What is VoIP ?

WHAT IS VOIP?
voip is the voice signal is separated into data frames, that are then stored
in data packets, and at last transported over ip network by voice communication
protocol. Currently, most VoIP systems use standards H.3231
or the Session Initiation Protocol (SIP)

VOIP PROTOCOLS
The two most generally used protocols for VoIP are the ITU normal H.323 and therefore the IETF
standard SIP. each are signalling protocols that established, maintain and terminate a VoIP
call. additionally, the Media entree management Protocol (MGCP)
provides a signalling and
control protocol between VoIP gateways and traditional PSTN (Public Switched
Telephone Network) gateways
H.323 may be a comprehensive protocol underneath the ITU-T specifications for causing voice,
video and information across a network. The H.323 specification includes many 
VOIP sub-protocols:

1. H.225 for specifying call controls (e.g. call setup and teardown);

2. H.235 for specifying the protection framework for H.323 and therefore the call setup;

3. H.245 for specifying media methods and parameter negotiations like terminal

capabilities;

4. H.450 for specifying supplementary services like call hold and call

waiting

SECURITY THREATS TO VOIP
VoIP systems accept an information network, which suggests security weaknesses and therefore the forms of
attacks related to any information network are doable. as an example, during a standard
telephone system, physical access to the telephone lines or a compromise of the workplace
private branch exchange (PBX) is needed for so as to conduct activities like wiretapping.
But for VoIP, voice is converted into ip packets that will travel through several
network access points. thus the information is exposed to several additional possible points of
attack that would be used for interception by intruders. In fact, all the protection risks
associated with ip, like pc viruses, Denial of Service and man within the middle
attacks, also are dangerous to VoIP systems.