For real-time communications, two different protocols are used to establish and release the connection between the two end systems: H.323 and SIP.
对于实时通信来说，有两种不同的协议用于建立和释放两个终端系统之间的连接：H.323 and SIP.
Both protocols provide a similar set of services but SIP is much simpler because it has less logical components.
这两种协议都提供类似的服务，但是SIP更简单，因为它的逻辑组件更少。
We have studied the SIP for the purpose of evaluating it and to make an implementation of a new service, the Internet Call Waiting (ICW).
我们对SIP进行了研究，目的是对其进行评估，并实现一种新的服务——互联网呼叫等待( ICW )。
It is a useful solution for the calls that otherwise would be lost when the line is busy and also for rejecting undesirable incoming calls.
这是一个有用的解决方案，可以解决电话占线时会丢失的呼叫，也可以拒绝不希望的来电。
On the other hand, it is a way of not wasting network resources and contributing to call completion.
另一方面，这是一种不浪费网络资源和帮助完成呼叫的方式。
Thus, pop-up dialogue boxes are presented to make it simpler and easier to the user whose satisfaction is always an important objective for an IP based service.
因此，弹出对话框是为了让用户更简单、更容易，用户的满意度一直是基于IP的服务的重要目标。
