4. Situation: Like a raging fire
     Accumulated time of VOIP on long-distance and international circuits has surpassed that of traditional tone Many operators are making good preparations , and hope to obtain a cup of a thick soup on this promising market.
    According to Synergy Research Group's estimate, Global enterprises' investment on internet phone sysem will go up to 5.3 billion dollars. Juniper investigation company points out, that : VOIP market will occupy 15.9 billion dollars of 47 billion dollars about broad band's growing business in 2009., and broad band's cut-over value will reach 43 billion dollars .Market of VOIP will become broad band's service businessmen's point of growth in main business.

5. Tendency: Break through bottleneck
     VOIP's bottleneck problems have always been focusing by relevant industries. In order to make VOIP become the first selecting measure for enterprises to solve problems about the growing need of communication, and make it steady exert effects during its application in enterprises, It needs many aspects of condition to be mature, such as:policy, criterion,quality of service,security, market and so on .

6. Safety problem
     Under the situation of VOIP, sound is the same as data package, just be " bag", so it is also troubled by attacks of virus and hackers. The amalgamation of digital net and sound increases the risk of attack. Ways of attacking digital network will appear at the melting network of sound and datas.Such as: refusing sever's attack. A consultant in Avaya company expresses that : "Once we etsp into the era of VOIP,current digital network security problems will transfer to communication of internet work.." Doubt aboutt the reliability of security restricts the development of IP. The most worrying security problem is network wiretapping.
Communication of . circuit exchanges style uses physical way to make sure its security of information., while for IP, ,people can use common digital package to intercept software, so as to get datas of sound illegally. Familiar ways of attacking are: breaking service of sound mailbox,virus's attack and so on.

7 It is widely acknowledged that: main elements affect VOIP's securiy are the following:
     ( 1) Product itself. The common technology of VOIP :establishment and control order is SIP and H.323 protocols. Generally speaking, they are all open, so that they are easily affected by virus and venomous attack.
     ( 2) Attack at DOS basing at the open door . Attackers send a lot of requests bringing false addresses, because these addresses are false sever can' receive feedback, until its resources become exhausted.
     ( 3) Service's filching .
We can't use style of paralleled yarn to dial IP phone, but we can get authority to use phone when we intercept user's code of entry. This is the same as adding another phone on the common simulating phone.
     ( 4) Detection of flow media .
A typical VoIP call is made up by two steps:establishment of order and construction of flow media. RTP and RCP are two protocols based on transmission on network, because protocols are open ,even a small part of flow media can be broadcast and it doesn't need any connections to the front and rear. If someone take way of sniffer to record all informaion from digital network, and use software to playback, all these can cause a trust crisis among employees for contents of communication.