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Accelerate as what the internet network grows rate, wu of be convinced of a few traditional report also gradually migratory arrived on Internet, among them, IP phone is an expands very quickly service. As a result of the open framework with constitutional Internet, make traditional telegraphic business obtained a lot of new features again in migratory process. Be based on the IP phone of open standard among them, can provide speech communication service to people with a variety of means.
　　
　 H.323 standard
　　
H.323 is put forward for multimedia conference system, included frequency and video two parts, do not put forward technically for IP phone, because suit a phone very much,work to the phone of this kind of IP of phone by gateway means, so by ” borrow ” the standard that comes over to regard IP as the phone. Just used H.323 not just to IP phone, still included other a series of proposals, among them H.225, H.245, H.235, H.450, H.341 waits. H.323 acted as here ” overall technology asks ” , call the IP phone that uses this kind of means normally consequently H.323 IP phone.
　　
H.323 is a relatively complete proposal plan, it offerred the working mode that a kind of concentration is handled and manages. The administrative pattern of mode of this kind of job and telegraphic net is consistent, apply to especially build to the compose of the IP telephone network of the phone from the phone. Theory and practice make clear, the IP phone system of dimensions of random of H.323 capable make it. The H.323 nature that because this has support of many soft hardware and good each other,operates a gender became most IP telephone network the first selection of subsidiary channels in the human body through which vital energy.
　　
Next, we serve trader through an IP phone of home already some IP telephone networks, use H.323 client to carry software, expanded easily already the function of some IP phone infrastructure. The means that can use similar and instant news report will to the user provide function of IP speech communication. Realize the function that communication of a lot of traditional speech cannot realize.
　　
Structure of IP telephone network
　　
The network system that forms this IP phone is comprised by the area that is in two different countries (see figure 1 network develop attacks structure) , every area used means of a Cisco 5350 by implement (the following abbreviation 5350) the core that serves as a network, this 5350 have two WAN mouth and opening of two aether net by appliance, can receive the local area network of this locality and modem of DDN base band repeatedly directly. Connect telephone network with general (PSTN) photograph join is block NP60 of unit of 4PRI and data processing of an IP speech through adding an E1 interface, will realize E1 (the B channel of 30 ISDN) with the road by implement photograph join, data of sound of antonym of real time ground undertakes H.323 compresses encode.
　　
The user of this locality PSTN that passes accredit needs to dial only 5350, in the speech of 5350 clew falls to be able to dial the PSTN telephone of another area, special undertake communicating conveniently. The record that at the same time server of attestation charge to an account still can save next communicating is used at in the future settle accounts. For the client that serves to using IP phone, need to pay this locality phone Fei Heyuan only under international the IP of long-distance telephone bill opens a telephone bill, and business of IP telephone service does not need hire costly international relay circuitry, need to pay fixed circuit hire fee only, can make through collection IP phone expense scores gain. The service mode that this is business of service of service of traditional IP telephone. We can see a bit very apparent, as a result of the road 2 o’clock by implement it is to place in Internet, besides dial from PSTN beyond this kinds of 5350 means, we can very easily visit through Internet directly 5350.
　　
OpenH323 plan
　　
Want to realize such function, choose even if use best can abide by H.323 and the 5350 software that have news report, will realize the call of IP phone through the computer. Such software actually exceedingly much, the software such as the NetMeeting that includes Microsoft, TalkRing can come true, but these software more or less used some of a few illicit to call with the function, cannot be linked together with H.323 equipment of the standard well quite receive, and the OpenH323 that develops below Equivalence company support plans however first-rate was abided by newest the standard of ITU H.323 V4 that announce, be based on POSIX 1.1 (can transplant standard of operating system industry) call the consultative warehouse that built a complete H.323, and still try a gender developed gateway of PSTN of draw together of one collar for a horse, net to defend, the applied process bag that the client carries inside. Because developing level to consider the otherness between different platform first-rately, so can first-rate is in all sorts of Unix kind operating system, move below Windows(win32) set operating system.
　　
　 Small try OpenPhone
　　
The process of IP speech application in OpenH323 plan is a software that is called OpenPhone, although this is a software that tries a gender only, can have supported the function of H.323 thoroughly however, also included news report of H.323 IP video of course, if high-speed network exists to join between node, can undertake completely real time visible communication.
　　
The software that whole OpenH323 plans can download from Http://www.openh323.org, the main part that runs need below Windows XP is the function library Pwlib.dll of H.323, the abstract layer Cygwin.dll of POSIX, below the System32 list that must put Windows XP, openPhone ability works normally, after OpenPhone is started, entered dial quickly interface (see a picture 2, openPhone interface pursues) , with a few commerce software comparing rises, really the interface is simpler, but we can see, primary functional options is very complete, after OpenPhone is started, started automatically breathe out to await condition, besides can undertake communicating through speech gateway beyond, still can undertake communicating with the computer of other and same moving OpenPhone. 　　
　　
In our use, the defer that discovers a network is met to communicating quality causes very big effect, because we check the Internet join that is in a local area network to be in,usable bandwidth difference compares different period of time big, be in so in the morning 9:00, midday 1:00 and in the evening 8:00 use effects differ completely. The Ping order that takes through Windows XP can check the delay that includes to ICMP, after defer is more than 300ms, in call the other side when, can shake bell, can establish link far from. Calculate defer to arrive in 200ms between 300ms, communicate quality is exceedingly poor also, so this kind application just also suits next adoption to receiving an environment like CableModem/DSL, resemble be being used at present very general dial be being received is essential cannot bear the weight of of this kind of application, it is so in the development process of the network, application also often can promote a certain domain the development of whole even industry. Conversely, in the foundation construction catchs up with after coming, can develop a more application again.
　　
This we just try to establish link between OpenPhone and 5350 speech gateway, so if the reader has fun at, can the join that oneself try to select a site and video communication.
　　
Last word
　　
In the development process of whole newsletter line of business we discover, business has all sorts of traditions to go up toward the network that is based on IP gradually the trend of integrated, interconnection, such doing is to raise single network to use efficiency first, avoid to repeat construction, can realize the appreciation function that a few traditional business cannot realize second through open IP network, through these appreciations the service creates the opportunity with new more. The article comes from: Le Cui?www.daozhou.net) is textual address: Http://www.daozhou.net/news/education/else/15982.shtml