintained till duration of call. This is a dual directional i.e. two ports in both directions are connected so it makes a circuit. There is a disadvantage in this system that Phone line can not differentiate between useful talking and silence. Like if conversation is going on between two persons then one will be talking and other will be listening so half of the transmission data is wasted in this case. Apart from this there are many instances when there is pause between conversation that silence is also handling as data and its transmission is a waste. Therefore, if these two issues can be handled then there will be transmitted only useful data and unnecessary instances will be eliminated. This cuts data transmission by more then half. VoIP technology takes care of this by using packet switching. In this case it opens connection just long enough to send bits of functional data called packet from one system to another. This situation is same as the user�s computer is making connection to any website when it is required otherwise internet connection will be very slow if it will continuously maintain connection within any web page. This type of system allows the network to send the call in packet along the least congested and inexpensive line that is available. It can be said that about three to four calls from a VoIP system could fit in the space of this call from a circuit switch system. This is the fundamental reason why VoIP is cheaper then conventional calling plans. There are different types of VoIP calling and some of them are mentioned below.

• ATA (Analog Telephone Adaptor): it is and adaptor that enables to make use of standard telephone for VoIP options. ATA converts analog signal to digital signal that can be easily transmitted through internet.
• IP phones: look just like normal phones with same keypad. The difference is only they substitute old style wall jack connector with Ethernet connectors so it gets plugged straightforwardly into the router.
• Computer to computer: it is the most frequent type of calling. This is the simplest and inexpensive way to use VoIP. These calls are exclusively free, only thing we need software that we can download from Internet. It needs a broadband or DSL connection, microphone, speaker and sound card to be activated for both sides of computers.
• Wi-Fi phones: The latest technology that is promising in the market and gaining popularity is Wi-Fi phones. This Phone lets people to make connections using a local wireless Internet access point seamlessly switched over to a cell network whenever necessary.

VoIP is not only for saving money but there are many other benefits to gain. It depends on IP service provider to have to get these. Some of the benefits are listed below.

�        Much cheaper long distance and international calls    Many features (depends on provider) like Email alert for new voicemail, web access to voicemail, auto forward, caller ID, call waiting caller ID, call forwarding etc.

�       Flexibility, when VoIP phone service is used the phone number is programmed into the converter and client can take converter and phone number everywhere in the world he wants. As long as we have access to Internet connection we can use our phone number. As the technology is rising fast and incredible amount of work is dedicated to VoIP, some of the disadvantages that are associated with VoIP are going to resolve time by time, it is predictable that after some time VoIP will have well known user acceptance.

B. WORKING OF VOIP:The Present phone system depends on a reliable but mainly incompetent method for connecting calls recognized as circuit switching. This method has been used for over a century. When a call is made between two people a connection is maintained in both directions between callers for the duration of the call. This dual directional characteristic gives the system the name circuit. If, for example, client made a 100-minute call the circuit would be continuously open and thus used between the two phones. Up until about 1960, this meant that every call had to have an authentic dedicated wire connecting the two phones. Thus a long distance call cost so much, because of paying for pieces of copper wire to be connected all the way from source phone to the destination phone and for that connection to stay constant throughout the call. Nowadays, nevertheless an analog call is converted after leaving the house to a digital signal, where a call can be combined with many others on a single fiber optic cable, While this system is definitely an enhancement over the past copper wire system and still quite incompetent. This incompetence is due in part to the fact that the telephone line can't differentiate between useful talking and unneeded silences. i.e., in a typical conversation while one person is talking the other person is listening. Thus the existing analog system uses roughly half its space sending ineffective messages like this silence. But there is also more information, even down to pauses in speech, which under a further efficient system can be successfully cut out rather than wasting the circuit space. This thought of only transmitting the noisy bits of a traditional phone call and saving a great deal on circuit space, is the basis of Packet-Switching, the substitute method to circuit switching that the VoIP phone system uses. Packet-Switching is the same method that is used when client view a website. For example a website is read, client�s computer is not maintaining a constant connection to the site but rather making connections to send and receive information only on an as needed basis. Just as this system allows the transfer of information over the Internet to work so quickly and it does work in the VoIP system. While circuit switching maintains a constant and open connection, packet switching opens connections just long enough to send bits of data called packets from one computer to another. This allows the network to send the call (in packets) along the least congested and cheapest lines available and also keeping the computer or IP phone free to send and receive messages and calls with other computers. This way of sending information makes the amount of information which must be transmitted for every call at least three to four times less for VoIP than the exact same call in a conventional telephone system. For this reason VoIP is so much cheaper than conventional calling plans.\

C. VOIP HARDWARE EQUIPMENT: VOIP systems take a wide variety of forms. Every computer is capable of providing VOIP. Microsoft�s NetMeeting is built in with windows provides some VOIP services. Apple Macintosh has iChat and Linux have a number of VOIP applications to choose from. In general the term of Voice over internet protocol is linked with equipment that provides the ability to dial telephone numbers and communicate with parties on the other end of a connection who have either another VOIP system or a traditional analog phone. The hardware equipments are SOFTPHONE, CONFERENCING UNITS, MOBILE UNITS, and TRADITIONAL TELEPHONE HANDSET.

1.    SOFTPHONE: With a headset, software, and low-cost connection service, any PC or workstation can be used as a VOIP unit, often referred to as a �soft phone�. Soft phone systems should not be used where security or privacy is concern. Worm, viruses, and other malicious software are frequent on PCs connected to the internet. Well known vulnerabilities in web browsers make it possible for attackers to download malicious software without a user�s knowledge, even if the user does nothing more than visit a compromised web site.Malicious software attached to email messages can also be installed without the user�s knowledge, in some cases even if the user does not open the attachment. These vulnerabilities result in unacceptably high risks in the use of �soft phones�, for most applications.  

2.    CONFERENCING UNITS: These provide the similar type of service as conventional conference calling phone systems, but since communication is handled over the Internet, they may also allow users to coordinate data communication services, such as a whiteboard that displays on computer monitors at both ends.

 3.    MOBILE UNITS: Wireless VOIP units are becoming more and more admired, in particular since many organizations already have an installed base of 802.11 networking equipment. Wireless VoiP products may present additional challenges if certain security issues are not watchfully addressed. The WEP security features of 802.11b provide little or no protection. The more recent WiFi Protected Access (WPA), a snapshot of the ongoing 802.11i standard, offers major improvements in security, and can aid the addition of wireless technology with VOIP.

 4.  TRADITIONAL TELEPHONE HANDSET: Usually these products have extra features beyond a simple handset with dial pad. Many have a small LCD screen that may provide browsing, instant messaging, a telephone directory, and also used in configuring the handset to gain access to enhanced features such as conference calls. Some of these units may have a �base station� design that provides the same convenience as a conventional cordless phone. In addition to end-user equipment, VOIP systems include a large number of other equipment, including call processors (call managers), gateways, routers, firewalls, and protocols.Most of these components have counterparts used in data networks, but the performance demands of VOIP mean that usual network software and hardware must be supplemented with particular VOIP equipment.

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