LinPhone开发文档一:SIP和VOIP简单介绍

原文地址:http://www.linphone.org/eng/documentation/guide/

What is SIP ?(什么是SIP)

SIP is a protocol for establishing Voice over IP calls. It is an open standard, published by the IETF organisation, who made the vast majority of internet protocols. It is inspired from e-mail and http. The following section describes the base principles of SIP from the user's standpoint, and how to make SIP calls. 

SIP是一个在IP网络上实现语音通话的协议.它是由IETF组织发布的一个开放标准,该组织制订了大量的因特网协议.SIP协议受到了e-mail 和 http协议的启发.下面我们从用户的角度来描述一下SIP的基本原理以及它是如何实现SIP通话的.

Direct SIP calls in local network(在局域网中实现SIP直拨)

Just enter sip:<hostname or IP address> in the SIP url bar of linphone to place a call to another linphone running in your network.

This works also on the public internet provided that the two machines have public IP addresses or appropriate firewall rules.

只需要在linphone中的SIP地址栏中输入sip:<主机名 or IP地址>就可以呼叫局域网中其他正在运行的linphone.这种方式同样适用于互联网上的两台计算机,但是要恰当的配置IP地址和防火墙规则.

Internet calls through a SIP proxy(通过SIP代理实现因特网通话)

On the public internet, because of dynamic IP addresses, mobility, firewalls, direct calls are not really usable. That's why the concept of SIP proxy exists: the proxy is responsible for routing calls whatever the IP address of end-users is. VoIP operators company are deploying SIP proxies on the internet to get SIP calls routed for their subscribers.

在互联网上,由于IP地址的变化,防火墙等因素的影响,直拨并不总是可用.这就是为什么会出现SIP代理的原因:SIP代理可以实现路由功能,而无需考虑用户的真实IP.VOIP运营商在互联网上部署了他们的SIP代理,从而为他们的客户提供路由功能.

In a first step, the user has to subscribe for the service by choosing a username (sometimes a number) and password. Your public sip identity is then sip:<your username>@<your voip provider>, this is the address that other people can use to reach you using SIP.

首先,用户要注册SIP帐号.注册之后,你的SIP识别地址就是sip:<用户名>@<VOIP运营商代码>,其他用户可以通过这个地址来向你发起SIP通话.

Then, by configuring the client (such as Linphone) to go through the proxy, you get a public sip address on the internet, in the same way you have an email address. Other people subscribed to this operator can be reached simply by typing their username or phone number.

The routing of pure internet calls is a service that is often free. Linphone.org is powering a free SIP proxy service, you can register here.

然后,设置下客户端的代理参数(例如linphone),就像获得邮箱地址一样,你就获得了一个因特网上的SIP地址.之后你就可以通过输入用户名或者电话号码来向同一VOIP运营商的用户发起会话.单纯的因特网通话通常都是免费的.Linphone.org就提供免费的SIP代理服务,你可以在这里注册

Calls to normal phone numbers(呼叫普通的电话号码)

VoIP operators for most of them also provide attractive prices to place VoIP to PSTN (= classical telephony) through their proxies and gateways. You could then call anybody in the world from your favourite linphone client, by simply entering his/her international phone number. The SIP username becomes a phone number.

VOIP运营商通常会提供VOIP呼叫PSTN(传统电话)的服务,而且这种价格一般都是非常低廉.你可以用你喜欢的linphone客户端呼叫世界上的任何人.这时候SIP用户名会变成电话号码

Choosing a voip operator(选择一个VOIP运营商)

The Linphone project is not affiliated with any VoIP or telecom operator, thus we do not recommend or promote any of them in particular. By typing "voip operator" in your favourite search engine you will get hundreds of answers. You can refine the search by country to get more pertinent answers.

Linphone is using the standard and well known SIP protocol. As such, it should be compatible with any voip operator using SIP for its network.

Linphone项目组不属于任何VOIP或电信运营商,所以我们不会向您推荐任何运营商.你可以通过搜索引擎来找到答案,同时输入国家名可能会获得更合适的答案.

Linphone使用的是标准的SIP协议,因此,可以和其他使用了SIP协议的VOIP运营商的网络兼容.