中英对照理解SIP中继的概念.doc

在我们学习 SIP 协议的过程中，对于一个概念要清楚，那就是 SIP 中继的概念。为了让大家更好地理解这

方面内容，我们采用中英文互译的对照形式，帮助大家了解这方面的知识，具体资料如下：

　　A SIP Trunk is a logical connection between an IP PBX and a Service Provider’s application servers

that allows voice over IP traffic to be exchanged between the two. When a call is placed from an internal

phone to an external number, the PBX sends the necessary information to the SIP Trunk provider who

establishes the call to the dialed number and acts as an intermediary for the call. All signaling and voice

traffic between the PBX and the provider is exchanged using SIP and RTP protocol packets over the IP

network.

charges. The provider can also terminate PSTN numbers, and route incoming calls for those numbers

back to the IP PBX over the SIP can also Trunk. This allows businesses to offer local phone numbers in

several geographical areas, but service them all from a single location.

　　如果数字被称为是一种传统的 PSTN 电话，树干提供 IP 数据包路由到 PSTN 网关是最接近的号码被

称为，以尽量减少可能的长途电话费。提供者也可以终止的 PSTN 号码，并在园区路线为这些号码来电返

回的 IP PBX 还可以干。这使得企业能够在几个地理区域提供本地电话号码，但服务从一个位置全部。

　　If the number being called can be reached over a SIP Trunk, the call does not need to be routed

over the PSTN, but can be carried on the IP network end to end. Providers can deliver these calls to

their customers for very little cost, and many offer them at no charge. Some service providers have

agreements and exchange calls for each others customers directly over their IP networks. Where no

　 　 The SIP Trunk can be provided by the Internet Service Provider, or by an independent Internet

Telephony Service Provider. In fact, there can be several parties involved, each one providing a

different part of the service needed to deliver the end-to-end communication: Internet access, SIP

termination, PSTN gateway, etc.

　　该 SIP 中继 可提供的互联网服务供应商，或由一个独立的 互联网电话服务提供商。事实上，可以有

几个当事人，每一个提供了所需提供的终端到终端的通讯：互联网接入，SIP 协议终止，PSTN 网关等服

务的不同部分

　　Because a SIP Trunk is not a physical connection, there is no explicit limit on the number of calls

that can be carried over a single trunk. Each call consumes a certain amount of network bandwidth, so

the number of calls is limited by the amount of bandwidth that can flow between the IP PBX and the