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.
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.
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.
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.
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.
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.
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.