This paper presents the problem of multicast address assignment and port blocking, and gives a simple blocking model and its simulation conclusion.

文章介绍了多播地址和端口的分配及阻塞问题，给出了一个简单的阻塞模型和模拟实验结论。

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Observers say that market forces are likely to keep carriers from engaging in widespread port blocking.

FORBES

If that happens, as many observers expect it will, phone companies like Madison River might be able to legally engage in port blocking.

FORBES: More Worries For VoIP Vendors

Colin Port wants six months' notice and an injunction blocking the interview process for his replacement.

BBC: Avon and Somerset police chief Colin Port takes PCC to court